Thickness modulation on semiconductor towards high performance gas sensors based on organic thin film transistors

Copper phthalocyanine (CuPc)-based organic thin film transistors (OTFTs) with various thicknesses of organic semiconductor were fabricated, and the corresponding gas sensing performance was systematically evaluated. In situ measurements of OTFTs under nitrogen dioxide (NO2) exposure showed a remarkable sensitivity enhancement from 7% to 241% by simply decreasing CuPc film thickness from 40 to 10 nm. CuPc films were analyzed by atomic force microscopy and grazing incidence X-ray diffraction. The results showed that thinner CuPc film, which enhances the interplay of CuPc film and NO2 analyte, is beneficial for NO2 diffusion and smaller CuPc grain formation, resulting in considerable sensing performance improvement.