Organic Thermoelectric Materials and Doping Mechanisms

Organic thermoelectric materials, comprised predominantly of conjugated polymers and small‐molecule semiconductors, have emerged as flexible, lightweight and solution‐processable alternatives to inorganic counterparts for waste‐heat recovery and wearable energy harvesting. Their performance is gauged by the Seebeck coefficient (voltage per unit temperature gradient), electrical conductivity and thermal conductivity, which together define the power factor and figure of merit (ZT). Central to optimisation is the precise manipulation of charge‐carrier concentration and morphology through chemical or electrochemical doping. Chemical doping introduces electron donors or acceptors into the organic matrix, adjusting the Fermi level and enabling p-type or n-type conduction. Key challenges remain in achieving high doping efficiency, uniform dopant distribution, air stability and mechanical robustness. Recent advances in molecular dopant design, polymer backbone engineering and novel doping strategies have driven record conductivities, enhanced Seebeck coefficients and reduced thermal conductivities, paving the way for next-generation flexible thermoelectric devices.

Research from Nature Portfolio

Recent studies have introduced a photocatalytic route to doping, where light‐activated catalysts and ambient oxygen effect mild p- and n-doping of a range of organic semiconductors at room temperature. This approach yields conductivities exceeding 3,000 S cm–1 and enables simultaneous p- and n-doping without strong chemical oxidants or reductants. In parallel, the design of conjugated polymers with a single, planar backbone conformation and high torsional barriers has demonstrated remarkable tolerance to dopant-induced disorder. Such polymers can be n-doped to conductivities above 120 S cm–1 while maintaining high structural order. Additionally, semiconducting polymers with tailored spin ground states have been shown to support both p- and n-doping with superior conductivities, owing to interchain interactions that facilitate efficient charge transport across doped domains.

Organic Thermoelectric Materials and Doping Mechanisms publication trend

The graph below shows the total number of articles in organic thermoelectric materials and doping mechanisms across all publications each year (not limited to Nature Index journals).

Technical terms

Seebeck coefficient: Voltage generated per unit temperature difference across a material.

Power factor: Product of electrical conductivity and square of the Seebeck coefficient, indicating energy conversion efficiency.

Figure of merit (ZT): Dimensionless measure of thermoelectric performance, defined as (power factor × temperature)/thermal conductivity.

Conjugated polymer: Organic macromolecule with alternating single and double bonds enabling delocalised charge transport.

n-type doping: Introduction of electron donors to increase electron concentration in a semiconductor.

p-type doping: Introduction of electron acceptors to increase hole concentration in a semiconductor.

Charge transfer complex: Molecular assembly where donor and acceptor components form partially ionic bonds, facilitating electrical conductivity.

References

1. Photocatalytic doping of organic semiconductors. Nature (2024).
2. Transparent charge transfer complex with high thermoelectric performance. Joule (2023).
3. Controlled Dedoping and Redoping of N‐Doped Poly(benzodifurandione) (n‐PBDF). Advanced Functional Materials (2024).
4. Naphthodithiophenediimide–Bithiopheneimide Copolymers for High‐Performance n‐Type Organic Thermoelectrics: Significant Impact of Backbone Orientation on Conductivity and Thermoelectric Performance. Advanced Materials (2020).
5. Approaching disorder-tolerant semiconducting polymers. Nature Communications (2021).
6. High-mobility semiconducting polymers with different spin ground states. Nature Communications (2022).