Dresden 2026 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Hybrid, Organic and Perovskite Optoelectronics and Photovoltaics III

CPP 37.2: Talk

Wednesday, March 11, 2026, 15:30–15:45, ZEU/LICH

A Universal Soft Upper Limit to the Seebeck Coefficient in Organic Thermoelectrics — •Dorothea Scheunemann¹, Zelong Li², Dennis Derewjanko¹, Yuqian Liu², Martijn Kemerink¹, and Guangzheng Zuo² — ¹Heidelberg University, Germany — ²Fudan University, Shanghai, P.R. China

Organic thermoelectrics have the potential to convert waste heat into electricity by utilizing lightweight and flexible polymers. Despite over a decade of intensive research, significant progress remains limited. A key factor is the trade-off between conductivity (σ) and Seebeck coefficient (S), which dictates the extent to which the power factor (PF=σ S²) can be optimized. Here, we combine an experimental data set for different polymers at variable doping levels to show that the S vs. σ curve is universal up to the maximum PF, followed by a material-dependent roll-off, when S and σ are normalized to their values at maximum PF. Furthermore, it is demonstrated that there is a soft upper limit for S (∼200µV/K), at which the optimal power factor is achieved. Combining tight-binding and kinetic Monte-Carlo modeling, we quantitatively explain this behavior in terms of quasi-free charges moving in a renormalized density of states of Gaussian shape, where the renormalization accounts for the screened interaction with the ionized dopants. These findings suggest that the trade-off only exists at the single-material level, which subsequently gives rise to practical design rules.

Keywords: organic thermoelectrics; Seebeck Coefficient; conjugated polymer; chemical doping