A Soluble Diketopyrrolopyrrole Derivative and Its Applications for Organic Phototransistors

A small molecular diketopyrrolopyrrole (DPP) derivative containing 2,4‐difluorinated phenyl groups, 3,6‐bis(5‐((E)‐2,4‐difluorostyryl)thiophen‐2‐yl)‐2,5‐bis(2‐ethylhexyl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (EHD2FV), was synthesized by a cross‐coupling reaction with 90% yield. The solid EHD2FV film exhibited a broad optical absorption up to 1000 nm, it featured a deep‐lying LUMO energy (4.49 eV). EHD2FV was employed as an electron acceptor (n‐type) for bulk heterojunction (BHJ) layers, which act as a sensing channel layer in organic phototransistors (OPTRs), while poly(3‐hexylthiophene) (P3HT) was introduced as an electron donor (p‐type). The OPTRs with the P3HT : EHD2FV BHJ layers were capable of sensing a deep red light (700 nm). The results showed that the best photosensing performance (photoresponsivity=337.1 mA/W) was achieved at the EHD2FV molar ratio of 0.05.