PhD grants : "Synthesis and study of pi-conjugated macromolecules for thermoelectric applications" (EMSTU)

• Keywords

Organic synthesis, pi-conjugated materials, Organic semiconductors, Electronic properties

• Profile and skills required

Highly motivated Master II student with a good background in

organic/macromolecular chemistry and characterization (NMR/IR/UVCyclovoltametry). Good communication skills in written and spoken English.

• Project description

Thermoelectric (TE) materials have the capability to convert heat to electricity or vice-versa. There are numerous places in our environment such as cars, buildings and industrial plants where heat waste could be recovered to generate electricity. Recently, doped conjugated polymers (CPs) have emerged as alternative materials to classical inorganic semiconductors since they are light, flexible, easy to process and can be operated at low temperatures (<200°C). Ideally, a good TE material should exhibit high charge conductivity s and Seebeck coefficient S and low thermal conductivity k which can be summarized in the dimensionless figure of merit at a given temperature T as ZT = sTS2/k= T.PF/k with PF the power factor in W/mK2. The dominant strategy to enhance the performances of TE polymers is based on the improvement of the charge conductivity that is intimately related to the doping mechanism of CPs. Research on organic TE materials has made significant progress in the last decade and remarkable ZT values up to 0.42 were obtained for p-type polymers such as PEDOT:PSS. However, despite recent efforts, doped p- and n-type CPs show lower TE performances with a PF limited to a few microW/mK2.

The successful candidate will develop new and innovative p- and more particularly n-type organic polymers for thermoelectric devices. A particular attention will be devoted to the control of the energy levels and the acceptor or donor character of the backbone. Solubilizing side-chains will also have an issue, not only as solubilizing groups but to improve the structural properties and solid-state order, in combination with either dopants.

• References

H. Zeng, M. Mohammed, V. Untilova, O. Boyron, N. Berton, P. Limelette, B. Schmaltz, M. Brinkmann, Fabrication of Oriented n-Type Thermoelectric Polymers by Polarity Switching in a DPP-Based Donor–Acceptor Copolymer Doped with FeCl3, Adv. Electron. Mater., 2021, 200880.

M. Lepinoy, P. Limelette, B. Schmaltz, F. Tran-Van, Thermopower scaling in conducting polymers, Sci. Rep., 2020, 10 (1), 8086.

D. Brault, M. Lepinoy, P. Limelette, B. Schmaltz, F. Tran Van, Electrical transport crossovers and thermopower in doped polyaniline conducting polymer. J. Appl. Phys., 2017, 122, 225104/5.

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