* oleg.salata@materials.ox.ac.uk; phone +44-1865-283713; fax +44-1865-847444; Unit 8, Begbroke Business and Science Park, Sandy Lane, Yarnton, Oxford OX5 1PF, UK Efficient Solution-Processed Dendrimer OLEDs O. V. Salata *a , Zugang Liu a , A. Safonov b , N. Mustapha b , Shih-Chun Lo c , Paul Burn c , Ifor Samuel d , Jonathan Markham d a Dept. of Materials, Univ. of Oxford, UK; b Opsys Limited, UK; c The Dyson Perrins Laboratory, Univ. of Oxford, UK; d Dept. of Physics & Astronomy, Univ. of St Andrews, UK ABSTRACT Light-emitting dendrimers are a new distinct class of material for OLEDs. Dendrimers consist of a light-emitting core, dendrons and surface groups. Dendrimers are designed for solution coating and have a number of advantages over conjugated polymers. We report our recent results for solution processed green dendrimer OLEDs. The OLEDs were fabricated by spin-coating a blend of first generation dendrimer/host material followed by the evaporation of a hole blocking layer and a LiF/Al cathode. Power efficiencies of 50 lm/W at practical brightness levels were achieved for these structures. Keywords: dendrimers, solution processing, OLED 1. INTRODUCTION Light-emitting materials have traditionally fallen into two main classes, namely small molecules 1 and conjugated polymers 2 . Conjugated polymers are solution processed whilst small molecule based organic light-emitting diodes are produced by evaporation. Light-emitting dendrimers are a new class of material for OLEDs 3 . Dendrimers consist of a light-emitting core, dendrons and surface groups. Dendrimers are solution processible and have a number of advantages over conjugated polymers. These include being produced by a modular synthetic route, which gives greater flexibility over controlling the properties and independent optimisation of the processing and electronic properties. Also, the generation of the dendrimer gives molecular control over the intermolecular interactions that are vital to OLED performance 4 . Finally, both fluorescent and phosphorescent dendrimers are easily accessible. Phosphorescent light-emitting materials can harness emission from singlet and triplet excited states so that it is possible to achieve OLEDs with 100% internal quantum efficiency. In contrast, in fluorescent materials, triplet formation leads to substantial loss of efficiency. Recently reported results for a single layer spin-coated dendrimer devices demonstrated the potential of the green phosphorescent dendrimer emitter 5 . In another recent work we reported some preliminary results for different combinations of host and hole blocking materials 6,7 in double layer devices. Here we report our latest improvements in the performance of double layer OLEDs based on the combination of the first generation green emitting dendrimer with 4,4’,4’’-tris(N-carbazolyl)triphenylamine (TCTA) 8 as a host material and 1,3,5-tris(2-N- phenylbenzimidazolyl)benzene (TPBI) 9 as a hole blocking/electron transporting material. Materials, Devices, and Systems for Display and Lighting, Fuxi Gan, Ming Hsien Wu, Lionel C. Kimerling, Editors, Proceedings of SPIE Vol. 4918 (2002) © 2002 SPIE · 0277-786X/02/$15.00 117 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 12/02/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx