Ultrahigh EQE (38.1%) Deep-UV Photodiode with Chemically-Doped Graphene as Hole Transport Layer

Improving the open-circuit voltage (V-OC) is a fundamental target for photovoltaic devices to obtain high photoelectric conversion efficiency (PCE). Here, it is reported that the chemical doping of graphene hole transport layer has a significant impact on the V-OC of solar-blind ultraviolet (SBUV) photovoltaic detectors. It has been demonstrated that the external quantum efficiency (EQE) of graphene/AlGaN/SiC heterojunction photovoltaic detectors increases from 21.6% to 38.1% when the Fermi level of graphene is precisely pulled down by a simple charge transfer process. Without sacrificing response speed, the approximate to 75% increase in EQE together with responsivity is the result of the enhancement of V-OC from 1.10 to 2.02 V. This work sheds light on the correlation between V-OC and graphene Fermi level in SBUV detectors, and provides effective avenues to modulate the PCE of photovoltaics.