Self-Power and High Gain Photodetection of Type-II MAPbBr3 Single Crystal Film/CdSeS Quantum Dots Heterojunction Photo-detector

Perovskite single-crystal films (SCFs) offer superior optoelectronic properties over polycrystalline counterparts but suffer from inefficient carrier extraction due to thickness exceeding carrier diffusion length. To overcome this limitation, we constructed a novel Type-II heterojunction by integrating MAPbBr 3 SCFs (<50 µm) with alloyed CdSeS quantum dots (QDs). The staggered band alignment creates a builtin electric field that drives efficient carrier separation, thus the heterojunction photodetector achieves an ultralow dark current of ~10 -11 A at 0 V bias and a high light on/off ratio exceeding 10 5 . Under 445 nm illumination (2.228 mW/cm 2 ) at 1 V bias, the device demonstrates a remarkable switching ratio of 184,313 and a specific detectivity (D * ) of 3.8×10 13 Jones. This work highlights the synergy between perovskite and Ⅱ-Ⅵ compound semiconductors in enabling self-driven, high-sensitivity photodetection through tailored Type-II heterojunction.