Effect of Solution Aging on Temperature Sensitivity of CNT/PEDOT:PSS

Abstract

This study fabricated temperature sensors with a mixture of carbon nanotube (CNT) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). CNT/PEDOT:PSS solutions with three different ratios—1/5, 1/9, and 1/13—prepared and aged for 0, 3, and 6 days. The temperature sensor was fabricated by drop-casting the aged solution onto a flexible polydimethylsiloxane (PDMS) substrate. As the aging time of CNT/PEDOT:PSS solutions with ratios of 1/5, 1/9, and 1/13 increased to 6 days, the temperature coefficient of resistance (TCR) of CNT/PEDOT:PSS decreased from −1.97, −1.99, and −2.15 (%/°C) to −2.80, −2.61, and −2.51 (%/°C) (i.e. temperature sensitivity increased) and temperature index (TI) also increased from 2242.5, 2249.1, and 2503.8 (K) to 3530.1, 3085.7, and 3002.5 (K), respectively. As the aging time of CNT/PEDOT:PSS solution increased to 6 days, its Seebeck coefficient increased from 52.4 to 114.5 μV K−1. These results show that the aging of CNT/PEDOT:PSS solution significantly increased the temperature sensitivity and Seebeck coefficient via the dedoping of PEDOT:PSS. This serves as a facile method to improve the temperature sensitivity of the CNT/PEDOT:PSS composite.