An ultra-low dark current AgBiS 2 CQDs NIR photodetector using ZnO/MXene bilayer electron transport layer for image sensor

Abstract AgBiS2 colloidal quantum dots (CQDs) possess excellent optoelectronic properties, including high absorption coefficient, environmental friendliness, and facile solution processability. They are regarded as promising candidates to replace toxic Pb and Hg-based CQDs in the field of optoelectronics. However, the energy-levels mismatch between electron transport layer (ETL) and photoactive layer in AgBiS2 CQDs photodetector affecting the performance of the device. To address this challenge, this study introduces ZnO/MXene bilayer ETL to optimize the interface energy-level alignment. A broad-spectrum, high-performance AgBiS2 CQDs photodetector has been realized, exhibiting an ultra-low dark current density of 6.1 × 10−8 A·cm−2, a broad detection spectrum ranges from 375 to 1120 nm, a specific detectivity (D*) of 7.8 × 1010 Jones at 980 nm, and a large linear dynamic range (LDR) of 80 dB. The device of bilayer ETL enhances the D* by 3.5 to 7 times compared to the control device by improving charge extraction and suppressing carrier recombination. Furthermore, integrating the photodetector with a thin-film transistor (TFT) array enables high-quality imaging under 850 nm near-infrared (NIR) illumination, demonstrating its significant potential for advanced image sensor applications.