Enhanced NO2 sensing performance in organic field-effect transistors via regioregularity-controlled P3HT blend films

Abstract

This study demonstrates that incorporating regiorandom poly(3-hexylthiophene) (RRa-P3HT) into regioregular poly(3-hexylthiophene) (RR-P3HT) films promotes the spontaneous self-assembly of RR-P3HT chains, thereby enhancing charge transport properties and providing a mechanistic understanding of this behavior. By optimizing the RRa-P3HT to RR-P3HT ratio, the gas-sensing performance of P3HT-based organic field-effect transistor (OFET) NO₂ sensors is significantly improved. This enhancement is attributed to the synergistic interplay between the electronic and morphological properties of the active layer, which facilitates both efficient signal transmission and increased gas diffusion. When 10 wt% RRa-P3HT is blended into the film, the charge carrier mobility increases 3.5-fold—from 0.015 to 0.069 cm² V⁻¹ s⁻¹. This combined improvement in carrier transport and molecular diffusion enables the device to achieve a responsivity of 481.5% at 10 ppm NO₂, which is approximately 190% higher than that of pristine RR-P3HT. Additionally, the response time is reduced to 1.69 minutes (a decrease of 0.25 minutes), while sensitivity rises significantly from 29.8 to 55.2% ppm⁻¹. These findings demonstrate that enhanced charge mobility is a key strategy for significantly improving the sensitivity of organic semiconducting gas sensors.