Infrared Colloidal Quantum Dot Imagers

Colloidal quantum dots (QDs) offer size-, shape-, and composition-tunable electronic and optical properties thus being used in a wide array of devices ranging from solar cells to light-emitting diodes. However, most of these applications are limited to the visible and near infrared (IR) region of the electromagnetic spectrum. In this talk, I will present our recent efforts to push the envelope of the applicability of these colloidal QDs towards short-wave and extended short wave IR applications. These colloidal quantum dot-based photodetectors present a promising path toward fabricating IR imagers at significantly reduced cost and complexity compared to state-of-the-art epitaxial grown quantum-well IR devices. This presentation will focus on the synthesis, characterization, and room temperature detector characteristics of HgTe based colloidal IR QDs. By utilizing a facile and low-cost dip-coating approach that generates compact large area colloidal QD-films with high charge carrier mobility and device uniformity, our lateral extended SWIR sensors show 2x improvement over state-of-the-art. Combining with optimized charge transport layers and a newly developed transparent top electrode in the SWIR and MWIR region of the electromagnetic spectrum, comparable performance to state-of-the-art vertical photodiodes is achieved with room temperature detectivity values of around 2.9*10¹¹ Jones at 1800 nm, even without a reflective metal layer commonly used to improve absorption. The presentation will also showcase our recent efforts in utilizing heavy metal free Ag₂Se QDs as a potential alternative in IR optolectronic devices. The approaches outlined above provide a promising pathway toward integration of IR colloidal QDs in imaging applications.