Van Der Waals Vertical GaSe/MoS2 Heterojunctions for High-responsivity Photodetectors and Sensitive Photovoltaic Devices

Van der Waals vertical heterojunctions based on MoS2 have garnered wide-ranging applications in sensing, flexible electronics, and optoelectronic detection due to their exceptional electrical, optical, and mechanical properties. Herein, we employed a chemical vapor deposition method to achieve controllable synthesis of monolayer MoS2 while investigating the underlying growth mechanism. Additionally, we fabricated GaSe/MoS2 heterojunctions through mechanical transfer techniques and utilize them as the foundation for photodetectors and photovoltaic devices. Remarkably, the GaSe/MoS2 photodetector exhibits a pronounced enhancement in the ultraviolet region (300-400nm) compared to MoS2 two-dimensional devices. Under 300nm excitation with a light power density of 0.564mW/cm2, the GaSe/MoS2 photodetector achieves a photo-responsivity of 42.6A/W and a detectivity of 8.17×1012Jones, surpassing monolayer MoS2 photodetectors by threefold under similar conditions. Furthermore, the GaSe/MoS2 heterojunction demonstrates a significantly improved light-to-dark current ratio of 5.75 during prolonged response, representing a remarkable 72.15% enhancement. Additionally, the GaSe/MoS2 photovoltaic device exhibits excellent rectification effects and a pronounced photovoltaic response in the ultraviolet region, with a fill factor of approximately 0.25 and an energy conversion efficiency of 0.00033% at the light wavelength of 350nm. The controllable synthesis of monolayer MoS2 and the fabrication of GaSe/MoS2 heterojunctions provide an effective approach for vertical heterojunction preparation utilizing two-dimensional materials, thereby driving their application in the field of optoelectronic devices.