Naoyuki Harada, Hayato Shoyama, Nutnicha Boonmong, Kiichi Mizukami, Yuya Watanabe, Pei Zhao, Masahiro Ehara, Yoichi Sasaki, Nobuo Kimizuka. "Sterically protected π-electron systems for efficient solid-state photon upconversion." Nature Communications, 2026. doi:10.1038/s41467-026-73898-0