Light-emitting device

1. A light-emitting device, comprising:

a light source configured to emit a first light at a first high temperature;

a wavelength conversion material, arranged on the light source, configured to generate a second light in response to an irradiation of the first light, and reach a second high temperature higher than the first high temperature under the irradiation of the first light; and

an optical element separated from the light source by a distance greater than zero, and arranged between the light source and the wavelength conversion material,

wherein the wavelength conversion material is unitary, and

wherein the optical element has a width larger than that of the light source.

2. The light-emitting device of claim 1 , wherein the first high temperature is of 70° C.˜90° C.

3. The light-emitting device of claim 1 , wherein the second high temperature is of 100° C.˜130° C.

4. The light-emitting device of claim 1 , wherein the light-emitting device comprises a light bulb or a light tube.

5. The light-emitting device of claim 1 , wherein the first light is mixed with the second light to produce a white light or a cyan light.

6. The light-emitting device of claim 1 , wherein the light-emitting device has a first color temperature at a lower temperature and a second color temperature at the first high temperature, the second color temperature is greater than the first color temperature.

7. The light-emitting device of claim 1 , wherein the optical element has a non-flat surface on which the wavelength conversion material is arranged.

8. The light-emitting device of claim 1 , further comprising a carrier on which the light source is arranged.