Bifunctional ZnTe Enables Top-Illuminated <i>p</i>-on-<i>n</i> PbS Quantum Dot Infrared Photodetectors and Imagers

Lead sulfide (PbS) colloidal quantum dot (CQD) photodetectors are promising devices for low-cost, high-performance, and large-area infrared imaging. For integration with readout integrated circuits (ROICs), top illumination is urgently required to ensure simultaneous light absorption and signal acquisition. However, the traditional best-performing p-on-n PbS CQD photodetectors rely on opaque top metal contacts, thus limiting the development of top-illuminated imagers. Herein, we addressed this issue by introducing a bifunctional ZnTe layer. The presence of the ZnTe layer─while allowing efficient hole collection─serves as a protective layer for the CQD layer during subsequent transparent electrode deposition. The resultant PbS CQD photodetectors based on the ZnTe layer show a specific detectivity of 2.09 × 1012 Jones at ≈1300 nm, representing approximately a 5-fold improvement over the control device (4.30 × 1011 Jones). This performance is comparable to that of the best PbS CQD photodetectors reported at similar wavelengths. The advantages of this architecture are further demonstrated by building a PbS CQD imager with a pixel array of 256 × 256, verifying the compatibility of photodetectors with ROICs.