Tunable WSe<sub>2</sub>–MoSe<sub>2</sub> Lateral\nHeterojunction Photodetector Based on Piezoelectric and Flexoelectric\nEffects

Two-dimensional transition metal dichalcogenides (TMDs)\nwith piezoelectric\neffects are ideal materials for future wearable devices. While enhancing\nthe piezoelectric performance by forming vertical heterojunctions,\nshortcomings such as contamination at the heterojunction interface\nand limited built-in electric field width have been noticed. In this\nwork, a lateral heterojunction of monolayer WSe<sub>2</sub>–MoSe<sub>2</sub> with type-II band alignment was employed to amplify the electromechanical\noptoelectronic efficiency. The considerable built-in field width (BFW)\nin the lateral heterojunction facilitates rapid separation of carriers.\nThe lattice mismatch induced a flexoelectric effect during the lateral\nheterojunction growth. The flexoelectric and piezoelectric effects\nunder external strain can regulate the photodetector performance of\nthe device. Under the compressive strain of −0.93%, the photocurrent\nincreased 9.1 times compared to the tensile strain of 0.47%. Flexoelectric\neffect can reduce the dark current under no external strain. This\nwork reveals the roles of flexoelectric and piezoelectric effects\nin enhancing photoelectric conversion, suggesting lateral heterojunction\ndevices may be applied in the field of flexible low-light detection.