A novel series of monodisperse conjugated oligomers were synthesized by inserting varied segments into blue-emitting oligofluorenes to complete the color gamut of light emission. Quantum mechanical calculations revealed that the electron transition dipoles lie largely parallel to the long molecular axes of the central segments responsible for light emission. The orientational order parameter characterizing molecular alignment in thermally processed glassy-nematic films was evaluated at 0.77 to 0.87 by UV-vis absorption dichroism. With an emission dichroic ratio ranging from 9.4 to 13.7, polarized photoluminescence provided further evidence that the long molecular axes are aligned with the nematic director. Polarized organic light-emitting diodes (OLEDs) comprising selected materials resulted in red and yellowish green light emission with dichroic ratios of 14.4 and 18.0 and luminance yields of 0.51 and 5.91 cd/A, respectively. These two sets of data represent the best performance to date of red and green polarized OLEDs.

A heptafluorene lightly doped with monodisperse conjugated oligomers is used for the first demonstration of organic polarized (see Figure) light‐emitting diodes utilizing Förster energy transfer. Emission of blue‐green, green, red, and white light is accomplished with a turn‐on voltage of < 4 V, peak polarization ratios of up to 26, integrated polarization ratios of up to 19, and luminance yields of up to 6.4 cd A–1.

Light‐emitting conjugated oligomers comprising anthracene, naphthalene, and fluorene units have been synthesized to investigate three configurations of blue organic light‐emitting diodes (OLEDs) that are designed to identify the origins of device instability. The transient OLED technique is employed to measure hole mobilities, which are found to be 3.1 × 10–4, 8.9 × 10–5, and 3.6 × 10–5 cm2 V–1 s–1 for three different blue‐light‐emitting model compounds with varying fluorene content. A higher hole mobility through the emissive layer results in a wider recombination zone, which, in turn, is responsible for a longer device lifetime and a lower drive voltage at the expense of luminance yield.

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