Possible Routes for Efficient Thermo-Electric Energy Conversion in a Molecular Junction.

In the context of designing an efficient thermoelectric energy-conversion device at nanoscale level, we suggest several important tuning parameters to enhance the performance of thermoelectric converters. We consider a simple molecular junction, which is always helpful to understand the basic mechanisms in a deeper way, where a benzene molecule is coupled to two external baths having unequal temperatures. The key component responsible for achieving better performance is associated with the asymmetric nature of transmission function, and in the present work, we show that it can be implemented in different ways by regulating the physical parameters involving the system. Employing a tight-binding framework we calculate electrical and thermal conductances, thermopower, and figure of merit (FOM) by using Landauer integrals, and thoroughly examine the critical roles played by molecule-to-lead (ML) interface geometry, magnetic field, chemical substituent group, ML coupling, and the direct coupling between the two leads. Our results show that a reasonably large FOM (≫1) can be obtained and lead to a possibility of regulating the efficiency by selectively tuning the physical parameters. We believe that the present analysis will enhance the understanding of designing efficient thermoelectric devices, and can be verified in a laboratory.