title: Highly efficient inverted polymer light-emitting diodes using surface modifications of ZnO layer.
abstract: Organic light-emitting diodes have been recently focused for flexible display and solid-state lighting applications and so much effort has been devoted to achieve highly efficient organic light-emitting diodes. Here, we improve the efficiency of inverted polymer light-emitting diodes by introducing a spontaneously formed ripple-shaped nanostructure of ZnO and applying an amine-based polar solvent treatment to the nanostructure of ZnO. The nanostructure of the ZnO layer improves the extraction of the waveguide modes inside the device structure, and a 2-ME+EA interlayer enhances the electron injection and hole blocking in addition to reducing exciton quenching between the polar-solvent-treated ZnO and the emissive layer. Therefore, our optimized inverted polymer light-emitting diodes have a luminous efficiency of 61.6 cd A(-1) and an external quantum efficiency of 17.8%, which are the highest efficiency values among polymer-based fluorescent light-emitting diodes that contain a single emissive layer.
authors.affiliation: School of Materials Science and Engineering and KIST-UNIST Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Bo Ram
authors.initials: BR
authors.lastname: Lee
authors.affiliation: School of Materials Science and Engineering and KIST-UNIST Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Eui Dae
authors.initials: ED
authors.lastname: Jung
authors.affiliation: Energy Nano Materials Research Center, Korea Electronics Technology Institute (KETI), 68 Yatap-dong, Bundang-gu, Seongnam-si, Gyeonggi-do 463-816, Republic of Korea.
authors.forename: Ji Sun
authors.initials: JS
authors.lastname: Park
authors.affiliation: School of Materials Science and Engineering and KIST-UNIST Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Yun Seok
authors.initials: YS
authors.lastname: Nam
authors.affiliation: Department of Chemistry and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Sa Hoon
authors.initials: SH
authors.lastname: Min
authors.affiliation: Department of Chemistry and Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Byeong-Su
authors.initials: BS
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering, Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764, South Korea.
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764, South Korea.
authors.forename: Jong-Ryul
authors.initials: JR
authors.lastname: Jeong
authors.affiliation: Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Friend
authors.affiliation: Department of Physics and Centre for Plastic Electronics, Imperial College London, Prince Consort Road, London SW7 2AZ, UK.
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Department of Materials Science &Engineering, KAIST, Daejeon 305-701, Republic of Korea.
authors.forename: Sang Ouk
authors.initials: SO
authors.lastname: Kim
authors.affiliation: School of Materials Science and Engineering and KIST-UNIST Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.
authors.forename: Myoung Hoon
authors.initials: MH
authors.lastname: Song