Influence of electrodes in enhancing the thermoelectric performance of Mn-Cn-Mn (n = 7) molecular chain

Abstract

The present study enlightens an in-depth investigation into the comparative analysis of thermoelectric performance between g-$C_4{N}_3$and graphene electrodes with a molecular chain of Mn-C_n-Mn ($n=7$), a one-dimensional (1-D) thermoelectric system as the molecular channel. The study explores the critical factors influencing the figure of merit (ZT) and the overall thermoelectric behaviour of these systems. Results demonstrate that at lower temperatures an efficient thermoelectric device with high ZT is obtained with g-$C_4{N}_3$electrodes; however, the same is not maintained above 225 K; instead, better and consistent thermoelectric performance at higher temperatures is obtained with Graphene electrodes. Our study therefore highlights the crucial role of the choice of electrodes in deciding final thermoelectric performance. The thermoelectric performance is analysed through the system's temperature dependence of the Seebeck coefficient, electrical conductance, and thermal conductance. It is observed that temperature dependence of Seebeck coefficient (S) has a direct impact on ZT variation. The high thermal conductivity (k) along with low S of graphene electrode is responsible for relatively lower ZT despite large higher electrical conductivity ($G_e).$Throughout the range of temperature variation, the electronic part of thermal conductivity (k) is found to be weaker than the phononic part in both systems.