All‐Solution‐Processable Hybrid Photothermoelectric Sensors with Carbon Nanotube Absorbers and Bismuth Composite Electrodes for Nondestructive Testing

While photothermoelectric (PTE) sensor sheets are potentially suitable for testing applications, such as nondestructive material identifications in ultrabroad millimeter‐wave infrared bands, their device designs have primarily employed a single‐material channel. Herein, PTE sensor sheets generally combine photoinduced heating with associated thermoelectric (TE) conversion phenomena, and the employment of a single‐material channel regulates device operations by missing opportunities for fully utilizing their fundamental parameters. For this situation, this work develops all‐solution‐processable and freely coatable (paintable) hybrid PTE sensors by an effective combination of the channel structure with bismuth composite (Bi com ) TE electrodes (Seebeck coefficient > 100 μV K −1 ) and efficient carbon nanotube film photothermal absorbers. This hybrid PTE sensor device stably forms its TE electrodes as easy‐to‐handle pastes of Bi com material powders with high Seebeck coefficients by effectively employing conductive solvents and surfactants. Following these material and process preparations, the hybrid PTE sensor functions in ultrabroadband regions beyond the conventional detectors with comparable sensitivities to the existing narrowband devices in individual ranges and provides diverse optical measurement opportunities. Indeed, the easy‐to‐handle device fabrication process and advantageous photodetection performances of the hybrid PTE sensor demonstrate high usability for nondestructive testing applications (noncontact inspections, panoramic 3D camera monitoring, and portable device setups).