Confined deep red light-detecting organic phototransistors with polymer gate-sensing layers consisting of indacenothiophene and dinitrobenzothiadiazole units†

Abstract

Here we report a novel conjugated polymer with deep red-light absorption, consisting of indacenothiophene (IDTT) and dinitrobenzothiadiazole (DNBT) units, which can be used as a gate-sensing layer (GSL) in organic phototransistors (OPTRs). The PIDTT–DNBT polymer was synthesized by the Stille coupling reaction between the IDTT monomer with tin end groups and the DNBT monomer with bromine end groups. The PIDTT–DNBT films showed two pronounced optical absorptions in the wavelength (λ) ranges of 350–470 nm and 470–800 nm and the highest occupied molecular orbital (HOMO) energy of −5.9 eV. The OPTRs with the PIDTT–DNBT GSLs operated in p-channel modes and exhibited noticeable photo-sensing performances under the illumination of three monochromatic lights (λ = 550, 670, and 700 nm). When visible light-cutting layers (VLCLs) were applied, the OPTRs with the PIDTT–DNBT GSLs could only sense deep-red light with a narrow spectral range of λ = 650–800 nm in the absence of other visible light interferences.