Self-assembled KCu ₇ S ₄ nanowire monolayers for self-powered near-infrared photodetectors

Near infrared light (NIR) photodetectors based on one-dimensional semiconductor nanowires have generated considerable interest due to their practical application in versatile fields. We present a facile yet efficient approach to rationally integrating KCu₇S₄ semiconductor nanowires by the Langmuir-Blodgett (LB) technique. A self-powered near infrared (NIR) light photodetector is fabricated by transferring a close-packed KCu₇S₄ nanowire monolayer to the surface of a silicon wafer. The as-fabricated Si/KCu₇S₄ heterojunction with a close-packed and well-aligned nanowire array exhibits splendid photovoltaic performance when illuminated by NIR light, allowing the detection of NIR light without an exterior power supply. The photodetector exhibits a high sensitivity to NIR light (980 nm, 295.3 μW cm^-2) with responsivity (R) 15 mA W^-1 and detectivity (D*) 2.15 × 10¹² cm Hz^1/2 W^-1. Significantly, the device shows the capability to work under high pulsed light irradiation up to 50 kHz with a high-speed response (response time τ_r 7.4 μs and recovery time τ_f 8.6 μs). This facilitates the fabrication of low-cost and high-speed photodetectors and integrated optoelectronic sensor circuitry.