Improvement of Device Efficiency by Cross-Linkable Interlayer in Blue Polymer Light-Emitting Diodes

• Published in: Molecular crystals and liquid crystals (Philadelphia, Pa. : 2003) Pa. : 2003), 2006-12, Vol.462 (1), p.249-256
• Main Authors: Lee, Seongyul, Park, Joonyoung, Lyu, Yiyeol, Lee, Soo-Hyoung
• Format: Article
• Language: English
• Subjects: cross-link; interlayer; organic light-emitting diodes
• ISSN: 1542-1406; 1563-5287
• DOI: 10.1080/15421400601013403

We report that high efficiency blue polymer light-emitting diodes obtained by adding a thin interlayer between a poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonic acid) (PEDT:PSS) hole transporter and emissive polymer. The one of OLED hole transporters, N,N′-bis(4-methylphenyl)-N,N′-diphenyl-1,4′-phenylenediamine (PDA), was modified with cross-linkable trichlorosilyl groups and used for the interlayer material. The devices, with configuration of indium tin oxide (ITO)/PEDT:PSS (65 nm)/interlayer (10-20 nm)/emitting polymer layer (70 nm)/BaF 2 (2 nm)/Ca (50 nm)/Al (300 nm), were fabricated by spin coating and thermal evaporation. In this device structure, the cross-linkable interlayer is more adherent and mechanically robust as well as impervious to spin coating of next emitting polymer layer and shows a better stability. In addition, the devices with the interlayer exhibit a higher luminescence and current efficiency than those in devices without the interlayer.