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.