Revealing the Fate of Photo-Generated Charges in Metal Halide Perovskites

Abstract

In this thesis, we have investigated the optoelectronic properties of metal halide perovskites with a special focus on their application in solar cells. In less than a decade of development, metal halide perovskites have yielded solar cells with efficiencies comparable to commercialized technologies. However, there has been limited knowledge about the fundamental properties of these materials. As mentioned in the introduction, the efficiency of perovskite-based solar cells is still not at its theoretical limit. In order to rationally design solar cells with maximized efficiencies, we need to understand which factors are currently limiting the performance of perovskite-based solar cells. In general, one of the first important processes in a solar cell is the absorption of light. For metal halide perovskites based on lead iodide, a thickness of 0.3 micrometer is already sufficient to absorb a substantial amount of visible (sun-)light, which makes these materials very suitable for solar cells. Furthermore, it is crucial that this absorbed light is converted into a current of moving charges, also known as electricity. Semiconductor materials such as silicon or metal halide perovskites have the ideal properties to generate a current of charges from light. In order to use this current however, the charges need to be collected. The efficiency with which charges are collected in a solar cell is closely related to its power conversion efficiency.