Herein, layer-structured β-InSemicrowires were obtainedviaa 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-InSecan 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-InSe, a lateral p-n junction based on CuInSe/InSemicrowire was subsequently assembledviaa simple solid-state reaction using these same layers. The lateral p-n junction, with a high rejection ratio of 10, exhibits excellent photovoltaic characteristics. In particular, a high on/off ratio of 4 × 10could be achieved under a light intensity of 25.18 mW cm(405 nm) without any power supply. Moreover, the dark current is 1.5 pA, which is smaller than most previous InSe-based photodetectors. The responsivity of the device can reach a highest value of 10.52 mA W. This value is comparable to those of pristine InSedevice at 0.1 V and CuInSedevice at 0.5 V. Also, the response times are one order of magnitude faster than those of pristine InSeand CuInSedevices. 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.