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

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 Cu₂SnS₃–Ga₂O₃ 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 ≈10⁵. The QD photodiode shows superior properties with responsivity of 0.258 A W⁻¹ and detectivity of 1.00 × 10¹³ 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.