Self-power and high gain photodetection of a type-II MAPbBr3 single-crystal film/CdSeS quantum dot heterojunction photodetector

Abstract

Perovskite single-crystal films (SCFs) offer superior optoelectronic properties over their polycrystalline counterparts but suffer from inefficient carrier extraction due to their thickness exceeding the carrier diffusion length. To overcome this limitation, we constructed a novel type-II heterojunction by integrating MAPbBr₃ SCFs (<50 μm) with alloyed CdSeS quantum dots (QDs). The staggered band alignment created a built-in electric field that drove efficient carrier separation; thus, the heterojunction photodetector achieved an ultralow dark current of ∼10⁻¹¹ A at 0 V bias and a high light on/off ratio exceeding 10⁵. Under 445 nm illumination (2.228 mW cm⁻²) at 1 V bias, the device demonstrated a remarkable switching ratio of 184 313 and a specific detectivity (D*) of 3.8 × 10¹³ Jones. This work highlights the synergy between perovskite and II–VI compound semiconductors in enabling self-driven, high-sensitivity photodetection through tailored type-II heterojunctions.