NO2‐Affinitive Amorphous Conjugated Polymer for Field‐Effect Transistor Sensor toward Improved NO2 Detection Capability

Abstract

AbstractThree conjugated polymers (CPs) containing indolocarbazole‐based similar conjugated frameworks are designed to investigate the NO2 detection capability of field‐effect transistor (FET) sensors. The partly linear aliphatic side chain strengthens the crystallization tendency of the CPs, but the crystallinity is critically degraded when introducing an ethylene oxide (EO)‐modified side chain to the same conjugated framework. Although the highly crystalline morphology of the CP helps to achieve high hole mobility, the NO2 response rate of the CP‐based FET sensor is severely deteriorated because of the suppression of NO2 diffusion into the CP matrix. The polar and flexible EO‐modified side chain is helpful to improve the NO2‐affinity of the CPs and induce favorable pathways for NO2 diffusion, ultimately providing enhanced detectivity with better NO2‐response characteristics. As a result, despite low charge carrier mobility due to pure amorphous nature, the CP with EO‐modified side chains provides an exceptional sensitivity of 180%/ppm upon NO2 (100 ppb) exposure for 50 s, including distinct detectivity toward other environmentally abundant harmful polar gases, such as SO2, NO, and NH3.