Light emitting device and electronic device
Color purity of a light emitting element is improved without an adverse effect such as reduction in voltage and luminance efficiency. The light emitting element has a light emitting laminated body including a light emitting layer between a pair of electrodes. A buffer layer is provided to be in contact with at least one of the electrodes. One of the electrodes is an electrode having high reflectance and the other is a translucent electrode. By employing a translucent electrode, light can be transmitted and reflected. An optical distance between the electrodes is adjusted in accordance with a thickness of the buffer layer, and accordingly, light can be resonated between the electrodes. The buffer layer is made of a composite material including an organic compound and a metal compound; therefore, voltage and luminance efficiency of the light emitting element is not affected even if a distance between the electrodes becomes long.
1. A light emitting device comprising first to third light emitting elements, the first to third light emitting elements each comprising:
a first electrode;
a first buffer layer over and in contact with the first electrode, the first buffer layer having a composite material including an organic compound which shows a hole transporting property and molybdenum oxide;
a hole transporting layer over the first buffer layer;
a light emitting layer over the hole transporting layer, the light emitting layer including a light emitting substance;
an electron transporting layer over the light emitting layer;
a second buffer layer over the electron transporting layer, the second buffer layer having the composite material; and
a second electrode over and in contact with the second buffer layer,
wherein one of the first and second electrodes is a reflective electrode and another of the first and second electrodes is a translucent electrode,
wherein the first to third light emitting elements emit red light, green light, and blue light, respectively,
wherein the second electrode, the hole transporting layer, and the electron transporting layer are shared by the first to third light emitting elements,
wherein a part of the hole transporting layer and a part of the electron transporting layer are in contact with each other,
wherein the light emitting device further comprises partition walls between the first and second light emitting elements and between the second and third light emitting elements,
wherein the partition walls cover edge portions of the first electrodes, and
wherein the hole transporting layer is in contact with the partition walls in a region between the first and second light emitting elements and in a region between the second and third light emitting elements.
2. The light emitting device according to claim 1 ,
wherein an optical distance between the first electrode and the second electrode of the first light emitting element is an integral multiple of half of a maximum wavelength of light extracted from the first light emitting element.
3. The light emitting device according to claim 1 ,
wherein the translucent electrode has reflectance of 10% or more with respect to light emitted from the light emitting layer.
4. The light emitting device according to claim 1 ,
wherein the translucent electrode comprises a material selected from a group consisting of tantalum, chromium, molybdenum, titanium, and titanium nitride.
5. The light emitting device according to claim 1 ,
wherein the reflective electrode has reflectance of 70 to 100% with respect to light emitted from the light emitting layer.
6. The light emitting device according to claim 1 ,
wherein the first to third light emitting elements are arranged in a delta array based on luminescent color thereof.
7. An electronic device including the light emitting device according to claim 1 in a display portion.
8. The light emitting device according to claim 1 ,
wherein the second buffer layer further comprises a layer having a function of generating electrons.
9. The light emitting device according to claim 1 ,
wherein the translucent electrode comprises a material selected from titanium and titanium nitride.
10. The light emitting device according to claim 1 , further comprising a partition wall between the first and second light emitting elements,
wherein the part of the hole transporting layer and the part of the electron transporting layer are in contact with each other over the partition wall.
11. The light emitting device according to claim 1 ,
wherein thicknesses of the first buffer layers of the first to third light emitting elements are different from each other, and
wherein thicknesses of the second buffer layers of the first to third light emitting elements are different from each other.
12. The light emitting device according to claim 1 ,
wherein thicknesses of the first electrodes of the first to third light emitting elements are substantially the same.