Slow Auger Recombination in Ag2Se Colloidal Quantum Dots

Shortwave Infrared Light Detection and Ranging Using Silver Telluride Quantum Dots

Shortwave infrared (SWIR) light, characterized as the "eye-safe" window, is considered extremely promising in various technological fields and particularly valuable for imaging and light detection and ranging (LiDAR) applications. Silver telluride (Ag2Te) colloidal quantum dots (CQDs), featuring RoHS-compliance, solution-processability, and CMOS compatibility, emerge as a potential contender for SWIR optoelectronics. Yet, further improvements in dark current, response speed, and linear dynamic range (LDR) are essential for meeting the rigorous demands of sensing and LiDAR applications. Here, it is shown that post-synthesis surface engineering and doping control significantly improve the dark current, response speed, and LDR of Ag₂Te CQD photodiodes, achieving a low dark current of 450 nA cm- 2 at -0.5 V, an LDR exceeding 150 dB, and a rapid response speed of ≈25 ns. A proof-of-concept LiDAR demonstration in the SWIR using a practical nanosecond diode laser achieves decimetre-level resolution at a distance exceeding 10 m. This work represents a key step in advancing SWIR CQDs toward consumer electronics and automotive markets.

In Situ Sintering of CdSe/CdS Nanocrystals under Electron Beam Irradiation

Colloidal semiconductor nanocrystals have attracted widespread attention due to their tremendous electrical and optical properties. Nanoparticles exhibit a strong tendency to aggregate and sinter in a short period of time during processing or use due to their large surface area-to-volume ratio, which may lead to significant changes in their required performance. Therefore, it is of great significance to conduct in-depth research on the sintering process and mechanism of nanoparticles to maintain their stability. Here, the sintering process of CdSe/CdS core/shell nanocrystals under continuous electron beam irradiation was studied using in situ transmission electron microscopy (TEM). In the early stages of sintering, CdSe/CdS nanocrystals approached each other at a distance of approximately 1-2 nm. As the exposure time to the electron beam increased, the movement of surface atoms on the nanocrystals led to contact between them. Subsequently, the atoms on the contact surfaces underwent rapid motion, resulting in the rapid formation of the neck between the particles. The neck formation between adjacent particles provides strong evidence of a sintering mechanism dominated by surface atom diffusion rather than Ostwald ripening. Further research in this area could lead to the development of improved methods to prevent sintering and enhance the stability of nanocrystals, ultimately contributing to the advancement of nanomaterial-based devices and materials with long-lasting performance.