Mid-Infrared Intraband Photodetector via High Carrier Mobility HgSe Colloidal Quantum Dots

In this work, a room-temperature mixed-phase ligand exchange method is developed to obtain a relatively high carrier mobility (∼1 cm 2 /(V s)) on HgSe intraband colloidal quantum dot solids without any observable trap state. What is more, the doping from 1S e to 1P e state in the conduction band could be precisely controlled by additional salts during this method, proved by optical and transport experiments. The high mobility and controllable doping benefit the mid-infrared photodetector utilizing the 1S e to 1P e transition, with a 1000-fold improvement in response speed, which is several μs, a 55-fold increase in responsivity, which is 77 mA/W, and a 10-fold increase in specific detectivity, which is above 1.7 × 10 9 Jones at 80 K. The high-performance photodetector could serve as an intraband infrared camera for thermal imaging, as well as a CO 2 gas sensor with a range from 0.25 to 2000 ppm.