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Page 26 of 33 Girase et al. Energy Mater. 2025, 5, 500132 https://dx.doi.org/10.20517/energymater.2025.14

energy level alignment, backbone rigidity, and intermolecular interactions influence doping behavior. For
instance, the P(PzDPP-CT2) and P(PzDPP-2FT) polymers developed by Yan et al. [123,145] showcase that
introducing electron-deficient pyrazine units and noncovalent interactions can enhance backbone planarity,
improve electron mobility, and sustain structural order even under high doping levels critical for long-term
stability. Similarly, polymers such as PDCNBT-DPP and PDCNBSe-DPP demonstrate deep-lying LUMOs
and reduced aromaticity from Se substitution yield significant improvements in conductivity and PF. These
examples highlight the need for rational design of DPP derivatives that can simultaneously achieve low
energy levels, high mobility, and doping resilience. Furthermore, as shown by the work on PTz-5-DPP and
P(DPP-DCNPz), low-crystallinity systems with mixed packing or transitional morphologies can offer better
dopant accommodation without large aggregate formation, contributing to stable high-performance TE
2
behavior. Very recently, the incorporation of electron-deficient heterocycles with high sp -N content, as in
PTz-DPP, effectively modulates the DOS near the Fermi level, promoting band-like charge transport and
significantly enhancing ZT. Moreover, p-type materials have shown excellent PFs, at times over
200 μW m K , which is much better than many conventional p-type polymers and other conjugated
-1
-2
polymers. n-type materials have also seen significant improvement, with some polymers reaching PFs of
over 100 μW m K . In the realm of p-type materials, PDPP-4T-EDOT has distinguished itself with an
-2
-1
impressive PF of 298.2 μW m K at an optimal doping concentration of 0.5 mM. In parallel, the methoxy-
-2
-1
functionalized P29DPP-BTOM achieved a commendable PF of 195 μW m K , illustrating the importance
-1
-2
of structural modifications to optimize doping efficiency and mobility. For n-type DPP-based materials,
-1
pDFSe stands out with a remarkable PF of 133.1 μW m K , marking a significant milestone in the
-2
development of n-type thermoelectric polymers. However, despite these advances, several key challenges
and opportunities remain. Further research in this regard is important to enhance the performance of n-
type and, in particular, to achieve efficiency levels comparable to or higher than those of p-type materials.
The trade-off between σ and the S remains a significant challenge, and therefore efforts in molecular
engineering and nano structuring are well justified to optimize this trade-off.
Overall, DPP-based materials are a promising candidate for efficient organic TE materials. The insights
gained from the comparative studies of p-type and n-type materials pave the way for optimizing these
promising TE materials. Although significant progress has been made in enhancing the thermoelectric
properties of DPP-based polymers, their implementation in practical devices such as flexible thermoelectric
modules or wearable energy harvesters remains limited. Future research should focus on scalable processing
techniques and device fabrication strategies to translate these promising materials into real-world
applications. Continued research and development in this field is expected to lead to significant advances in
the field.

DECLARATIONS
Authors’ contributions
Proposed the topic of this review: Kim, Y. H.
Manuscript writing: Girase, J. D.; Kim, Y. H.
Data curation: Girase, J. D.; Kim, I. C.

Availability of data and materials
Not applicable.

Financial support and sponsorship
This research was supported by the National Research Foundation (NRF) of Korea (Grant numbers RS-
2023-00301974, RS-2024-00336766 and RS-2024-00406548).