Optimization of inverted architecture methylammonium lead iodide perovskite devices and the effects of water on device performance

Abstract

Methylammonium lead halide perovskites have reached the forefront of next-generation photovoltaic technologies, recently demonstrating a record 20.1 % power conversion efficiency. This thesis details the optimization of solution-processed methylammonium lead iodide perovskites in a planar, inverted device architecture. Sequential deposition of the precursor materials, followed by thermally induced conversion into crystalline perovskite, was found to produce the most uniform film morphology. By controlling the processing atmosphere and relative quantities of deposited precursor, reproducibly efficient perovskite devices were achieved. A controlled investigation into the effects of water on the photovoltaic performance of perovskites is also presented. Small volumes of water, consistent with those absorbed by air-exposed solvents, were incorporated directly into the perovskite precursor solutions. Increasing water concentrations negatively impacted device performance, exaggerated the current-voltage hysteresis, and introduced different transient behaviours compared to the anhydrous devices. Unexpectedly, the addition of water was also found to improve the long-term device stability.