Highly Sensitive Low Voltage Semitransparent Organic Phototransistor via Synergistic Film Orientation and Dielectric Engineering

Abstract Organic phototransistors (OPTs) with high responsivity and low-voltage operation are crucial for future optoelectronic applications. Herein, we demonstrate a semitransparent low-voltage OPT by integrating a highly oriented organic semiconductor thin film with an ion-conducting dielectric interface. The active semiconductor layer was fabricated using the facile unidirectional floating film transfer method (UFTM), enabling long-range molecular alignment and improved charge transport pathways. Efficient low-voltage operation was achieved using a solution-processable lithium–alumina (Li–Al2O3) ion-conducting dielectric, which facilitates strong electric-double-layer (EDL) charge modulation at the semiconductor/dielectric interface. The synergistic effect of UFTM-induced molecular ordering and dielectric engineering significantly enhances the photodetection performance, resulting in a high responsivity exceeding 127 A W–1 and estimated shot-noise-limited specific detectivity (DShot*) on the order of 1013 Jones. The improved performance is attributed to enhanced photogenerated carrier transport, reduced trapping effects, and efficient interfacial charge modulation. These results demonstrate the potential of semitransparent, low-voltage organic phototransistors for future energy-efficient optoelectronic applications.