Surface steered aligned gradient inorganic lead halide perovskite CsPbBrxI3−x nanowires for use in photodetectors

Abstract

Explicit control over the orientation and yield of aligned planar nanowires (NWs) offers a unique blueprint for the facile integration of sophisticated functional devices with ultra-high compactness. In this report, vapor-phase synthesis produces a massive parallel assembly of nanowires owing to the graphoepitaxial effect exhibited by the annealed M-plane sapphire surface. The nanochannels on the substrate surface serve as natural templates and define the position, growth direction, and length of NWs. Microstructure characterizations and strong band-edge photoluminescence (PL) reveal the superior quality crystal structure of CsPbBrxI3-x NWs. The NW's axially asynchronous bromide-iodide composition provides a graded bandgap with two advantages: broad gamut absorption and a dominant unidirectional built-in electric field. The electric field promotes charge carrier transportation via an energy-funneling process, as demonstrated by the outstanding performance of the CsPbBrxI3-x NW photodetector, which has a responsivity of 370 A/W and a brisk photoresponse time of about 4 ms. Bright PL observation even after 100 days of storage at room temperature (RT) and 25 % relative humidity (RH) conditions indicates a boost in monoclinic phase stability and improved environmental degradation resistance. This work presents the feasibility of massive-scale synthesis of parallel NWs and their direct integration into circuits and functional systems for smart and efficient spectrometers, image sensors, optical communication, chemical or biological detection, and other optoelectronic applications.