Due to thermal carriers generated by a narrow mid-infrared energy gap, cooling is always necessary to achieve ideal photodetection. In quantum dot (QD), the electron thermal generation should be reduced with quantum confinement in all three dimensions. As a result, there would be a great potential to realize high-operating-temperature (HOT) QD mid-IR photodetectors, though not yet achieved. Taking the advantages of colloidal nanocrystals’ solution processability and precise doping control by surface dipoles, this work demonstrates a HOT mid-infrared photodetector with a QD gradient homojunction. The detector achieves background-limited performance with D* = 2.7 × 1011 Jones on 4.2 μm at 80 K, above 1011 Jones until 200 K, above 1010 Jones until 280 K, and 7.6 × 109 Jones on 3.5 μm at 300 K. The external quantum efficiency also achieves more than 77% with responsivity 2.7 A/W at zero bias. The applications such as spectrometers, chemical sensors, and thermal cameras, are also approved, which motivate interest in low-cost, solution-processed and high-performance mid-infrared photodetection beyond epitaxial growth bulk photodetectors.

Silicon-based complementary metal oxide semiconductor (CMOS) devices have dominated the technological revolution in the past decades. With increasing demands in machine vision, autonomous driving, and artificial intelligence, silicon CMOS imagers, as the major optical information input devices, face great challenges in spectral sensing ranges. In this paper, we demonstrate the development of CMOS-compatible infrared colloidal quantum-dot (CQD) imagers in the broadband short-wave and mid-wave infrared ranges (SWIR and MWIR, 1.5–5 μm). A new device architecture of trapping-mode detectors is proposed, fabricated, and demonstrated with lowered darkcurrents and improved responsivity. The CMOS-compatible fabrication process is completed with two-step sequential spin-coating processes of intrinsic and doped HgTe CQDs on an 8 in. CMOS readout wafer with photoresponse non-uniformity (PRNU) down to 4%, dead pixel rate of 0%, external quantum efficiency up to 175%, and detectivity as high as 2 × 1011 Jones for extended SWIR at 300 K and 8 × 1010 Jones for MWIR at 80 K. Both SWIR images and MWIR thermal images are demonstrated with great potential for semiconductor inspection, chemical identification, and temperature monitoring.

Dual-band photodetectors have attracted enormous attention because of their potential in optical communication, biochemical detection, and environmental monitoring. Colloidal quantum dots (CQDs) are promising materials for dual-band photodetectors because of...

Due to the appeal of room temperature operation and low‐cost potential, colloidal quantum dots (CQDs) have become an alternative to traditional epitaxial materials for infrared photodetection. However, various device structure designs and different functional material layers are required to obtain high photodetection performances for different infrared subranges. In this work, a straightforward method is introduced for building CQD p‐i‐n homojunction as well as the inverted n‐i‐p homojunction photodetector, by preparing various doping type and density CQD inks with a mixed phase ligand exchange method. It is approved that both normal and inverted homojunctions show the specific detectivity D* as high as 1012‐1011 Jones and external quantum efficiency near 90% at high operating temperature. It is also approved that the method works for multiple infrared subranges such as 1.5 µm that covers the conventional wavelength for fiber‐optical communication (1530–1565 nm), 1.3–1.9 µm that is about the short‐wave infrared (SWIR), 1.3–2.5 µm that covers extend SWIR (beyond the standard InGaAs sensors, 1.75 µm), and 3.6 µm that belongs to mid‐wave infrared (MWIR). Applications such as spectrometer and infrared imager are also demonstrated.

Colloidal quantum dot (CQD)–based photodetectors are promising alternatives to bulk semiconductor-based detectors to be monolithically integrated with complementary metal-oxide semiconductor readout integrated circuits avoiding high-cost epitaxial growth methods and complicated flip-bonding processes. To date, photovoltaic (PV) single-pixel detectors have led to the best performance with background-limit infrared photodetection performance. However, the nonuniform and uncontrollable doping methods and complex device configuration restrict the focal plane array (FPA) imagers to operate in PV mode. Here, we propose a controllable in situ electric field–activated doping method to construct lateral p-n junctions in the short-wave infrared (SWIR) mercury telluride (HgTe) CQD–based photodetectors with a simple planar configuration. The planar p-n junction FPA imagers with 640 × 512 pixels (15-μm pixel pitch) are fabricated and exhibit substantially improved performance compared with photoconductor imagers before activation. High-resolution SWIR infrared imaging is demonstrated with great potential for various applications including semiconductor inspection, food safety, and chemical analysis.