Effects of Side Chain on High Temperature Operation Stability of Conjugated Polymers

Understanding high-temperature operation in organic semiconductors remains elusive. Here, we studied the effect of two alkyl side-chains, 2-octyldodecyl (C1) and 4-decyltetracecyl (C3), on the thermal stability of two types of conjugated polymer backbones: isoindigo (IID) and diketopyrolopyrrole (DPP). All polymers remain functional with high on/off ratio in ambient air at temperature up to 220 °C. However, the use of longer side-chain C3 lowers the π–π stacking distance and enables more thermally stable polymer thin film field-effect-transistors. Specifically, IID-C3 and DPP-C3 exhibited less alteration in threshold voltage as well as a reduction in effective mobility at high temperature. This behavior emphasizes the importance of close π–π stacking distance on charge transport properties of conjugated polymers and their thermal stability. This study is a starting point to deconvolute the intricate mechanism of charge transport in polymer thin films at elevated temperatures.