Highly Sensitive Polymer Phototransistor Based on the Synergistic Effect of Chemical and Physical Blending in D (Donor)–A (Acceptor) Copolymers

Abstract

Abstract Organic phototransistors (OPTs) based on donor–acceptor copolymers (PBTIDBIBDFs) using chemical blending of different ratios of isoindigo and benzodifurandione units and physical blending with insulating polymers are investigated. The photoresponse of the OPT devices can be synergistically tuned by combining chemical and physical blending. The film morphology and the mobility of the devices can be adjusted using chemical blending, while the photoresponse is greatly enhanced by physical blending with poly(1,4‐butylene adipate) (PBA). The photoresponse of the blending polymer PBTIDBIBDF‐5 with PBA exhibits photo‐/dark current ratio ( P ) of 3.45 × 10 4 and responsivity ( R ) of 128 A W −1 . The R value shows a remarkable 4.9 × 10 4 times increase due to the synergistic effect of chemical and physical blending, with an ultralow detection limit of 0.03 mW cm −2 . The highly sensitive OPT performance is attributed to the synergistic effect of chemical and physical blending, which changes the energy level and increases the energy trap density. Furthermore, flexible low‐voltage OPTs are fabricated and the photoresponse parameters P and R of the devices reach 5.7 × 10 4 and 180 mA W −1 , respectively. This process is cost‐effective and provides a novel method for the fabrication of high‐photosensitivity, low‐voltage, and flexible OPTs.