Enhancing the performance of PbS:CsPbBr₃ bulk-heterojunction photodetectors by treating with imidazolium-based ionic liquids

All-inorganic lead halide perovskites and quantum dots (QDs) have gained significant attention since their emergence, owing to their immense potential for applications in optoelectronic devices. Here, enhanced-performance broadband photodetectors based on the bulk-heterostructure of a CsPbBr₃ perovskite and PbS colloidal quantum dots (CQDs) are presented, and 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF₄) ionic liquids as a dual-purpose additive were introduced in the blended film to regulate the surface of QDs by facilitating surface passivation, adjusting energy levels, and coupling with longer alkyl chains as compared to iodide ions (I⁻). As a result, a superior-quality bulk-heterostructure based photodetector with long-term stability was obtained, showing outstanding performance in photodetection across the visible to near-infrared wavelength range, demonstrating a high photoresponsivity of 22.4 A W⁻¹ with a response time of 16.2 ms and a specific detectivity of 1.58 × 10¹⁴ Jones under 405 nm illumination. Thus, this work provides a novel modification strategy for PbS:CsPbBr₃ as a promising material for novel optoelectronics.