Aluminum Doping and Nanocolumnar Structure Enable Dark-Current Suppressed PbS Nanocrystalline Photodiode for Near-Infrared Detection and Imaging.

Near-Infrared (NIR) detectors are crucial for applications like autonomous driving, food safety, and disease diagnosis. However, conventional photodetectors rely on complex epitaxial processes and costly single-crystalline substrates yet still suffer from high dark current and limited detection performance at room temperature. Many of these detectors require deep cooling to mitigate dark current and suppress random fluctuations induced by carrier thermal excitation. Herein, an exceptionally low-dark-current is presented, self-powered NIR photodiode detector based on a solution-processed PbS nanocrystalline film and its CdS/PbS heterojunction. The photodiode offers the state-of-the-art dark current density of 20 nA cm⁻ (-10 mV bias) at room temperature, much lower than some PbS commercial photodetectors. It also exhibits a high detectivity of 7.98 × 10 Jones under total noise, a responsivity of 130 mA W⁻¹ and a wide linear dynamic range of 84 dB for 970 nm illumination at 0 V bias. These improved performances are attributed to the interfacial energy band engineering through aluminum doping and the enhanced photocarrier collection by nanocolumnar structure of the device. Furthermore, this study demonstrates the capability of the PbS photodiode for NIR imaging, opening a new avenue for the development of high-sensitivity NIR photodetector and imaging at room temperature.