title: Carbazole dendrimers as solution-processable thermally activated delayed-fluorescence materials.
abstract: Recently, thermally activated delayed fluorescence (TADF) materials have received increasing attention as effective emitters for organic light-emitting diodes (OLEDs). However, most of them are usually employed as dopants in a host material. In this report, carbazole dendrimers with a triphenyl-s-triazine core are reported, which are the first solution-processable, non-doped, high-molecular-weight TADF materials. The dendrimers were obtained by a new and facile synthetic route using the tert-butyldimethylsilyl moiety as a protecting group. All dendrimers showed TADF in toluene. Measurements of the temperature-dependent luminescence lifetime revealed that spin-coated neat films also showed TADF with moderate quantum yields. OLED devices incorporating these dendrimers as spin-coated emitting layers gave external quantum efficiencies of up to a 3.4 %, which suggests that this device is harvesting triplet excitons. This result indicates that carbazole dendrimers with attached acceptors are potential TADF materials owing to their polarized electronic structure (with HOMO-LUMO separation).
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta Midori-ku, Yokohama 226-8503 (Japan).
authors.forename: Ken
authors.initials: K
authors.lastname: Albrecht
authors.forename: Kenichi
authors.initials: K
authors.lastname: Matsuoka
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Fujita
authors.forename: Kimihisa
authors.initials: K
authors.lastname: Yamamoto
keywords: carbazoles; dendrimers; electroluminescence; fluorescence