title: Near-Infrared-to-Visible Photon Upconversion Sensitized by a Metal Complex with Spin-Forbidden yet Strong S0-T1 Absorption.
abstract: Near-infrared (NIR)-to-visible (vis) photon upconversion (UC) is useful for various applications; however, it remains challenging in triplet-triplet annihilation-based UC, mainly due to the energy loss during the S1-to-T1 intersystem crossing (ISC) of molecular sensitizers. In this work, we circumvent this energy loss by employing a sensitizer with direct S0-to-T1 absorption in the NIR region. A mixed solution of an osmium complex having a strong S0-T1 absorption and rubrene emitter upconverts NIR light (λ = 938 nm) to visible light (λ = 570 nm). Sensitizer-doped emitter nanoparticles are prepared by re-precipitation and dispersed into an oxygen-barrier polymer. The obtained composite film shows a stable NIR-to-vis UC emission based on triplet energy migration (TEM), even in air. A high UC quantum yield of 3.1% is observed for this TEM-UC system, expanding the scope of molecular sensitizers for NIR-to-vis UC.
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems, Kyushu University , 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Shogo
authors.initials: S
authors.lastname: Amemori
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems, Kyushu University , 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sasaki
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems, Kyushu University , 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.|PRESTO, JST , Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yanai
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems, Kyushu University , 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kimizuka