Prof. Hyo Jae Yoon’s team publishes heat-to-electricity energy conversion on one molecule thick film

The power factor-structure correlation was investigated at the molecular level.

The result was published in American Chemical Society (ACS) Central Science, 

a prominent journal in the field of chemistry-centered convergence research.

▲ (From the left) Prof. Hyo Jae Yoon and his students Sohyun Park and Seohyun Kang.

Prof. Hyo Jae Yoon’s Team of the Department of Chemistry in the College of Science studied the thermoelectric properties of one molecule thick films and reported that the heat-to-electricity energy conversion can be achieved on a film of molecular scale thickness.

The result of the study, supported by the Individual Basic Research Program and the Priority Research Centers Program of the National Research Foundation of Korea, was published in the 5 December issue of the American Chemical Society (ACS) Central Science (Impact factor: 12.837), an authoritative journal in the field of chemistry-centered convergence research.

* Title of Article: Power Factor of One Molecule Thick Films and Length Dependence

* Link to Article: https://pubs.acs.org/doi/abs/10.1021/acscentsci.9b01042

* Authors: Sohyun Park (Korea University, first author), Seohyun Kang (Korea University, first co-author) and Hyo Jae Yoon (Korea University, corresponding author) (three authors)

The present study was conducted on the basis of a large-area (~μm2) molecular-level thermoelectric system (Nano Letters, 2018; Title of Article: A New Approach for Large-Area Thermoelectric Junctions with Liquid Eutectic Gallium-Indium Electrode), reported by the same team in 2018 for the first time. The present study showed that the structure-property correlation can be conducted by the power factors at the molecular level, presenting a new paradigm for thermoelectric studies.

The research team focused on the finding that the Seebeck coefficient and electric conductivity can be measured using a liquid gallium-indium alloy without damaging an extremely thin monomolecular film, and measured the power factor values, which are widely employed in thermoelectric studies, at the single molecule thickness level. The charge transfer in a single molecule or a single molecular layer itself is a very challenging and intriguing topic of basic science. Conventional organic thermoelectric devices have not facilitated accurate understanding of thermoelectric properties at a molecular level due to the complicated structure of their organic layers and the presence of various interfaces.

The research team investigated structure-power factor correlations by minimizing complexity and then provided a novel theoretical model that is applicable to further power factor experiments. Since the model enables one to study molecules of various structures, the design of organic thermoelectric devices based on this model will significantly affect basic research on charge transfer in organic substances.

[Description of Figure]

[Figure 1] A schematic illustration of a large-area molecular junction structure and a description of the power factor simulation study with various one molecule thick organic films including oligophenylene and oligothiophene.

[Terms]

1) Thermoelectric effect

Thermoelectric effect refers to the essential mechanism by which electric energy is generated from temperature differences in the surrounding environment. The thermoelectric effect is a very interesting research topic from environmental and scientific perspectives because it enables the recycling of thermal energy.

2) Seebeck Coefficient

The Seebeck coefficient represents the efficiency of converting thermal energy into electric energy. A larger Seebeck coefficient means a larger voltage is generated from the same temperature difference.