Near-infrared (NIR) photodetection plays an indispensable role in imaging systems, optical communications, biomedical monitoring, and intelligent sensing. However, conventional high-performance photodetectors often rely on lead or mercury-based quantum dots, whose toxicity raises serious concerns for commercialization and environmental safety. AgBiS 2 colloidal quantum dots (CQDs) have emerged as a promising lead-free candidate due to their low toxicity, high absorption coefficient, solution processability, and broad-spectrum response. Nevertheless, the energy-level mismatch between the electron transport layer (ETL) and the photoactive layer causes severe interfacial recombination and high dark current, greatly restricting detection sensitivity and imaging quality.
To address this critical bottleneck, a research team led by Prof. Bingkun Chen and Prof. Guohui Li developed a high-performance NIR photodetector by introducing a ZnO/MXene bilayer electron transport layer to optimize interfacial energy alignment, suppress leakage current, and boost charge extraction.
The study was published in Nano Research on June 25, 2026.
The team demonstrated that the bilayer structure effectively optimizes interface band matching, passivates interfacial defects, and accelerates electron transport. The optimized device achieves an ultra-low dark current density of 6.1×10 -8 A cm -2 , the lowest value reported for AgBiS 2 CQD photodetectors so far. It exhibits a broad detection spectrum from 375 nm to 1120 nm, a high specific detectivity of 7.8×10 10 Jones at 980 nm, and an outstanding linear dynamic range of 80 dB. Compared with traditional single-ETL devices, the detectivity is enhanced by 3.5 to 7 times.
“The ZnO/MXene bilayer design significantly reduces the electron injection barrier and suppresses dark current, while ensuring efficient photogenerated carrier extraction,” explained Prof. Bingkun Chen. “This strategy greatly improves signal-to-noise performance and makes weak-light detection much more reliable.”
To demonstrate practical application, the team integrated the photodetector with a 64×64 TFT array and successfully realized clear, stable near-infrared imaging at 850 nm. The results show great potential for high-sensitivity, low-toxicity NIR image sensors.
“This work provides a universal and effective interface engineering method for green quantum dot optoelectronics,” added Prof. Guohui Li. “It opens a new pathway for developing high-performance, eco-friendly, and scalable near-infrared imaging devices.”
Other contributors include Huihui Pi, Cheng Ding, Yuxuan Liu, and Henan Yang from the School of Optics and Photonics, Beijing Institute of Technology; Yanxia Cui from the College of Electronic Information and Optical Engineering, Taiyuan University of Technology.
This work was supported by the National Natural Science Foundation of China (U21A20496, 62174117, 62205235, 12104334, 62305242), the Foundation Enhancement Program (2021-JCJQ-2JJ-0199), Beijing Goldbridge Project (ZZ22002), the Fundamental Research Program of Shanxi Province (202303021212030), and the Scientific and Technological Innovation Program of Beijing Institute of Technology (2025CX11007).
DOI Link:
https://doi.org/10.26599/NR.2026.94908699
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.
Nano Research
ZnO/MXene bilayer electron transport layer enables ultra-low dark current AgBiS₂ quantum dot near-infrared photodetector for high-performance imaging
25-Jun-2026