Co-Solvent Strategy Enables High-Performance Printing Organic Thermoelectric via Synergistic Modulation of...

Organic thermoelectric (OTE) hold great promise in printed electrical generator and portable devices, whereas scalable coating is rarely concerned in fabricating high-performance OTE for the hurdles of coordinating high crystallization and flow homogeneity. In this work, a co-solvent strategy assisted blade-coating achieves power factor (PF) breakthrough for P3HT through synergistically modulating the crystallization kinetics and rheological property. By incorporating orthogonal solvent n-hexane (HEX) into host solvent chloroform (CF), the solubility and pre-aggregation of P3HT are effectively modulated to promote nucleation/crystal-growth during film-forming. Faster P3HT crystal nucleation/growth and relatively slower co-solvent evaporation endow better-matched crystallization rates, leading to improved molecular assembly. Combined with crystallization-inducing effect of multi-layer blade-coating, significantly enhanced crystallinity is obtained. In addition, solubility parameters variation alters the molecular arrangements into mix-orientation, which is beneficial for doping and alleviating the thermoelectric trade-off. Meanwhile, the viscosity and surface tension of the solution can be accommodated to restrain capillary flow, reinforcing the film uniformity. Consequently, under the optimal co-solvent ratio of CF:HEX = 7:3 (vol/vol), a conductivity of 605.39 S•cm^-1 and a new record PF of 204.62 µW•m^-1•K^-2 are reached for P3HT. The study opens a meaningful path for printing high-performance OTE, revealing the potential for scalable production of OTE architecture.