Thermally-induced charge carrier population control on graphene nanoribbons

Abstract

Organic thermoelectric devices allow the conversion of heat into electricity in a sustainable way, making them strong candidates to solve the present energy crisis. In this context, integrating graphene nanoribbons (GNRs) into thermoelectrics holds great potential for addressing this challenge. The development of a physical description of charge carriers under thermal influence is a paramount step toward this objective. However, to this day, the effects of temperature on charged quasiparticles hosted on GNRs remain elusive. In this work, we propose an adaptation to the long-established Su–Schrieffer–Heeger (SSH) model Hamiltonian to accommodate thermal effects on GNRs. The results show that random lattice deformations can significantly alter polarons’ and bipolarons’ localization profiles. Moreover, we report a thermally-induced re-balance of carrier stability. As temperature increases, the probability of observing bipolarons decays in favor of the formation of two independent polarons. The results are especially relevant to Seeback-based thermoelectrics because they rely on temperature gradients. With the thermal stability of charge carriers, local thermal differences could regulate GNR-based currents with quasiparticle population control.