Solution‐processed PbS colloidal quantum dots (CQDs) are promising optoelectronic materials for next‐generation infrared imagers due to their monolithic integratability with silicon readout circuit and tunable bandgap controlled by CQDs size. However, large‐size PbS CQDs (diameter >4 nm) for longer shortwave‐infrared photodetection consist mainly of {100} facets with incomplete surface passivation and unsatisfied stability. Here, it is reported that perovskite‐bridged PbS CQDs, in which the {100} facets of the CQDs are epitaxially bridged with CsPbI3–xBrx perovskite, can achieve improved passivation and enhanced stability in comparison with the traditional strategies. The resultant infrared CQDs photodiodes exhibit significantly reduced dark current, nearly 50% enhanced photoresponse, and improved work stability. These superior properties synergistically produce the most balanced performance (with a high −3 dB bandwidth of 42 kHz and an impressive specific detectivity of 6.2 × 1012 Jones) among the reported CQDs photodetectors.

PbS colloidal quantum dot (CQD) infrared photodiodes have attracted wide attention due to the prospect of developing cost-effective infrared imaging technology. Presently, ZnO films are widely used as the electron transport layer (ETL) of PbS CQDs infrared photodiodes. However, ZnO-based devices still suffer from the problems of large dark current and low repeatability, which are caused by the low crystallinity and sensitive surface of ZnO films. Here, we effectively optimized the device performance of PbS CQDs infrared photodiode via diminishing the influence of adsorbed H2O at the ZnO/PbS CQDs interface. The polar (002) ZnO crystal plane showed much higher adsorption energy of H2O molecules compared with other nonpolar planes, which could reduce the interface defects induced by detrimentally adsorbed H2O. Based on the sputtering method, we obtained the [002]-oriented and high-crystallinity ZnO ETL and effectively suppressed the adsorption of detrimental H2O molecules. The prepared PbS CQDs infrared photodiode with the sputtered ZnO ETL demonstrated lower dark current density, higher external quantum efficiency, and faster photoresponse compared with the sol–gel ZnO device. Simulation results further unveiled the relationship between interface defects and device dark current. Finally, a high-performance sputtered ZnO/PbS CQDs device was obtained with a specific detectivity of 2.15 × 1012 Jones at −3 dB bandwidth (94.6 kHz).

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Solution-processed colloidal quantum dots (CQDs) photodiodes are compatible for monolithic integration with silicon-based readout circuit, enabling high-performance and low-cost infrared imaging. However, operation stability of CQDs photodiodes has rarely been explored, which is one of the main obstacles for CQDs imaging commercialization. Here, we reveal that the performance deterioration of the CQDs photodiodes under strong electric field at high temperature is mainly attributed to ion migration in CQDs film, clearly clarified by aging photoconductors based on each functional layer of CQDs photodiodes. The halide ion migration through vacancy increases the defect density of the CQDs layer and blocks device interfaces, resulting in increased dark current density and postponed saturation voltage. We introduce polyimide (PI) into CQDs film to efficiently block the pathway for halide ion migration. As a result, the CQDs photodiodes with PI achieve greatly improved operation stability over 27 h under 104 V/cm electric field at 85 °C.

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Solution-processed colloidal quantum dot (CQD) photodiodes are compatible for monolithic integration with silicon-based readout circuitry, enabling ultrahigh resolution and ultralow cost infrared imagers. However, top-illuminated CQD photodiodes for longer infrared imaging suffer from mismatched energy band alignment between narrow-bandgap CQDs and the electron transport layer. In this work, we designed a new top-illuminated structure by replacing the sputtered ZnO layer with a SnO 2 layer by atomic layer deposition. Benefiting from matched energy band alignment and improved heterogeneous interface, our top-illuminated CQD photodiodes achieve a broad-band response up to 1650 nm. At 220 K, these SnO 2 -based devices exhibit an ultralow dark current density of 3.5 nA cm −2 at −10 mV, reaching the noise limit for passive night vision. The detectivity is 4.1 × 10 12 Jones at 1530 nm. These SnO 2 -based devices also demonstrate exceptional operation stability. By integrating with silicon-based readout circuitry, our CQD imager realizes water/oil discrimination and see-through smoke imaging.