High-Performance Photodetectors Based on Solution-Processed Epitaxial Grown Hybrid Halide Perovskites

Hybrid organic-inorganic halide perovskites (HOIPs) have recently attracted tremendous attention because of their excellent semiconducting and optoelectronic properties, which exist despite their morphology and crystallinity being far inferior to those of more mature semiconductors, such as silicon and III-V compound semiconductors. Heteroepitaxy can provide a route to achieving high-performance HOIP devices when high crystalline quality and smooth morphology are required, but work on heteroepitaxial HOIPs has not previously been reported. Here, we demonstrate epitaxial growth of methylammonium lead iodide (MAPbI₃) on single crystal KCl substrates with smooth morphology and the highest carrier recombination lifetime (∼213 ns) yet reported for nonsingle crystalline MAPbI₃. Experimental Raman spectra agree well with theoretical calculations, presenting in particular a sharp peak at 290 cm^-1 for the torsional mode of the organic cations, a marker of orientational order and typically lacking in previous reports. Photodetectors were fabricated showing excellent performance, confirming the high quality of the epitaxial MAPbI₃ thin films. This work provides a new strategy to enhance the performance of all HOIPs-based devices.