Design of room-temperature infrared photothermoelectric detectors based on CNT/PEDOT:PSS composites

Abstract

Self-powered, flexible, and uncooled mid-wavelength infrared (MWIR) detectors based on the photothermoelectric (PTE) mechanism are promising for the next-generation wearable Internet of Things (IoT). The photovoltage of PTE detectors is controlled by the Seebeck coefficient and temperature difference under local or global illumination. Previous PTE detectors show a less outstanding performance enhancement, and their potential applications have been reported rarely. Herein, we propose two PTE detectors utilizing carbon nanotube/poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (CNT/PEDOT:PSS) composites for application in non-contact body gesture monitoring and non-destructive tracking (NDT). The flexible single-pixel detector exhibits a peak detectivity of 1.9 × 10⁷ Jones under broadband blackbody radiation. The detector can be easily attached to eyeglasses, and apparent photocurrent variations have been observed when the eyes are blinking. Furthermore, this detector shows a stable photoresponse for 300 curve cycles at a 4.5 cm bending radius, and a minimum degeneration of less than 10% after two months. The Si-based PTE detector shows a similar responsivity and detectivity performance, but a faster response than suspended detectors. A crossing pattern of photocurrent mapping is illustrated, which demonstrates the MWIR NDT. Additionally, the Si substrate helps in maintaining a more stable photoresponse and there is no degradation even after 84 days. Our results open a new path toward low-cost and high-performance wearable flexible applications as well as other biomedical or IoT-related aspects.