Light emitting device with spherical back mirror
A method is provided for fabricating an organic light emitting device (OLED) with a spherical back mirror. The method forms a spherical curvature in the substrate and deposits a metal film overlying the spherical curvature, forming a spherical back mirror. A transparent isolation layer is formed overlying the spherical back mirror having a planar top surface. A transparent first electrode layer is formed overlying the isolation layer, and a transparent second electrode layer is formed overlying the first electrode layer. A stack is interposed between the first and second electrode layers. The stack is made up of an electron transport layer adjacent the cathode, a light-emitting (electron injection) layer adjacent to the electron transport layer, a hole transport layer adjacent to the light-emitting layer, and a hole injection layer adjacent to the hole transport layer. The order of the stack layering is dependent which electrode is the anode.
1. An organic light, emitting device (OLED) with a spherical back mirror, the LED comprising:
a transparent first electrode layer;
a transparent second electrode layer overlying the first electrode layer;
an electron transport layer interposed between the first and second electrode layers;
a light-emitting layer adjacent to the electron transport layer;
a hole transport layer adjacent to the light-emitting layer;
a hole injection layer adjacent to the hole transport layer; and,
a spherical back mirror concave top surface underlying the first electrode layer;
a transparent isolation layer interposed between the first electrode layer and the spherical back mirror concave surface;
wherein the first electrode layer has a bottom surface;
wherein the spherical back mirror has a spherical curve defined by a radius of curvature (R);
wherein a first interface exists between the light-emission layer and the hole transport layer;
wherein a distance between the first interface and the first electrode layer bottom surface is h2;
wherein the isolation layer has a thickness (h1) between a center the spherical back mirror and the first electrode layer bottom surface; and,
wherein (h1+h2)/R is in a range of 0.2 to 0.4.
2. The OLED of claim 1 wherein h2 is in a range of 100 to 300 nanometers (nm);
wherein the spherical back mirror has a value of R in a range of 3 to 110 microns; and,
wherein h1 is in a range of 0.6 to 44 microns.
3. The OLED of claim 1 further comprising:
an inorganic capsulation layer overlying the second electrode layer.
4. The OLED of claim 3 further comprising:
a glass layer overlying the inorganic capsulation layer.
5. The OLED of claim 1 wherein the spherical back mirror has a maximum length in a range of 3.6 to 176 microns.
6. The OLED of claim 1 wherein the spherical back mirror has a uniform radius of curvature.
7. The OLED of claim 1 wherein the spherical back mirror is a material selected from a group consisting of Ag, Al, W, Mo, MoW, and Au.
8. The OLED of claim 1 wherein the isolation layer, first electrode layer, light-emitting layer, electron transport layer, hole injection layer, hole transport layer, and second electrode layer each have a refractive index of 1.75, with a tolerance of ±6%, in the visible wavelengths of light.