ZnS/Carbon Quantum Dot Heterojunction Phototransistors for Solar-Blind Ultraviolet Detection

ZnS/Carbon quantum dots (QDs) vertical heterojunction field-effect phototransistors were fabricated by a solution-based process. The light-absorbing QD layer is deposited by using ZnS QDs with a size of 2.2 nm and a bandgap at 4.5 eV, resulting in a cutoff at wavelengths at ~ 290 nm. The demonstrated phototransistor shows a photoresponsivity of 137 mA/W, EQE of 66.6 %, and response times of 0.2 s, which is attributed to the effective carrier separation at the vertical heterojunction in depletion mode. The results show that the chosen architecture is a promising design for solution-processed UV photodetectors.