Series Photothermoelectric Coupling Between Two Composite Materials for a Freely Attachable Broadband Imaging Sheet

Abstract

As flexible wearable sensors and imagers are receiving attention from diverse social sectors, the freely attachable photothermoelectric (PTE) conversion technique should be evaluated to develop a highly usable safety sensor network. Although carbon nanotube (CNT)‐related materials should be effective, the key parameters/structures that maximize PTE conversion have not been clarified, thus hindering optimum device design and practical use. Herein, the flexible, sensitive broadband photodetection operation based on a coupling configuration between the CNT film photo/heat/electron channel and metal electrode is evaluated. Experimental PTE measurements and steady‐state thermal distribution simulations reveal that a series coupling of a p‐type CNT film channel and a highly negative Seebeck coefficient counter metal electrode facilitate superior photodetection performances than those of a parallel coupling configuration. Furthermore, subsequent device designs provide sensitive broadband photodetection from the millimeter‐wave to visible light wavelength regions with a minimum noise equivalent power of 5 pWHz−1/2 in an uncooled nonvacuum condition. Simultaneously, the mechanical flexibility of the proposed photodetector allows for its use in freely attachable sheet imager applications on curvilinear objects, and the nondestructive 3D photomonitoring of a defective intricately bent sample is demonstrated.