Ion transport in caesium lead halide perovskites

Abstract

Perovskite solar cells have gained a great deal of attention in the energy research community, both in academia and industry. They are considered as promising candidates for replacing existing commercial solar cells, given their high efficiency (up to 23%) and simple, cost effective synthesis. However, there are still numerous challenges for their commercialisation. The two major issues are their short lifetimes and hysteresis in their current-voltage curve. This thesis aims at studying ion transport in perovkites, which is considered as the culprit behind these problems. Very little is known about the exact mechanism of ion transport in perovskites and there exist conflicting results in literature about its relation to perovskite solar cell efficiencies. Through this thesis, we aim at resolving some of the ambiguities revolving around ion transport by discussing its dependence on phase of crystal and the type of ion in the per- ovskite. In this regard, we have found, using nudged elastic band method, the activation energy barriers for transport of halide ions, mediated by vacancy defects, in cesium halide perovskites (CsPbX3, X = Cl, Br, I) for different crystal phases. Our study is important for further understanding of perovskites because there is no existing literature on dependency of ion transport on phases of perovskites.