Sustainable Perovskite Solar Cells

With the current climate emergency, an alternative to greenhouse-gas producing fossil fuels must be found urgently. More energy, in the form of photons, strikes the Earth's surface in a minute than all the energy used to power the planet in a year, so solar energy is an evident candidate for a renewable alternative. Perovskite solar cells look to address the limitations of established crystalline silicon and thin-film photovoltaics such as copper indium gallium selenide (CIGS) devices. The components of perovskite solar cells are both earth-abundant and can be prepared at low temperature using solution-based methods, whereas established device fabrication methods are energy intensive and metals used are rare. This means fabrication is cheaper and requires less energy, thus these devices will be more market-competitive in the energy sector.

The research undertaken within this PhD aims to accelerate developments towards fully "green" solar technology. Currently, fabrication techniques involve the use of hazardous and environmentally damaging solvents, such as N,N-dimethylformamide (DMF) to form the perovskite absorber layer. Also, commercialisation relies on the removal of lead completely from the perovskite or developing a method to remove and recycle lead from the environment whilst containing it safely in a solar cell.

Part of this project endeavours to find an alternative solvent for device fabrication in order to reduce environmental impact and aid up-scaling of these devices. The question is whether an alternative solvent can be found that forms a uniform Perovskite layer, and whether this solvent has minimal environmental impact. Recently, more 'green' solvents have been developed and are derived from plants or bio-waste, so initially there will be investigations to see if any of these solvents are compatible for perovskite formation and following this, incorporating perovskite absorbers into solar cells. Additionally, there is the potential for creating devices from lead removed from the environment, which addresses the issue of lead-removal from polluted ecosystems. Recent research uses functionalised graphene oxide (GO) sheets or nanoparticles for the selective removal of lead from waste water. A main issue currently is the desorption of lead from the materials for re-use. Throughout the course of this project these will be an additional focus on bio-derived additives or alternatives to improve device stability, increase ease of fabrication, and aid in increasing device efficiency.
This project is a collaboration between the Gibson and Docampo groups with multidisciplinary teams so access to training of this equipment and facilities can be proved with ease. During this project, methodology will include the full characterisation of novel perovskite devices using an array of new materials in various stages of fabrication. These devices will be characterised by the standard techniques of UV-Vis, current-voltage curves, incident photon conversion efficiency, and impedance. Additionally, electronic properties of these novel devices will be probed using X-ray photoelectron spectroscopy and electrochemical measurements to map energy levels. To analyse the surface of the absorber and assess its compatibility for use in a solar cell, techniques such as scanning electron microscopy, atomic force microscopy and X-ray diffraction will be used. Methods for lead extraction will be explored which will include chemical synthesis techniques for ligand-coated GO sheets or aerogels, in addition to the synthesis of novel nanomaterials for selective lead removal and recovery. Overall, this project will combine materials synthesis, using sustainable approaches, with solar cell assembly and testing.