White organic light emitting device and process for production thereof
The present invention relates to a white organic light emitting device (WOLED) comprising an electroluminescent material (ELM) and a Bragg converter disposed adjacent to the ELM. In addition, the invention also relates to a method for producing white light using said WOLED, use of the WOLED for producing white light, and a process for producing said WOLED.
1. A white organic light emitting device (WOLED) comprising
an organic light-emitting device (OLED) comprising an electroluminescent medium (ELM), and
a Bragg converter comprising pairs of alternating layers of high refractive index material and low refractive index material disposed immediately adjacent to the OLED,
wherein the ELM comprises a single organic light emitting layer (EML) that emits light of a broad range with part of its emission located at ultraviolet and blue wavelengths and the Bragg converter that converts the light from the OLED to a different color by suppressing UV radiation by its stop band and enhancing outcoupling of the red-shifted emission through Bragg modes.
2. The WOLED of claim 1 , wherein the ELM comprises a reflective layer disposed on one side of the EML.
3. The WOLED of claim 2 , wherein the Bragg converter is arranged on the side of the ELM opposite to the reflective layer.
4. The WOLED of claim 1 , wherein the emitting part of the OLED comprises an anode, an electron injection layer, a light emitting layer, a hole blocking layer, a hole injection layer and a cathode.
5. The WOLED of claim 1 , wherein the Bragg converter comprises transparent oxides of dielectric materials such as oxides of silicon, tantalum, titanium, hafnium, or mixtures thereof.
6. The WOLED of claim 5 , wherein the Bragg converter comprises oxides of silicon or tantalum such as silica and tantalum pentoxide.
7. The WOLED of claim 2 , wherein the WOLED may optionally be arranged on a substrate disposed below the reflective layer.
8. The WOLED of claim 7 , wherein the substrate may be any optically flat solid material onto which the reflective layer can be deposited.
9. The WOLED of claim 7 , wherein the substrate is attached to the side of the OLED opposite to the Bragg converter.
10. The WOLED of claim 1 comprising an aluminium anode, a MoO 3 hole-injector, a TDAF (2,7-bis [9,9-di (4-methylphenyl)-fluoren-2-yl]-9,9-di(4-methylphenyl) fluorene) emission layer, a BPhen (4,7-diphenyl-1,10-phenanthroline) hole blocking layer, a LiF electron injection layer, an aluminium cathode, and a Bragg converter comprising alternating layers of SiO 2 and Ta 2 O 5.
11. A process for the production of a WOLED of claim 1 , said process comprising the steps of
a. sequentially depositing the anode and hole injecting layers through a patterned shadow mask,
b. sequentially depositing the light emitting layer, the hole blocking layer, the electron injection layer, and the cathode layer through a patterned shadow mask, and
c. direct sputtering of the Bragg converter layers onto the surface of the cathode through a patterned shadow mask.
12. A method for producing white light with a device comprising a WOLED of claim 1 .