Light-Emitting Organic Materials with Variable Charge Injection and Transport Properties

Abstract

Novel light-emitting organic materials comprising conjugated oligomers chemically attached via a\nflexible spacer to an electron- or hole-conducting core were designed for tunable charge injection and\ntransport properties. Representative glassy-isotropic and glassy-liquid-crystalline (i.e., noncrystalline solid)\nmaterials were synthesized and characterized; they were found to exhibit a glass transition temperature\nand a clearing point close to 140 and 250 °C, respectively; an orientational order parameter of 0.75; a\nphotoluminescence quantum yield up to 51%; and HOMO and LUMO energy levels intermediate between\nthose of blue-emitting oligofluorenes and the ITO and Mg/Ag electrodes commonly used in organic\nlight-emitting diodes, OLEDs. This class of materials will help to balance charge injection and transport\nand to spread out the charge recombination zone, thereby significantly improving the device efficiency\nand lifetime of unpolarized and polarized OLEDs.