  Broadband infrared photodetectors have profound importance in diverse
applications including security, gas sensing, bioimaging, spectroscopy for food
quality, and recycling, just to name a few. Yet, these applications can
currently be served by expensive epitaxially grown photodetectors, limiting
their market potential and social impact. The use of colloidal quantum dots
(CQDs) and 2D-materials in a hybrid layout is an attractive alternative to
design low-cost CMOS-compatible infrared photodetectors. However, the spectral
sensitivity of these conventional hybrid detectors has been restricted to 2.1
um. Herein, we present a hybrid structure comprising MoS2 with PbSe CQDs to
extend their sensitivity further towards the mid-wave infrared, up to 3 um. We
achieve room temperature responsivity of 137.6 A/W and a detectivity of 7.7
10^10 Jones at 2.55 um owing to highly efficient photoexcited carrier
separation at the interface of MoS2 and PbSe in combination with an
oxide-coating to reduce dark current; the highest value yet for a PbSe based
hybrid device. These findings strongly support the successful fabrication of
hybrid devices which may pave the pathway for cost-effective, high performance,
next-generation, novel photodetectors.
