(Invited) Creation of High-Performance Perovskite Solar Cells Using Lithium Ion Endohedral Fullerenes

Abstract

It was started to be realized that lithium-ion endohedral fullerenes are useful materials for electronic devices as shown by Li+@C60 enhancing performance in perovskite solar cells.1) Li+@C60 has high electron affinity, and has oxidation ability to take an electron from organic semiconductors instantly only by mixing these materials. Hereat Li+@C60 has been expected as a p-type dopant to improve performance of organic semiconductors. On the other hand, our next target is a neutral lithium endohedral fullerene (Li@C60) as an n-type dopant for electron donation. To date, Li@C60 has been prepared through electrolysis as electrochemical reduction. This method requires us to use electrochemical instruments and elaborate technique to control current/voltage and temperature by a skillful researcher. To solve this issue, we investigated the synthesis of Li@C60 by facile and scalable chemical reduction of Li+@C60.2) Treatment of Li+@C60 with decamethylferrocene as a commercially available mild chemical reductant afforded the neutral Li@C60 in 81% isolated yield. The product exists as mainly dimer form in solid state containing minute amount the monomer form, which part is ESR active. XRD, ESR, and Raman spectroscopic measurements revealed characteristics of this solid. In this talk, we will introduce fabrication and performance of organic thin-film devices involving Li+@C60 and/or Li@C60.1) It was found that Li@C60, which was derived from Li+@C60 with accepting an electron from organic semiconducting molecules, scavenged intruding oxygen molecules into the devices to improve the lifetime of the organic semiconducting devices.3,4) 【References】1) I. Jeon, H. Ueno, S. Seo, K. Aitola, R. Nishikubo, A. Saeki, H. Okada, G. Boschloo, S. Maruyama, Y. Matsuo, Angew. Chem. Int. Ed. 2018, 57, 4607.2) H. Okada, H. Ueno, Y. Takabayashi, T. Nakagawa, M. Vrankić, J. Arvanitidis, T. Kusamoto, K. Prassides, Y. Matsuo, Carbon 2019, 53, 467.3) H. Ueno, I. Jeon, H.-S. Lin, A. Thote, T. Nakagawa, H. Okada, S. Izawa, M. Hiramoto, H. Daiguji, S. Maruyama, Y. Matsuo, Chem. Commun. 2019, 55, 118374) I. Jeon, A. Shawky, H.-S. Lin, S. Seo, H. Okada, J.-W. Lee, A. Pal, S. Tan, A. Anisimov, E. I. Kauppinen, Y. Yang, S. Manzhos, S. Maruyama, Y. Matsuo, J. Am. Chem. Soc. 2019, 141, 16553.