Mitigating the – trade-off in D–A conjugated polymer thermoelectrics doping-induced microstructural reconfiguration

Abstract

Achieving simultaneous enhancement of electrical conductivity (σ) and the Seebeck coefficient (S) remains a central challenge in developing high-performance organic thermoelectrics (OTEs). Here, we demonstrate that this trade-off can be mitigated in a novel donor–acceptor (D–A) conjugated polymer, PDPPEDOT, through the precise control of microstructural evolution induced by F4TCNQ doping. Spectroscopic analyses (UV-vis-NIR, Raman, and XPS) confirm efficient charge transfer between the PDPPEDOT backbone and F4TCNQ. Microstructural characterization via GIWAXS and AFM reveals that moderate doping (10 mg mL−1) acts as a structural template, promoting ordered molecular packing and uniform nanocrystalline domain formation, whereas excessive doping disrupts this structural integrity. Benefiting from optimized microstructural packing, the PDPPEDOT thin film can achieve a high electrical conductivity of 10.71 S cm−1 while maintaining a Seebeck coefficient of 76.75 μV K−1, yielding a maximum power factor of 6.31 μW m−1 K−2 with a characteristic “volcano-shaped” trend. This study highlights doping-induced microstructural regulation as an efficient strategy for mitigating the trade-off between thermoelectric parameters and advancing next-generation high-performance D–A-type organic thermoelectric materials.