In this Customer Catch up, we speak with Dr. Rodrigo García from Professor Matt Davies’ Applied Photochemistry and Circular Economy Group at Swansea University.
Perovskite solar cells are a particular focus for this group. Dr. García explained to us what perovskites are and how they are revolutinsing the field of solar photovoltaics:
“Perovskite solar cells are an emerging type of photovoltaic technology, that over the last decade has had an unprecedented improvement in performance”.
Advances in perovskite technology are mainly due to the inherent properties of the active layer – a semiconductor material with a perovskite crystal structure, ABX3 where where A and B are cations and X is a halogen.
The chemical composition of the perovskite layer can be easily tuned to control the bandgap of the material as well as its photoluminescent, chemical, and physical properties. Being able to manipulate these properties allows scientists to optimise the material for specific applications – including their incorporation into tandem solar cells. Most commonly, perovskite layers with very high absorption of visible light, and a bandgap ideal for the active layer of a solar cell device are employed. Crucially, these perovskite layer do not need to be thick to generate an efficient charge – reducing material and manufacturing costs.
However, the field is still emerging and developments are ongoing to overcome some problems: “There are, of course, a lot of challenges with this technology, particularly regarding stability and designing for end of life, but research across the scientific community is looking to solve these challenges to create a truly sustainable and suitable complement to current commercial photovoltaic technologies and to accelerate their pathway towards commercialisation”.
Sustainable Perovskite Solar Cell Development
The group have a particular interest in the sustainable development of perovskite solar cells. Professor Matt Davies, group PI, is the UNESCO Chair in Sustainable Energy Development.
One focus of the group is to employ steady-state and time-resolved photoluminescence and electroluminescence techniques to study and understand fundamental features of devices and materials employed in renewable energy (particularly emerging photovoltaic devices). Understanding these properties means they can improve their performance, stability, and overall sustainability prior commercialization.1
Dr. García explained “We believe that now is the right time to implement a truly sustainable approach for the technologies of the future.” As part of this effort, the group are part of the SPECIFIC UK Innovation and Knowledge Centre, a multidisciplinary Centre that focuses on developing and testing “Active Buildings” – buildings that can generate, store and release their own heat and electricity from solar energy.2
They are constantly working to link fundamental research to real world applications, and some of the technologies employed in the active buildings are currently being developed in this centre, including fully printable perovskite solar cells.3
In addition to their work with the SPECIFIC Innovation and Knowledge Centre, the group is involved in several major international collaborations. These include the UNESCO Chair in Sustainable Energy Technologies, and TEA@SUNRISE, a global initiative addressing energy poverty through the development of next-generation solar technologies. Both initiatives share a strong commitment to Sustainable Development Goal 7—ensuring access to affordable, reliable, sustainable, and modern energy for all. The group also leads REACH-PSM, an Ayrton Challenge-funded project focused on establishing sustainable, locally manufactured perovskite solar modules (PSMs) in collaboration with partners across Africa and the UK.
An example of the group’s commitment to developing more sustainable methods for producing perovskites is a recent study that they published investigating solvents used in the perovskite manufacturing process.
“For this technology to be a real complement to current commercial photovoltaic devices, they need to be designed to be truly sustainable and most of the state-of-the-art devices currently reported in literature are fabricated with toxic or environmentally hazardous solvents, which is particularly problematic if this technology is to be applied to a large scale”.4,5
The group are exploring greener solvents that can be used to fabricate perovskite layers without compromising their properties. Their publication, authored by PhD student Alex Doolin, proposed a comprehensive guide for selection of green solvents for the fabrication of perovskite films and that found some promising candidates for replacing dimethylformamide (DMF) in the fabrication of perovskite films. They found that the alternative solvents actually resulted in improved crystallinity, photoluminescence and crystal size uniformity than those prepared with traditional solvents.6
“We expect that this work can be used for future development of green solvent systems for the fabrication of perovskite solar cells, particularly towards commercialisation”.
How does Edinburgh Instruments Improve Research
Dr. Rodrigo García with the FLS1000 from Edinburgh Instruments.
The group uses an Edinburgh Instruments FLS1000 Photoluminescence with MicroPL accessory and AGILE supercontinuum source upgrades. Dr. García told us how these are vital to their research:
“We employ plenty of steady-state and time-resolved photoluminescence (TRPL) characterisation of materials in our group. Particularly, we’re very interested in accurately measuring time-resolved photoluminescence of active layers in solar cells, and the effects that the interfaces and selective layers may have in the overall response of the TRPL measurement.”
As the group are interested in the effects of changing precursor materials, reusing precursor materials and/or fabrication processes have on the fundamental properties of the active layer and, ultimately on the performance of the final device, data obtained from using the FLS1000 can help provide guidelines for improving the perovskite technology. They recently upgraded to the AGILE supercontinuum light source, having previously used a fixed wavelength EPL laser to excite their samples. The AGILE now means then can investigate samples that do not interact with a fixed wavelength:
“Having the AGILE laser now, we can apply excitation wavelengths of a very wide range, and still be able to accurately measure the TRPL response of the materials, including covering materials used for a wide variety of applications”.
An important property affecting the performance of a photovoltaic device is the uniformity of the perovskite layer. The MicroPL upgrade allows the group to explore the surface of the sample and accurately measure the TRPL response of different sections of the layer and can provide information about the effects of the synthesis process, uniformity of layers, the effects of edges and impurities and, carefully employed, of the effect of interfaces in the response of the sample
“We are also capable now to create TRPL mapping of our samples and make it as detailed and with as much resolution as we need, and because it is coupled with the AGILE laser system, it can be employed both with transparent and non-transparent substrates, such as metallic substrates or plastics.”
Additionally, the group also have an FS5 Spectrofluorometer, to round up, Dr. García said:
“We have been collaborating with Edinburgh Instruments for quite some time now. The FS5 and the FLS1000 spectrofluorometers in our labs are very easy to use, and the software is quite user-friendly. I constantly train staff and students in these pieces of equipment, and because of the simplicity of their use, the students can quickly work independently. In addition, I’ve had the opportunity to interact with several people from Edinburgh Instruments over the years and they are always accessible and friendly, and reply quite quickly whenever I have a question, I need information or I’m facing difficulties with the equipment and for me, this is very valuable from a company”.
We thank Dr. Rodrigo García for working with us on this blog. We can’t wait to hear more about the incredibly important work that the group are carrying out to provide a greener and more sustainable future. You can read about the group’s research on their website: Applied Photochemistry and Circular Economy Group.
Prof. Matthew Davies’ Applied Photochemistry Group, Swansea University
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