Molecular doping is crucial in conjugated polymers (CPs) for achieving thermoelectric performance. Although strong dopants such as AuCl3 and CN6-CP induce p-type doping, their poor stability limit their practical applicability. In contrast, moderate molecular dopants such as F4-TCNQ exhibit enhanced stability relative to strong dopants. Furthermore, they induce relatively lower carrier densities, leading to higher Seebeck coefficients and power factor. However, conventional donor-acceptor (D-A) polymers show low doping efficiency with F4-TCNQ because of their deep HOMO energy levels.
In this study, the introduction of the thienoisoindigo (TIIG) acceptor unit enables control of energy-level alignment and molecular structure, thereby overcoming limited doping efficiency of donor-acceptor polymers with moderate molecular dopants and achieving both high thermoelectric performance and improved stability.