A van der Waals heterojunction composed of molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers has been demonstrated to function as a diode and exhibit a photovoltaic effect. The device, fabricated by stacking monolayers on a silicon dioxide substrate, shows a photovoltaic response upon optical illumination, with a photovoltaic effect arising from charge transfer across the interface. The junction is electrically tunable and can be operated as a photodiode or photovoltaic cell. The device exhibits a photovoltaic effect due to the type-II band alignment, where the lowest energy electron states are in MoS₂ and the highest energy hole states are in WSe₂. The photovoltaic response is confirmed by measuring the current-voltage characteristics under different illumination intensities. The device shows a photovoltaic response with a photovoltaic efficiency of approximately 1.5%. The photovoltaic effect is attributed to the separation of electron-hole pairs at the interface, leading to a photocurrent. The device also demonstrates a photovoltaic power conversion efficiency of approximately 0.2%. The results suggest that van der Waals heterojunctions could be used for photovoltaic energy conversion, with potential applications in solar cells. The study highlights the potential of two-dimensional materials in photovoltaic technology, with the possibility of achieving higher efficiencies through stacking or plasmonic enhancement. The device is fabricated using a combination of mechanical exfoliation and precise stacking techniques, with the final structure verified by optical microscopy and Raman spectroscopy. The device's performance is characterized by its ability to generate a photocurrent under illumination, with the photovoltaic effect being dependent on the gate voltage and the band alignment of the materials. The study also discusses the potential of using van der Waals heterojunctions in photovoltaic applications, with the possibility of achieving higher efficiencies through further optimization of the device structure and materials. The results demonstrate the potential of two-dimensional materials in photovoltaic technology, with the possibility of achieving higher efficiencies through further research and development.A van der Waals heterojunction composed of molybdenum disulfide (MoS₂) and tungsten diselenide (WSe₂) monolayers has been demonstrated to function as a diode and exhibit a photovoltaic effect. The device, fabricated by stacking monolayers on a silicon dioxide substrate, shows a photovoltaic response upon optical illumination, with a photovoltaic effect arising from charge transfer across the interface. The junction is electrically tunable and can be operated as a photodiode or photovoltaic cell. The device exhibits a photovoltaic effect due to the type-II band alignment, where the lowest energy electron states are in MoS₂ and the highest energy hole states are in WSe₂. The photovoltaic response is confirmed by measuring the current-voltage characteristics under different illumination intensities. The device shows a photovoltaic response with a photovoltaic efficiency of approximately 1.5%. The photovoltaic effect is attributed to the separation of electron-hole pairs at the interface, leading to a photocurrent. The device also demonstrates a photovoltaic power conversion efficiency of approximately 0.2%. The results suggest that van der Waals heterojunctions could be used for photovoltaic energy conversion, with potential applications in solar cells. The study highlights the potential of two-dimensional materials in photovoltaic technology, with the possibility of achieving higher efficiencies through stacking or plasmonic enhancement. The device is fabricated using a combination of mechanical exfoliation and precise stacking techniques, with the final structure verified by optical microscopy and Raman spectroscopy. The device's performance is characterized by its ability to generate a photocurrent under illumination, with the photovoltaic effect being dependent on the gate voltage and the band alignment of the materials. The study also discusses the potential of using van der Waals heterojunctions in photovoltaic applications, with the possibility of achieving higher efficiencies through further optimization of the device structure and materials. The results demonstrate the potential of two-dimensional materials in photovoltaic technology, with the possibility of achieving higher efficiencies through further research and development.