In collaboration with the Quantum Science and Technology Research and Development Organization, Tohoku University, Idea International Co., Ltd., and others, Professor Yoichi Yamada of the University of Tsukuba and others directly observed the electronic state of lithium-encapsulated fullerenes, which are expected to be next-generation materials, at the molecular level. The detailed analysis was successful for the first time.
Fullerenes are soccer ball-shaped molecules composed of carbon atoms, and it is thought that physical properties can be changed by wrapping various atoms and molecules in the space inside them (encapsulated fullerenes).This research group has succeeded in creating fullerenes containing lithium ions, and due to their excellent electron acceptability, they are expected to be applied as organic electronics devices such as organic solar cells and supercapacitors. The electronic properties required for that purpose have not yet been fully understood.This is because it was difficult to control the contained fullerenes in a monatomic layer and arrange them on the substrate in order to evaluate the behavior on the metal substrate required for functional analysis as a material.
In this study, we found a method to sublimate this encapsulated fullerene in a vacuum in the form of a "salt" bound to fluorine or phosphorus and adsorb it to a metal substrate with a monatomic layer. Was successfully measured for the first time.Furthermore, detailed analysis was performed by comparing the measured electronic states with the theoretical calculation results, and it was clarified that the contained lithium exists in the fullerene in the state of almost monovalent cations.We also found that the charge distribution in fullerenes changes when a negative high voltage is applied, and showed the possibility that the charge can be controlled by the applied voltage.
This result is said to pave the way for the practical application of next-generation organic semiconductor materials using lithium-encapsulating fullerenes.
Paper information:[Carbon] Electronic structure of Li + @ C60: Photoelectron spectroscopy of the Li + @ C60 [PF6-] salt and STM of the single Li + @ C60 molecules on Cu (111)
