Energy Level Engineering of PbS Quantum Dots via Aluminum Surface Modification for High-Performance Infrared Photodetectors

Solution-processed lead sulfide quantum dot (PbS QD) photodetectors are promising candidates for use as infrared imagers. However, as the absorption spectra of PbS QDs extend to long wavelengths, their conduction band level is too deep to construct a cascaded energy band structure with electron-transport layers (ETLs). Herein, a matched cascade band structure constructed by aluminum surface modification (Al-SM) PbS QDs and ETLs is reported. This strategy is proposed to mediate the band level of small bandgap (0.74 eV) PbS QDs. Compared with the control devices, the photodiodes fabricated through this method achieve a 3.2 times lower dark current density of approximately 842 nA/cm² at -0.1 V bias and a 3 times higher specific detectivity of 1.5 × 10¹¹ Jones at 1650 nm, improving the air storage stability significantly. These findings suggest that the Al-SM strategy in PbS QDs can mediate energy level shifts, providing a way to optimize the performance of QD optoelectronic devices.