Ultrahigh thermoelectric power factor in flexible hybrid inorganic-organic superlattice

Hybrid inorganic-organic superlattice with an electron-transmitting but phonon-blocking structure has emerged as a promising flexible thin film thermoelectric material. However, the substantial challenge in optimizing carrier concentration without disrupting the superlattice structure prevents further improvement of the thermoelectric performance. Here we demonstrate a strategy for carrier optimization in a hybrid inorganic-organic superlattice of TiS2[tetrabutylammonium](x)[hexylammonium](y), where the organic layers are composed of a random mixture of tetrabutylammonium and hexylammonium molecules. By vacuum heating the hybrid materials at an intermediate temperature, the hexylammonium molecules with a lower boiling point are selectively de-intercalated, which reduces the electron density due to the requirement of electroneutrality. The tetrabutylammonium molecules with a higher boiling point remain to support and stabilize the superlattice structure. The carrier concentration can thus be effectively reduced, resulting in a remarkably high power factor of 904 mu Wm(-1) K-2 at 300 K for flexible thermoelectrics, approaching the values achieved in conventional inorganic semiconductors.