Light-emitting device

1. A light-emitting device, comprising:

a metal reflective layer;

a first transparent conductive oxide layer having a first refractive index;

a second transparent conductive oxide layer having a second refractive index different from the first refractive index, and being between the metal reflective layer and the first transparent conductive oxide layer; and

a light-emitting stack layer electrically connected to the second transparent conductive oxide layer substantially through the first transparent conductive layer;

wherein there is no light absorbing material between the metal reflective layer and the first transparent conductive oxide layer, and

wherein the first transparent conductive oxide layer has an average grain size larger than that of the second transparent conductive oxide layer.

2. The light-emitting device of claim 1 , further comprising:

a substrate; and

an adhesive layer between the substrate and the metal reflective layer.

3. The light-emitting device of claim 1 , wherein the first refractive index is smaller than the second refractive index.

4. The light-emitting device of the claim 1 , wherein at least one of the first transparent conductive oxide layer and the second transparent conductive oxide layer comprises a material selected from the group consisting of indium, tin, aluminum, stannum (Sn), cadmium (Cd), antimony, and zinc.

5. The light-emitting device of claim 1 , wherein at least one of first transparent conductive oxide layer and the second transparent conductive oxide layer comprises a material selected from the group consisting of ITO, AZO, SnCdO, ATO, ZnO, and ZTO.

6. The light-emitting device of claim 1 , wherein the first transparent conductive oxide layer is in direct contact with the second transparent conductive oxide layer.

7. The light-emitting device of claim 1 , wherein the first transparent conductive oxide layer and the second transparent conductive oxide layer substantially have the same width.

8. A light-emitting device, comprising:

a metal reflective layer;

a first transparent conductive oxide layer having a first average grain size;

a second transparent conductive oxide layer having a second average grain size different from the first average grain size, and being between the metal reflective layer and the first transparent conductive oxide layer; and

a light-emitting stack layer electrically connected to the second transparent conductive oxide layer substantially through the first transparent conductive layer;

wherein there is no light absorbing material between the metal reflective layer and the first transparent conductive oxide layer.

9. The light-emitting device of claim 8 , further comprising:

a substrate; and

an adhesive layer between the substrate and the metal reflective layer.

10. The light-emitting device of claim 8 , wherein the first average grain size is larger than the second average grain size.

11. The light-emitting device of claim 8 , wherein the first transparent conductive oxide layer has a refractive index different from that of the second transparent conductive oxide layer.

12. The light-emitting device of claim 8 , wherein at least one of the first transparent conductive oxide layer and the second transparent conductive oxide layer comprises a material selected from the group consisting of indium, tin, aluminum, stannum (Sn), cadmium (Cd), antimony, and zinc.

13. The light-emitting device of claim 8 , wherein at least one of first transparent conductive oxide layer and the second transparent conductive oxide layer comprises a material selected from the group consisting of ITO, AZO, SnCdO, ATO, ZnO, or ZTO.

14. The light-emitting device of claim 8 , wherein the first transparent conductive oxide layer is in direct contact with the second transparent conductive oxide layer.

15. The light-emitting device of claim 8 , wherein the first transparent conductive oxide layer and the second transparent conductive oxide layer substantially have the same width.

16. A light-emitting device, comprising:

a light-emitting stack layer;

a first transparent conductive oxide layer having a first refractive index;

a second transparent conductive oxide layer having a second refractive index different from the first refractive index, and electrically connected to the light-emitting stack layer substantially through the first transparent conductive layer; and

a transparent dielectric barrier layer between the light-emitting stack layer and the second transparent conductive oxide layer.

17. The light-emitting device of claim 16 , further comprising:

a substrate; and

an adhesive layer between the substrate and the light-emitting stack layer.

18. The light-emitting device of claim 16 , wherein the transparent dielectric barrier layer is narrower than the second transparent conductive oxide layer.

19. The light-emitting device of claim 16 , further comprising an electrode just above the transparent dielectric barrier layer.