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PbS colloidal quantum dot (CQD) photodiodes possess high photoresponsivity and broad spectral sensitivity, making them tremendously attractive for low-cost short-wave infrared (SWIR) sensing. A critical challenge in achieving high detectivity in SWIR photodiodes is to minimize their reverse bias dark current density (Jdark) and elucidate the origin of Jdark. We demonstrate in this work how the self-formed AlOx at the ZnO/Al interface dramatically reduced Jdark of the PbS CQD SWIR photodiodes. In such a simple and controlled way, the interfacial states were thoroughly passivated by post-exposure to dry air, which could block the dominant pathways for minority hole injection from Al electrode. The treated photodiode showed low Jdark down to 1.58 × 10−7 A/cm2 at –0.5 V, high photoresponsivity of 0.62 A/W, and high specific detectivity of 2.05 × 1012 Jones at 1413 nm, establishing a readily approach to optimizing detectivity in PbS CQD SWIR photodetectors. [ABSTRACT FROM AUTHOR]

Minimizing reverse bias dark current density (Jdark) while retaining high external quantum efficiency is crucial for promising applications of perovskite photodiodes, and it remains challenging to elucidate the ultimate origin of Jdark. It is demonstrated in this study that the surface defects induced by iodine vacancies are the main cause of Jdark in perovskite photodiodes. In a targeted way, the surface defects are thoroughly passivated through a simple treatment with butylamine hydroiodide to form ultrathin 2D perovskite on its 3D bulk. In the passivated perovskite photodiodes, Jdark as low as 3.78 × 10‐10 A cm‐2 at ‐0.1 V is achieved, and the photoresponse is also enhanced, especially at low light intensities. A combination of the two improvements realizes high specific detectivity up to 1.46 × 1012 Jones in the devices. It is clarified that the trap states induced by the surface defects can not only raise the generation‐recombination current density associated with the Shockley–Read–Hall mechanisms in the dark (increasing Jdark), but also provide additional carrier recombination paths under light illumination (decreasing photocurrent). The critical role of surface defects on Jdark of perovskite photodiodes suggests that making trap‐free perovskite thin films, for example, by fine preparation and/or surface engineering, is a top priority for high‐performance perovskite photodiodes. [ABSTRACT FROM AUTHOR]

Monolithically integrated pixels, with stacked PbS colloidal quantum dot (CQD) photodiodes and organic blocking diodes, are developed as the building block for constructing a short‐wavelength infrared (SWIR) crossbar imaging array. Arising from the back‐to‐back stacked configuration and a favorable energy level alignment, holes are blocked from the photodiode at zero and forward biases, which results in the normally‐OFF behavior of the pixels. Based on such device characteristics, the monolithically integrated pixels can effectively suppress electrical crosstalk under illumination in the crossbar array and consume nearly zero standby power. Furthermore, an 8×8 crossbar imaging array with both high imaging quality and low power consumption is achieved, which features as a high‐performance visible–SWIR imaging sensor. [ABSTRACT FROM AUTHOR]

A simple and effective strategy, that is the use of 2-Methoxyethanol rather than anhydrous ethanol as the ZnO precursor solvent, is developed to greatly improve the photoresponsivity in the PbS colloidal quantum dot (CQD)/ZnO heterojunction short-wavelength infrared (SWIR) photodiodes. This approach significantly modifies the PbS/ZnO interface through an increase of electron concentration and a reduction of surface defects in the ZnO layer, which is critical to suppressing carrier recombination at the PbS/ZnO interface. The optimized photodiodes show superior figures of merit, including low dark current density of 1.28 $\times \,\,10^{-{8}}$ A/cm2 at −0.5 V, high photoresponsivity of 0.47 A/W and high specific detectivity of 2.22 $\times \,\,10^{{12}}$ Jones at 1413 nm, and fast response/recovery time of 6.8/8.6 $\mu \text{s}$. [ABSTRACT FROM AUTHOR]