Fermi-Surface Modulation of Graphene Synergistically Enhances the Open-Circuit Voltage and Quantum Efficiency of Photovoltaic Solar-Blind Ultraviolet Detectors.

Increasing the open-circuit voltage (VOC) is of a great significance to achieve high photoelectric conversion efficiency in photovoltaic applications. Here, we present a simple NO2 doping strategy that can significantly modulate the VOC of graphene-based solar-blind ultraviolet photodetectors from 0.96 to 1.84 V. The intriguing result can be demonstrated by the fact that NO2 doping lowers the Fermi surface of graphene and thus enhances quasi-Fermi level splitting of the whole device under illumination. The >103% increase of both external quantum efficiency and photoresponsivity compared to before doping is the result of a 0.88 V increase in the VOC. Our work sheds light on the forming mechanism of VOC in graphene-based photovoltaic detectors and further suggests alternative pathways to enhance the VOC of photovoltaic devices with high efficiency.