TWI580070B - Light emitting device with light extraction layer and fabricating method thereof - Google Patents

Description

Light-emitting element with light extraction layer and method of manufacturing same

The present invention relates to a light-emitting element and a method of fabricating the same, and more particularly to a light-emitting element with a light-extraction layer embedded in a refractive index-matched light extraction layer for reducing the difference in refractive index between the light-emitting layer and the package layer, and a method of manufacturing the same .

In recent years, with the rapid development of semiconductor technology and the rise of energy-saving awareness, the replacement of traditional lighting and display devices with Light Emitting Diodes (LEDs) has gradually been accepted and even become the most watched industry. one.

In general, conventional light-emitting diodes do not have a refractive index mismatch between the luminescent material (ie, the luminescent layer) and the air or encapsulant (ie, the encapsulating layer), so most of the photons will thus produce total reflection, so that the photons are only When it is smaller than the critical angle, it can penetrate the encapsulation layer and become visible light visible to the naked eye. As for the photons that cannot be penetrated, it is slowly absorbed inside the light-emitting diode, which causes a problem of poor luminous efficiency. For example, in the current most common blue light-emitting diode material "GaN" in the light-emitting layer, the refractive index "n _GaN " is between "2.5" and "2.8", and the other blue light-emitting diode The bulk material "InGaN" has a refractive index "n _InGaN " of about "3.3"; the red light-emitting diode material "GaAs" has a refractive index "n _GaAs " of about "4", and the refractive indices of these materials are all The difference in refractive index from the air medium or encapsulation layer is not small. If the refractive index difference between the luminescent layer and the external medium (such as air or encapsulation layer) can be reduced, it will help to extract the original limitation inside the illuminating diode. Photon.

In view of this, some manufacturers have proposed to use a high refractive index encapsulant as an encapsulation layer to encapsulate the light emitting diode, and even doping the encapsulant with a material having a scattering mechanism, such as: phosphor powder, "TiO2" powder, ......and many more. In addition, there are also factories The package structure of the light-emitting diode is changed to reduce the total reflection state in order to improve the light output efficiency. However, the use of a high refractive index encapsulant as an encapsulation layer is costly and difficult to obtain. As a result of changing the package structure of the LED, packaging difficulty is caused, and the package process yield is affected. Therefore, the above two methods cannot effectively solve the illumination. Inefficient problem

In summary, it can be seen that there has been a long-standing problem in the prior art that the luminous efficiency of the light-emitting diode cannot be effectively solved. Therefore, it is necessary to propose an improved technical means to solve this problem.

In view of the problems of the prior art, the present invention discloses a light-emitting element having a light extraction layer and a method of manufacturing the same.

The light-emitting element with a light extraction layer disclosed in the present invention comprises: a light-emitting layer, a light extraction layer and an encapsulation layer. The light-emitting layer is configured to combine electrons and holes and generate a plurality of photons; the light extraction layer is formed on the light-emitting layer by an organic material, and is doped with a metal material for adjusting a refractive index of the light extraction layer to increase the Photon transmittance, wherein the material of the light extraction layer is tris(8-hydroxyquinoline)aluminum (Alq3) and 4,4'-bis[N-(1-naphthyl)-N-anilino]biphenyl ( One of 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl, NPB); an encapsulation layer is formed on the light extraction layer to protect the light-emitting element and to cause the photon Penetrate this encapsulation layer.

The method for manufacturing a light-emitting element with a light extraction layer disclosed in the present invention includes the steps of: providing a light-emitting layer for combining electrons and holes and generating a plurality of photons; and forming a light extraction layer with an organic material on the light-emitting layer, and Doping a metal material in the light extraction layer to adjust the refractive index of the light extraction layer to increase the transmittance of the photon, wherein The material of the light extraction layer is tris(8-hydroxyquinoline)aluminum (Alq3) and 4,4'-bis[N-(1-naphthyl)-N-anilino]biphenyl (4,4'-bis[ One of N-(1-naphthyl)-N-phenyl-amino]biphenyl, NPB); and forming an encapsulation layer on the light extraction layer to protect the light-emitting element and pass the photon through the encapsulation layer.

The components disclosed in the present invention and the manufacturing method thereof are as above, and the difference from the prior art is that the present invention is to embed a light extraction layer between the light emitting layer and the encapsulating layer to reduce the refractive index difference between the light emitting layer and the encapsulating layer, and The light extraction layer is doped with a metal material to adjust the refractive index of the light extraction layer.

Through the above technical means, the present invention can achieve the technical effect of improving the luminous efficiency of the light-emitting element.

The embodiments of the present invention will be described in detail below with reference to the drawings and embodiments, so that the application of the technical means to solve the technical problems and achieve the technical effects can be fully understood and implemented.

First, a light-emitting element having a light-extracting layer of the present invention will be described. Please refer to FIG. 1 and FIG. 1 is a schematic cross-sectional view of a light-emitting element having a light extraction layer according to the present invention. The light-emitting element 10a includes: The light-emitting layer 11, the light extraction layer 12, and the encapsulation layer 13. The luminescent layer 11 is configured to combine electrons and holes and generate a plurality of photons, and the luminescent layer 11 may be composed of a material layer for generating photons, such as a light emitting diode, an organic light emitting diode, and the like. For example, if the light-emitting layer 11 is a light-emitting diode, the light-emitting layer 11 includes at least doped N-type impurities (also referred to as "donor"), for example, germanium (Si), phosphorus. a semiconductor layer of a pentavalent element such as (P), arsenic (As), antimony (Sb), etc. (ie, an N-type semiconductor layer), and doped with a P-type impurity (also referred to as a "receptor") ),Such as: a semiconductor layer of a trivalent element such as magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), etc. (ie, a P-type semiconductor layer) to provide electrons, respectively A hole is formed and the two are combined for photoelectric conversion. In practical implementation, the active layer between the N-type semiconductor layer and the P-type semiconductor layer may have a multi-quantum well (MQW) structure or a quantum dot structure, so that the electrons and the holes are more easily confined together. Increase the brightness of the light, that is, increase the proportion of electrical energy converted into light energy. Since the light-emitting diode structure and the multi-quantum well structure are all conventional techniques, no further description will be given here. In particular, the reason why the light-emitting element 10a does not include a substrate (not shown) is because the light-emitting layer 11 is successfully formed on the substrate, and the substrate is removed by a conventional technique such as laser or polishing. As a result, the luminous efficiency and the heat dissipation effect of the light-emitting element 10a can be improved.

As described above, if the light-emitting layer 11 is an organic light-emitting diode, at least an indium tin oxide (ITO), an organic light-emitting layer, and a cathode layer are stacked on each other (not shown), wherein the light-emitting layer 11 is oxidized. Indium tin is a transparent anode material with high light transmittance, low electrical resistance, high chemical stability and easy etching. When voltage is applied to indium tin oxide and cathode layer, the two will be provided separately. Holes and electrons, where the holes and electrons combine with the organic light-emitting layer between the indium tin oxide and the cathode layer and provide energy to generate photons. The organic light-emitting layer may be a fluorescent or phosphorescent material, and the energy level difference of the compound is adjusted by modifying the molecular structure or the functional group. Since the layers of the organic light-emitting diode are conventional technologies, they are no longer used here. Repeat more.

The light extraction layer 12 is formed on the light-emitting layer 11 and is doped with a metal material such as aluminum, silver, etc. to adjust the refractive index of the light extraction layer 12 to increase the light-emitting layer 11 The photon transmittance, the metal material can be doped in the light extraction layer 12 by co-evaporation, and the refractive index is in the range of "1.5" to "2.5". The material and the thickness of the light extraction layer 12 can be adjusted according to the resonance of the photons, and the light extraction layer 12 can be even coated on the side of the light-emitting layer 11 or the light-emitting layer 11. In practical implementation, the light extraction layer 12 can be "4,4'-bis[N-(1-naphthyl)-N-anilino]biphenyl (4,4'-bis[N-(1-naphthyl) -N-phenyl-amino]biphenyl, NPB)", "tris(8-hydroxyquinoline)aluminum (Alq3)", etc., such as a material having a refractive index between the light-emitting layer 11 and the encapsulating layer 13 . In particular, the present invention does not limit the material of the light extraction layer 12 by the above examples, and any material having a refractive index between the refractive indices of the light-emitting layer 11 and the package layer 13 does not deviate from the application scope of the present invention. In the absence of the encapsulation layer 13, the refractive index of the light extraction layer 12 is achieved by a material between the refractive indices of the luminescent layer 11 and the encapsulation layer 13, and the refractive index can be based on the doped metal material. The concentration is appropriately adjusted. For example, the richer the concentration of the doped metal material, the higher the refractive index will be. On the contrary, the lower the concentration of the doped metal material, the lower the refractive index will be.

The encapsulation layer 13 is formed over the light extraction layer 12 to protect the light emitting element 10a, and the photons generated by the light emitting layer 11 are penetrated through the encapsulation layer 13. In practical implementation, the encapsulating layer 13 may be made of silicone or epoxy resin and has a refractive index of about "1.5". Since the encapsulation layer 13 is a conventional technique, it will not be described here.

As shown in FIG. 2, FIG. 2 is a flow chart of a method for manufacturing a light-emitting element having a light extraction layer according to the present invention, which includes providing a light-emitting layer 11 for combining electrons and holes and generating a plurality of photons. (Step 210); forming a light extraction layer 12 on the light-emitting layer 11, and doping a metal material on the light extraction layer 12 for adjusting the refractive index of the light extraction layer 12 to increase the transmittance of the photons (step 220) An encapsulation layer 13 is formed on the light extraction layer 12 to protect the light-emitting element 10a and to pass the photons through the encapsulation layer 13 (step 230). Through the above steps, the light-emitting layer 11 and the encapsulation layer 13 can be transmitted. The light extraction layer 12 is interposed to reduce the refractive index difference between the light-emitting layer 11 and the encapsulation layer 13, and the light extraction layer 12 is doped with a metal material to adjust the refractive index of the light extraction layer 12.

Please refer to FIG. 3A. FIG. 3A is a schematic cross-sectional view showing a second embodiment of a light-emitting element having a light extraction layer according to the present invention. As mentioned above, the substrate of the light-emitting element 10a is removed by laser or the like in order to increase luminous efficiency and heat dissipation. However, in actual implementation, the light-emitting element 10b, which is also illustrated in FIG. 3A, may retain the substrate 14 under the light-emitting layer 11. The substrate 14 may be a sapphire substrate, a silicon substrate, or a germanium (Ge). a substrate, a tantalum carbide (SiC) substrate, a gallium arsenide (GaAs) substrate, or a glass substrate, for use as an evaporation, sputtering, or printing film, the steaming The plating method may be selected from, but not limited to, Metal-organic Chemical Vapor Deposition (MOCVD). In particular, the substrate 14 of the present invention is not limited to the various photovoltaic material substrates listed above, and any substrate capable of functioning as a photovoltaic element does not depart from the scope of application of the present invention.

Please refer to "FIG. 3B", and FIG. 3B is a schematic cross-sectional view showing a third embodiment of a light-emitting element having a light extraction layer of the present invention. As mentioned above, the light extraction layer 12 is formed on the light-emitting layer 11 to cover the side of the light-emitting layer 11 or the light-emitting layer 11. In actual practice, the light-emitting layer 11 is used as an example. The coating method can form the light extraction layer 12 on the surface of the light-emitting layer 11 to cover the entire light-emitting layer 11 as in the light-emitting element 10c illustrated in FIG. 3B. Next, an encapsulation layer 13 is formed over the light extraction layer 12 to protect the light-emitting element 10c. The difference between the side of the light-extracting layer 12 and the light-emitting layer 11 is that the light-emitting layer 11 is not covered by the light-emitting layer 11 at the bottom of the light-emitting layer 11, and therefore will not be further described herein.

Next, please refer to "3C" and "3C" is a schematic cross-sectional view showing a fourth embodiment of a light-emitting element having a light extraction layer of the present invention. If the light-emitting element 10d does not remove the substrate 14 by laser, the light extraction layer 12 may cover the side of the light-emitting layer 11 as shown in FIG. 3C. At this time, a part of the light extraction layer 12 is in contact with the substrate 14, and then the encapsulation layer 13 is formed on the light extraction layer 12 for protecting the light-emitting element 10d.

Finally, as shown in "Fig. 4", "Fig. 4" is a schematic diagram for improving the luminous efficiency of the light-emitting element by applying the present invention. When the light extraction layer 12 is not provided, if the photons generated by the light-emitting layer 11 are smaller than the first critical angle 41, the photons will penetrate the boundary between the light-emitting layer 11 and the encapsulation layer 13 (eg, photons are indicated by solid arrows). It is shown that photons larger than the first critical angle 41 are reflected and confined in the luminescent layer 11 until absorbed. However, when the light extraction layer 12 of the present invention is provided between the light-emitting layer 11 and the encapsulation layer 13, the photons generated by the light-emitting layer 11 will penetrate the light-emitting layer 11 and the light extraction layer 12 when it is smaller than the second critical angle 42. The boundaries between the two (e.g., photons are indicated by dashed arrows), and photons larger than the second critical angle 42 are still reflected and confined in the luminescent layer 11 until absorbed. However, since the second critical angle 42 is larger than the first critical angle 41, relatively, the photon capable of penetrating the luminescent layer 11 will be much more than the original photo-extraction layer 12, so that the luminous efficiency of the illuminating element can be improved. .

In summary, it is understood that the difference between the present invention and the prior art is that the light extraction layer 12 is embedded between the light-emitting layer 11 and the encapsulation layer 13 to reduce the refractive index difference between the light-emitting layer 11 and the encapsulation layer 13, and The light extraction layer 12 is doped with a metal material to adjust the refractive index of the light extraction layer 12, and the technical problems can be solved by the prior art, thereby improving the luminous efficiency of the light-emitting elements (10a-10d). Technical efficacy.

While the present invention has been described above in the foregoing embodiments, it is not intended to limit the invention, and the invention may be modified and modified without departing from the spirit and scope of the invention. The scope of patent protection shall be subject to the definition of the scope of the patent application attached to this specification.

10a~10d‧‧‧Lighting elements with light extraction layer

11‧‧‧Lighting layer

12‧‧‧Light extraction layer

13‧‧‧Encapsulation layer

14‧‧‧Substrate

41‧‧‧first critical angle

42‧‧‧second critical angle

Step 210‧‧‧ provides a luminescent layer for combining electrons and holes and generating multiple photons

Step 220 ‧ ‧ forming a light extraction layer on the luminescent layer, and doping a metal material on the light extraction layer to adjust a refractive index of the light extraction layer to increase the transmittance of the photons

Step 230‧ ‧ forming an encapsulation layer on the light extraction layer for protecting the light-emitting elements and allowing the photons to penetrate the package layer

Fig. 1 is a schematic cross-sectional view showing a first embodiment of a light-emitting element having a light extraction layer of the present invention.

Fig. 2 is a flow chart showing a method of manufacturing a light-emitting element having a light extraction layer of the present invention.

Fig. 3A is a schematic cross-sectional view showing a second embodiment of a light-emitting element having a light extraction layer of the present invention.

Fig. 3B is a schematic cross-sectional view showing a third embodiment of the light-emitting element having the light extraction layer of the present invention.

Fig. 3C is a schematic cross-sectional view showing a fourth embodiment of the light-emitting element having the light extraction layer of the present invention.

Fig. 4 is a schematic view showing the improvement of the luminous efficiency of the light-emitting element of the present invention.

10a. . . Light-emitting element

11. . . Luminous layer

12. . . Light extraction layer

13. . . Encapsulation layer

Claims (8)

A light-emitting element having a light extraction layer, comprising: a light-emitting layer for combining electrons and holes and generating a plurality of photons; and a light extraction layer formed on the light-emitting layer by an organic material and doped a hetero-metal material for adjusting a refractive index of the photo-extraction layer to increase the transmittance of the photons, wherein the photo-extraction layer is made of tris(8-hydroxyquinoline)aluminum (Alq3) and 4,4 One of '-[N-(1-naphthyl)-N-phenylamino]biphenyl, NPB); And an encapsulation layer formed on the photo-extraction layer for protecting the light-emitting elements and allowing the photons to penetrate the encapsulation layer. The light-emitting element having a light extraction layer according to claim 1, wherein the metal material comprises at least one of aluminum and silver, and is doped in the light extraction layer by co-evaporation. The light-emitting element with a light extraction layer according to claim 1, wherein the thickness of the light extraction layer is adjusted according to the resonance of the photons, and the light extraction layer covers the light-emitting layer or covers the light-emitting layer. Side of it. A light-emitting element having a light extraction layer as described in claim 1, wherein the refractive index is in the range of 1.5 to 2.5. A method for manufacturing a light-emitting element having a light extraction layer, comprising the steps of: providing a light-emitting layer for combining electrons and holes and generating a plurality of photons; forming a light extraction layer on the light-emitting layer with an organic material, and The light extraction layer is doped with a metal material for adjusting a refractive index of the light extraction layer to increase the transmittance of the photons. The material of the light extraction layer is three (8-hydroxyl). Alkyl quinolate) aluminum (Alq3) and 4,4'-bis[N-(1-naphthyl)-N-anilino]biphenyl (4,4'-bis[N-(1-naphthyl)-N- One of phenyl-amino]biphenyl, NPB); and an encapsulation layer formed on the light extraction layer for protecting the light-emitting elements and allowing the photons to penetrate the encapsulation layer. The method for producing a light-emitting element having a light extraction layer according to claim 5, wherein the metal material comprises at least one of aluminum and silver, and is doped in the light extraction layer by co-evaporation. The method for manufacturing a light-emitting element having a light extraction layer according to claim 5, wherein the thickness of the light extraction layer is adjusted according to resonance of the photons, and the light extraction layer covers the light-emitting layer or coating The side of the luminescent layer. A method of producing a light-emitting element having a light extraction layer according to claim 5, wherein the refractive index is in the range of 1.5 to 2.5.