Interfacially-Engineered HgTe Colloidal Quantum Dot Photodiodes Using Self-Assembled Monolayer

Colloidal quantum dot (CQD) photodetectors hold promise for a new generation of infrared imaging with low cost and large array integration. In spite of great progress, it remains crucial to further improve the detector performance. In this study, we report HgTe CQD photodetectors with improved performance by leveraging an interfacial engineering approach. This is achieved by introducing self-assembled monolayers (SAMs) between the bottom electrode and the hole-transport CQD layer. Our analysis elucidates the multiple roles of SAMs in band alignment, interface passivation, and improved film quality in CQD devices. The HgTe CQD photodiodes achieve a suppressed dark current density of 4.59 × 10^–7 A/cm² at −0.4 V, coupled with an external quantum efficiency (EQE) of 54.59% and a record-specific detectivity of 2.1 × 10¹² Jones at a wavelength ∼1700 nm. By integration with Si-based readout integrated circuits, a HgTe CQD short-wave infrared imager with 640 × 512 pixels was fabricated, and infrared imaging was finally demonstrated. This study highlights the importance of interface engineering in achieving high-performance CQD optoelectronic devices.