Synthesis and Nanostructuring of Heteroazulene-Materials for Thermoelectric Generators

The effectiveness of a thermoelectric material is given by ZT, the so-called figure of merit. The main challenge for enhancing ZT is enhancing the electrical conductivity and the Seebeck coefficient S, while reducing the thermal conductivity at the same time. For organic materials, however, increasing the conductivity relies on doping (p- and ntype). This has been performed for PEDOT:PSS and PEDOT:Tos in recent studies. It was found that there is a natural limit depending on the molecular orientation of the polymer chains meaning, that highly ordered structures can conduct more carrier than non-oriented ones.
Thus, the orientation of polymer chains via an innovative method using hydrophilic / hydrophobic interactions during polymerization is provided. We can employ this method for PEDOT nanowires that can easily be processed and printed. However, novel materials are needed to build a unipolar device. Thus, we prepare as well p-doped but also ndoped polymers that stem from our already existing collaboration. Our key material here is 6Hcyclohepta[c]thiophen-6-one (CETO), since it is easily achievable through condensation reactions, upscale-able for commercialization and chemically attractive for functionalization. Its structural properties (i.e. dipole of 7.6 D) and electrical conductivity when doped (p- or n-type) show great promise for such a device that will double the efficiency of state of the art thermoelectric generators. 

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