Energy-dependent carrier scattering at weak localizations leading to decoupling of thermopower and conductivity

Deeper optimization in thermoelectric performance requires innovative methodologies to balance the trade-off between thermopower (S) and conductivity (a). The energy-dependent scattering mechanism provides a promising way to decouple S and a, however, the physical origin is still ambiguous. Here, the energy-dependent scattering is revisited and demonstrated by a graphene aerogel with the tunable curvature of graphene sheet in geometry. Interestingly, the 2D carrier state is delivered to the 3D graphene aerogel, besides the presence of weak-localization within transport gap. The curvature serves as a controller to turn on or off the weak-localization and the weak anti-localization by modulating the competition between the elastic inter- or intra-valley scattering and the inelastic back-scattering. In thermoelectricity, the curvature triggers a carrier concentration-independent increase in S owing to the energy-dependent scattering behavior of charge carriers at the weak-localizations. Moreover, the ultralow thermal conductivity of 0.042 W/(mK) is also achieved in graphene aerogels, depicting a "phononglass electron-crystal" characteristic. This study deepens a physical insight into the thermoelectric decoupling by the energy-dependent scattering mechanism and demonstrates its feasibility for thermoelectric optimization.