Studying charge transport in functioning perovskite solar cells with THz pump-probe spectroscopy

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To mitigate the effect of climate change, society must embrace clean and renewable energy sources as alternatives to fossil fuels. As more energy reaches the Earth's surface in one hour than is consumed in one year, solar energy is one of the most promising options. In recent years, hybrid metal halide perovskites have been extensively investigated for use in photovoltaic cells due to their ease of synthesis and increasingly high power conversion efficiencies for both single-junction and tandem solar cells. To facilitate further progress in this field, a greater understanding of the basic optoelectronic properties of hybrid metal halide perovskites is essential as these properties govern the overall efficiency of devices. Until now, most optoelectronic studies have been performed on isolated perovskite thin films. While these studies have been valuable for understanding the fundamentals of charge transport within the perovskite layers, a perovskite solar cell is comprised of many more components included charge transfer layers and electrodes. This project will evaluate charge-carrier recombination and charge-carrier mobility in fully-functioning devices in order to gain a better picture of the overall charge transport mechanisms. It will primarily use Optical-Pump THz Probe (OPTP) Spectroscopy, which is a versatile technique for analyzing photoconductivity with sub-picosecond time resolution. OPTP studies will be performed in the Warwick Centre for Ultrafast Spectroscopy alongside other steady-state and time-resolved analysis including photoluminescence spectroscopy.