Ultrahigh Detectivity From Multi-Interfaces Engineered Near-Infrared Colloidal Quantum Dot Photodetectors

Low noise (inoise) and high responsivity (R) are significant factors for Lead sulfide (PbS) colloidal quantum dots (CQDs) photodetectors implementing high specific detectivity (D*). However, the simultaneous achievement of the above two factors is still challenging due to the complicated roles of interfaces and the difficulties in comprehensive interface modification by individual strategy. Here, we propose a well-designed PbS CQD nearinfrared (NIR) photodiode with high performance by multiinterface engineering. First, the well-passivated interface of a photo-active layer is obtained by high-quality n-type CQD inks and gentle ligands cross-linked p-type CQD solid films, which leads to low defect density and thus extremely low device dark current (similar to 70 nA center dot cm(-2)). Second, the construction of LiF and MoOx carrier-selective layers in the electrode interfaces greatly increases the photogenerated charge carrier extraction efficiency due to the enhanced built-in electric field, which promotes a high R to 0.61 A center dot W-1 at 1100 nm. Both the two modifications enable low inoise and high R. Hence the device exhibits an ultrahigh D* up to 1.42 x 10(12) Jones. The further demonstration of high-precision biological health monitoring in both visible and infrared bands by this device illustrates its huge potential in ultra-sensitive broadband optoelectronic applications.