Interfacial Band Engineering in ZnO‐Carbon Quantum Dot Hybrids for Next‐Generation Ultraviolet Photodetectors

Planar zinc oxide (ZnO) based ultraviolet (UV) photodetectors are emerging for low‐power optoelectronic applications but often suffer from limited responsivity due to surface recombination and inefficient carrier separation. In this work, we demonstrate vertically aligned ZnO nanorods (ZNRs) coated with nitrogen‐doped carbon quantum dots (NCQDs) hybrid UV photodetector. Compared to the (zinc oxide thin film) ZTF device, which exhibits a photocurrent density on the order of 10 −5 Acm −2 at ±1 V, the ZNR device shows improved light absorption and directional charge transport, yielding a photocurrent density of ∼10 −4 Acm −2 and an external quantum efficiency (EQE) of ∼75%. Upon incorporation of NCQDs, the photocurrent density increases by more than two orders of magnitude, reaching the 10 −2 Acm −2 range, accompanied by a responsivity exceeding 2 AW −1 and an EQE approaching 730%. This pronounced enhancement is attributed to stepwise conduction band alignment that promotes electron accumulation in the ZnO channel, along with CQD‐induced surface passivation and long‐lived interfacial trapping. These results highlight the importance of vertically oriented architecture, interfacial band engineering and controlled carrier trapping in realizing high‐gain ZnO‐based UV photodetectors, offering a scalable strategy for low‐power next‐generation optoelectronic platforms.