Large-Area and Broadband Thermoelectric Infrared Detection in a Carbon Nanotube Black-Body Absorber.

Zhang, Mingyu; Ban, Dayan; Xu, Chao; Yeow, John T W · ACS Nano · 2019

basic_science · Level V

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Abstract

Room-temperature mid- and far-infrared photodetectors and energy harvesters meet diverse upcoming demands including health condition monitoring, industrial inspection, and miniaturized power-source for Internet of Things. However, the cryogenic cooling requirement for III-V semiconductors and the inefficient light absorption in two-dimensional (2D) materials, for example, graphene (2.3%) and black phosphorus (∼3%), have hindered mid- and far-infrared optoelectronics from widespread applications. Here, we demonstrate a self-powered infrared photodetector as well as energy harvester <i>via</i> employing vertical photothermoelectric (PTE) effect of a carbon nanotube forest (CNTF). In the self-assembled anti-reflecting CNTF, 99.4% reflection suppression is observed, resulting in a broadband detectivity of 1.9 × 10<sup>7</sup> cm Hz<sup>1/2</sup> in 2.5-25 μm spectral range and peak detectivity of 2.3 × 10<sup>9</sup> cm Hz<sup>1/2</sup> at 4.3 THz <i>via</i> nonlithography fabrication. By virtue of vertical architecture, this photodetector exhibits enhanced sensitivity to weak and unfocused infrared illumination, which mitigates the high actuating power density in conventional PTE or field-effect detectors and renders practical infrared detection in the real life.