OLED with improved light outcoupling
View Patent ↗An OLED may include regions of a material having a refractive index less than that of the substrate, or of the organic region, allowing for emitted light in a waveguide mode to be extracted into air. These regions can be placed adjacent to the emissive regions of an OLED in a direction parallel to the electrodes. The substrate may also be given a nonstandard shape to further improve the conversion of waveguide mode and/or glass mode light to air mode. The outcoupling efficiency of such a device may be up to two to three times the efficiency of a standard OLED. Methods for fabricating such a transparent or top-emitting OLED is also provided.
1. An organic light-emitting device comprising:
a substrate;
a first electrode disposed over the substrate;
an organic layer disposed over the first electrode, the organic layer comprising:
a first region comprising an organic emissive material; and
a second region comprising a transparent low-index material embedded within the organic layer in the form of a grid oriented in a plane parallel to the first electrode, wherein the grid has a periodic pattern with a periodicity of 5-20 μm, wherein the low-index material has a refractive index less than the refractive index of the organic emissive material; and
a second electrode disposed over the organic layer;
wherein at least one of the first and second electrodes is a transparent electrode;
wherein the device emits white light;
wherein the thickness of the transparent low-index material extends from a surface of the first electrode to a surface of the second electrode; and,
wherein the low-index material has a refractive index less than the refractive index of the substrate.
2. The device of claim 1 , wherein the device is a top-transmitting OLED.
3. The device of claim 1 , wherein the low-index material has a refractive index of 1.0 to 1.3.
4. The device of claim 3 , wherein the refractive index of the low-index material is 0.15 to 0.4 less than the refractive index of the substrate.
5. The device of claim 1 , wherein the grid is oriented in a plane parallel to both the first electrode and to the second electrode.
6. The device of claim 1 , further comprising a microlens sheet disposed below the substrate, such that a convex side of the microlens sheet faces in the direction opposite the substrate.
7. The device of claim 1 , wherein the low-index material is selected from the group consisting of aerogel, polytetrafluoroethylene, a graded film of SiO 2 , a graded film of TiO 2 , and layers of SiO 2 nanorods.
8. The device of claim 1 , wherein the refractive index of the low-index material is 0.15 to 0.4 less than the refractive index of the substrate.
9. The device of claim 1 , wherein the low-index material is selected from the group consisting of aerogel, polytetrafluoroethylene, a graded film of SiO 2 , and layers of SiO 2 nanorods.
10. The device of claim 1 , wherein the low-index material is selected from the group consisting of polytetrafluoroethylene, a graded film of SiO 2 , and layers of SiO 2 nanorods.
11. A method of manufacturing a light-emitting device, comprising:
depositing a first electrode over a substrate;
depositing a grid of a low-index material over the first electrode with a periodicity of 5-20 μm, the low-index material having a refractive index of 1.0 to 1.3;
depositing an organic emissive material over the grid such that the organic emissive material is in direct contact with the grid or with the first electrode; and
depositing a second electrode over the organic emissive material;
wherein at least one of the first and second electrodes is a transparent electrode; and wherein the grid of the low-index material redirects light emitted by the organic emissive material from a waveguide node to a direction that may escape the device through the transparent electrode;
wherein the device emits white light;
wherein the thickness of the low-index material extends from a surface of the first electrode to a surface of the second electrode; and,
wherein the refractive index of the low-index material is less than the refractive index of the substrate.
12. The method of claim 11 , wherein the refractive index of the low-index material is 0.15 to 0.4 less than the refractive index of the substrate.