Light-emitting device, light-emitting apparatus, electronic device, and lighting device
A novel light-emitting device with a microcavity structure which can improve the emission efficiency compared to the conventional one is provided. In a light-emitting device with a microcavity structure that emits light in a near-infrared range, reflectance of one or both of a first electrode (reflective electrode) and a second electrode (semi-transmissive and semi-reflective electrode) with respect to light in a near-infrared range (e.g., light with a wavelength of 850 nm) is higher than the reflectance thereof with respect to light in a visible light range (greater than or equal to 400 nm and less than 750 nm).
1. A light-emitting device comprising an EL layer between a first electrode and a second electrode,
wherein the first electrode is a reflective electrode and the second electrode is a semi-transmissive and semi-reflective electrode,
wherein the EL layer emits light having an emission peak in a wavelength range from 750 nm to 1000 nm, and
wherein reflectance of one or both of the first electrode and the second electrode with respect to light with a wavelength of 850 nm is higher than the reflectance thereof with respect to light with a wavelength of 500 nm.
2. The light-emitting device according to claim 1 ,
wherein the second electrode has a thickness greater than or equal to 20 nm and less than or equal to 60 nm.
3. The light-emitting device according to claim 1 , further comprising:
an organic layer that is in contact with the second electrode and sandwiches the second electrode with the EL layer,
wherein the organic layer has a refractive index of greater than or equal to 1.7.
4. The light-emitting device according to claim 3 ,
wherein a thickness of the organic layer is greater than or equal to 80 nm and less than or equal to 160 nm.
5. The light-emitting device according to claim 1 ,
wherein at least one of the first electrode and the second electrode comprises at least one of gold (Au), silver (Ag), and copper (Cu).
6. The light-emitting device according to claim 1 ,
wherein the reflectance of the first electrode with respect to light with a wavelength of 850 nm is higher than or equal to 90%.
7. The light-emitting device according to claim 1 ,
wherein the reflectance of the second electrode with respect to light with a wavelength of 850 nm is higher than or equal to 90%.
8. A light-emitting apparatus comprising:
the light-emitting device according to claim 1 ; and
an FPC.
9. An electronic device comprising:
the light-emitting apparatus according to claim 8 ; and
at least one of a microphone, a camera, an operation button, an external connection portion, and a speaker.
10. A lighting device comprising:
the light-emitting device according to claim 1 ; and
at least one of a housing and a cover.
11. A light-emitting device comprising an EL layer between a first electrode and a second electrode,
wherein the first electrode is a reflective electrode and the second electrode is a semi-transmissive and semi-reflective electrode,
wherein the EL layer comprises a light-emitting substance having an emission peak in a wavelength range from 750 nm to 1000 nm, and
wherein a peak of emission spectrum of light emitted from the EL layer has longer wavelength than the emission peak of the light-emitting substance.
12. The light-emitting device according to claim 11 ,
wherein at least one of the first electrode and the second electrode comprises at least one of gold (Au), silver (Ag), and copper (Cu).
13. The light-emitting device according to claim 11 ,
wherein the reflectance of the first electrode with respect to light with a wavelength of 850 nm is higher than or equal to 90%.
14. The light-emitting device according to claim 11 ,
wherein the reflectance of the second electrode with respect to light with a wavelength of 850 nm is higher than or equal to 90%.
15. The light-emitting device according to claim 11 ,
wherein the light-emitting substance is a phosphorescent substance.
16. The light-emitting device according to claim 11 ,
wherein the light-emitting substance is an organometallic complex represented by General Formula (G1):
wherein:
each of R 1 to R 11 independently represents hydrogen or an alkyl group having 1 to 6 carbon atoms,
at least two of R 1 to R 4 represent an alkyl group having 1 to 6 carbon atoms,
at least two of R 5 to R 9 represent an alkyl group having 1 to 6 carbon atoms,
X represents a substituted or unsubstituted benzene ring or naphthalene ring, and
n is 2 or 3; and L represents a monoanionic ligand.
17. A light-emitting apparatus comprising:
the light-emitting device according to claim 11 ; and
an FPC.
18. An electronic device comprising:
the light-emitting apparatus according to claim 17 ; and
at least one of a microphone, a camera, an operation button, an external connection portion, and a speaker.
19. A lighting device comprising:
the light-emitting device according to claim 11 ; and
at least one of a housing and a cover.