The PbS Colloidal Quantum Dots (CQDs) have garnered significant attention in the realm of infrared Photodetectors (PDs) owing to their advantageous features, such as monolithic integration with silicon-based readout circuits, high-performance and cost-effective infrared imaging. Nevertheless, the inherent characteristics of PbS CQD materials, namely their high surface area and energy, render them exceedingly susceptible to temperature and environmental influences, triggering CQD fusion and giving rise to trap states that ultimately impair the performance of PbS CQD PDs. This is one of the vital obstacles limiting the CQD imaging commercialization, thereby the PbS CQD stability needs to be tackled. In this study, we direct our focus towards the hole transport layer, i.e., 1, 2-ethanedithiol (EDT)-capped PbS CQDs, and propose an oxidation strategy aimed at impeding the PbS CQD fusion phenomenon and the generation of defects. Through the implementation of this strategy, the enhanced stability of CQDs ensured a greatly improved stability of PbS PDs, even under harsh environmental conditions characterized by 85 °C, 85% Relative Humidity (RH) in an N2 environment.
HgTe Colloidal Quantum Dots (CQDs) have garnered wide interests in the area of cost-effective infrared imaging technology. In this study, we developed a low-temperature drop-by-drop method to synthesize branched HgTe CQDs with well-defined bandtail states, resulting in enhanced excitonic absorption compared to conventional spherical quantum dots. By carefully adjusting the synthesis temperatures, we successfully obtained Short-Wave Infrared (SWIR) CQDs tunable within the range of 1.5 to approximately 3 μm. Furthermore, we improved the long-term stability of the photodetectors by incorporating CdTe nanocrystals, in place of the traditional Ag2Te, as the Hole Transport Layer (HTL). As a result, our SWIR HgTe CQD photodetectors exhibited a room-temperature detectivity of 1.2 × 1011 Jones at the 1.7 μm cutoff absorption edge.
HgTe colloidal quantum dots (CQDs) are appealing candidates for infrared photodetection due to their facile tuning of infrared absorption, solution-processability and compatibility with silicon electronics for imaging. Traditional HgTe CQD synthesis suffers from CQD aggregation or air-sensitive tellurium (Te) precursor. Here, monodisperse HgTe CQDs with sharp excitonic absorption edge and tunable response from 1.7 μm to 6.3 μm are synthesized via a ligand-engineered approach. Thanks to their accessible CQD surface, both the carrier concentration and polarity can be readily tuned by ligand-induced surface gating. The transport property studies present a record electron mobility up to 18 cm2 V-1 s-1. Short wave infrared photodetectors achieve a high room-temperature detectivity beyond 1011 Jones at the wavelength of 1550 nm. The synthesis strategy is expected to enrich the applications of HgTe CQDs and promote the fast development of CQD infrared detection technology.
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