Boosting Bidirectional Photoresponse with Wavelength Selectivity through Ambipolar Transport Modulation

Abstract Negative photoconductive phototransistors, referring to transistors that exhibit a decrease in photocurrent under illumination, have the potential to revolutionize optoelectronic applications involving light, such as optoelectronic logic circuits and visual neural simulation. Currently, achieving negative photoconductivity (NPC) requires complex material design or interface structure construction. However, achieving precise control over NPC behaviors poses a significant challenge. Herein, a simple yet effective strategy is demonstrated for realizing controllable NPC responses in organic phototransistors through ambipolar transport modulation. Due to the controversy between the preferred exciton dissociation/charge separation direction and the gate electric field driven charge drift direction, the main semiconductor channel (n‐ or p‐channel) exhibits NPC behavior under illumination. The validity of this mechanism has been confirmed through intensive studies by varying the component and combination of the p‐n heterostructure. Moreover, devices utilizing ambipolar transport exhibit a wavelength‐selectivity NPC response due to the absorption characteristics of the combined semiconductor materials. Most encouragingly, by incorporating both negative and positve photoconductivity along with wavelength‐selective responses, high‐contrast image sensing, information encryption and decryption, as well as optoelectronic logic circuit design is successfully achieved. This work promotes the design and development of bidirectional optoelectronic devices and offers a new route for developing attractive multifunctional optoelectronic devices.