Towards dual-band shot-wave and mid-wave infrared focal plane array by using colloidal quantum dots

Infrared multispectral imaging with focal plane array (FPA) is attracting great interest with increasing demand for sensitive, low-cost and scalable devices that can distinguish coincident spectral information. However, the widespread use of such detectors is still limited by the complex material growth process, low energy band tunability, and high defect density in epitaxial semiconductors like HgCdTe, InSb, and InGaAs, which hinders the development of dual-band detectors. In contrast, the solution-processability and wide spectral tunability of colloidal quantum dots (CQDs) have inspired various inexpensive, high-performance optoelectronic devices. Here, we demonstrate a two-terminal CQDs dual-band detector, which provides bias-switchable spectral response in two distinct bands. A vertical stack of two rectifying junctions in “back-to-back” diodes configuration is created by engineering a strong and spatially stable doping process. By controlling the bias polarity and magnitude, the detector can be rapidly switched between short-wave infrared (SWIR) and mid-wave infrared (MWIR) at modulation frequencies up to 100 kHz with D* above 10¹⁰ Jones at cryogenic temperature. The emergence of colloidal quantum dots demonstrated some potential routes leading to dual-band infrared imaging FPA.