The catalyst-free growth of layer-structured CuInSe2/β-In2Se3 microwires for ultrasensitive self-powered photodetectors based on a lateral p–n junction

Abstract

Herein, layer-structured β-In₂Se₃ microwires were obtained via a facile chemical vapour deposition (CVD) method without any catalyst. As a novel kind of building block for constructing photodetectors, this one-dimensional (1D) layer-structured β-In₂Se₃ can overcome issues relating to the persistent photoconductance effects of 1D materials and the insufficient optical absorption of two-dimensional (2D) layered materials. Utilizing the high carrier mobility of layered β-In₂Se₃, a lateral p–n junction based on CuInSe₂/In₂Se₃ microwire was subsequently assembled via a simple solid-state reaction using these same layers. The lateral p–n junction, with a high rejection ratio of 10², exhibits excellent photovoltaic characteristics. In particular, a high on/off ratio of 4 × 10² could be achieved under a light intensity of 25.18 mW cm⁻² (405 nm) without any power supply. Moreover, the dark current is 1.5 pA, which is smaller than most previous In_xSe_y-based photodetectors. The responsivity of the device can reach a highest value of 10.52 mA W⁻¹. This value is comparable to those of pristine In₂Se₃ device at 0.1 V and CuInSe₂ device at 0.5 V. Also, the response times are one order of magnitude faster than those of pristine In₂Se₃ and CuInSe₂ devices. This work offers new insight into the rational design of 1D or quasi-1D multilayer semiconductors for use in high-performance, low-cost, and energy-efficient photodetectors.