Infrared Detection Achieved by Controlling Thermionic Emission in Organic Transistors

Commercial inorganic infrared (IR) photodetectors have important applications in night vision, medical imaging, remote sensing, and other fields, but still face the challenges of operating at low temperatures and high costs. Organic semiconductor (OSC)-based IR detectors can operate at room temperature and have the advantages of flexibility and large-area processing. Consequently, they have important application prospects. However, high-performance OSCs usually have wide bandgaps, which makes it difficult for them to directly absorb IR light for detection. Overcoming the bandgap limitations of OSCs to achieve IR detection is extremely challenging. Herein, the organic field-effect transistors (OFETs) are prepared using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrodes that exhibit photothermal effects under infrared irradiation and can form Schottky contacts with numerous OSCs. The electrodes can effectively absorb IR light and release heat, which increases the temperature of the electrode–OSC contact region and promotes thermionic emission, resulting in a change in the electrical properties of the device to achieve an IR response. Using this strategy, the prepared OFET exhibits a high photosensitivity of 1.42 × 105 and a detectivity of 2.12 × 108 Jones at 808 nm and also exhibits a distinguishable IR response at different light intensities. Moreover, the invisible IR light signal is converted into a visible green light signal via a circuit design. This study provides a universally applicable solution to achieve IR detection using OFETs, which furthers their application potential.