Giant thermopower and figure of merit of semiconducting polaronic nanolayers

Polarons—electrons coupled with lattice vibrations—play a key role in transport and optical properties of many semiconductors. Here, we calculate the energy spectrum and thermopower of Fröhlich polarons confined to a potential well as a function of the well thickness. We show that the polaron mass enhancement in 2+ϵ dimensions explains a giant thermoelectric power recently observed in doped semiconducting nanolayers (multiple quantum wells) and propose a route for enhancing the performance of thermoelectric energy nanoconverters by increasing their figure of merit by more than one order of magnitude.