“The GCRF START grant has been an excellent opportunity to support UK and international computational research, enabling engagement with experimentalists both within and outside of the START community. Membership of the START network enables us all to benefit from the wider networks we partner with globally, bringing scientists and research closer together, no matter where we are based. I hope to continue to build on the research links forged in Europe, Africa, Australasia, and Asia.” – Dr Michael Higham, Cardiff University (UK) and UK Catalysis Hub 

Addressing emissions-linked climate change using electricity produced from renewable sources can present some complex challenges. One of these is the requirement that nations construct extensive electrical infrastructures, something which may be problematic for some developing nations. On the other hand, clean and sustainably produced liquid combustible fuels can be readily adapted for use in existing infrastructures based around gasoline fuel. To this end, scientists are conducting studies combined with carbon capture technology, photocatalytic water splitting, and catalytic processes to convert methanol to hydrocarbons. The aim is to develop a “synthetic” carbon cycle that mimics nature (albeit on much faster timescale), instead of the burning of fossil fuels which takes place at a rate which far exceeds that which nature can cope with.  

Dr Michael Higham is a GCRF START Postdoctoral Research Assistant (PDRA) and an Associate of the UK Catalysis Hub – a consortium of universities involved in catalysis research led by Cardiff, Bath and Manchester universities. Based at Harwell’s  Research Complex in Oxfordshire and until recently, a PDRA at Cardiff University, Michael brings his expertise in computational modelling to projects that focus on developing catalytic processes for more effective clean fuel production, minimisation and valorisation of waste byproducts, and reducing harmful gaseous emissions. These projects stretch across several research networks within the UK and further afield. 

The growing global interest in developing a new carbon cycle by enabling sustainable liquid combustible fuels ties in with Sustainable Development Goals (SDGs) for Energy (SDG 7) and Climate Action (SDG 3), Industry, Innovation, and Infrastructure (SDG 9). The goal of Reduced Inequalities (SDG 10)  is also supported through making clean, sustainable energy more accessible to developing nations, rather than the preserve of the wealthiest countries. By enabling the development of a range of clean energy technologies (such as synthetic combustible fuels, photovoltaics, battery technologies, and others), different nations with varying economic and geographical circumstances can aim to adopt technologies suited to their needs. This links with the Goal for Sustainable Cities and Communities (SDG 11) by making sustainability an accessible and achievable goal for all. 

Providing computational insights for experimental work utilising the synchrotron facilities at the UK’s national synchrotron, Diamond Light Source (Diamond), Michael works closely with Professor Sir Richard Catlow, Foreign Secretary of the Royal Society, GCRF START Co-I and Professor at the UK’s University College London (UCL) and Cardiff University.  Their aim is to gain a better understanding of catalyst systems for CO₂ valorisation, which is the conversion of waste pollutant gas into clean fuels for clean and affordable energy application. This research concerns improving understanding of catalytic processes on an atomic scale by using computational methods to explore catalysts for methanol synthesis and Fischer-Tropsch synthesis, which are important processes to convert CO₂ (a contributor to global warming and a product of burning fossil fuels) into combustible liquid fuels.  

Michael has seen several successful publications involving his work which have been made possible through the GCRF START grant. These include a detailed and exhaustive computational investigation of the mechanism of CO₂ conversion to methanol over copper surfaces, published in Dalton Transactions¹ in May 2020. In this work, the powerful computational tools available in Density Functional Theory (DFT) techniques were applied to investigate all possible mechanistic routes for this reaction, elucidating the elementary processes in this reaction, thus informing, and providing an investigative framework for ongoing investigations into the more complex copper / zinc oxide (Cu/ZnO)-based systems, which is more representative of industrial methanol synthesis catalysts.  

Shedding light on, and corroborating macro-scale observations – collaborations in the UK and Australia 

Additionally, Michael has contributed to a joint publication with experimental colleagues from the UK’s Catalysis Hub team, the University of New South Wales (UNSW), and RMIT University, Australia, investigating thermo- and photo-catalytic processes in CO₂ conversion to methanol over alumina (Al₂O₃) supported Cu/ZnO catalysts. Published in Nature Communications² (March 2020), this research explores a synergistic mechanism (i.e. involving active participation of both the Cu and ZnO components of the catalyst, rather than ZnO merely acting as an inert support material) for CO₂ conversion taking place at the Cu/ZnO interface, with DFT calculations being applied to assist the rationalisation of experimental valence band spectra, which can provide useful insights into the electronic structure of catalyst materials and potentially explain  observed catalytic activity.  

Further computational investigations have been conducted to better understand the role of reconstruction of polar ZnO surfaces in determining the morphology of supported Cu clusters, employing unbiased Monte Carlo global optimisation techniques to obtain the most stable structures for small Cu clusters supported on stable ZnO surfaces, which will enable subsequent studies to model elementary surface processes using surface models that are realistic and representative of typical Cu/ZnO catalysts. The work was published in October 2020 in the Journal of Materials Chemistry A³. 

Through an ongoing collaboration with Dr Michael Stamatakis (University College London), Michael is busy extending the work published in the Dalton Transactions paper by conducting kinetic Monte Carlo simulations  (which rely on random sampling of a probability distribution obtained from the previously conducted calculations published in the Dalton Transactions paper, in order to elucidate macroscopic kinetic behaviour based on atomistic simulations) for the metallic Cu systems investigated previously to obtain novel insights into the impact of reaction conditions, such as temperature and pressure, on the reaction mechanism and product distribution.  

Furthermore, additional ongoing collaborations with Dr Rosa Arrigo (University of Salford) and Dr Matthew Quesne (Cardiff University) are exploring the mechanism of the electrocatalytic reduction of CO₂ over bimetallic Cu/Zn systems, with computational insights supporting experimental in situ X-ray absorption spectroscopy studies undertaken at the Diamond synchrotron. It is intended that both collaborations will result in high-impact publications in leading, internationally recognised journals.  

UK-Africa partnerships and atomic scale perspectives  

“As long as there is funding for us to do research, we are going to build collaborations, and this provides a great deal of added value. By bringing African and UK researchers together, there is a greater opportunity for UK, European and African research networks to overlap and integrate. As we have seen from several successful collaborations, this is the wider impact of the GCRF START grant.” 

Dr Michael Higham, UK Catalysis Hub and Cardiff University

Through the START network, Michael works with colleagues in Africa on studies ranging from investigating adsorption induced magnetisation changes in nickel catalysts, to research into bimetallic catalysts for CO₂ hydrogenation of environmental and industrial importance. Using computer simulations and modelling to shed light on, and corroborate macro-scale observations in actual experiments, atomic scale information is possible that might otherwise be difficult to measure in situ.  

One example is the experimental results from Michael’s collaboration with Professor Michael Claeys Dominic De Oliveira at UCT’s Centre for Catalysis and South Africa’s DST-NRF Centre of Excellence in Catalysis – c*Change. This collaboration began in 2019 during Michael’s GCRF START grant-funded secondment to UCT. The project explores the effect of adsorption on magnetisation of Ni surfaces and will be featured in a manuscript the team are preparing for submission in the coming months. The overarching aim is to use computational work to valorise the new techniques in Dominic’s experimental work using UCT’s Centre for Catalysis’ unique in situ magnetometer – a tool that few other institutions have access to. This work is important because it demonstrates how changes in magnetisation of catalyst nanoparticles can vary under real reactionary conditions such as high pressure and high temperature and is a good way to see what is happening on the catalyst’s surface in a way that allows the reproduction of industrial conditions. 

“When it comes to computational aspects of chemistry, one has to spend a great deal of time looking at how we might model catalyst surfaces and think about what questions to ask as these are complex, multi component systems” says Michael. “We can test hypotheses for explanations of observed real-world behaviour, and on the flipside, we can use what we already know about well-studied systems to examine new, novel materials, and therefore help to direct future experimental studies.” 

“We are going to focus initially on the impact of hydrogen and water species (H, O, OH, and H₂O), on the surface magnetisation as Dominic already has plenty of experimental results for this from UCT’s in-situ magnetometer,” Michael adds. “The magnetometer is a really unique bit of kit and is a world’s first⁴. I also envisage a similar investigation looking at C-containing species relevant for Fischer-Tropsch synthesis, which we intend to result in an additional publication once we have enough experimental data. I am running a couple of additional calculations and writing my contribution to the manuscript in the coming weeks. Early indications show that there are changes in the magnetisation when conditions are varied.” 

“If we can understand what is causing those changes in magnetisation, then we can investigate various species present on the catalyst’s surface, which is where the computational aspect comes in,” Michael explains. “I can look at the sort of species we might expect and test lots of different species on those surfaces and see what the calculations might suggest. Once we understand these, we can use this approach for other catalytic systems.”  

Another example of UK-Africa collaboration is Michael’s work with Dr Mohamed Fadlalla and Christopher Mullins (UCT ‘s Centre of Catalysis and c*Change) on bimetallic alloy catalysts for methanol synthesis and conversion. This work also involves another UK group of catalysis researchers led by GCRF START Co-I, Dr Peter Wells from the University of Southampton’s Chemistry Department in the UK.  

“In early December 2019, our team from the University of Cape Town and Southampton University visited the Diamond Light Source synchrotron and used the B18 beamline to study the influence of substituents in the ferrite structure on the reduction behaviour and carbon dioxide hydrogenation reaction to valuable products (e.g., fuels),” Mohamed Fadlalla says. “The next step is Michael’s computational work to help us to calculate certain insights from the results such as how the catalyst looks and how the reactant is interacting with the catalyst.” 

The computational calculations will examine the catalytic product distributions which provide detailed insights into possible explanations for observed catalyst selectivity, as Michael explains below, 

“Through modelling adsorption energies, activation energies and reaction energies we hope to shed light on what happens on the catalyst’s surface. We want to compare the observed, experimental data with the calculations. Mohamed has been doing a lot of very good experimental work. I hope to get more involved once they are in a position for me to complement their experimental work with my computational input, should they need my assistance.”  

Michael adds, 

“These partnerships are important for the African and the UK research communities, not least for knowledge exchange in the search for sustainable, clean energy sources to tackle climate change. What we have seen in our interactions with our African colleagues is that they do great science and innovation on a far lower budget than most developed countries despite facing greater funding challenges than we generally do. Their expertise is world-class, and we should therefore be supporting these groups and collaborating closely with them so that the benefit from such excellent research has international as well as local impact.”  

Commenting on the collaboration with Michael Higham and START, Prof. Michael Claeys, Director of c*Change said,  

“Computational experts like Dr Michael Higham can predict how certain catalysts perform and we can try to confirm that with our techniques which is a reciprocal learning process. This expertise informs us, and we inform them through the results which is something a single group can’t do because very specific expertise is needed. Collaborating provides some of the most powerful learning opportunities which really shape your people.” 

Developing mentoring skills and teaming up with ‘virtual’ visiting students in Germany and Singapore 

Michael Higham has also teamed up with ‘virtual’ visiting students David Jurado (in Germany) and Yong Rui Poh (in Singapore) – collaborations which have worked well despite the challenges posed by the Covid-19 pandemic and remote working. Michael reports that both students have been “performing excellently”, which is promising not only due to the science but also because this is the first time Michael has mentored and supervised students. Although both students started with little experience of computational work, they have gained experience and have many interesting results⁵. David was able to send his calculations remotely from Germany and Yong Rui Poh could log onto UK super computers from the other side of the world without leaving Singapore. They are currently working on determining transition states for some processes, but once this is complete, should be ready to write up the manuscripts. It is hoped, given the breadth and detail of this work, that two manuscripts will be submitted.  

“David has completed his Master’s thesis and will remain as a PhD student in Prof. Ingo Krossing’s group at the University of Freiburg, Germany,” Michael explains. “We intend to continue to work with David and Ingo on David’s Doctoral research, with David having prepared an ambitious proposal for his PhD studies. Meanwhile, Yong Rui has concluded his studies at the National University of Singapore and will begin his PhD studies at University of California, San Diego, USA, with the potential for more collaboration in the future. 

 Commenting on what he has learnt from this collaboration, Michael says, 

“This has been a positive and rewarding experience for me and shows how remote collaborations can be very fruitful. Thinking about follow on opportunities for START, I would be very happy to work with students at African universities in a similar way. If there is a reliable internet and a computer terminal, there is no reason why I couldn’t also assist and mentor students in Africa.” 

Michael is now embarking on a new postdoctoral appointment with Prof. Sir Richard Catlow’s group at UCL working in collaboration with Prof. Justin Hargreaves (University of Glasgow) to investigate transition metal nitride catalysts for ammonia synthesis. He will remain based largely at the Catalysis Hub at Harwell, and whilst this involves some new projects, he fully intends for there to be continuity between his current work and START collaborations.  

“We have put a lot of groundwork into our collaborations through START. Although the funding for these is currently uncertain, we will always do research with the best people for the projects we work on through the Catalysis Hub and others. Prof. Claeys’ group in Cape Town is an excellent group. Whatever happens, I see no reason why we wouldn’t continue these collaborations. They are some of the best in the field!” 

“In closing,” Michael adds, “I want to thank Professor Richard Catlow who has been incredible to work with through the START network, not only as an eminent scientist but also as demonstrating the importance of networking which I have benefitted a great deal from and learnt from. I have, myself, had access to Richard’s very large network of researchers who I would otherwise have not had contact with.” 

Professor Sir Richard Catlow comments, 

“Michael’s work, while exploring exciting fundamental scientific problems is contributing to the key challenges which must be met if we are to achieve the goal of global sustainability. His projects, which are typical of the whole START community, also illustrate how modern science is a global activity bringing together scientists at all career stages and with complementary skill sets. The GCRF START initiative can be proud of what it has achieved.” 

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Footnotes

¹ Mechanism of CO₂ conversion to methanol over Cu(110) and Cu(100) surfaces. M. D. Higham, M. G. Quesne and C. R. A. Catlow, Dalton Trans., 2020, 49, 8478 DOI: 10.1039/D0DT00754D 

² Xie, B., Wong, R.J., Tan, T.H. et al. Synergistic ultraviolet and visible light photo-activation enables intensified low-temperature methanol synthesis over copper/zinc oxide/alumina. Nat Commun 11, 1615 (2020). https://doi.org/10.1038/s41467-020-15445-z 

³ Morphology of Cu clusters supported on reconstructed polar ZnO (0001) and (000) Surfaces. M. D. Higham, D. Mora-Fonz, A. A. Sokol, S. M. Woodley and C. R. A. Catlow, J. Mater. Chem. A, 2020, 8, 22840 DOI: 10.1039/D0TA08351H 

⁴ The in situ magnetometer can analyse ferromagnetic materials under actual operating conditions, including high temperature and pressure (500°C, 50 bar) with the ability to control gas and/or liquid flows through the material. This makes it an indispensable tool for advanced research and industrial catalytic process optimisation.  

⁵ David has focused more on the CO₂ hydrogenation mechanism via HCOO*, COOH*, HCOOH*, H₂COO* and OCH₂OH*, whereas Yong Rui has been looking at CO₂ dissociation, and subsequent hydrogenation of the resulting CO* to HCO*, HCOH*, and H₂CO*, as well as the processes that are common to both mechanisms (namely H₂CO* hydrogenation to either CH₂OH* or CH₃O*, and the subsequent hydrogenation of these two species to give the product, methanol).  

“The future of all technologies is ‘smart’ and this is why Organic Solar Cells (OSCs) research is vital. OSCs can act as efficient energy sources in these contexts, given the advantages they offer over current silicon solar cells due to their unique properties – from abundant materials to scalable production processes. The goal is to meet sustainable development goals (SDGs) and the growing global demand through innovative, world class solar energy research, in which Britain is a leading player. The GCRF START grant has provided us with access to these important research opportunities.”

Dr Pascal Kaienburg, University of Oxford, UK

As countries move toward rebuilding their economies in the wake of the COVID-19 pandemic, the UN and COP26 call for recovery plans to create “a profound, systemic shift to a more sustainable economy that works for both people and the planet”[1].  OSCs are solar cells made primarily from earth-abundant carbon-based compounds. They have great potential to significantly contribute to the COP26 vision of a “cleaner, greener, energy resilient” future through the development of the next generation of affordable renewable solar energy sources, from small scale-applications to large power stations around the world. This could be to supply the grid with electricity or integrated into off grid solutions and combined with storage to unlock novel applications which current silicon solar cells struggle to or cannot provide.

To this end, researchers from the University of the Witwatersrand (Wits) in South Africa and the University of Oxford in the UK are investigating the OSC microstructure to understand how they perform under varying conditions to find ways of enhancing the OSCs’ performance. Funded by the GCRF START grant, the aim is to gain unique insights at unprecedented resolution using state-of-the-art synchrotron techniques at the UK’s national synchrotron, Diamond Light Source (Diamond), amongst other techniques and facilities.

The UK has a strong record of solar cell research and the Department of Physics at the University of Oxford is an essential part of this research landscape. Led by Professor Moritz Riede, who is also a GCRF START Co-Investigator (Co-I), scientists in Oxford’s AFMD group conduct research into vacuum processing of OSCs. The precedent for upscaled vacuum fabrication of the related multi-billion-pound organic light-emitting diode (OLED) industry highlights the potential of vacuum-based processing for a range of ‘smart’ applications including OSCs. Indeed, leading companies commercialising OSCs apply vacuum deposition in their ‘solar film’ PV solutions.

To meet this growing demand for vacuum-based research opportunities, a National Thin-Film Cluster Facility for Advanced Functional Materials is currently being installed at the University of Oxford funded by the Engineering and Physical Sciences Research Council (EPSRC), the Wolfson Foundation and the University of Oxford, with Prof. Riede as the Technical Lead. The facility will place the UK at the centre of the development of next-generation materials and devices for applications in energy, photonics and electronics and act as an epicentre for novel thin film development within the UK.

Quantifying Organic Solar Cell charge transport 

OSCs can be readily processed from solution or created by vacuum deposition. They have the advantage of being flexible, lightweight, affordable in production, and perform well under indoor lighting and elevated temperatures. With the potential to be made semi-transparent and to selectively absorb certain colors in the sun spectrum, they can, for example, enable energy-harvesting semi-transparent office windows or solar energy to be harvested and at the same time grow crops with the transmitted light. These advantages make OSCs suitable for integration into building facades and lightweight roof constructions – such as greenhouses – as well as to power sensors and transmitters for the rapidly evolving Internet of Things (IoT). However, with increasing OSC performance, the transport of charges that carry the energy absorbed from incoming light to the extracting contact in the solar cell has become a bottleneck for the technology over the past years that researchers across the world seek to tackle.

Dr Pascal Kaienburg is a GCRF START-funded Postdoctoral Research Assistant (PDRA) in Prof. Riede’s AFMD group making great strides in his research on quantifying organic solar cell charge transport, amongst other research areas. The aim of Pascal’s research is to link OSC opto-electronic characterisation with the microstructure of the light-absorbing thin films. This involves fabricating OSCs by thermal evaporation in vacuum in corresponding deposition chambers at the University of Oxford together with collaborators testing the microstructure at various synchrotron and neutron facilities worldwide including Diamond, which sits at the heart of the GCRF START grant.

“Solar energy has to be cheap enough to install where needed and useable with ‘smart’ applications, as well as large scale integrated options,” says Pascal. “Ultimately, with my research we want charges to become faster and reduce losses for better systems to make solar cells more efficient and the technology more competitive.  Currently, there are silicon solar parks and silicon solar panels on buildings around the world, but to tap into new markets and applications, we need cost effective technologies with unique physical properties and organic solar cells offer these.”

This research involves quantifying and investigating different behaviours of the carbon-based, i.e., organic molecules in an OSC, such as better or worse charge transport, the nanoscale morphology in which the mix of molecules arrange, and most importantly, the interplay between the two. To gain control over the OSC’s behaviour, deposition conditions such as mixing ratio and deposition temperature are varied and optimised. Diamond in the UK, the Advanced Light Source in Berkeley, USA, the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, and the UK’s ISIS neutron and muon source are being used to test OSCs in-situ and ex-situ to generate microstructural data. The data gathered in opto-electronic measurements allows Pascal to quantify the charge transport, before linking them with morphological data at Diamond regularly acquired by his colleague, Dr Thomas Derrien[2], who is also part of the START network; then working with chemists to design new organic solar cell molecules using this data to guide the design.

“The data looks good. I am not sure yet when we go to publication, but it won’t be long,” Pascal adds. “I’m very grateful to the GCRF START grant which has funded me to do this research and boosted my skills at the same time. Engaging with experts on microstructure characterisation has taught me and also allowed me to publish as co-author on other aspects of organic solar cells.”

Understanding how organic solar cells organise themselves and the effect on performance

Dr Thomas Derrien was a PDRA at Diamond from 2018-2021. His project focused on understanding how OSCs organise themselves and how this affects the performance of the solar cells. This work in collaboration with Prof. Riede’s group, made extensive use of an evaporation chamber, MINERVA, developed at Diamond. MINERVA enables researchers to thermally evaporate organic solar cell molecules while under synchrotron X-ray illumination enabling X-ray scattering images to be collected as the molecules are deposited on surfaces. From the X-ray scattering images, the structure, orientation, and crystallinity of the molecules can be deduced, all of which can have effects on solar cells performance. Another aspect of the project was to upgrade the MINERVA chamber to be include a third evaporation source in order to allow the study of more complex molecular mixtures and multilayer structures.

New UK-Africa solar energy research collaborations through the GCRF START grant

With the GCRF START grant, researchers like Pascal, Thomas, and Prof. Riede have teamed up with their counterparts in Africa, providing new perspectives on renewable solar energy research across different continents and research institutes. For example, the scientists from Africa contribute novel interesting materials that the UK scientists have not yet explored, and the UK scientists share knowledge about characterisation techniques with their African collaborators.  

Dr Francis Otieno and Professor Daniel Wamwangi – both originally from Kenya – are based at the University of the Witwatersrand (Wits), South Africa. A member of the Energy Materials Research Group at Wits, which is led by GCRF START Co-I, Professor Dave Billing[3], Francis is a GCRF START funded Postdoctoral Research Fellow (PDRF) exploring the fabrication and testing of thin films-based solar cell devices including organics, perovskites and dye sensitised solar cells. In addition, he is looking into ways of enhancing their performance through nanoparticles technology such as plasmonics and spectral conversion thin films – research that is aimed at realising an efficient, cheaper source of solar energy and device-making for local and global markets. Prof. Wamwangi focuses on supplementary light management schemes and cost-effective materials, including organic molecules based on polymers and inorganic materials (metal halide perovskites – a hybrid between inorganic and organic materials, which can be solution- or vacuum-processed).

The GCRF START grant has been instrumental in exposing both scientists to expertise in the characterisation of OSC devices, such as evaporated fabrication techniques used by the AFMD Oxford University researchers, and access to synchrotron techniques at Diamond. The learning is mutual and in 2019, the grant enabled the Oxford University researchers to visit the University of Cape Town, South Africa, for a joint Energy Materials workshop. There they learnt more about African perspectives on Solar energy and other aspects of energy materials research, sharing their learning and ideas with their African colleagues.

“The GCRF START grant is very interesting because most research grants are focused exclusively on the science but START has the additional key element of capacity building both in Africa and the UK,” says Thomas. “It makes you think as a researcher about different angles on research… and allows us to build a network of collaborators. Pascal and I are in different institutions, but we have been able to work together and learn from each other through START, much like the collaborators we work with in Africa. Ultimately, the need for solar cells is huge in Africa so there is a large potential market for the UK to engage with. The potential to deploy the solar cells in Africa is much, much bigger than in Europe due to more sunlight, less existing electricity coverage and a large and growing population.”

In another example, Mohamed Abdelaal – an MSc. student from Egypt’s Ain Shams University in Cairo – was seconded in 2020 to the AFMD group in Oxford for several weeks. Despite the disruption of having to cut short his stay due to Covid-19 pandemic restrictions, he was able to conduct experiments at the University of Oxford and Diamond prior to returning home, with access provided by the GCRF START grant. Mohamed learnt new experimental techniques and applied computer modelling to explore the potential of simulating growth to better understand solar cell microstructure and how it affects performance. As a result, Mohamed has a joint publication from this work.

“The GCRF START grant allows us all to do better research, and with Daniel and Francis we collaborate on through several characterisation techniques,” Pascal explains. “By learning from each other’s knowledge and perspectives – including joint research visits and co-authoring new projects and publications – START has initiated new UK-African research opportunities which we aim to continue.”

Beyond ‘GCRF START 1’: creating a legacy of solar energy solutions for global challenges

To ensure the continuation of vital research collaborations and networks supported by ‘GCRF START’, follow-on opportunities are being explored. One option is through access to facilities like the new National Thin-Film Cluster Facility for Advanced Functional Materials, which will process a range of advanced functional materials including those for OSC and perovskite solar cells. Building on the success of the GCRF START grant, collaborators from this project and Dr Celine Omondi and Dr Victor Odari (MMUST, Kenya) – new partners from the African continent – are piloting how African countries can best benefit from these new capabilities established in Oxford.

Solar cells research investigated through START can be dominated by those with access to the best equipment, which is usually prohibitively expensive for most. With this new facility in Oxford, the goals of a newly commenced GCRF-funded UK-Africa project – ‘A Foundry for Research into emerging Photovoltaic Materials’ – are twofold: a) continue to investigate key physical questions on perovskite and organic solar cells; b) pilot a foundry model –  aka “mail-order” for bespoke samples designed in Africa and made at this facility before being sent back to Africa – to see whether this concept is feasible and could be implemented in a similar pan-African research facility located on the African continent.

“I’m really excited about this project, which should demonstrate that something that is state-of-the-art in computer-chip manufacturing – the foundry model – works for research in advanced functional materials as well. We hope that such opportunities will benefit research in Africa and bring both economic and social benefits down the line, as well as being a stepping-stone to future larger projects led by a thriving and growing research community in Africa,” says Prof. Riede, the Principal Investigator of Oxford University’s Foundry project.

In another example, being part of the START collaboration has helped Francis to win a British Council Newton travel grant, allowing him to visit the AFMD group in Oxford for a period of six weeks later this year (2021). This would not have been possible without the skills and opportunities received through the GCRF START grant, enabling him to ‘give back’ to the next generation of students following in his footsteps, as Francis explains below,

“Not only has GCRF START funded my two and a half years’ Postdoctoral Research Fellowship at the University of the Witwatersrand, but it has also really exposed me to new skills, with access to advanced equipment at Diamond Light Source, the Advanced Functional Materials and Devices Group at the University of Oxford, and the Materials Physics Group at Sheffield University in the UK. As a GCRF START PDRF, I was able to buy research materials and made and strengthened South Africa-UK collaborations. But the benefit and legacy does not stop with me. Finding alternative cheaper sources using locally available materials such as organic polymers forms the basis of my research. It is this learning that I pass on to the next generation of scientists. My findings form the basis of my solar cell technology teaching for undergraduate and postgraduate students and research fellows back home in Africa.”

Post-pandemic recovery plans and ‘smart’ solar energy solutions

To address the planetary emergency, “post-pandemic recovery plans need to trigger long-term systemic shifts that will change the trajectory of CO2 levels in the atmosphere” (UN SDG 13 – Climate Action). This is where ‘smart’ solar energy solutions can play a role, says Pascal. Almost all applications use sensors in manufacturing and increasingly in domestic contexts, requiring a decentralised power source for these smart applications. The aim is to move away completely from externally charged batteries and power the sensors with solar cells, although integrated battery storage backup is possible, with batteries charged by OSCs.

Without the need for complex wiring and the frequent changing of batteries, OSCs could make the overseeing of manufacturing processes using sensors more efficient, as well as the heating of homes and workplaces, especially where hundreds of sensors are located throughout a building. From mounting OSCs on smoke detectors to integrating them into the fabric of electric vehicles to extend their travel range, to making a significant impact in the ‘power market’ – the applications of OSCs are numerous and so are the opportunities to reduce carbon footprints while improving lives and livelihoods.

“It makes sense to produce customised solutions locally which in turn creates jobs,” says Pascal. “For example, integrating OSCs into building facades requires customisation, which is an advantage as customisation increases the value. Lightweight OSCs are particularly advantageous in countries with less solidly constructed buildings and housing, particularly in sunny, warmer climates in Africa and South East Asia where thin walls may not bear the heavier loads of silicon solar cells. Another exciting option of growing interest is agricultural Photovoltaics (PV). Solar panels are located on agricultural fields, providing dual use of the area. Covering entire fields with semi-transparent or selectively absorbing OSCs, crops can still be grown while solar energy is harvested from the sunlight.”

With research progress and cost reductions due to growth of production (something that silicon solar cells, the incumbent, have well demonstrated), OSCs have the potential to eventually produce electricity at lower cost than silicon solar cells in large scale applications. This offers an exciting future of inexpensive electricity that can be scaled to the dimensions needed to make a difference in the world’s energy system.

Read more about the UN’s Sustainable Development Goals here

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[1] The UN Secretary-General has proposed six climate-positive actions for governments to take as they build back their economies and societies.  These include investing funds “in the future, not the past, and flow to sustainable sectors and projects that help the environment and the climate.” Also see: https://sdgs.un.org/2030agenda

[2] Thomas Derrien is a GCRF START member and in his role at Diamond was funded as a Postdoctoral Research Assistant by the GCRF START grant.

[3] Prof Dave Billing is Professor in the School of Chemistry and Co-PI of the Energy Materials Research Group at the University of the Witwatersrand (Wits), South Africa, and also Assistant Dean in the Faculty of Science at Wits.

“When I saw the opportunity to be a part of a GCRF START team in the UK, I was very motivated to join the group. My aim is to make connections with people and be the link between researchers in Africa and groups in the UK which brings benefit to both. START has made my dream real; it has enabled something one can’t do by oneself because you need a team, and you need funding. There is no other better way to do our research than through the START collaboration.”

Dr Khaled Mohammed, University of Southampton, UK

Our team at the University of Southampton (UK) is focussed on the application of in situ and operando methods to all aspects of catalysis; this covers all areas of a catalyst’s “life-cycle” – from formation and operational behaviour, to eventually understanding what causes it to lose performance. A catalyst is a chemical substance widely used in large-scale chemical industry to enhance reactivity and selectivity towards target products of the reaction of interest without itself being consumed in the reaction.

However, the complex nature of such material requires an advanced tool to understand its behaviour under operating conditions fundamental to the chemical industry and in the drive to increase sustainability for the future of our planet. Extensive knowledge and experience in using synchrotron radiation sources is therefore vital to understand the complex nature of catalysts and to develop new technologies here in the UK and globally. Through the START collaboration, our knowledge and hands-on-experience in this area is shared with our African partners as they develop their own catalysis and synchrotron research programmes.

My name is Khaled Mohammed, and I am a Postdoctoral Research Fellow (PDRF) in Synchrotron Methods for Catalysis within Chemistry at the University of Southampton. Funded by the GCRF START grant, I joined START in October 2019 to work with Dr Peter Wells’ team – Peter is a GCRF START Co-Investigator (Co-I) and an Associate Professor within Chemistry at Southampton, holding a joint appointment with the UK’s national synchrotron, Diamond Light Source (Diamond). I joined the START project only a matter of months before the global COVID-19 pandemic and research has been challenging in this period. Despite this, I have contributed to several published studies[1] as a GCRF START PDRF.

Here I explain my perspectives on what START means as an African researcher in the UK.  My role involves contributing to British and international research, and I see myself as an ‘ambassador’ for my country (Egypt), making connections to people and being a link between researchers in the UK and those in other African countries.

Joining the START network at the University of Southampton, UK

My experience using such facilities, with particular emphasis on operando and time-resolved X-ray absorption fine structure spectroscopy (XAFS), dates back to my PhD studies at the University of Southampton (2010 – 2014) and my previous role as a Research Associate at University College London (2013 – 2015), where our group had the opportunity to use the facilities at the Research Complex at Harwell and the Beamline Allocated Group (BAG) at Diamond. In November 2015, I decided to go back to my home country, Egypt, to start a new academic role at Sohag University as a Lecturer in chemistry. I was very keen and motivated about the role with its many teaching activities. A few months later, however, I realised that my scientific research was limited in this role by the fact that there was no access to a synchrotron, which does not exist on the African continent.

On the bright side, however, I had the opportunity to speak with my colleagues in Egypt who have no experience in using such synchrotron tools and I could share with them the knowledge I had gained in the UK.  In addition, I could give lectures and seminars on the key questions about synchrotrons to the next generation of scientists: How does a synchrotron work?  What type of experiments do we do with synchrotrons? Which beamlines are available to use to support our research?

My colleagues in Egypt were excited about this subject, but it was also a challenge as the facilities are good but not good enough to do the level of advanced experiments / topics that one can do with synchrotrons. People are very motivated to do these advanced topics, such as characterisation of materials for catalysts and applications, but the problem is we do not have the funding or access to these kinds of experiments. Therefore, when I saw the opportunity to be a part of a START team, I was very motivated to join the group at Southampton.

Catalysts and synchrotrons for renewable energy – the hydrogenation of furfural for biofuels

I was born in Sohag city, Egypt, where I lived for most of my childhood. I loved studying science at school, especially the physical sciences, and I dreamt about becoming a scientist to help provide power for the city where I lived – at that time access to electricity was very intermittent.  Outside the city, I wanted to help people who lived in the countryside where, at that time, there was no electricity at all. Later, my dreams shifted to chemistry and I was motivated and inspired to develop pharmaceuticals. I had seen my grandfather suffering with illness and die prematurely due to lack of available medicines.

Today, I find myself inspired by these experiences working in catalysis with applications in renewable energy where waste biomass is converted to liquid biofuels (Bioenergy), or waste CO₂ is converted to high value chemicals that can be used in our daily life, or as an alternative to fossil fuels. These applications rely on catalysts but to make this process more sustainable and efficient, advanced techniques are required to understand how the catalysts work under operating conditions. It is a big challenge for African researchers to access the facilities and techniques needed for this type of work. Like my dreams when I was younger, I take great pride in trying to provide something useful to society. What I love about START is that it brings these dreams to reality.

A good example of the kind of research I have collaborated on is the hydrogenation of furfural. Furfural is a bio-derived molecule and can be converted to many useful products, including the generation of liquid fuels; it is therefore a renewable energy feedstock. However, bio-derived compounds are highly functionalised, this means they have many parts of the molecular structure that can undergo chemical change. Palladium (Pd) nanoparticles are widely used as an active component in furfural hydrogenation – a specific type of reaction that involves the addition of hydrogen to a compound – however, selectivity to specific products is a big challenge. In addition, Pd is a very scarce element and there are significant concerns about the sustainability of using such elements, both from an economic perspective and the environmental impact of mining such rare materials.

In our recent paper, [ACS Catal. 2020, 10(10), 5483–5492 (https://pubs.acs.org/doi/10.1021/acscatal.0c00414)], we demonstrated that a Pd/NiO catalyst can hydrogenate furfural using a dual site process; the Pd splits the H₂ molecule into adsorbed hydrogen atoms onto the Pd surface, the adsorbed hydrogen then migrates onto the NiO surface where the furfural molecule is selectively transformed. For materials like this, we need to use advanced tools at Diamond Light Source, e.g. X-ray absorption spectroscopy, to understand more about our materials and their unique properties that allow them to function as catalysts.

In the shadow of the Covid-19 pandemic – facilitating UK-African research through cross-disciplinary teamwork

“START has and continues to be a fantastic opportunity for the UK to work in concert with our African partners. Our futures are intertwined; we share the same global challenge of treading more lightly on our planet, be it to mitigate climate change or to preserve our natural world, whilst simultaneously sustaining our growing populations. New functional materials are needed to underpin the emerging sustainable technologies that allow us to tackle these challenges and START is an important gateway for sharing the tools and expertise to accelerate these advances.”

Dr Peter Wells, University of Southampton, UK

During the pandemic, the GCRF START grant has enabled us to stay productive and self-motivated, for which we are truly grateful. Although access to laboratory and synchrotron facilities has been limited, we have been able to continue our work remotely. We set goals including research activities, data reduction/analysis and submitting new beamline proposals. In addition, we participated in many on-line activities including workshops, seminars, and social activities with all participants in START.  

The environment in the group here at Southampton has been excellent. There are things you can’t just learn by talking; we have learnt by doing research-based experiments together. Peter has taught me a lot. If I do an experiment, I give the idea to Peter, and then we do some tests to validate which beamline to use and what we need to adjust and optimise before we go ahead.

When I was in Egypt – before I got involved in START – I tried to do collaborations with people here in the UK.  I could do the basics and prepare materials, but I couldn’t correlate the structure-performance relationship without beamtime experiments. Being here in the UK, interacting with experienced scientists, has enabled me to see what is new and to push things forward through START, sharing what I learn with my African colleagues.

A great achievement has been international collaborations across a range of disciplines. After joining START in 2019, I found the group already working with Professor Michael Claeys’ Group at the University of Cape Town (UCT) in South Africa. I soon got involved in this project working with Dr Mohamed Fadlalla and Chris Mullins on research using the B18 beamline at Diamond to assess, in situ, the effect of substituents in ferrite structure with the general formula of AB₂O₄. These are used in a wide range of catalytic reactions including the Haber-Bosch process, water-gas shift reaction, dehydrogenation of ethylbenzene, and Fischer-Tropsch synthesis (FTS) to produce liquid hydrocarbons/fuels.

I was able to assist Mohamed with his experiment in December 2020. We had to submit a proposal and get it accepted (to do this you have to submit initial results like a proof of concept). Once accepted, the experiment had to be done in a specific time frame. But before Mohamed came over to the UK to conduct the experiment, tests had to be carried out for optimisation of the materials. This takes time so I did this first to ensure the experiment ran smoothly when he arrived.  

There are lots of other things that must be organised and managed before experiments like these, therefore my role has been to optimise as much as possible to increase the chance of success. Since then, we have assisted Mohamed and his colleagues in data analysis for publication. This successful beamtime experiment motivated us to explore new ideas, for example, in making catalysts with well-isolated active sites – mainly cobalt in tetrahedron sites to be used in preferential oxidation of carbon monoxide.

The future with START – ‘follow on’ opportunities for UK and African energy materials research

“START is a fantastic opportunity for the UK to work in concert with our African partners to tackle shared challenges. It is clear that the excitement generated can be inspirational and helps to further integrate research partnerships.”  – Dr Peter Wells, University of Southampton, UK

We are discussing our new research ideas going forward with Mohamed and another colleague of his, GCRF START Postdoc – Dr Thulani Nyathi – and have set goals and tasks for two ‘follow-on’ projects currently in the pipeline. As a result, I am in the process of sending some samples to Mohamed and Thulani for the preferential oxidation of carbon monoxide. This research has the dual benefit of reducing the harmful effects of carbon monoxide and using the carbon monoxide captured to make useful chemicals for energy, such as fuel cell storage to power vehicles and other devices.

We are also very impressed with the facilities and equipment at UCT, some of which we don’t have here in the UK, and which could be beneficial to access in the future. On a practical level, routine visits are important for hands-on experience (sadly due to the Covid-19 pandemic my visit to UCT in 2020 was cancelled), therefore continuing remote options in the meantime is vital for sharing ideas.

Perspectives from our collaborators in South Africa on the impact of START

Here I want to share testimonials from Dr Thulani Nyathi and Dr Mohamed Fadlalla demonstrating their perspectives on our UK-Africa collaborations.

Thulani said,

“I first worked with Dr Peter Wells’ group prior to the GCRF START programme through a collaboration also involving the UK Catalysis Hub (located on the Harwell Science and Innovation Campus in Oxfordshire) and with Dr Emma Gibson’s group in Chemistry at the University of Glasgow, funded by the EPSRC (grant EP/R026815/1). This included my first visit to a synchrotron facility – Diamond Light Source – and my first exposure to two in situ techniques, XAS and DRIFTS, which were used to study supported cobalt oxide catalysts for the preferential oxidation of carbon monoxide (CO-PrOx).

This collaboration proved to be highly successful as it was concluded with a very good publication[2] in ACS Catalysis in 2019. Through the GCRF START programme (grant ST/R002754/1), I have continued to work with Peter’s group and Emma’s group, using the Block Allocation Group sessions administered by the UK Catalysis Hub, to analyse fresh and spent catalysts for the CO-PrOx reaction. I was then able to conclude my PhD thesis in September 2020 and publish a second paper in Applied Catalysis B: Environmental in June 2021[3].

There exists on-going work between the Southampton and UCT groups where we try to study substituted iron oxide and alloy catalysts for use in the hydrogenation of carbon dioxide (a greenhouse gas) to value-added chemicals. This work has already involved a trip to Diamond in 2019 and the results obtained will feature in a paper we aim to publish later in 2021. I hope to make more trips to Diamond and to continue working with the Southampton and Glasgow groups in the upcoming years.”

Mohamed said,

“The highly seamless collaboration with Dr Peter Wells and Dr Khaled Mohammed from the University of Southampton has led to a more profound collective understanding of the catalytic materials under activation and under working conditions using in situ and ex situ synchrotron-based techniques. Owing to the successful and harmonious collaboration between the two research groups thus far, further partnership is in the works to investigate catalyst structure/activity/selectivity correlations in the energy material field.”

START’s achievements and the future – “a great work for great value”

When I look back at what has been achieved and then look forward to the future, I ask myself the question: If there wasn’t a START network/project, how would people who don’t know about synchrotron techniques know about these opportunities? START not only transfers knowledge and enhances capacity, but it also builds awareness a bit like an advertisement. It helps us know where and how to apply to synchrotrons like Diamond for beamtime and shows us what is possible and how to do the experiments in the right way. And synchrotron techniques give unprecedented insights essential for our research. If there hadn’t been a GCRF START grant to fund these possibilities, it would have delayed our research because collaborations like START boost and speed up the process and findings.

In Africa we need the fundamental facilities to train the next generation ready to use synchrotrons. More locally, in Egypt, we need capacity-building facilities to do initial experiments and fundamental research. For example, a catalytic reactor would be very useful for scientists to do some reactions. We can do the preparation – we can buy the chemicals – but to do the catalytic reactions we need a reactor where we can do the experiments in optimised conditions.

We also need a ‘Centre for Catalysis’ in Egypt where we can teach the new generation to develop sufficient skills to collaborate with the UK and other countries for advanced experiments and push the research forward. If research hubs could be set up across Africa, like the Catalysis labs at UCT, this would be fantastic and START could be an ideal vehicle to make this happen. Another route is through funding agencies like the British Council/Newton Funding which provide travel grants and other support for researchers in developing countries. 

To summarise the achievements of the GCRF START grant and what START means to me: I would describe it as “a great work for great value”, and all this despite massive setbacks caused by the Covid-19 pandemic.

START does great work that allows scientists from developing countries to gain knowledge and experience from leading scientists in the UK and to reciprocate, as my role shows. It does great work because it offers opportunities for us to work with scientists from all over the world on a level playing field. Ultimately, the greatest value from my perspective is that we work hard to provide (in a sustainable way) energy/electricity, medicines and many other applications for people who don’t have these fundamental things, enabling a better life for the future – what value is bigger or better than this?

Read more about the UN’s Sustainable Development Goals here

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[1] [1] ACS Catal. 2020, 10(10), 5483–5492 (https://pubs.acs.org/doi/10.1021/acscatal.0c00414) – This work has significant implications for the upgrading of bioderived feedstocks, suggesting alternative ways for promoting selective transformations and reducing the reliance on precious metals. [2] Phys. Chem. Chem. Phys., 2020,22, 18774-18787 (https://pubs.rsc.org/en/content/articlelanding/2020/CP/D0CP00793E#!divAbstract) – This study demonstrates the complexity of mechanochemically prepared materials and through careful choice of characterisation methods how their properties can be understood. Synchrotron techniques, such as X-ray absorption spectroscopy (XAS), have multiple benefits, which aid the in-depth understanding of chemically important yet complex systems. [3] Nanoscale Adv., 2019,1, 2546-2552 (https://pubs.rsc.org/en/content/articlelanding/2019/NA/C9NA00159J#!divAbstract) –  Using state-of-the-art beamlines, this study demonstrates how X-ray absorption fine structure (XAFS) techniques are now able to provide accurate structural information on nano-sized colloidal Au solutions at μM concentrations. 

[2] ACS Catal. 2019, 9, 8, 7166–7178, Publication Date: June 28, 2019 https://doi.org/10.1021/acscatal.9b00685. Copyright © 2019 American Chemical Society

[3]  Author: Thulani M. Nyathi, Mohamed I. Fadlalla, Nico Fischer, Andrew P.E. York, Ezra J. Olivier, Emma K. Gibson, Peter P. Wells, Michael Claeys. Publication: Applied Catalysis B: Environmental. Publisher: Elsevier. Date: 15 November 2021. https://doi.org/10.1016/j.apcatb.2021.120450

Scientists in the UK’s University of Sheffield’s Electronic and Photonic Molecular Materials Group (EPMM) work on the development and optimisation of thin-film photovoltaic devices (solar cells) for sustainable energy solutions. The advantage of these type of devices is that they can convert sunlight to electrical power with high efficiency, with such materials being easy and cheap to process, potentially allowing ‘sustainable’ solar cells to be manufactured at high volume and low cost. This is important given the rising global energy demand and need for electrification in remote, rural areas, particularly in Africa, where national grids are often over-constrained.

The EPMM Group, which collaborates with the GCRF START grant, focuses on two classes of materials: perovskites[1], [2] and polymer fullerene blends. Industry standard silicon solar cells require very high temperature processing and expensive controlled environments (clean rooms) for their manufacture, whereas hybrid-perovskites solar can be fabricated at low temperatures using liquid-based processing which reduces costs and makes their production easily scalable. However, one of the biggest challenges with these hybrid-perovskites is their reduced stability compared to silicon. The Group is therefore investigating these materials to understand how best they can be optimised for the next generation of solar energy devices.

Investigating affordable energy solutions with the GCRF START grant

In their research, the EPMM scientists have benefitted from the GCRF START grant, enabling them to get involved in new international collaborations as well as access the UK’s national synchrotron, Diamond Light Source (Diamond), where they use synchrotron techniques such as X-ray scattering to research halide perovskites, a potential material for the next generation of low-cost photovoltaics.

“Using Diamond allows us to explore the structure of these materials at length-scales corresponding to atomic and molecular bonds, we have found that understanding the structure of these materials is absolutely critical in developing our understanding of how they ‘work’ in devices. Ultimately, this understanding helps in developing new materials or new ways to process existing materials to get optimum performance (efficiency) out of our solar cells.”

Prof. David Lidzey, GCRF START Co-I and Director of the EPMM Group

The GCRF START grant has also funded Dr Onkar Game’s one-year Postdoctoral position in the EPMM Group during which time he has both undertaken his own experiments on perovskites and worked very closely with various PhD students in the Group. Prof. Lidzey reports that Dr Game’s input has been invaluable, this flexible work-pattern maximising the amount of research using the funding available.

“The GCRF START grant provided me a unique opportunity to make use of world class structural characterisation facilities at Diamond” says Dr Game. “Working with PhD student Joel Smith, we utilised the in-situ Grazing Incidence Wide Angle X-ray Scattering (GIWAXS) facility at the I22 beamline in Diamond to identify the factors affecting the degradation of perovskite crystal commonly used in perovskite-PV devices[3]. This helped us to tune the composition of perovskite crystal to make it more stable towards moisture and light induced degradation. I also enjoyed setting up the in-situ measurements with Joel on understanding of solvent-induced liquification and crystallisation of perovskite using GIWAXS on Diamond’s I07 beamline,” Dr Game adds.  

Collaborative research on Perovskites: the effects of composition and temperature

Dr Claire Greenland completed her PhD in the EPMM Group supervised by Prof. Lidzey. She has been working on perovskites and has been particularly interested in how the structure of such materials are affected by their composition and local temperature. This work was done in close collaboration through the GCRF START network with the Energy Materials Research Group at the University of the Witwatersrand (Wits), South Africa, led by GCRF START Co-I, Prof. Dave Billing. In this research, Claire studied one type of popular perovskite called a ‘mixed cation’ perovskite, and used X-ray scattering to characterise the structure of the perovskite as it was cooled down to very low temperature (-190 °C). She also measured the ability of the perovskite to absorb and emit light over the same temperature range. In these studies, Claire was looking for changes in the crystal-phase as the temperature was changed.

Understanding such processes is important, as the temperature at which some phase changes occur are within the expected operational temperature of the solar cell and understanding the effect on the properties of the materials in the solar cell forms a critical part of the understanding of how such materials (and devices) work.

“Interestingly, the structure of the perovskite crystal is not fixed, but can vary as a function of temperature, being ‘cubic’ at room temperature and starting to change to a ‘tetragonal’ phase around -13 °C, with a second low-temperature phase identified at -180 °C,” Prof. Lidzey explains. “Through careful analysis, these changes in crystal structure could be correlated with changes in the optical properties of the perovskite.”

This research was supported with assistance from Wits University scientist, Adam Shnier. Adam met members of the Sheffield team at a GCRF START meeting in 2018, hosted by the Energy Materials Research Group at Wits.

“Adam Shnier provided us invaluable support in the analysis of the X-ray scattering data, allowing us to understand how the crystal structure changed with temperature,” Prof. Lidzey says. “With support from the GCRF START grant, Adam was able to travel to the UK in 2019 and assist us in some scattering experiments performed at Diamond and became an important part of the team.”  

“At the 2018 GCRF START meeting, I met a PhD student, Joel Smith, from the University of Sheffield who works on the same type of materials,” says Adam. “Joel and his colleagues are experienced at making high quality, efficient devices; while at Wits, we are experienced in making other materials that can be used for these devices and studying their crystal structures. As the 2019 GCRF START meeting was being held in the UK, we planned a research visit where I would spend a week working with Joel and his colleague Dr Onkar Game in Prof. David Lidzey’s laboratory at Sheffield. The purpose was to share technical knowledge. They were more than happy to share their experiences with these materials which instilled me with a plenty of ideas and information to share with my colleagues at home in South Africa.”

The research was published in January 2020[4] and formed a very important part of Claire’s PhD thesis. Claire has since passed her PhD viva and has come back to Sheffield in the position of ‘University teacher’. While she is not currently working on perovskites, her knowledge of materials physics and experience in understanding complex phenomena are proving invaluable in teaching electromagnetism to 1^st year undergraduate students and will also be useful in the 2^nd year lab experiments that she is developing and running, says Prof. Lidzey.

‘The GCRF START collaboration enabled me to collaborate with academics from Wits University in South Africa, which greatly enriched my work due to their expertise in X-ray diffraction and crystal structure,” Claire explains.  “I collaborated mainly with Adam Shnier, who was able to computationally model the X-ray diffraction data taken at a range of temperatures on mixed cation perovskites. This modelling revealed the temperature dependence of a variety of crystal parameters, which not only allowed us to identify phase transitions in these materials but also to correlate crystal structure with photoluminescence properties.”

“I really enjoyed working with Adam, and his insight on all things related to crystal structure and phase was invaluable to my work,” Claire adds. “These studies shed light on the fundamental properties of perovskites and how these vary as a function of temperature – such studies are a key part of solar cell optimisation, because real world solar cells must operate under a wide range of temperatures. So, it’s really cool to know that this project was part of the push towards cheap and efficient solar cell materials, which are an essential part of tackling climate change.”  

Perovskite ‘healing’ for high-speed manufacture processes

PhD student Joel Smith has also been working on perovskites. Here, however, he has been interested perovskite recrystallisation processes using solvent molecules. In this process, a perovskite film is exposed to a solvent gas, with this exposure causing the solid perovskite film to melt into a different solid or liquid form. Once the gas is removed or when heated, this material crystallises back into a ‘healed’ perovskite. The advantage of this process is that the quality of the perovskite film can be substantially improved. Practically, this could be used to improve the quality of perovskite films deposited in a high-speed manufacture process such as spray coating.

The first part of this work was led by Dr Onkar Game and investigated how treatment with one type of solvent had some unexpected effects on the perovskite film microstructure. This included measurements on thin films at Diamond to understand how these changes in microstructure affected the perovskite’s ability to withstand different challenging environments³. As part of his PhD, Joel undertook experiments at Diamond where he used X-ray scattering to monitor the very rapid changes in the structure of the perovskite film as it turned into a liquid and then back into the perovskite.

“Here we were able to resolve crystal structures of new intermediate compounds that formed in the liquid, and we could evidence the improvement in crystal structure caused by the healing process,” explains Prof. Lidzey, “Importantly, we also showed that this process could be enhanced by changing the temperature at which healing took place.”

Joel is currently writing a paper on this work which has formed part of his PhD thesis. He is set to start his Postdoctoral research in Prof. Henry Snaith’s group at the University of Oxford, working on advanced perovskite solar cell devices.

“Bringing together expertise from our different institutions in the UK and Africa through collaborating with the GCRF START grant has allowed us to investigate the crystallisation behaviour and stability of perovskites in new ways at Diamond Light Source,” says Joel. “More generally, we have been able to assist each other in fabricating, characterising and understanding these materials by sharing experience and facilities. The wider START community has been valuable as a mutually supportive network for us to develop as independent researchers, and most importantly, to grow the synchrotron research community in Africa.”

Commenting on the need for affordable, renewable energy solutions in Africa and the importance of collaboration to tackle global energy challenges, Prof. Billing said,

“The synergy in GCRF START collaborations of having people from different backgrounds tackle a problem makes the solution more robust. Creativity is important to most Africans, and we need to be involved in these creative solutions. Also, if you co-develop through collaboration, you have a sense of ownership which is what we set out to do through the GCRF START grant.”

“Everything costs energy, fundamentally,” Prof. Billing adds. “Silicon uses a lot of energy in its making to make solar cells so I think the best we can do as humans is look at remediation and balance. The GCRF START grant asks us to consider questions in our research around the global challenges like: am I using components that are sustainable? Are we using elements which are abundant, affordable, and environmentally compatible? If you think about a rural village which is cooking using wood charcoal, they are energy poor and lighting will be paraffin or candles. If you can find a cheap source of energy there and you can bring in lighting, that is life changing!”

Read more about the Sustainable Development Goals for Energy (SDG 7).

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[1] Here, “perovskite” is a name for a class of crystalline material, and there are many different combinations of starting materials that can be used to make a perovskite. Some of these materials absorb sunlight more efficiently, and others have greater environmental stability (both important characteristics for practical applications of solar cells).

[2] Bishop, J.E., Read, C.D., Smith, J.A. et al. Fully Spray-Coated Triple-Cation Perovskite Solar Cells. Sci Rep 10, 6610 (2020). https://doi.org/10.1038/s41598-020-63674-5. This work demonstrates the possibility for spray-coating to fabricate high efficiency and low-cost perovskite solar cells at speed.

[3] Onkar S. Game, Joel A. Smith et al.  Solvent vapour annealing of methylammonium lead halide perovskite: what’s the catch? J. Mater. Chem. A, 8, 2020, 10943-10956 DOI: 10.1039/D0TA03023F 

[4] Greenland, Claire, Adam Shnier, Sai K. Rajendran, Joel A. Smith, Onkar S. Game, Daniel Wamwangi, Graham A. Turnbull, Ifor DW Samuel, David G. Billing, and David G. Lidzey. “Correlating Phase Behavior with Photophysical Properties in Mixed‐Cation Mixed‐Halide Perovskite Thin Films.” Advanced Energy Materials 10, no. 4 (2020): 1901350 (https://doi.org/10.1002/aenm.201901350)