Colloidal Quantum-Dot Heterojunctions for Multimodal VIS–NIR–SWIR Imaging and Computational Spectroscopy

Abstract Spectral-selective photodetection across the visible to short-wave infrared (VIS–SWIR) range is highly desirable for advanced imaging and sensing applications. Here, we report a bias-switchable colloidal quantum-dot (CQD) n–p–n photodetector based on vertically stacked PbS and PbSe CQD heterojunctions with oppositely oriented built-in electric fields. This architecture allows electric-field redistribution under external bias, enabling controllable carrier transport and wavelength-dependent response. A ZnTe interlayer is introduced to suppress dark current and enhance bias-polarity-dependent spectral selectivity. By reversing the bias polarity, the device electrically switches between VIS + near-infrared (NIR) and NIR + SWIR detection modes within a single pixel. The photodetector exhibits low dark current densities and high detectivities of 4.3 × 1011, 2.6 × 1011, and 1.6 × 1011 Jones at 600, 1000, and 1550 nm, respectively. Integration with a silicon thin-film transistor readout circuit enables multimodal VIS–NIR–SWIR imaging, and multilayer perceptron–assisted learning further enables high-quality spectral reconstruction. These results highlight the potential of this CQD n–p–n architecture for multispectral imaging and compact computational spectrometer applications.