Visible to mid-wave infrared PbS/HgTe colloidal quantum dot imagers

Photodetection over a broad spectral range is necessary for multispectral sensing and imaging. Despite the fact that broadband single-element detectors with high performance have been demonstrated with various low-dimensional materials, broadband focal plane array imagers have been rarely reported. Here we propose a stacked lead sulfide/mercury telluride colloidal quantum dot photodetector configuration with optimized graded energy gaps. This architecture allows for ultrabroadband spectral response from 0.4 to 5.0 µm, with responsivity values of 0.23, 0.31, 0.83 and 0.71 A W−1 at 0.4, 0.7, 2.2 and 4.2 µm, respectively. We also fabricate a focal plane array imager with a resolution of 640 × 512, a low photoresponse non-uniformity down to 6% and a noise equivalent temperature difference as low as 34 mK. We demonstrate broadband imaging by simultaneously capturing both short-wave infrared and mid-wave infrared information, as well as multispectral imaging in the red, green, blue, short-wave infrared and mid-wave infrared channels, using a set of optical filters. Graded-energy-gap lead sulfide/mercury telluride stacked quantum dots enable photodetection and imaging in a focal plane array configuration from the visible (0.4 µm) to the mid-wave infrared (about 5 µm) region.