Halide Perovskites, HaPs, make up a group of semiconducting materials with excellent light absorption and good electrical charge transport properties, which is remarkable given their low-temperature solution preparation. In my Ph.D. research, I investigated fundamental optoelectronic properties of HaP semiconductors to elucidate dominant charge transport mechanisms, with emphasis on providing design tools for high-efficiency solar cells to help transform the renewable, solar energy landscape.
I will show how I characterized Fermi level positions and studied the self-doping mechanism of different HaP materials by using a suite of in situ measurements. My main conclusion was that halide vacancy defects (surface, interface, or bulk) and electron sharing between oxygen and the HaP surface, drive Fermi level changes. The former had been postulated but not experimentally shown, until my work. By elucidating the electric field distribution and photovoltage losses I could show that Br-based HaP device efficiency is limited mainly by a (relatively) high defect density at the anode/semiconductor interface.
