Interfacial-Bulk Synergistic Passivation for High-Performance Self-Powered CsPbBr₃ Quantum Dot Photodetectors

While lead halide perovskite quantum dots (QDs) offer exceptional optoelectronic properties for photodetection, their performance and stability are severely limited by pervasive surface and bulk defects in film form. To address this critical challenge, we report a synergistic interfacial-bulk dual passivation strategy. This approach combines interface engineering between the hole transport layer (HTL) and the active layer with bulk heterojunction optimization within the active layer. Specifically, a hybrid active layer of CsPbBr₃ QDs and poly(3-hexylthiophene) (P3HT) is employed, which simultaneously passivates QDs surface defects, improves film morphology, and establishes a built-in electric field for efficient charge separation and transport. Concurrently, nonradiative recombination in the films was significantly mitigated through the effective passivation of interfacial defects between the HTL and the active layer, achieved by a hybrid passivator comprising tributylphosphine oxide (TBPO, C₁₂H₂₇OP) and calcium bromide (CaBr₂). The resultant self-powered photodetector achieves an ultralow dark current of 2.01 × 10^-13 A. Under 0.25 mW/cm² illumination at zero bias, the optimized photodetector demonstrates outstanding performance: a high responsivity of 1.25 A/W, a specific detectivity of 9.85 × 10¹⁴ Jones, and a photosensitivity of 6.25 × 10⁷. This work provides a generalized defect-management paradigm for developing high-performance, self-powered perovskite optoelectronic devices.