Enhanced performance of solution-processed broadband photodiodes by epitaxially blending MAPbBr₃ quantum dots and ternary PbS_xSe_1-x quantum dots as the active layer

Organic-inorganic hybrid photodetectors attract more and more interest, since they can combine the advantages of both organic and inorganic materials into one device, and broadband photodetectors are widely used in many scientific and industrial fields. In this work, we demonstrate the enhanced-performance solution-processed broadband photodiodes by epitaxially blending organo-lead halide perovskite (MAPbBr₃) colloidal quantum dots (CQDs) with ternary PbS_xSe_1-x CQDs as the active layer. As a result, the interfacial features of the hetero-epitaxial nanocomposite MAPbBr₃:PbS_xSe_1-x enables the design and perception of functionalities that are not available for the single-phase constituents or layered devices. By combining the high electrical transport properties of MAPbBr₃ QDs with the highly radiative efficiency of PbS_0.4Se_0.6 QDs, the photodiodes ITO/ZnO/PbS_0.4Se_0.6:MAPbBr₃/Au exhibit a maximum photoresponsivity and specific detectivity of 21.48 A W^-1 and 3.59 ×10¹³ Jones, 22.16 A W^-1 and 3.70 ×10¹³ Jones at room temperature under 49.8 μW cm^-2 532 nm laser and 62 μW cm^-2 980 nm laser, respectively. This is higher than that of the layered photodiodes ITO/ZnO/PbS_0.4Se_0.6/MAPbBr₃/Au, pure perovskite (MAPbBr₃) (or PbS_0.4Se_0.6) QD-based photodiodes reported previously, and it is also better than the traditional inorganic semiconductor-based photodetectors. Our experimental results indicate that epitaxially-aligned nanocomposites (MAPbBr₃:PbS_xSe_1-x) exhibit remarkable optoelectronic properties that are traceable to their atomic-scale crystalline coherence, and one can utilize the excellent photocarrier diffusion from PbS_xSe_1-x into the perovskite to enhance the device performance from the UV-visible to infrared region.