Abstract
Solar cells play an important part in the worldwide transition to green energy. Conventional solar cells are based on semiconducting materials which we understand well on the fundamental level. Until now, silicium has been the semiconductor of choice for photovoltaic applications. Recently, a new and promising class of materials, lead-halide perovskites, have been found, rivaling silicium based optoelectronic devices in power efficiency at a cost effective way. They exhibit strong absorption, low electron-hole recombination rates and high charge carrier mobility. However, these observed qualities still lack full theoretical understanding. In particular, the temperature dependence of the mobility and the band gap cannot be explained by models with harmonic lattice oscillations. In this project, we will follow the direction that theoretical and experimental research is pointing us to. It is believed that anharmonic lattice vibrations play a crucial role in the unique properties of these materials. We aim to take into account this anharmonicity in a theoretical description of the microscopic behavior of the charge carriers. Moreover, we will look at the effects of spin-orbit coupling and interactions with multiple phonon branches, which are expected to add significant contributions as well. All these effects might be the key to understanding lead-halide perovskites at the fundamental level, which might allow synthesizing even more efficient solar cell semiconductors.
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