Recent advances in mid-infrared photodetection based on colloidal quantum dots: Challenges and possible solutions

Current mid-wave infrared (MWIR) photodetectors are generally too expensive to be used in civil scenarios. HgTe colloidal quantum dots (CQDs) are among the most promising alternatives to MWIR photodetection due to their broad and tunable spectra. In recent decades, chemical synthesis of HgTe CQDs and HgTe CQD-based photodetectors have been extensively studied. However, there are still many challenges that hinder further improvement and deserve better understanding. In this review, we first summarize the key achievements in chemical synthesis and device optimization. We describe how chemical synthesis of HgTe CQDs has evolved in recent decades and, specifically, how the quality of HgTe CQDs has been improved by adjusting the method for injecting Te precursors. We also explain efforts to optimize the dimensions of photoconductors, modulate carrier dynamics in phototransistors with bilayer channels or dual gates, and align energy levels at electrode contacts or in the p-n junctions in photodiodes. The key challenges addressed of the evolution and the reasons for the strategies used in each stage are discussed. Finally, we also discussed the possible solutions to the still-existing challenges and future research directions in the field of HgTe CQDs-based photodetection.