Strategic Design of A1–π–A2-Type Polymer Acceptors for Highly Sensitive Near-Infrared All-Polymer Photodetectors

Abstract

Near infrared (NIR) photodetectors (PDs) attain a great attention for their advanced optoelectornic applications such as high-resolusion biomedical sensors. In particular, all-polymer PDs composed of electron-donating and electron-accepting polymers in their active layer offer the advantage of various donor and acceptor combinations for easily tunable absorption spectra and electronic properties, along with superior mechanical durability and stability. In this study, two A₁–π–A₂-type polymer acceptors are developed for efficient NIR light detection at 860 nm. The electron-accepting diketopyrrolopyrrole (DPP) and dicyano-substituted quinoxaline (Qx) units are linked through a dithiophene π-bridge to generate the first polymer acceptor PD-T-Qx2CN. Subsequently, fluorine atoms are introduced at the para-positions of the benzene rings at the 2,3-positions of the Qx moiety, yielding the second acceptor, PD-T-FQx2CN. Notably, both polymer acceptors formed efficient bulk heterojunction networks with poly- polymer donor (3-hexylthiophene (P3HT)). The P3HT:PD-T-FQx2CN-based NIR PDs, owing to the affirmative contributions of the F substituent along the backbone, exhibited superior specific detectivities compared to the P3HT:PD-T-Qx2CN-based PDs. The P3HT:PD-T-FQx2CN-based NIR PDs exhibited excellent photoplethysmography (PPG) sensor properties. This research provides valuable insights into the structural-property relationships of A₁–π–A₂-type polymeric acceptors, aiding in the development of high-performance all-polymer NIR PDs.