Graphene-enabled interface engineering for bias-tunable UV-visible photodetection in an InGaN/Cs₃Cu₂I₅ heterojunction

The InGaN/Cs₃Cu₂I₅ heterojunction shows great potential for UV-visible photodetection due to the superior optoelectronic properties of both materials. However, its performance is limited by poor crystallinity of Cs₃Cu₂I₅ and inefficient interfacial carrier transport. To address these issues, we introduce a graphene (Gr) interlayer and construct an InGaN/Gr/Cs₃Cu₂I₅ heterojunction photodetector via thermal evaporation. The device exhibits a dark current of 2.2 × 10^-8 A and a maximum responsivity of 0.57 A/W at -2 V under 405 nm illumination and with rise/fall times of 240.2/256.5 μs, respectively. Bias-tunable UV-visible photoresponse and successful detection of 405 nm OOK-modulated signals are further demonstrated. These findings establish Gr interface engineering as an effective strategy for simultaneously improving halide-film growth and heterointerfacial carrier transport.