Colloidal quantum dot photodetectors with 10-ns response time and 80% quantum efficiency at 1,550 nm

Fast and sensitive infrared (IR) photodetection is of interest for depth imaging that is fundamental to machine vision, augmented reality, and autonomous driving. Colloidal quantum dots (CQDs) are appealing candidates for this goal: in contrast with III-V semiconductors, they offer facile tuning of IR absorption and enable ease of integration via solution processing. So far, the best short-wave IR CQD photodetectors have been limited to 70-ns response time and quantum efficiency of 17% at 1,450 nm. To advance the field using CQDs, large-diameter CQDs are needed that combine passivation with efficient charge transport. Here, we report an efficient ligand-exchange route that tailors the halide passivants and introduces an added exchange step crucial to efficient passivation, removal of unwanted organics, and charge transport. In devices, the CQD solids give rise to external quantum efficiency greater than 80% at 1,550 nm, a measured detectivity of 8 x 10(11) Jones, and a 10-ns response time.