Additive engineering for high-performance polythiophene gas sensors incorporating functional amine additive with strong binding energy for NO2

Abstract

Conjugated polymers have strong potential for use in next-generation portable gas sensors owing to their light weight and flexibility. Despite the vast potential of conjugated polymers, for practical applications their reliability and performance in organic gas sensors are insufficient. To enhance the performance of organic gas sensors, herein, amine functional groups were added to the active layer of poly(3-hexylthiophene) (P3HT). Incorporating a functional additive into polymers is an efficient approach for improving the gas-sensing performance. All P3HT films with amine additives showed higher sensitivity for the target gases than the pristine film, where the P3HT film with tris(2-aminoethyl)amine (TAEA) containing four amine groups afforded the highest responsivity, response, and recovery rates. TAEA incorporation increased the sensitivity from 0.49 %/ppm to 5.3 %/ppm. Amine functional groups can interact strongly with NO₂ gas; therefore, the additives were expected to enhance the selectivity for NO₂ molecules. However, the addition of a high volume ratio of the amine additive induced precipitation of P3HT owing to the low solubility of the polymer. These nonhomogeneous P3HT films afforded inferior gas-sensing performance, indicating that an appropriate amount of additive is required to enhance the gas-sensor performance.