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

Improving the open-circuit voltage (VOC) 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 VOC 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 ≈75% increase in EQE together with responsivity is the result of the enhancement of VOC from 1.10 to 2.02 V. This work sheds light on the correlation between VOC and graphene Fermi level in SBUV detectors, and provides effective avenues to modulate the PCE of photovoltaics.