Gate‐Tunable Photovoltaic Efficiency in Graphene‐Sandwiched PdSe₂ Photodetectors with Restrained Carrier Recombination

Abstract The exploration of various two‐dimensional (2D) materials provides a promising platform for constructing van der Waals heterojunction (vdWH) photovoltaic devices. The photovoltaic efficiency of such devices is still a challenge due to the recombination of photogenerated carriers resulting from the intrinsic doping property of materials. Here, PdSe₂‐based graphene‐sandwiched vertical devices with high photovoltaic efficiency are constructed. As the graphene‐sandwiched structure limits the diffusion length to tens of nanometers, the carrier recombination during diffusion is spontaneously reduced. Moreover, due to the low‐resistance contact of graphene/PdSe₂, the Fermi level and carrier density of PdSe₂ can still be significantly tuned by gate voltage, which leads to a sharp enhancement of built‐in field and photovoltaic effect. As a result, the Gr/PdSe₂/MoS₂/Gr vdWH photovoltaic device shows a high power conversion efficiency of 3.9% and an open circuit voltage of 0.6 V under 650 nm laser illumination at room temperature. The present work provides an efficient scheme for the design of high‐efficiency 2D material photovoltaic devices.