A Self-Powered Photovoltaic Photodetector Based on a Lateral WSe₂-WSe₂ Homojunction

Lateral homojunctions made of two-dimensional (2D) layered materials are promising for optoelectronic and electronic applications. Here, we report the lateral WSe₂-WSe₂ homojunction photodiodes formed spontaneously by thickness modulation in which there are unique band structures of a unilateral depletion region. The electrically tunable junctions can be switched from n-n to p-p diodes, and the corresponding rectification ratio increases from about 1 to 1.2 × 10⁴. In addition, an obvious photovoltaic behavior is observed at zero gate voltage, which exhibits a large open voltage of 0.49 V and a short-circuit current of 0.125 nA under visible light irradiation. In addition, due to the unilateral depletion region, the diode can achieve a high detectivity of 4.4 × 10¹⁰ Jones and a fast photoresponse speed of 0.18 ms at V_g = 0 and V_ds = 0. The studies not only demonstrated the great potential of the lateral homojunction photodiodes for a self-power photodetector but also allowed for the development of other functional devices, such as a nonvolatile programmable diode for logic rectifiers.