Photodetector Based on Pyroelectric Vinylidene Fluoride Copolymer/Thermoelectric Carbon Nanotube for Simultaneous Detection of Dynamic and Static Heat Sources

Thermal-type infrared (IR) sensors have the potential to detect heat sources such as the human body and gases at ambient temperatures. These sensors are primarily categorized into two types according to their detection mechanism: pyroelectric and thermoelectric sensors. Pyroelectric sensors can detect temperature changes only upon IR irradiation and require additional mechanical chopper systems to detect stationary heat sources, thus increasing the device weight, cost, and energy consumption. In contrast, thermoelectric sensors can generate a constant voltage response according to the Seebeck effect as long as a temperature gradient is maintained, enabling the detection of quiescent IR sources. This conceptual study demonstrates that the combined sensors of pyroelectric vinylidene fluoride copolymer (P(VDF-TrFE)) and thermoelectric carbon nanotube (CNT) films can detect moving and quiescent heat sources using a single device. The CNTs also act as photothermal conversion materials to provide temperature changes and gradients to the P(VDF-TrFE) and CNT layers, thus inducing pyroelectric and thermoelectric effects, respectively. A comparison between the wavelength dispersion of the voltage sensitivities and optical absorption spectrum of the CNTs indicated wavelength selectivity of the photothermal conversion efficiency of the CNTs, especially in the near-IR region. In addition, we present a potential device design for achieving a remarkable improvement in the thermoelectric voltage sensitivity via the modularization of autoxidized p-type CNT films with their chemically n-doped counterparts, arranged in a floral shape. Our device design enables single-device detection of both dynamic and static heat sources with reduced energy consumption, using clean and abundant materials.