1. Field
Embodiments relate to an organic light-emitting device, light equipment including the same, and an organic light-emitting display (OLED) apparatus including the same.
2. Description of the Related Art
An organic-light emitting device includes an organic light-emitting layer formed between electrodes opposite to each other. Electrons injected from one of the electrodes are combined with holes injected from the other one of the electrodes in the organic light-emitting layer. Molecules that emit light from the organic light-emitting layer are excited and return to a ground state through the combination so as to emit power as light.
The light emitted from the organic light-emitting layer of the organic-light emitting device does not have a predetermined directivity, i.e., the light is emitted in random directions having a statistically homogenous angular distribution. A ratio of the number of photons that are not consumed and actually reach an observer to the total number of photons generated in the organic light-emitting layer of the organic-light emitting device, i.e., out-coupling efficiency “ηout,” is about 1/(2ηorg2), where a reflective index of the organic light-emitting layer is “ηorg.” If a general refractive index “ηorg” of 1.75 is substituted for the reflective index “ηorg” of the organic light-emitting layer, the out-coupling efficiency “ηout” is about 16%.
The out-coupling efficiency “ηout” of the organic-light emitting device limits overall an external quantum efficiency and a power factor. The external quantum efficiency and the power factor determine a total amount of consumed power of the organic-light emitting device and thus greatly affect a lifespan of the organic-light emitting device. Accordingly, many efforts to increase an external quantum efficiency and a power factor have been made.
It is a feature of an embodiment to provide an organic light-emitting device for improving out-coupling efficiency, and light equipment including the organic light-emitting device, and an organic light-emitting display (OLED) apparatus including the organic-light emitting device.
At least one of the above and other features and advantages may be realized by providing an organic light-emitting device, including a substrate, a first electrode layer on the substrate, a patterned refractive layer on the first electrode layer, a taper angle between a patterned end of the refractive layer and a surface of the first electrode being about 20 to about 60 degrees, the refractive layer including a material having a different refractive index from that of one of the first electrode layer and an organic light-emitting layer, the organic light-emitting layer that covers the refractive layer and is on the first electrode, the organic light-emitting layer contacting the patterned end of the refractive layer, and a second electrode layer on the organic light-emitting layer.
At least one of the first and second electrode layers may be a transparent electrode.
The refractive layer may have a lower refractive index than that of one of the organic light-emitting layer and the first electrode layer
The refractive index of the refractive layer may be about 1 to about 1.55.
The refractive layer may be transparent to visible light, and may include at least one of a porous material, a fluorinated compound, an oxide, a nitride, a silicon compound, and a polymer organic material.
The taper angle may be about 30 to about 60 degrees.
The refractive layer may be regularly patterned, and may be parallel with the first and second electrode layers.
A periodic interval of the pattern of the refractive layer may be larger than a wavelength of light emitted from the organic light-emitting device.
The taper angle may be about 30 to about 60 degrees.
The refractive layer may have a higher refractive index than that of one of the organic light-emitting layer and the first electrode layer.
The refractive index of the refractive layer may be about 1.9 to about 2.8.
The refractive layer may be transparent to visible light, and may include at least one of a carbide, an oxide, a nitride, a sulfide, and a selenium compound.
The refractive layer may be regularly patterned, and may be parallel with the first and second electrode layers.
A periodic interval of the regularly patterned refractive layer may be larger than a wavelength of light emitted from the organic light-emitting device.
The taper angle may be about 30 to about 60 degrees.
The organic light-emitting device may further include a microlens array (MLA) on an outer surface of the substrate, the MLA having a refractive index of about 1.45 to about 1.8.
The MLA may have a periodic interval.
A size and a periodic interval of the MLA may be larger than a wavelength of light emitted from the organic light-emitting device.
The MLA may be transparent to visible light, and may include at least one of an oxide, a nitride, a silicon compound, and a polymer organic material.
At least one of the above and other features and advantages may also be realized by providing a light equipment including an organic-light emitting device according to an embodiment.
At least one of the above and other features and advantages may also be realized by providing an organic light-emitting display apparatus including an organic light-emitting device according to an embodiment.
The above and other features and advantages will become more apparent to those of skill in the art by describing in detail example embodiments with reference to the attached drawings, in which:
Korean Patent Application No. 10-2009-0123991, filed on Dec. 14, 2010, in the Korean Intellectual Property Office, and entitled: “Organic-Light Emitting Device, Light Equipment Including the Same, and Organic Light-Emitting Display Apparatus Including the Same,” is incorporated by reference herein in its entirety.
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.
In the example embodiment illustrated in
The substrate 110 may be, e.g., a glass substrate using SiO2 as a main component, a plastic substrate, or a substrate formed of various types of materials. The organic light-emitting device 100 of the present embodiment may be applied to a top-emission organic light-emitting device (for emitting light toward the second electrode layer 150), may be applied to a bottom-emission organic light-emitting device (for emitting light toward the substrate 110), or may be applied to a two-sided emission organic light-emitting device. In the following description, the organic-light emitting device 100 of the present embodiment is a bottom-emission organic light-emitting device which emits the light toward the substrate 110. In this case, the substrate 110 is a transparent substrate.
In the example embodiment shown in
The low refractive layer 130 may have a lower refractive index than the first electrode 120 and/or the organic light-emitting layer 140. The low refractive layer 130 may be regularly patterned on the first electrode layer 120, and may have a pattern such as a grid pattern, a check pattern, a randomly distributed pattern, or other various types of patterns.
The refractive index of the low refractive layer 130 may be lower than a refractive index of ITO (n=1.8). The refractive index of the low refractive layer 130 may be lower than a refractive index of the organic light-emitting layer 140 (n=1.7-1.8). The refractive index of the low refractive layer 130 may be about 1 to about 1.55 in the present embodiment. In an implementation, the refractive index of the low refractive layer 130 may be at least 1 and up to 1.55. The low refractive layer 130 may include a material that is transparent to visible light, e.g., one or more of a porous material, a fluorinated compound, an oxide, a nitride, a silicon compound, or a polymer organic material. In an implementation, the low refractive layer 130 may include SiO2 as the material that is transparent to visible light.
The low refractive layer 130 may have a patterned end, which may form a taper with an angle “θ” that is about 20° to about 60° with a surface of the first electrode layer 120. In an implementation, the taper angle “θ” may be about 30° to about 60°.
As shown in
In the example embodiment shown in
If the organic light-emitting layer 140 is formed of the small molecular weight organic material organic material, a hole injection layer (HIL) (not shown), a hole transport layer (HTL) (not shown), an electron transport layer (ETL) (not shown), an electron injection layer (EIL) (not shown), and the like may be stacked in a single or complex structure with the organic light-emitting layer 140, with the organic light-emitting layer 140 disposed among the HIL, the HTL, the ETL, the EIL, and the like. Copper phthalocyanine (CuPc), N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), tris-8-hydroxyquinoline aluminum (Alq3), or the like may be used as an organic material of the organic light-emitting layer 140. If the organic light-emitting layer 140 is formed of the polymer organic material, a HIL (not shown) may be further formed from the organic light-emitting layer 140 toward an anode electrode. In this case, the HIL may be formed of poly(3,4-ethylenedioxythiophene) (PEDOT), and the organic light-emitting layer 140 may be formed of a polymer organic material such as poly-phenylenevinylene (PPV), polyfluorene, and the like.
In the example embodiment shown in
Referring to
If an end of the low refractive layer 130 does not have a predetermined taper angle, i.e., if the end of the low refractive layer has a taper angle of 90°, a refractive index of the low refractive layer 130 is approximately 1 to refract light through the low refractive layer 130 one time and then emit the reflected light to the outside. If the low refractive layer 130 is formed of a low refractive material such as SiO2 using a well-known process, light is refracted from the low refractive layer 130 several times, and refraction angles of the light are summed to be emitted to the outside. This case indicates that a probability of emitting light generated from and trapped in one pixel through a next pixel to the outside becomes high. Thus, if the end of the low refractive layer has a taper angle of 90°, pixel blurring or cross-talking between pixels are not inhibited, and a path of the light guided through an ITO layer or the like becomes longer. As a result, a probability of absorbing the light is high, which does not increase out-coupling efficiency.
This will now be described in more detail with reference to
Each light emitting part “P” is distributed within a range of 201 μm×201 μm so as to correspond to the size of one pixel. Each of the low refractive layers 130 and 30 is widely distributed in a regular pattern having a size of 3 μm×3 μm within a range between 10,000 μm×1,000 μm in order to check effects on adjacent pixels. Each substrate 110 and 10 is formed to a thickness of 700 μm.
Referring to
If the low refractive layer 130 has the taper angle of 45°, a photoreceiver having a size of 1400 μm×1400 μm receives most of the power of light emitted from a pixel having a size of 201 μm×201 μm. Thus, although the size of the photoreceiver is increased, the power hardly changes. If the low refractive layer 30 has the taper angle of 90°, power of light emitting from a pixel having a size of 201 μm×201 μm is continuously increased after the size of the pixel is increased to 1400 μm×1400 μm. In other words, photons having a low probability of meeting the low refractive layer 30 having the taper angle of 90° one time and being emitted outside the substrate 10 are reflected from the substrate 10, meet the low refractive layer 30 two times, and emitted. Sometimes, a few of the photons meet the low refractive layer 30 three times and are emitted. However, photons which have met the low refractive layer 130 having the taper angle of 45° are mostly emitted when meeting the low refractive layer 130 two times.
Referring to
As described above, an organic light-emitting device including a low refractive layer having a predetermined taper angle “θ” may improve out-coupling efficiency and inhibits an increase in pixel blurring in comparison with an organic light-emitting device including a low refractive layer having a taper angle of 90°. Light equipment including the organic light-emitting device and an organic light-emitting display (OLED) apparatus including the organic-light emitting device may also improve out-coupling efficiency and inhibit an increase in pixel blurring.
In the third and fourth embodiments, respective microlens arrays 160A and 160B are shown. Referring to
The organic light-emitting device 100A, 100B may otherwise be the same as the organic light-emitting device 100, i.e., apart from further including the MLA 160A or 160B. Thus, the following description will focus on the microlens arrays of the organic light-emitting devices 100A, 100B.
The MLA 160A or 160B may be formed on an outer surface of the substrate 110. In the example embodiment shown in
Referring to
In the representations shown in
As described above, the out-coupling efficiency may be improved by using the MLA 160 alone. However, the out-coupling efficiency may be maximized when both the MLA 160 and the low refractive layer 130 patterned to have a predetermined angle are used together. The MLA 160 may emit only a portion of light trapped in the substrate 110 to the outside. Thus, if the MLA 160 and the low refractive layer 130 are used together, light trapped in the organic light-emitting layer 140 and the first electrode layer 120 may be converted into the light refracted from the low refractive layer 130 and trapped in the substrate 100. The light is finally emitted through the MLA 160 to the outside. Thus, out-coupling efficiency may be significantly improved.
The out-coupling efficiency of an organic light-emitting device including the MLA and the low refractive layer is illustrated in
Organic light-emitting devices according to embodiments of the present invention will now be described with reference to
In the example embodiment shown in
The organic light-emitting device 200 includes the high refractive layer 230 instead of the low refractive layer 130 of the organic light-emitting device 100 of the first embodiment, and characteristics relating to this difference will be described in detail below.
The organic light-emitting device 200 may be applied to a top-emission organic light emitting device (which emits light toward the second electrode layer 250), may be applied to a bottom-emission organic light emitting device (which emits light toward the substrate 210), or may be applied to a two-sided light emitting device. The organic light-emitting device 200 that will be described below is a bottom-emission organic light emitting device. In this case, the substrate 210 may be formed of, e.g., transparent glass, and the first electrode layer 220 may be a transparent electrode formed of, e.g., ITO.
The high refractive layer 230 may have a higher refractive index than the first electrode layer 220. The high refractive layer 230 may have a higher refractive index than the organic light-emitting layer 240. The high refractive layer 230 may have a higher refractive index may be regularly patterned on the first electrode 220. The high refractive layer 230 may have a grid pattern, a check pattern, a random pattern, or the like.
The refractive index of the high refractive layer 230 may be higher than a refractive index of the ITO (n=1.8) of the first electrode layer 220. The refractive index of the high refractive layer 230 may be higher than a refractive index of the organic light-emitting layer 240 (n=1.7˜1.8). The refractive index of the high refractive layer 230 may be about 1.9 to about 2.8. The high refractive layer 230 may include a material transparent to visible light, e.g., a carbide, an oxide, a nitride, a sulfide, and/or a selenium (Se) compound.
A patterned end of the high refractive layer 230 may form a taper angle “θ” of about 20° to about 60° with a surface of the first electrode layer 220.
In the example embodiment shown in
In the example embodiment shown in
The high refractive layer 230 of the organic light-emitting device 200 may be regularly patterned to have a predetermined taper angle, as in the first embodiment. Thus, out-coupling efficiency may be improved, and an increase in pixel blurring may be inhibited. An MLA (not shown in
Referring to
Therefore, an organic light-emitting device including a high refractive layer having a predetermined taper angle “θ” may improve out-coupling efficiency and inhibit an increase in pixel blurring in comparison with an organic light-emitting device including a high refractive layer having a taper angle of 90°. Also, light equipment including the organic light-emitting device and an OLED apparatus including the organic light-emitting device may also improve the out-coupling efficiency and inhibit the increase in pixel blurring.
As described above, an organic light-emitting device including a refractive layer having a predetermined taper angle “θ” according to embodiments may improve out-coupling efficiency. Light equipment including the organic light-emitting device and an OLED apparatus including the organic light-emitting device may also exhibit improved out-coupling efficiency. Further, where the organic light-emitting device and the OLED apparatus are used without an MLA, the organic light-emitting device and the OLED apparatus may improve out-coupling efficiency with an inhibition of pixel blurring.
Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
Number | Date | Country | Kind |
---|---|---|---|
10-2009-0123991 | Dec 2009 | KR | national |