title: Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials.
abstract: Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin-orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels-Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage.
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Min Sang
authors.initials: MS
authors.lastname: Kwon
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Youngchang
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Electrical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Caleb
authors.initials: C
authors.lastname: Coburn
authors.affiliation: Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Phillips
authors.affiliation: Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Kyeongwoon
authors.initials: K
authors.lastname: Chung
authors.affiliation: Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Apoorv
authors.initials: A
authors.lastname: Shanker
authors.affiliation: Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Jaehun
authors.initials: J
authors.lastname: Jung
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Gunho
authors.initials: G
authors.lastname: Kim
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Pipe
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Electrical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Forrest
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Applied Organic Materials Engineering, Inha University, Incheon 402-751, Korea.
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Youk
authors.affiliation: Madrid Institute for Advanced Studies-IMDEA Nanoscience, Calle Faraday 8, Ciudad Universitaria de Cantoblanco, Madrid 28049, Spain.
authors.forename: Johannes
authors.initials: J
authors.lastname: Gierschner
authors.affiliation: Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.|Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.|Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Jinsang
authors.initials: J
authors.lastname: Kim