Energy-Distinguishable Bipolar UV Photoelectron Injection from LiCl-Promoted FAPbCl3 Perovskite Nanorods

High-performance optoelectronic devices, such as solar cells and light-emitting diodes, have been fabricated on lead halide perovskites owing to their superior carrier properties. However, charge transports in such optoelectronics are intrinsically directional due to the existence of p-n junctions, which thus lacks any potential to elucidate any perturbations in light or electricity during energy conversion. Here, with the presence of LiCl additive in formamidinium chloride (FACl) solution, as-grown LiCl:FAPbCl3 nanorods demonstrated greatly enhanced crystllinity and UV photoresponse as compared to pristine FAPbCl3 nanostructures without LiCl additive. Most importantly, LiCl:FAPbCl3 nanorod film exhibits unprecedented distinguishability to UV photons with different energies and oscillating intensities, as in the form of bipolar and periodically oscillatory photocurrents. This work could advance the fundamental understanding of photoinduced carrier processes in halide perovskites and facilitate the development of novel UV-based optical communications.