The paper reports on the photovoltaic effect in a van der Waals heterojunction composed of molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers. These materials are held together by van der Waals forces and exhibit atomically sharp interfaces. The junction is electrically tunable, and under appropriate gate bias, it functions as an atomically thin diode. Upon optical illumination, charge transfer occurs across the planar interface, leading to a photovoltaic effect. The device's performance is analyzed through current-voltage (J-V) characteristics and power conversion efficiency measurements. The results show that the device can be used for solar energy conversion, with a power conversion efficiency of approximately 0.2%. The study highlights the potential of van der Waals heterojunctions in photovoltaic applications, particularly in the context of large-scale production of two-dimensional crystals.The paper reports on the photovoltaic effect in a van der Waals heterojunction composed of molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers. These materials are held together by van der Waals forces and exhibit atomically sharp interfaces. The junction is electrically tunable, and under appropriate gate bias, it functions as an atomically thin diode. Upon optical illumination, charge transfer occurs across the planar interface, leading to a photovoltaic effect. The device's performance is analyzed through current-voltage (J-V) characteristics and power conversion efficiency measurements. The results show that the device can be used for solar energy conversion, with a power conversion efficiency of approximately 0.2%. The study highlights the potential of van der Waals heterojunctions in photovoltaic applications, particularly in the context of large-scale production of two-dimensional crystals.