Single-Crystal Halide Perovskites for High Efficiency Photovoltaics

Abstract

Lead halide perovskite solar cells (PSCs) are considered the fastest growing photovoltaic technology, reaching an outstanding certified power conversion efficiency of 24.2% in just 10 years. The best performing PSCs are based on polycrystalline films, where the presence of grain boundaries and ultra-fast crystallization limit the further development of their performance by increasing the bulk and surface defects. Compared to their polycrystalline counterparts, single crystals of lead halide perovskites have been shown to possess much lower trap-state densities and diffusion lengths exceeding 100𝜇m. In this thesis, using a solution space-limited inverse temperature crystallization method, twenty-microns thick single crystals of MAPbI3 are grown directly on the charge selective contact to construct highly reproducible p-i-n inverted type solar cells with fill factors(FF) as high as 84.3% and power conversion efficiencies (PCEs) exceeding 21% under 1 sun illumination (AM 1.5G). A key requisite for high PCEs is avoiding surface hydration, in which moisture attacks the perovskite/transporting layer interface and causes a significant decrease in short-circuit current. These solar cells set a record for single crystal PSCs, and highlight the potential of single crystal PSCs in furthering perovskite photovoltaic technology.