Band edge emission enhanced organic light emitting diode-based devices that emit multiple light wavelengths
Light emitting photonic crystals that comprise organic light emitting diodes and that are capable of emitting multiple wavelengths of light simultaneously and methods for fabricating the same are disclosed. Disclosed light emitting photonic crystals emit light at wavelengths at the two edges of a stop-band. Methods for adjusting the width of stop-bands of disclosed devices are also disclosed.
1. A single light emitting photonic crystal having an organic electroluminescent emitter material disposed within the single light emitting photonic crystal:
wherein the organic electroluminescent emitter material comprises an organic light emitting material localized in a zone having less than 10% of an optical thickness of the single light emitting photonic crystal, and has a free space emission spectrum that at least in part overlaps a stop-band of the single light emitting photonic crystal,
wherein the single light emitting photonic crystal emits light at a wavelength corresponding to an edge of the stop-band that the organic electroluminescent emitter materials overlaps, and further comprises a stack of layers of varying refractive index,
wherein a layer of lower index of refraction materials comprises the organic electroluminescent emitter material, and
wherein the stack of layers has a periodic modulation, measured in optical thickness, of refractive index with a period of modulation of λ/2 wherein λ equals a central wavelength of the single light emitting photonic crystal stop-band.
2. The single light emitting photonic crystal of claim 1 ,
wherein the stack of layers of varying refractive index comprised by the single light emitting photonic crystal comprises at least one pair of layers of materials with different refractive indices that, in turn, comprises a first layer of material with a higher refractive index and a second layer of a material with a lower refractive index,
wherein the total optical thicknesses of the two layers combined equals λ/2, and
wherein λ equals a central wavelength of the single light emitting photonic crystal stop-band.
3. The single light emitting photonic crystal of claim 2 wherein the first layer of material and the second layer of material do not have the same optical thickness.
4. The single light emitting photonic crystal of claim 1 wherein the period of the refractive index modulation through the stack of layers is disrupted from between one to seven times by insertion of a layer of constant refractive index having an optical thickness equal to (2n+1)λ/4 wherein n is an integer between 1 and 3 and wherein λ is the central wavelength of the stop-band of the single light emitting photonic crystal.
5. The single light emitting photonic crystal of claim 4 wherein the period of the refractive index modulation through the stack of layers is disrupted one time by a layer having a thickness of 3λ/4 and wherein said layer that disrupts the refractive index modulation of the layer stack comprises the organic electroluminescent emitter material.
6. The single light emitting photonic crystal of claim 1 , wherein the edge of the stop-band occurs at a wavelength at which measured radiance of free space luminescent light emission by the organic electroluminescent emitter material is greater than one-quarter of the peak radiance of the free space luminescent emission spectrum of the emitter material.
7. The light emitting device of claim 1 , further comprising:
one or more additional light emitting photonic crystals, each having photoluminescent material disposed within the single light emitting photonic crystal,
wherein in each of the other single light emitting photonic crystals the photoluminescent material has a free space emission spectrum that at least in part overlaps the stop-band of that light emitting photonic crystal,
wherein each of the additional single light emitting photonic crystals emits light at a wavelength corresponding to an edge of a stop-band,
wherein each of the additional single light emitting photonic crystals has a periodically varying refractive index, and
wherein emission of light from the one more other single light emitting photonic crystals is produced when light from the first single light emitting photonic crystal is absorbed by the photoluminescent material in those other single light emitting photonic crystals energizing them into photoluminescent light emission.
8. The single photonic crystal of claim 1 , wherein the single light emitting photonic crystal emits light at a wavelength corresponding to the short wavelength edge of the stop-band,
wherein a second organic electroluminescent emitter material is disposed within the single light emitting photonic crystal,
wherein the second organic electroluminescent emitter material has a free space emission spectrum that at least in part overlaps a stop-band of the single light emitting photonic crystal,
wherein the single light emitting photonic crystal also emits light at a wavelength corresponding to the long wavelength edge of the stop-band that the second organic electroluminescent emitter material overlaps.
9. The single light emitting photonic crystal of claim 1 , wherein the layer comprising the electroluminescent material and additional organic materials, each having a low index of refraction respective to an adjacent layer, is located adjacent to a metallic reflector.
10. A single light emitting photonic crystal having an organic electroluminescent emitter material disposed within the single light emitting photonic crystal, comprising a stack of layers having a periodic modulation, measured in optical thickness, of refractive index with a period of modulation of λ/2, wherein λ equals a central wavelength of the single light emitting photonic crystal stop-band, and an emitter configured to emit light into one or more stop-bands thereby causing the single light emitting photonic crystal to emit light associated with two separate and distinct stop-band edges.
11. A single light emitting photonic crystal having an organic electroluminescent emitter material disposed within the single light emitting photonic crystal, comprising a stack of layers having a periodic modulation, measured in optical thickness, of refractive index with a period of modulation of λ/2, wherein 2 equals a central wavelength of the single light emitting photonic crystal stop-band, wherein the period of the refractive index modulation through the stack of layers is disrupted from between one to seven times by insertion of a layer of constant refractive index having an optical thickness equal to (2n+1)λ/4 wherein n is an integer between 1 and 3 and wherein λ is the central wavelength of the stop-band of the single light emitting photonic crystal.