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

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 2D materials, e.g. 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 via employing vertical photo-thermoelectric (PTE) effect of a carbon nanotube forest (CNTF). 99.4% reflection suppression is observed in the self-assembled anti-reflecting CNTF, resulting in a broadband detectivity of 1.9×107 cm Hz1/2 in 2.5~25 µm spectral range and peak detectivity of 2.3×109 cm Hz1/2 at 4.3 THz via non-lithography 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.