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Girase et al. Energy Mater. 2025, 5, 500132 https://dx.doi.org/10.20517/energymater.2025.14 Page 23 of 33

(~7 cm V s ) and exceptional σ (~997 S cm ) after doping with FeCl , which was higher than its sulfur
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3
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analog. It reached a PF of 364 μW m K and a record ZT of 0.25 at low doping levels, demonstrating its
potential to develop high-performance organic TE materials.
Similarly, the methoxy-functionalized P29DPP-BTOM exhibits a remarkable PF of 195 μW m K , which is
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substantiated by the judicious introduction of methoxy groups in the polymer backbone. These methoxy
substituents increase the lamellar stacking distance of the polymer matrix and thus allow the dopant
diffusion in a more effective way, directly increasing the doping efficiency, especially for larger dopants,
including FeCl3. P29DPP-BTOM exhibits excellent σ up to 242.4 S cm with a high S. Optimization of TE
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performance requires such a balance between conductivity and S, and thus P29DPP-BTOM becomes a
strong competitor in this field. In comparison, although some other polymers, such as PDPP3T, also show
excellent properties in regard to hole mobility and σ, the overall thermoelectric efficiency is less than
PDPP-4T-EDOT. For instance, although PDPP3T has good performance in organic thin-film transistors, it
only yields a high PF of 276 μW m K under optimal doping conditions, which is still lower than that of
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PDPP-4T-EDOT.
However, P29DPP-BTOM’s design illustrates the effectiveness of structural optimization to enhance doping
efficiency and mobility and also underlines the importance of tailored strategies in polymer design for
optimizing TE materials. The comparative study of σ and PF of DPP-based p-type thermoelectric polymers
over time is shown in Figure 8A and chemical structures of the high performance p-type thermoelectric
polymer are shown in Figure 8B.

Comparative study in n-type DPP-based thermoelectric polymers
In the search for advanced n-type thermoelectric polymers, several novel materials have emerged, each
demonstrating unique structural features and electron-transport properties. Among these, the significant
examples are P(PzDPP-CT2), PTz-5-DPP, ThDPP-CNBTz, PTz-DPP and pDFSe. The compound
P(PzDPP-CT2), which incorporates pyrazine groups and cyano-functionalized bithiophene, has shown an
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excellent σ of 8.4 S cm and a PF of 57.3 μW m K . Such performance indicates a remarkable EA and
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effective charge transport, which is supported by intramolecular hydrogen bonding interactions.
PTz-5-DPP, synthesized through oxidative direct arylation polycondensation, exhibited strikingly high
capabilities with σ over 8.38 S cm and a PF close to 106.0 μW m K , illustrating the advantages of efficient
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synthesis for practical applications. On the other side, ThDPP-CNBTz, PTz-DPP and pDFSe also show
excellent thermoelectric properties. ThDPP-CNBTz, with a thiophene-flanked DPP backbone, showed a
high σ of 50.6 S cm and a PF of 126.8 μW m K after n-doping, thus showing high potential for flexible
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devices. Similarly, PTz-DPP in a recent study by increasing the nitrogen content in the polymer backbones
and using amphipathic side chains, the compound shows enhanced solubility, morphology, and doping
efficiency with the n-type dopant N-DMBI of the polymers. With higher nitrogen content, the DOS at the
Fermi level increased, making it easier for polaron formation and leading to improved charge transport
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properties. PTz-DPP exhibited superior performance with high σ (63.8 S cm ), and PF of 111.8 μW m K -2
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because of negligible structural perturbation, retained molecular order, and hopping to band-like charge
transport transition. On the other hand, pDFSe, based on a noncovalently fused-ring design, showed a
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remarkably high conductivity of 62.6 S cm and the best PF of 133.1 μW m K , indicating its efficacy in
facilitating charge-carrier mobility in amorphous structures. While individual polymers each have their own
respective advantages, the remarkably high PF of pDFSe positions it at the forefront of n-type organic TE
materials, making it a promising candidate for future applications. In general, this comparative study
demonstrates that pDFSe not only beats others but also marks an essential development in the evolution of
n-type TE materials. The comparative study of σ and PF of DPP-based n-type TE polymers over time is
shown in Figure 9A and chemical structures of the high performance p-type thermoelectric polymer are