Thermoelectric Power Factor Enhancement in Hybrid Solid/Liquid Porous Material Systems: A Simulation Approach

Prior experimental work has demonstrated the possibility of large improvements in the thermoelectric (TE) power factor of porous media when intercalated with electrolytes filling their pores [1]. Surprisingly, in many cases both the electrical conductivity and Seebeck coefficient were increased, offering large improvements to the power factor (PF). These improvements were attributed to charge exchange between the solid medium and the electrolyte, with strong dependence on the type of solid and the type of electrolyte used.<br/><br/>In this work we examine theoretically this complex system and provide directions for optimization. For this, we have developed an advanced simulator and theoretical models to accurately describe the TE behavior of a hybrid porous-solid/electrolyte system in the presence of large degree of nanostructuring. We have developed a novel Monte Carlo algorithm specifically designed for large scale thermoelectric simulations in porous nanostructured media [2]. Our code includes may features beyond the state-of-the-art in Monte Carlo simulations, which allow for drastic computational savings of at least an order of magnitude, making large scale simulations feasible. We then developed a model for the addition of the electrolyte within the pores of the solid medium, whose interaction with the solid is computed in a self-consistent manner by solving the Poisson equation. This provides the charge exchange and band variations that the solid thermoelectric material experiences. Once this is achieved, the Monte Carlo simulator provides the thermoelectric coefficients.<br/><br/>We show that it is possible to achieve very high power factor improvements using this solid/liquid hybrid material direction. This happens in two ways: 1) Appropriate choice of an electrolyte can cause favourable band bending in the solid material, resulting in increased carrier density and conductivity, at the levels which optimize the power factor. 2) Rather than relying on intentional doping, we enhance charge density within the material domain by the use of the electrolytes into the pores. This avoids the strong ionized impurity scattering associated with the doping typically required, since now this is achieved electrostatically.<br/><br/>Finally, the simulator we present goes beyond this system, and can be generally used to enable the understanding of transport in highly disordered nanostructured TE materials in a very effective and efficient way.<br/><br/><b><i><u>Acknowledgements:</u></i></b><br/>This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 863222 (UncorrelaTEd).<br/><br/><b><i><u>References:</u></i></b><br/>[1] L. Marquez-Garcia, B. Beltraan-Pitarch, D. Powell, G. Min, and J. García-Cannadas, ACS Applied Energy Materials 1, 254 (2018)<br/>[2] Pankaj Priyadarshi and Neophytos Neophytou, ‘Computationally efficient Monte Carlo electron transport algorithm for nanostructured thermoelectric material configurations,’ Journal of Applied Physics 133, 054301 (2023).