Superior thermoelectric performance via "anti-reflection" enabled double-barrier structures

Abstract

We demonstrate theoretically using the atomistic non-equilibrium Green's function formalism with the inclusion of self-consistent charging, the design of a superior thermoelectric generator based on an "anti-reflection" coated double barrier resonant tunnelling diode. Unlike a typical double barrier device, we show that enabling the anti-reflection design facilitates a "boxcar" type feature in its transmission spectrum, which significantly enhances the thermoelectric performance. It is demonstrated that the best operating regime of this device offers a maximum power in the range of $0.7$ to $0.9 MW/m^{2}$ at efficiencies ranging from $46$ to $54\%$ of Carnot efficiency. The physics of charge and heat transport in the ballistic regime of operation helps us gain additional insights on how a large number of transverse current carrying modes boost the output power and simultaneously how the diminishing effects of high-energy parasitic currents aid the efficiency. Finally, a comparative study with a conventional double barrier thermoelectric is presented in terms of standard performance parameters which clearly reveals the performance benefits of enabling an anti-reflection coating.