Low-Voltage, High-Sensitivity NIR Ambipolar Organic Phototransistor Based on a Non-Fullerene Acceptor

This study presents the development of a high-performance, low-voltage near-infrared (NIR) organic phototransistor (OPT) utilizing the non-fullerene acceptor Y6 as the ambipolar channel material and an aluminum oxide (Al₂O₃) gate dielectric modified with an optimized octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM). The combination of Y6's strong NIR absorption and balanced ambipolar charge transport, along with the high dielectric constant of Al₂O₃ and the tailored interface provided by the ODPA-SAM, significantly enhances device performance. Systematic optimization of ODPA treatment conditions improved Y6 film crystallinity and minimized interfacial defects, thereby facilitating efficient charge transport. The fabricated OPT exhibited strong photoresponse under NIR illumination for both p- and n-type conduction at low operating voltages (≤|5| V), demonstrating high photoresponsivity and sensitivity. In addition, the device showed relatively fast response times (tens to hundreds of milliseconds) for both electron and hole transport. Compared with previous reports, the Y6-based OPT achieved superior sensitivity, responsivity, and detectivity for NIR detection, underscoring the potential of non-fullerene acceptors and interface engineering in next-generation, low-power optoelectronic applications. This work represents a key step toward the realization of high-performance, flexible, and cost-effective NIR sensing technologies.