Transmittance contrast-induced photocurrent: A general strategy for self-powered photodetectors based on MXene electrodes

Abstract

The regulation of carrier generation and transport by Schottky junctions enables effective optoelectronic conversion in optoelectronic devices. A simple and general strategy to spontaneously generate photocurrent is of great significance for self-powered photodetectors but is still being pursued. Here, we propose that a photocurrent can be induced at zero bias by the transmittance contrast of MXene electrodes in MXene/semiconductor Schottky junctions. Two MXene electrodes with a large transmittance contrast (84%) between the thin and thick zones were deposited on the surface of a semiconductor wafer using a simple and robust solution route. Kelvin probe force microscopy tests indicated that the photocurrent at zero bias could be attributed to asymmetric carrier generation and transport between the two Schottky junctions under illumination. As a demonstration, the MXene/GaN ultraviolet (UV) photodetector exhibits excellent performance superior to its counterpart without transmittance contrast, including high responsivity (81 mA W^–1), fast response speed (less than 31 and 29 ms) and ultrahigh on/off ratio (1.33 × 10⁶), and good UV imaging capability. Furthermore, this strategy has proven to be universal for first- to third-generation semiconductors such as Si and GaAs. These results provide a facile and cost-effective route for high-performance self-powered photodetectors and demonstrate the versatile and promising applications of MXene electrodes in optoelectronics.