  Polarons - electrons coupled with lattice vibrations - play a key role in the
transport and optical properties of many systems of reduced dimension and
dimensionality. Their confinement affects drastically the phonon, polaron,
bipolaron and multi-polaron properties of quantum wells. Here we calculate the
energy spectrum and thermopower of polarons confined to a potential well as a
function of the well thickness. We show that the polaron mass enhancement in
2+epsilon dimensions explains a giant thermolectric power recently observed in
doped semiconducting nanolayers (multiple quantum wells (MQWs)), and propose a
route for enhancing the performance of thermoelectric energy nanoconverters
increasing their figure of merit by more than one order of magnitude.
