Light-Emitting Fluorene Photoreactive Liquid Crystals for Organic Electroluminescence

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• 作者：Mathew P. Aldred ; Amanda J. Eastwood ; Stephen M. Kelly ; Panos Vlachos ; Adam E. A. Contoret ; Simon R. Farrar ; Bassam Mansoor ; Mary O'Neill ; and W. Chung Tsoi
• 刊名：Chemistry of Materials
• 出版年：2004
• 出版时间：November 30, 2004
• 年：2004
• 卷：16
• 期：24
• 页码：4928 - 4936
• 全文大小：300K
• 年卷期：v.16,no.24(November 30, 2004)
• ISSN：1520-5002

文摘

Light-emitting liquid crystals for organic light-emitting diodes (OLEDs) require low-temperature liquid crystal phases for room-temperature processing and a range of molecularenergies for electron and hole injection, as well as tunable color and color purity for multicolorOLEDs. We report a number of light-emitting polymerizable liquid crystals (reactivemesogens) based on 2,7-disubstituted-9,9-dialkylfluorene, whose energy levels can be tunedfor optimized charge injection and light emission. As a consequence of these systematicproperty/structure investigations small molecule reactive mesogens have been synthezised,which exhibit low melting points, even below room temperature and nematic phases aboveroom temperature as single components. Many of the molecules retain a supercooled nematicphase on cooling to room temperature. Simple binary eutectic mixtures of reactive mesogenswith identical aromatic cores form light-emitting nematic phases at room temperature witha high clearing point to generate a high order parameter. The ionization potential of six-ring fluorene reactive mesogens can be tuned between 4.93 and 5.57 eV by chemicalmodification of the aromatic cores. Similarly the emission spectrum can be tuned from blueto green. A typical performance for an OLED using such liquid crystalline materials as across-linked polymer network is described.