A\nSelf-Powered Photovoltaic Photodetector Based on a Lateral WSe₂‑WSe₂ Homojunction

Abstract

Lateral\nhomojunctions made of two-dimensional (2D) layered materials are promising\nfor optoelectronic and electronic applications. Here, we report the\nlateral WSe₂-WSe₂ homojunction photodiodes formed\nspontaneously by thickness modulation in which there are unique band\nstructures of a unilateral depletion region. The electrically tunable\njunctions can be switched from n–n to p–p diodes, and\nthe corresponding rectification ratio increases from about 1 to 1.2\n× 10⁴. In addition, an obvious photovoltaic behavior\nis observed at zero gate voltage, which exhibits a large open voltage\nof 0.49 V and a short-circuit current of 0.125 nA under visible light\nirradiation. In addition, due to the unilateral depletion region,\nthe diode can achieve a high detectivity of 4.4 × 10¹⁰ Jones and a fast photoresponse speed of 0.18 ms at <i>V</i>_g = 0 and <i>V</i>_ds = 0. The studies\nnot only demonstrated the great potential of the lateral homojunction\nphotodiodes for a self-power photodetector but also allowed for the\ndevelopment of other functional devices, such as a nonvolatile programmable\ndiode for logic rectifiers.