Short-wave infrared organic phototransistors with strong infrared-absorbing polytriarylamine by electron-transfer doping

Short-wavelength infrared (SWIR) sensors have attracted keen attention due to the increasing necessity in a variety of scientific and industrial applications, including biomedical and information technology fields. Because conventional SWIR sensors are made of inorganic materials with rigid and brittle characteristics, organic materials with a discrete SWIR absorption are required for flexible SWIR sensors in the flexible electronics era. Here, we demonstrate that a polytriarylamine, poly[N,N '-bis(4-butylphenyl)-N,N '-bis(phenyl)benzidine] (PolyTPD), can absorb almost full range of SWIR wavelength (lambda = 1000-3200 nm) after 48 h doping with tris(pentafluorophenyl)borane (BCF). The spectroscopic characterization disclosed that an electron transfer from PolyTPD to BCF created a new low energy level (gap) state leading to the SWIR absorption in the BCF-doped PolyTPD complexes. Organic phototransistors (OPTRs) with the BCF-doped PolyTPD films as a gate-sensing layer could detect the SWIR light with a reasonable photoresponsivity of similar to 538 mA W-1 (lambda = 1500 nm), similar to 541 mA W-1 (lambda = 2000 nm), and similar to 222 mA W-1 (lambda = 3000 nm). The present breakthrough SWIR-OPTR technology can pave a way for further advances in SWIR-absorbing organic materials and flexible SWIR sensors.

Automated summary

Short-wavelength infrared (SWIR) sensors are important in scientific and industrial applications, requiring flexible organic materials for their development. Doping PolyTPD material can enable broad SWIR absorption and be used in organic phototransistors with high photoresponsivity.