Highly Sensitive and Fast‐Response Hybrid Phototransistors Enabled by Dynamic Photogating in Anthradithiophene‐Metal Oxide Heterojunctions
Ahasan Ullah, Roshell Lamug, Xueqiao Zhang, Oksana Ostroverkhova, Li‐Jing Cheng
Abstract
Abstract This study presents a high‐performance organic–inorganic hybrid phototransistor featuring a heterojunction formed by photoactive anthradithiophene (ADT) derivatives and a bottom‐gate indium gallium zinc oxide (IGZO) thin‐film transistor (TFT). Two ADT derivatives with silicon‐ or germanium‐containing side chains are explored for device development. The band alignment at the heterojunction facilitates efficient electron transfer and accumulation of photogenerated holes in ADT, driving a photogating effect to modulate IGZO conductivity. Unlike conventional photogating, mediated by carrier trapping with inherently slow response speeds, this device uses trap‐suppressed ADT, achieved through blending with nonconductive polymers, to enable high‐speed photogating. An optimized negative gate voltage creates a synergistic effect, driving the IGZO TFT into a partially depleted subthreshold state and significantly enhancing detectivity and sensing current. Photoluminescence and wavelength‐dependent photoresponse confirm charge transfer between ADT and IGZO, identifying the photoinduced threshold voltage shift as the key mechanism for improved performance. Simulations further elucidate the photodetection process under varying conditions. The phototransistor achieves a linear dynamic range over 100 dB, responsivity of up to 2.80 A W −1 , detectivity exceeding 10 13 Jones, and rapid response with <4 ms rise and <10 ms fall times. These characteristics make it highly suitable for machine vision and low‐power photosensor applications.