OLED Materials for Polarized, Tunable Color (and White) Emission

University of Rochester
posted on 08/19/2008

This invention relates to a new class of organic light emitting diode (OLED) materials and devices that are capable of producing efficient polarized light in particular colors (blue, green, red) as defined by the chemical structure of the materials selected.

Suggested Uses

This technology provides an efficient source for the polarized light and can be used as power-saving light sources in liquid crystal displays (LCD), which account for the bulk of flat panel display market today. Current LCDs use absorptive polarizers and color filters, which limit efficiency of the back-light to about 4%. The materials of this invention would enable much more efficient power utilization. Linearly polarized OLEDs of this invention are also potentially useful in electroluminescent displays with reduced glare and increased contrast, as well as in projection displays and in stereoscopic imaging systems.

Advantages

The invention describes OLED devices capable of producing polarized light. The light-emitting layer includes a fluorene or mixture of oligomeric fluorenes. In contrast to p-conjugated polymers reported in the past, the mono-disperse conjugated oligomers are characterized by a well-defined and uniform molecular structure and by chemical purity (via recrystallization or column chromatography). The oligomers can be therefore be produced with better chemical purity and morphology and, because of their mechanical properties, they tend to be easier to coat uniformly. Full color and white-light OLED devices have been built with these materials, with a polarization ratio up to 27 and a luminance yield up to 1 cd/A, a turn-on voltage as low as 6V and voltage-independent chromaticity.

Detailed Description

This invention relates to a new class of organic light emitting diode (OLED) materials and devices that are capable of producing efficient polarized light in particular colors (blue, green, red) as defined by the chemical structure of the materials selected. Because this technology could provide an efficient source for the polarized light, they have the potential to be used as power-saving light sources in liquid crystal displays (LCD), which account for the bulk of flat panel display market today. Current LCDs use absorptive polarizers and color filters, which limit efficiency of the back-light to about 4%. The materials of this invention would enable much more efficient power utilization. Linearly polarized OLEDs of this invention are also potentially useful in electroluminescent displays with reduced glare and increased contrast, as well as in projection displays and in stereoscopic imaging systems.

The invention describes OLED devices that comprise a substrate, an anode and a cathode, a uniaxial alignment layer disposed between the electrodes and a light-emitting layer disposed over the uniaxial alignment layer and capable of producing polarized light, and a carrier confinement layer disposed over the light emitting layer and wherein the carrier confinement layer blocks either holes, electrons, or excitrons. The light-emitting layer includes a fluorene or mixture of oligomeric fluorenes. In contrast to p-conjugated polymers reported in the past, the mono-disperse conjugated oligomers are characterized by a well-defined and uniform molecular structure and by chemical purity (via recrystallization or column chromatography). The oligomers can be therefore be produced with better chemical purity and morphology and, because of their mechanical properties, they tend to be easier to coat uniformly. Full color and white-light OLED devices have been built with these materials, with a polarization ratio up to 27 and a luminance yield up to 1 cd/A, a turn-on voltage as low as 6V and voltage-independent chromaticity.

File Number: 2-11141-03033

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