Blue light emitting semiconductor nanocrystal materials
A semiconductor nanocrystal includes a core including a first semiconductor material and an overcoating including a second semiconductor material. A monodisperse population of the nanocrystals emits blue light over a narrow range of wavelengths with a high quantum efficiency.
1. A method of making a nanocrystal comprising contacting a monodisperse population of semiconductor nanocrystals with an M-containing compound, an X-donor, and an amine, at temperature sufficient to individually overcoat the nanocrystals, wherein the overcoated nanocrystals are substantially free of deep-trap emission sites, and the overcoated nanocrystals when excited emit blue light.
2. The method of claim 1 , wherein the amine is a primary alkenyl amine.
3. The method of claim 1 , wherein the amine is a C 2 -C 20 primary alkenyl amine.
4. The method of claim 1 , wherein the amine is oleylamine.
5. The method of claim 1 , wherein the monodisperse population of semiconductor nanocrystals includes CdS nanocrystals.
6. The method of claim 1 , wherein the monodisperse population of semiconductor nanocrystals has a rms deviation in diameter of no greater than 10%.
7. The method of claim 1 , wherein the monodisperse population of semiconductor nanocrystals has a rms deviation in diameter of no greater than 5%.
8. The method of claim 5 , wherein the M-containing compound includes Zn and the X-donor includes S.
9. The method of claim 1 , wherein the overcoated nanocrystals when excited emit blue light with a quantum efficiency of at least 10%.
10. The method of claim 9 , wherein the blue light has a peak wavelength shorter than 470 nm.
11. The method of claim 1 , wherein the overcoated nanocrystals when excited emit blue light with a quantum efficiency of at least 30%.
12. The method of claim 1 , wherein the overcoated nanocrystals when excited emit blue light with a quantum efficiency of at least 50%.
13. The method of claim 1 , wherein the blue light has a full width at half maximum of not more than 40 nm.
14. The method of claim 1 , wherein the blue light has a full width at half maximum of not more than 30 nm.
15. The method of claim 14 , wherein the overcoated nanocrystals when excited emit blue light with a quantum efficiency of at least 20%.
16. The method of claim 1 , wherein the blue light has a full width at half maximum of not more than 20 nm.
17. The method of claim 1 , wherein the blue light has a peak wavelength shorter than 470 nm.
18. The method of claim 1 , wherein the blue light has an intensity at least five times greater than an intensity of the deep trap emission.
19. The method of claim 1 , wherein the blue light has an intensity at least ten times greater than an intensity of the deep trap emission.
20. The method of claim 1 , wherein the blue light has an intensity at least twenty times greater than an intensity of the deep trap emission.