Quantum‐Dots Photosensor with Wide Bandgap P‐Type and N‐Type Oxide Semiconductors for High Detectivity and Responsivity

Abstract The photodiode is a promising architecture for photodetection because of its fast response and high external quantum efficiency (EQE). The photodiode requires high detectivity, responsivity, and low dark current for various applications. Here, a new structure of quantum‐dots (QD) photodiode is reported for ultraviolet (UV), blue, green, and red light sensing using a red QD layer between p‐type and n‐type metal‐oxide semiconductors. CdZnSeS/ZnS QD is used for photoabsorption with p‐type Cu 2 SnS 3 –Ga 2 O 3 and n‐type Li doped ZnO (LZO) for carrier collection. The QD photodiode has a low dark current density of 2.08 nA cm −2 at −1 V leading to high rectification ratio of ≈10 5 . The QD photodiode shows superior properties with responsivity of 0.258 A W −1 and detectivity of 1.00 × 10 13 Jones at −1 V under green illumination. The rise and fall times of QD photodiode are 2.1 and 2.6 ms, respectively. The QD photodiode on a flexible polyimide (PI) substrate is also demonstrated, exhibiting stable characteristics under bending test of 20 000 cycles at a bending radius of 0.32 mm.