Shortwave infrared organic phototransistors with improved performance via conjugated polymer blends and a metal reflector gate architecture

Abstract

Shortwave infrared (SWIR) photodetectors based on organic semiconductors hold promising potential for various applications. However, they face significant challenges, including poor air stability and low photoresponse. Here, a dual-optimization strategy is demonstrated to enhance SWIR organic phototransistor performance through the synergistic integration of material composition and device architecture engineering. A binary blend system combines a SWIR-absorbing low-bandgap polymer with another donor-acceptor type conjugated polymer possessing air-stability and high charge carrier mobility, forming a highly ordered co-crystalline structure with edge-on orientation that effectively improves both environmental stability and SWIR detection performance. Additionally, an embedded metal reflector gate architecture incorporating a high-k dielectric is designed to simultaneously enhance light absorption and enable low-voltage operation. The optimized phototransistors exhibit significantly improved photoresponse at 1310 nm with reduced operation voltage, achieving a photoresponsivity of 11.7 A W-1 and detectivity of 1.78 x 1011 Jones at -20 V gate bias. This work demonstrates that the integration of nanoscale morphology control and optical device engineering offers an effective approach toward high-performance SWIR organic photodetectors.