Interplay of electron and phonon channels in the refrigeration through molecular junctions

TL;DR

This study investigates how molecular junctions, specifically oligophenylenes, can be optimized for cooling by analyzing electron and phonon transport, with potential temperature reductions of several Kelvin.

Contribution

The paper combines NEGF and DFTB methods to analyze thermoelectric cooling in molecular junctions and proposes strategies for high-performance cooling devices.

Findings

OPE3 molecular junctions can achieve cooling of several Kelvin.

Optimal bias voltages enhance Peltier cooling power.

Key electronic and thermal parameters influence cooling efficiency.

Abstract

Due to their structured density of states, molecular junctions provide rich resources to filter and control the flow of electrons and phonons. Here we compute the out of equilibrium current-voltage characteristics and dissipated heat of some recently synthesized oligophenylenes (OPE3) using the Density Functional based Tight-Binding (DFTB) method within Non-Equilibrium Green's Function Theory (NEGF). We analyze the Peltier cooling power for these molecular junctions as function of a bias voltage and investigate the parameters that lead to optimal cooling performance. In order to quantify the attainable temperature reduction, an electro-thermal circuit model is presented, in which the key electronic and thermal transport parameters enter. Overall, our results demonstrate that the studied OPE3 devices are compatible with temperature reductions of several K. Based on the results, some strategies to enable high performance devices for cooling applications are briefly discussed.