Light emitting diodes with reflective sidewalls comprising porous particles
Sidewall reflectors disposed on the sidewalls of an LED or pcLED comprise porous (for example, hollow) high refractive index light scattering particles dispersed in a transparent binder. The porous particles exhibit a high refractive index contrast and corresponding strong scattering at the interfaces between the porous particle material and one or more air-filled voids in each particle. These sidewall reflectors can provide light confinement with thin reflector structures, allowing close spacing between LEDs and pcLEDs, and may be advantageously employed in microLED arrays.
1. A light emitting device comprising:
a substrate;
a semiconductor light emitting diode disposed on the substrate, the semiconductor diode comprising a top surface, an oppositely positioned bottom surface adjacent the substrate, and sidewalls connecting the top and bottom surfaces of the semiconductor diode;
a wavelength converting structure comprising a top light output surface, an oppositely positioned bottom surface adjacent the top surface of the semiconductor light emitting diode, and side walls connecting the top and bottom surfaces of the wavelength converting structure; and
reflectors disposed on only the sidewalls of the wavelength converting structure and the semiconductor light emitting diode, the reflectors comprising porous light scattering particles dispersed in a transparent binder, the porous light scattering particles each comprising one or more gas-filled voids defined by inner surfaces of the porous light scattering particles, the reflectors substantially preventing transmission of light exiting the light emitting device through the side walls of the semiconductor diode or through the side walls of the wavelength converting structure.
2. The light emitting device of claim 1 , the porous light scattering particles having a refractive index of greater than or equal to 2.0 and pores with a refractive index of 1.
3. The light emitting device of claim 1 , the porous light scattering particles having diameters of 0.3 microns to 10 microns.
4. The light emitting device of claim 1 , the porous light scattering particles having a bimodal size distribution with a first peak at a first diameter and a second peak at one fourth or less of the first diameter.
5. The light emitting device of claim 1 , the porous light scattering particles having pores with diameters of 100 nanometers to 500 nanometers.
6. The light emitting device of claim 1 , at least some of the porous light scattering particles comprising a hydrophobic coating.
7. The light emitting device of claim 6 , the porous light scattering particles having pores, with internal surfaces of at least some of the pores being coated by the hydrophobic coating.
8. The light emitting device of claim 1 :
the porous light scattering particles having a refractive index of greater than or equal to 2.0;
the porous light scattering particles having pores with a refractive index of 1; and
the porous light scattering particles each comprising a hydrophobic coating.
9. The light emitting device of claim 8 , the porous light scattering particles having diameters of 0.3 microns to 10 microns.
10. The light emitting device of claim 9 , the pores having diameters of 200 nanometers to 250 nanometers.
11. A light emitting device comprising:
a plurality of phosphor converted light emitting diodes disposed on a shared substrate with adjacent pairs of the phosphor converted light emitting diodes separated by corresponding gaps; and
a light scattering composition filling only the gaps to form corresponding sidewall reflectors shared by corresponding adjacent pairs of the phosphor converted light emitting diodes, the light scattering composition comprising porous light scattering particles dispersed in a transparent binder, the porous light scattering particles each comprising one or more gas-filled voids defined by inner surfaces of the porous light scattering particles, the sidewall reflectors substantially preventing transmission of light across the gaps between the corresponding adjacent pairs of the phosphor converted light emitting diodes.
12. The light emitting device of claim 11 , each gap having a corresponding width between a corresponding adjacent pair of the phosphor converted light emitting diodes of less than or equal to 50 microns.
13. The light emitting device of claim 12 , each gap having a corresponding width between a corresponding adjacent pair of the phosphor converted light emitting diodes of less than or equal to 15 microns.
14. The light emitting device of claim 11 , the porous light scattering particles having a refractive index of greater than or equal to 2.0 and pores with a refractive index of 1.
15. The light emitting device of claim 11 , the porous light scattering particles having diameters of 0.3 microns to 10 microns.
16. The light emitting device of claim 11 , the porous light scattering particles having pores with diameters of 100 nanometers to 500 nanometers.
17. The light emitting device of claim 11 , the porous light scattering particles each comprising a hydrophobic coating.
18. The light emitting device of claim 17 , the porous light scattering particles having pores, with internal surfaces of at least some of the pores in the porous light scattering particles being coated by the hydrophobic coating.
19. The light emitting device of claim 11 :
each gap having a corresponding width between a corresponding adjacent pair of the phosphor converted light emitting diodes of less than or equal to 50 microns;
the porous light scattering particles having a refractive index of greater than or equal to 2.0 and diameters of 0.3 microns to 10 microns;
the porous light scattering particles having pores with diameters of 100 nanometers to 500 nanometers and a refractive index of 1; and
the porous light scattering particles each comprising a hydrophobic coating.
20. The light emitting device of claim 19 , each gap having a corresponding width between a corresponding adjacent pair of the phosphor converted light emitting diodes of less than or equal to 15 microns.