Entropy production in photovoltaic-thermoelectric nanodevices from the non-equilibrium Green's function formalism

TL;DR

This paper develops a non-equilibrium Green's function approach to analyze entropy production in photovoltaic-thermoelectric nanodevices, revealing conditions under which entropy production can be negative, challenging traditional thermodynamics.

Contribution

It introduces a formalism to calculate entropy production in hybrid photovoltaic-thermoelectric nanosystems considering strong coupling effects.

Findings

Entropy production is positive for specific photon energies.

Broadened emission spectra can lead to negative entropy production.

Results question the second law of thermodynamics in strongly coupled nanosystems.

Abstract

We derive the expressions of photon energy and particle currents inside an open nanosystem interacting with light using non-equilibrium Green's functions. The model allows different temperatures for the electron reservoirs, which basically defines a photovoltaic-thermoelectric hybrid. Thanks to these expressions, we formulate the steady-state entropy production rate to assess the efficiency of reversible photovoltaic-thermoelectric nanodevices. Next, quantum dot based nanojunctions are closely examined. We show that entropy production is always positive when one considers spontaneous emission of photons with a specific energy, while in general the emission spectrum is broadened, notably for strong coupling to reservoirs. In this latter case, when the emission is integrated over all the energies of the spectrum, we find that entropy production can reach negative values. This result provides matter to question the second law of thermodynamics for interacting nanosystems beyond the assumption of weak coupling.