Copper Iodide and Copper (I) Oxide Based Hole Transport Materials for Methylammonium Lead Iodide Photovoltaic Device Optimization
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Methylammonium lead iodide perovskite solar cells have attracted much research attention in the last decade due to skyrocketing device performance and very low cost of production. However, despite great improvements in these devices, many of their commonly used constituent materials have stability issues that contribute to limiting the lifetime and performance of the solar cell. One device component that has been scrutinized recently is the hole transport layer, which has often been made from expensive and unstable conductive organic polymers such as poly(3,4-ethylenedioxythiophene) polystyrenesulfonate. This work attempts to replace the hole transport layer of a methylammonium lead iodide perovskite solar cell with an inorganic copper-based compound while still maintaining device performance and ease of sample processing. The particular materials studied for this are copper iodide and copper oxide. The layer processing for solar cell devices included single-step solution spin coating, low temperature thermal annealing, and thermal evaporation. Hole transport layer samples were characterized by several analysis techniques that revealed the relevant physical and electrical properties. Photovoltaic cells were characterized for device performance metrics by current-voltage analysis under AM1.5G simulated solar illumination. Device parameters that could not be directly observed were calculated by fitting measured curves to a current-voltage curve model. Results confirm that copper iodide and copper oxide thin films are a viable hole transport layer option for organic perovskite photovoltaic cells with performance results matching or exceeding those of devices using a poly(3,4-ethylenedioxythiophene) polystyrenesulfonate hole transport layer.