Polymer morphology and interfacial charge transfer dominate over energy-dependent scattering in organic-inorganic thermoelectrics

Abstract

Hybrid (organic-inorganic) materials have emerged as a promising class of thermoelectric materials, achieving power factors (S2σ) exceeding those of either constituent. The mechanism of this enhancement is still under debate, and pinpointing the underlying physics has proven difficult. In this work, we combine transport measurements with theoretical simulations and first principles calculations on a prototypical PEDOT:PSS-Te(Cux) nanowire hybrid material system to understand the effect of templating and charge redistribution on the thermoelectric performance. Further, we apply the recently developed Kang-Snyder charge transport model to show that scattering of holes in the hybrid system, defined by the energy-dependent scattering parameter, remains the same as in the host polymer matrix; performance is instead dictated by polymer morphology manifested in an energy-independent transport coefficient. We build upon this language to explain thermoelectric behavior in a variety of PEDOT and P3HT based hybrids acting as a guide for future work in multiphase materials.

Improved Alignment of PEDOT:PSS Induced by in-situ Crystallization of “Green” Dimethylsulfone Molecules to Enhance the Polymer Thermoelectric Performance

“…Thus, an optimum power factor can be obtained via higher energy-filtering efficiency through the joint adjunct between nanoparticles and CPs (Choi et al, 2016). The highest ZT obtained so far is about <0.5 and mechanism for the hybrid materials is unfortunately not fully understood due to many challenging factors involved in the complicated system (Zhang et al, 2010; Kumar et al, 2018). The third approach is to tune the surface morphology through various doping approaches or post-treatments.…”

Correlating charge and thermoelectric transport to paracrystallinity in conducting polymers

“…In fact, a large broadening of DOS tail (~1 eV) has been reported in highly disordered PEDOT: PSS thin films using ultraviolet photoelectric spectroscopy measurements 16 , which agrees well with our fitted values of w for PEDOT:PSS. Several experiments were able to successfully align PEDOT, and hence enhance its electrical conductivity 17,18 . On the other hand, P3HT and PBTTT possess a distinct monomer structure with additional side chains, which help in enhancing the electronic coupling in the π−π stacking direction by facilitating the backbones to be aligned in 2D planes 19 .…”

In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks

“…However, reimagined, it can provide a powerful knob for manipulating electronic TE properties (S and σ) 32,33 . Bound ligands, tailored through solution-processed ligand exchange 34 , can potentially enable doping of the parent nanomaterials by charge transfer at the interface or by hybridizing and modifying local densities of states (DOS) 33,[35][36][37] . Such solution surface modification can be coupled with colloidal bottom-up synthesis of nanomaterials in a low-cost and high-throughput commercially viable process yielding dimensionally and chemically precise structures 38,39 .…”