A Colloidal Quantum Dot Thermistor and Bolometer.

Abstract

Bolometric detection offers a compelling route to room-temperature mid- and long-wave infrared (MWIR/LWIR) photodetection by measuring temperature-induced conductivity changes in a thermistor element thermally coupled to an absorber. However, conventional thermistor materials such as vanadium oxide (VO_x) and amorphous silicon (a-Si) exhibit moderate temperature coefficient of resistance (TCR) values (-2 to -3%/K). Higher TCRs have been achieved using SiGe/Si quantum wells (∼-5%/K), yet these require costly epitaxial growth and further improvements are hindered by lattice mismatch-induced defects. Here, we report a novel thermistor platform based on colloidal quantum dots (CQDs) that circumvents these limitations by exploiting their lattice-mismatch-free nature. By tuning the size and surface chemistry of lead chalcogenide CQDs, we engineer the energetic potential landscape to modulate thermal activation energy, achieving TCR values of up to -9%/K. We further integrate this CQD thermistor with a plasmonic metamaterial absorber (PMA), enabling room-temperature wavelength-selective photodetection across the mid- to long-wave infrared (MWIR/LWIR) spectrum. The bolometer detectors exhibited LWIR response with a time constant of ∼8 ms and room-temperature detectivity approaching 10⁶ Jones at 9 µm, without using microelectromechanical systems (MEMS) technology.