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Page 10 of 33 Girase et al. Energy Mater. 2025, 5, 500132 https://dx.doi.org/10.20517/energymater.2025.14

DPP-TT, which facilitates efficient charge transport via close packing and crystalline microstructures. The
introduction of g32T-TT raises the HOMO level, improving charge transfer upon doping. Additionally, the
dual incorporation of long alkyl chains and OEG side chains improves solubility and stabilizes dopants
while fine-tuning the morphology of the films. Notably, the copolymer PDPP-g 2T achieves an impressive
0.3
3
σ of 360 S cm , S of 56 µV K , and PF of 110 μW m K , significantly outperforming its counterparts
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-1
-1
-2
-1
PDPP-TT having PF 38 μW m K . The enhanced doping efficiency, high carrier mobility exceeding
-2
1 cm V s , and improved crystallinity marked by strong π-π stacking contribute to the exceptional TE
2
-1 -1
performance of these random copolymers, highlighting their potential for flexible electronic
applications . Mao et al. come up with a novel strategy that involves improvement in the crystallinity of
[103]
the D-A polymer using the incorporation of tert-butoxycarbonyl (t-Boc) groups as thermos-cleavable side
chains in p-type donor-acceptor DPP-based copolymers (PDPPS-X) for enhancement in the TE
performance. The bulky and branched t-Boc groups ensure the polymers maintain good solubility for
effective solution processing, while their subsequent removal significantly improves intermolecular stacking,
leading to enhanced charge mobility. Thermal treatment facilitates crystalline domain formation through
hydrogen-bonded networks, crucial for conductivity improvements. Results showed that PDPPS-5, tailored
with optimal thermocleavable side chains, achieved the highest PF of 26.4 μW m K and σ of 96.0 S cm at
-1
-1
-2
room temperature. Thus, the strategic incorporation of thermo-cleavable side chains effectively enhances
crystallinity, charge mobility, and ultimately, TE performance .
[104]
Zhong et al. come up with a strategic approach to enhance the TE performance of D-A polymers through
donor engineering, specifically by substituting the dithieno[3,2-b:2’,3’-d]pyrrole (DTP) moiety
(PDTP-DPP) with a carbazole (CZ) unit (PCZ-DPP) while retaining the DPP acceptor. This modification
results in significantly elevated HOMO levels and reduced energy gaps, facilitating more effective p-doping.
Density functional theory (DFT) calculations indicate that PDTP-DPP exhibits expanded HOMO
distributions and decreased structural disorder compared to PCZ-DPP, which lowers the Coulomb and
charge transfer energy barriers at varying doping concentrations. Consequently, even though PCZ-DPP has
a higher intrinsic hole mobility (0.01 cm V s ) than PDTP-DPP (0.005 cm V s ), the TE performance of
-1 -1
-1 -1
2
2
-2
PDTP-DPP is noticeably superior, achieving an optimal PF of 10.8 μW m K -fivefold greater than that of
-1
-2
-1
PCZ-DPP which has a PF of 1.8 μW m K . Additionally, at elevated temperatures (488K), PDTP-DPP
-1
demonstrates enhanced TE performance, with a PF exceeding 85.5 μW m K , attributed to its favorable
-2
molecular characteristics that support thermal-induced dedoping and thermally activated carrier
hopping .
[105]
Lee et al. synthesized a new D-A conjugated polymer, C6-ICPDPP, to enhance TE performance by
integrating electron-donating fused benzene, thiophene, and cyclopentadithiophene (CDT) units, with the
electron-accepting DPP core in the polymer backbone. Through extended π-conjugation, this novel
structural design promoted efficient charge transfer by achieving outstanding planarity. Using FeCl only
3
p-type dopants, C6-ICPDPP demonstrated both p-type and n-type thermoelectric activity, likely due to the
bulk of charge carriers from positive to negative as the concentration of FeCl doping increases. The impact
3
of solvent type [chlorobenzene (CB) and chloroform] on film morphology, doping efficiency, and oxidation
degree was also systematically investigated. Films processed from CB, a solvent with a higher boiling point,
showed enhanced dopant diffusion and a greater degree of oxidation, contributing to improved TE
performance. Two optimized PFs and σ were obtained for p-type: 1.32 μW m K and 0.204 S cm and
-2
-1
-1
n-type: 0.410 μW m K and 0.0664 S cm . The extended planar backbones in D-A CP appears great
-1
-1
-2
potential to optimize thermoelectric properties, with the prospects for p-type and n-type behavior using a
[106]
single dopant, whereby the effect of solvent and film structure on device performances is realized .
Furthermore, DPP-MeDTP polymer has demonstrated improved thermoelectric properties through the