How bilayer excitons can greatly enhance thermoelectric efficiency

Presently, a major nanotechnological challenge is to design thermoelectric devices that have a high figure of merit. To that end, we propose to use bilayer excitons in two-dimensional nanostructures. Bilayer exciton systems are shown to have an improved thermopower and an enhanced electric counterflow and thermal conductivity, with respect to regular semiconductor-based thermoelectrics. We suggest an experimental realization of a bilayer exciton thermocouple. Based on current experimental parameters, a bilayer exciton heterostructures of $p$- and $n$-doped Bi$_2$Te$_3$ can enhance the figure of merit an order of magnitude compared to bulk Bi$_2$Te$_3$. Another material suggestion is to make a bilayer out of electron-doped SrTiO$_3$ and hole-doped Ca$_3$Co$_4$O$_9$.