Theoretical study on the Cs/Cs-O adsorbed graphene/semiconductor heterojunction anode for thermionic converters

Graphene/semiconductor heterojunction anodes can significantly enhance the output voltage by the photovoltaic effect. However, a significant challenge arises from the high intrinsic work function of heterojunction surfaces, which limits efficient electron emission. In this study, we explored the potential of low work function materials modified by Cs/Cs-O adsorption as anodes for thermionic (TI) converters through first principles calculations. The results demonstrate that the work functions of the graphene/MoS₂ and the graphene/n-type Si surfaces with only Cs coating can decrease to 1.48 eV and 2.46 eV, respectively. The multiple Cs-O atoms co-adsorption enhances the dipole moment, resulting in a further reduction of the work function of the graphene/MoS₂ surface to 1.25 eV. In addition, the impact of work function on the performance of TI converters is revealed by using concentrated solar energy as heat source. The highest conversion efficiency achieves 15.25% for the Cs-4O: Gr/MoS₂ anode. This study establishes a robust foundation for further advancement of the TI converters with graphene/semiconductor heterojunction anodes.

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