Abstract
Controlling the molecular orientation of conjugated polymers is a vital yet complex process to modulate their optoelectronic properties along with boosting device performance. Here we propose a molecular-force-driven anisotropy strategy to modulate the molecular orientation of conjugated polymers. This strategy relies on the intermolecular interactions, gauged by the Hansen solubility parameters framework, to provide solvent selection criteria for conjugated polymers that render films with a preferential orientation. We showcase molecular-force-driven anisotropy to overcome the inverse coupling between the electrical conductivity and Seebeck coefficient in solution-processed organic thermoelectrics, a major challenge in the field. Our kinetic Monte Carlo simulations suggest that edge-on orientations break the trade-off by increasing the in-plane delocalization length. The molecular-force-driven anisotropy approach yields a power factor of 115 μW m−1 K−2 and a figure of merit of 0.17 at room temperature for the doped n-type 2DPP-2CNTVT:N-DMBI system. This power factor is 20 times larger than that of conventional doping approaches.
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Data availability
The main data supporting the findings of this study are available within the Article and its Supplementary Information. Alternative formats for raw data files may be requested from the corresponding authors. 2D GIWAXS diffractograms of P3HT, N2200 and 2DPP-2CNTVT are available via the KAUST repository at https://doi.org/10.25781/KAUST-1709U (ref. 55). Source data are provided with this paper.
Code availability
Code for the KMC and three-phase model is available from M.K. upon request.
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Acknowledgements
D.R.V. and D.B. thank the King Abdullah University of Science and Technology (KAUST) Office of Research Administration (ORA), award no. ORA-CRG2022-4668. We also would like to thank C. Muller for fruitful discussions on the influence of ionized species on the assembly of the morphology of doped CPs. M.K. thanks the Carl Zeiss Foundation for financial support. D.B., G.C. and S.M. acknowledge support from the UK–Saudi Challenge Fund grant from the British Council’s Going Global Partnerships programme.
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D.R.V. and D.B. supervised the work. D.R.V. conceived the idea and wrote the manuscript, as well as performed the AFM and GIWAXS characterizations. D.D. and M.K. performed and supervised the computational modelling. D.R.V., Y.L. and Y.Z. fabricated the devices and measured the electronic properties. D.R.V., Y.Z. and S.J. determined the HSPs. A.B. and X.G. carried out the AFM-IR characterization and analysis. A.S. performed the ultraviolet photoelectron spectroscopy and low-energy inverse photoemission spectroscopy measurements. J.H. performed the density functional theory calculations. O.Z.A. and Y.Z. performed the thermal conductivity measurements and analysis. M.G.-R. provided technical assistance with setup designs for characterization. S.M. and G.C. performed the STM measurements. All authors contributed to manuscript editing and revision.
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Extended data
Extended Data Fig. 1 N-DMBI’s Ra vs solvents and polymer.
The Ra between N-DMBI and 2DPP-2CNTVT is equal to that of N-DMBI and o-DCB this means that N-DMBI is equally likely to interact with either of them. N-DMBI’s Ra to CB is larger than that of 2DPP-2CNTVT meaning that the dopant will more likely interact with the CP.
Extended Data Fig. 2 CP solution aggregation behaviour upon addition of dopant.
a) In a perfect solvent, polymer chains are fully dissociated. b) In an intermediate solvent, polymer chains are both fully dissociated and forming small lamellar aggregates. c) Partial solvents give result to large polymer aggregates. Addition of dopant in a perfect solvent result in good CP-dopant intercalation owing to full dissociation of polymer aggregates, without a significant change in the aggregation behaviour. This is similar to adding a dopant in an intermediate solvent, where the CP has lower or affinity for the dopant than for the solvent (d). This should produce minimal effect on the resulting thin film morphology. In contrast, adding a dopant to an intermediate solvent (e) where the CP has similar or higher affinity for the dopant than for the solvent, a competing interaction is triggered that increases the polymer aggregates in solution. This case should result in an increase in the crystalline fraction and the EFR. Finally, in (f), adding dopants in a bad solvent should result in a decrease in the aggregates, due to the dopant attempting to intercalate with the CP. This should produce a film with hindered crystallinity and lower EFR.
Supplementary information
Supplementary Information
Supplementary Note 1, Figs. 1–29 and Tables 1–5.
Supplementary Data 1
2DPP-2CNTVT density-functional-theory-optimized atomic coordinates.
Source data
Source Data Fig. 2
TE properties calculated using KMC, plotted in Fig.2c–e. Charge paths in the anisotropically and isotropically generated morphologies plotted in Fig. 2f,g.
Source Data Fig. 3
SS function and solvent coordinates shown in Fig. 3c, EFR dependence on Ra and BP plotted in Fig. 3d,f and change in EFR versus Ra plotted in Fig. 3g.
Source Data Fig. 4
d spacing, relative crystallinity and EFR from the GIWAXS data plotted in Fig. 4d–g.
Source Data Fig. 5
OFET transfer curves shown in Fig. 5a,b. Thermal conductivity plotted in Fig. 5c. Seebeck coefficient versus conductivity plotted in Fig. 5d. PF versus EFR plotted in Fig. 5e. Previously reported TE properties plotted in Fig. 5f. Temperature-dependent PF and ZT plotted in Fig. 5g.
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Rosas Villalva, D., Derewjanko, D., Zhang, Y. et al. Intermolecular-force-driven anisotropy breaks the thermoelectric trade-off in n-type conjugated polymers. Nat. Mater. 24, 1236–1244 (2025). https://doi.org/10.1038/s41563-025-02207-9
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DOI: https://doi.org/10.1038/s41563-025-02207-9
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