Minimising recombination losses in novel solar cell materials

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Semiconductors with ferroelectric (FE) properties are potentially interesting for application to solar cells as they may offer a route to minimise recombination losses. The V-VI-VII materials family (such as SbSI) and halide perovskites are examples of FE materials that also have the benefit of native defects that are benign (i.e. with energies that lie out of the band gap). Both properties suggest these materials could perform well as defect tolerant materials for solar cells. The V-VI-VII family is also interesting because of the tendency to grow in one dimensional, molecular type structures, which could embody interesting new physics as well as an isotropy that could be exploited in devices. However, to date these material systems have hardly been studied in solar cells. In this project, the student will design an appropriate device model for these ferroelectric semiconductors and use it to relate band structure to the fundamental processes in photovoltaic conversion, to analyse experimental measurements and design test devices. He will characterise materials with a wide range of material and device characterisation tools, including spectroscopic (photoluminescence, Raman, electroluminescence) electrical (transient current and voltage, impedance spectroscopy, current-voltage) and structural analysis techniques, to define material properties. The project takes advantage of a collaboration with physicists at Cardiff University (Profs Emyr Macdonald and Min Gao) who plan to grow such materials and with theorists (Prof Aron Walsh and Dr Jarvist Frost) at Bath who have made preliminary bandstructure calculations. The project will also build on the strong experience of the device physics, materials science and modelling of solar cell materials in EXSS (Nelson, Ekins-Daukes, Barnes), including substantial recent experience with lead halide perovskites.