Organic light emitting display device

An organic light emitting display device (OLED) including: a substrate including a plurality of pixel units; first electrodes disposed in the pixel units; first subsidiary electrodes completely covering the top surfaces of corresponding ones of the first electrodes; first electrode protection units disposed on edges of the first electrodes on which the first subsidiary electrodes are not disposed; a pixel defining layer disposed on the substrate, having holes to expose the first electrodes; a light emission layer; and a second electrode disposed on the light emission layer. The light emission layer includes organic emission layers (EMLs) disposed on the first electrodes. The light emission layer may include subsidiary hole injection layers disposed on selected ones of the first electrodes, to vary a distance between the first electrodes and portions of the second electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 2009-7384, filed on Jan. 30, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein, by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to an organic light emitting display device (OLED).

2. Description of the Related Art

An organic light emitting display device (OLED) is a self-emissive display device, in which a voltage is applied to an organic thin layer including an anode, a cathode, and an organic emission layer (EML) interposed between the anode and the cathode, so that electrons and holes recombine in the organic EML, to emit light. In comparison with a cathode ray tube (CRT) or a liquid crystal display (LCD), an OLED may be lighter, thinner, have a wider viewing angle, a faster response speed, and lower power consumption.

A full-color OLED may exhibit different luminous efficiencies in different sub-pixels, that is, according to the colors of the emission materials therein. Typically, a green (G) emission material may have a higher luminous efficiency than a red (R) emission material or a blue (B) emission material. The R emission material may also have a higher luminous efficiency than the B emission material.

Thus, various conventional methods have been used in an attempt to produce OLEDs having a high luminous efficiency and luminance, by forming organic EMLs or organic thin layers, of respective sub-pixels to different thickness, so as to vary the optical thicknesses of the sub-pixels. However, the formation of the organic EMLs or organic thin layers, of the respective sub-pixels to different thicknesses involves a complicated process involving the use of a fine metal mask, which leads to an increase in failures, such as stains or dim spots, thus reducing yields.

SUMMARY OF THE INVENTION

Aspects of the present invention provide an organic light emitting display device (OLED) having a reduced failure rate and an improved optical efficiency.

According to an aspect of the present invention, there is provided an OLED including: a substrate including: a plurality of pixel units; first electrodes disposed in each of the pixel units, on the substrate; first subsidiary electrodes completely covering the top surfaces of selected ones of the first electrodes; first electrode protection units disposed on edges of the first electrodes on which the first subsidiary electrodes are not disposed; a pixel defining layer disposed on the substrate, having holes to expose the first electrodes; a light emission layer disposed on the pixel defining layer, including organic emission layers (EMLs) disposed on each of first electrodes; and a second electrode disposed on the light emission layer. The light emission layer may also include subsidiary layers disposed on selected ones of the first electrodes, to vary a distance between the first electrodes and corresponding portions of the second electrode.

According to aspects of the present invention, the light emission layer may include at least one layer selected from the group consisting of a hole injection layer (HIL), a hole transport layer (HTL), a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL).

According to aspects of the present invention, the subsidiary HILs may be formed of the same material as the layer selected from the group.

According to aspects of the present invention, the subsidiary layers may be formed adjacent to the layer selected from the group.

According to aspects of the present invention, the first subsidiary electrodes may be formed of at least one selected from the group consisting of indium tin oxide (ITO), aluminium zinc oxide (AZO), gallium zinc oxide (GZO), and indium zinc oxide (IZO).

According to aspects of the present invention, the first subsidiary electrodes and the first electrode protection units may be formed of the same material.

According to aspects of the present invention, the first electrode protection units may be completely covered by the pixel defining layer.

According to aspects of the present invention, the pixel units comprise red (R), green (G), and blue (B) pixel units.

According to aspects of the present invention, the first subsidiary electrodes may be disposed on the first electrodes in the R pixel units, the subsidiary layers may be disposed in the G pixel units, and the first subsidiary electrodes may be thicker than the subsidiary HILs.

According to aspects of the present invention, the subsidiary layers may be disposed in the R and G pixel units, and the subsidiary layers may be thicker than the first subsidiary electrodes.

According to aspects of the present invention, the first subsidiary electrodes, which have the same thickness, may be disposed in the R and G pixel units, and the subsidiary layers may be disposed in the R pixel units.

According to aspects of the present invention, the first electrodes may be reflective electrodes, and the second electrode may be a semitransparent electrode.

According to another aspect of the present invention, there is provided an OLED including: a substrate including a plurality of pixel units; first electrodes disposed in each of the pixel units, on the substrate; first subsidiary electrodes completely covering the top surfaces of selected ones of the first electrodes, second electrodes complete covering other selected ones of the first electrodes and having a different thickness than the first subsidiary electrodes; first electrode protection units is disposed on edges of the first electrodes, on which the first and second subsidiary electrodes are not formed; a pixel defining layer disposed on the substrate, having holes to expose the first electrodes; a light emission layer including organic EMLs disposed on each of the first electrodes; and a second electrode disposed on the light emission layer.

According to aspects of the present invention, the light emission layer may include at least one layer selected from the group consisting of an HIL, an HTL, an HBL, an ETL, and an EIL.

According to aspects of the present invention, the first and second subsidiary electrodes, and the first electrode protection units may be formed of the same material.

According to aspects of the present invention, the first electrode protection units may be completely covered by the pixel defining layer.

According to aspects of the present invention, the pixel units may include R, G, and B pixel units.

According to aspects of the present invention, the first and second subsidiary electrodes may be disposed on the first electrodes of the R and G pixel units, respectively, and the first subsidiary electrodes may be thicker than the second subsidiary electrodes.

According to aspects of the present invention, the first electrodes may be reflective electrodes, and the second electrode may be a semitransparent electrode.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Herein, when a first element is referred to as being formed or disposed on a second element, the first element can be disposed directly on the second element, or one or more other elements may be disposed therebetween. When a first element is referred to as being formed or disposed directly on a second element, no other elements are disposed therebetween.

FIG. 1is a cross-sectional view of a portion of an organic light emitting display device (OLED)100, according to an exemplary embodiment of the present invention, andFIGS. 2 through 6are cross-sectional views illustrating a process of fabricating the OLED100. Referring toFIG. 1, the OLED100may include first through third pixel units (sub-pixels)120,130, and140disposed on a substrate110.

The substrate110may be a transparent glass material including SiO2as a main component. Of course, the substrate110may be formed of an opaque material, or of another material, such as plastic. A buffer layer (not shown) formed of SiO2and/or SiNXmay be disposed on the substrate110, to improve surface smoothness and prevent diffusion of impurities. In the case of an active-matrix OLED (AMOLED), a plurality of thin-film transistors (TFTs) (not shown) may be further provided on the substrate110and connected to the respective pixel units120,130, and140.

For brevity, the first, second, and third pixel units120,130, and140are described as producing red (R), green (G), and blue (B) colors, respectively, but the present invention is not limited thereto. In other words, each of the pixel units120,130, and140may produce any one of R, G, and B colors, in any order. Also, a full-color OLED may be embodied by a color combination other than the combination of R, G, and B. Furthermore, a full-color OLED may be embodied by a combination of a different number of pixel units (e.g., a combination of four pixel units) rather than the shown combination of three pixel units.

First electrodes121,131, and141may be disposed in the first, second, and third pixel units120,130, and140, respectively. The first electrodes121,131, and141may be reflective electrodes. The first electrodes121,131, and141may be formed of a reflective metal, such as silver (Ag), aluminum (Al), gold (Au), platinum (Pt), chrome (Cr), or an alloy thereof. Also, the first electrodes121,131, and141may be include two or three layers of indium tin oxide (ITO) or indium zinc oxide (IZO), on and/or under a reflective metal layer.

Referring toFIG. 2, a subsidiary electrode material120may be deposited on the first electrodes121,131, and141. The subsidiary electrode material120may be formed of at least one selected from the group consisting of ITO, aluminum zinc oxide (AZO), gallium zinc oxide (GZO), and IZO. Although not shown, a photoresist (PR) may be coated on the subsidiary electrode material120.

Referring toFIG. 3, the coated PR may be exposed and developed. A portion P1of the coated PR, covering the first electrode121of the first pixel unit120, and portions P2and P3of the coated PR, covering edges of the first electrodes131and141of the second and third pixel units130and140, remain on the subsidiary electrode material120, while the rest of the PR is removed.FIG. 3illustrates a case where positive PR is used, but the present invention is not limited thereto, as a negative PR may be used instead.

Referring toFIG. 4, the subsidiary electrode material120may be etched using the portions P1, P2, and P3as a mask. As a result, a first subsidiary electrode122may be formed on the first electrode121, and first electrode protection units132and142may be formed on edges of the first electrodes131and141, of the second and third pixel units130and140, respectively. The first electrode protection units132and142may prevent damage to the edges of the first electrodes131and141, during the etching of the PR.

Referring toFIG. 5, a pixel defining layer150may be formed. The formation of the pixel defining layer150may include coating an organic insulating layer formed of, for example, an acryl resin, on the resultant structure ofFIG. 4, to a predetermined thickness, and patterning the organic insulating layer to form emission regions. In the present exemplary embodiment, the pixel defining layer150may be patterned to expose the first subsidiary electrode122and the first electrodes131and141. The pixel defining layer150may also be patterned to cover the edges of the first electrode121and the first subsidiary electrode122, and also completely cover the first electrode protection units132and142.

Referring toFIG. 6, a hole injection layer (HIL)161, a subsidiary HIL162, and a hole transport layer (HTL)163may be formed on the resultant structure ofFIG. 5. The HIL161may be formed to cover all of the respective pixel units120,130, and140. The HIL161may be formed of a conventional material, such as copper phthalocyanine (CuPc) or 4,4′,4″-tris(N-(3-methylphenyl)-N-phenylamino)triphenylamine (MTDATA). In the present exemplary embodiment, since the first electrodes121,131, and141are used as anodes, the HIL161may be first formed as a common layer, on the first electrodes121,131, and141. However, when the first electrodes121,131, and141are used as cathodes, an electron injection layer (EIL) may be first formed, instead of the HIL161.

The subsidiary HIL162may be formed in the opening of the second pixel unit130. The subsidiary HIL162may be thinner than the first subsidiary electrode122. Thus, an optical distance L12of the second pixel unit130may be less than an optical distance L11of the first pixel unit120, and may be greater than an optical distance L13of the third pixel unit140, thereby increasing the optical efficiency of the OLED100. In the present embodiment, since a fine metal mask is used only once, during the formation of the subsidiary HIL162, a failure rate, resulting from stains and dim spots associated with mask use, is reduced. The subsidiary HIL162may be formed of the same material as the HIL161.

The HTL163may be formed to cover both the HIL161and the subsidiary HIL162. The HTL163may be formed of a material, such as N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) or poly(3,4-ethylenedioxythiophene) (PEDOT). The subsidiary HIL162may be formed of the same material as the HTL163.

Referring toFIG. 1, organic emission layers (EMLs)123,133, and143, capable of producing R, B, and G colors, respectively, may be respectively formed on the HTL163, in the pixel units120,130, and140. The (red) organic EML123may include carbazole biphenyl (CBP) or mCP, as a host, and may include, as a dopant, at least one phosphorescent material selected from the group consisting of bis(1-phenylisoquinoline)acetylacetonate iridium (PIQIr(acac)), bis(1-phenylquinoline)acetylacetonate iridium (PQIr(acac), tris(1-phenylquinoline) iridium (PQIr), and octaethylporphyrin platinum (PtPEP). Alternatively, the red organic EML123may be formed of a fluorescent material, such as PED:Eu(DBM)3(Phen) or perylene.

The (green) organic EML133may include CBP or mCP as a host and may include a phosphorescent material such as fac tris(2-phenylpyridine) iridium (Ir(ppy)3) as a dopant. Alternatively, the organic EML133may include a fluorescent material, such as tris(8-hydroxyquinoline) aluminum (Alq3).

The (blue) organic EML143may include a fluorescent material selected from the group consisting of DPVBi, spiro-DPVBi, spiro-6P, distilled benzene (DSB), distyryl arylene (DSA), PFO polymers, and PPV polymers. The organic EML143may be formed of a fluorescent material, so as to prevent its optical characteristics from becoming unstable, which may occur when it is formed of a phosphorescent material.

The organic EMLs123,133, and143may be formed using a conventional process, such as laser induced thermal imaging (LITI), inkjet printing, or vacuum evaporation. Although not shown, a hole blocking layer (HBL) may be formed of a conventional material, on the organic EMLs123,133, and143. For example, the HBL may be formed of bis(2-methy-8-quinolinato)-4-phenylphenolate aluminum (BAlq).

Referring toFIG. 1, an electron transport layer (ETL)165and an electron injection layer (EIL)167may be formed on the organic EMLs123,133, and143. The ETL165may include a polycyclic hydrocarbon derivative, a heterocyclic compound, or tris(8-hydroxyquinolinato) aluminum (Alq3). The EIL167may be formed of LiF, Liq, NaF, or Naq. Collectively, the organic EMLs123,133, and143; the HIL161, the HTL163, the ETL165, the EIL167, and the subsidiary HIL162may be referred to as a light emission layer160, however the present invention is not limited thereto. In particular, various layers may be added to, or omitted from, the light emission layer160.

A second electrode170(common electrode) may be formed on the light emission layer160. The second electrode170may be formed of a semitransparent metal, which may be an alloy of magnesium (Mg) and silver (Ag), or one selected from the group consisting of Ag, aluminum (Al), gold (Au), platinum(Pt), chrome (Cr), and an alloy thereof. When formed of a semitransparent metal, the second electrode170may be formed to a thickness sufficient to obtain a reflection rate of about 5%, or higher, and a transmission rate of about 50%.

In an OLED according to the present exemplary embodiment, a subsidiary electrode with a predetermined thickness is formed on a first electrode, in a first pixel unit, and a subsidiary thin layer with a smaller thickness is formed in a second pixel unit, so that an optical distance of the second pixel unit can be less than that of the first pixel unit, and greater than that of a third pixel unit, thereby optimizing the optical efficiency of the OLED100. Also, a protection unit is formed on an edge of first electrodes formed in each of the second and third pixel units, to prevent damage thereto. Furthermore, since a subsidiary thin layer is formed only once, a fine metal mask for controlling the optical distance is used only once, thereby reducing failure rates.

FIG. 7is a cross-sectional view of an OLED200, according to another exemplary embodiment of the present invention. Hereinafter, only the differences between the OLED100and the OLED200will be described in detail. Referring toFIG. 7, the OLED200may include first through third pixel units (sub-pixels)220,230, and240disposed on a substrate210. Like in the previous embodiment, the first pixel unit220may produce an R color, the second pixel unit230may produce a G color, and the third pixel unit240may produce a B color.

First electrodes (reflective electrodes)221,231, and241may be formed in the pixel units220,230, and240, respectively. A first subsidiary electrode232may be formed on the first electrode231, while first electrode protection units222and242may be formed on edges of the first electrodes221and241, respectively.

A pixel defining layer250may be patterned to expose the first subsidiary electrode222and the first electrodes221and241. The pixel defining layer250may be patterned to cover edges of the first electrode231and the first subsidiary electrode232, and also completely cover the first electrode protection units222and242.

An HIL261and an HTL263may be formed on the pixel defining layer250, the first electrodes221and241, and the first subsidiary electrode232. A subsidiary HIL262may be formed to a predetermined thickness, in the first pixel unit220. The subsidiary HIL262may be thicker than the first subsidiary electrode232. The subsidiary HIL262may be formed of the same material as the HIL261. The HTL263may be formed to cover both the HIL261and the subsidiary HIL262.

Organic EMLs223,233, and243, capable of producing R, G, and B colors, may be formed on the HTL263, in the pixel units220,230, and240, respectively. An ETL265and an EIL267may be sequentially formed on the organic EMLs223,233, and243. A second electrode270may be formed on the EIL267, as a common electrode. The second electrode270may be formed of a semitransparent metal. Collectively, the organic EMLs223,233, and243; the HIL261, the HTL263, the ETL265, the EIL267, and the subsidiary HIL262may be referred to as a light emission layer260, however the present invention is not limited thereto. In particular, various layers may be added to, or omitted from, the light emission layer260.

As a result, an optical distance L22of the second pixel unit230may be less than an optical distance L21of the first pixel unit220, and may be greater than an optical distance L23of the third pixel unit240, thereby increasing the optical efficiency of the OLED200. Also, in the present exemplary embodiment, since a fine metal mask is used only once, to form the subsidiary HIL262, a failure rate, due to stains and dim spots, is reduced. In addition, the first electrode protection units222and242, formed on the edges of the first electrodes221and241, may prevent damage to the edges of the first electrodes221and241, during the etching of a PR.

FIG. 8is a cross-sectional view of an OLED300, according to yet another exemplary embodiment of the present invention. Hereinafter differences between the OLED100and the OLED300will be described in detail. Referring toFIG. 8, the OLED300may include first through third pixel units (sub-pixels)320,330, and340disposed on a substrate310. Like in the previous exemplary embodiments, the first pixel unit320may produce an R color, the second pixel unit330may produce a G color, and the third pixel unit340may produce a B color.

First electrodes321,331, and341(reflective electrodes) may be formed in the pixel units320,330, and340, respectively. First subsidiary electrodes322and332may be formed on the first electrodes321and331, respectively, while a first electrode protection unit342may be formed on edges of the first electrode341. The first subsidiary electrode322may be as thick as the first subsidiary electrode332.

A pixel defining layer350may be patterned to expose the first subsidiary electrodes322and332, and the first electrode341. The pixel defining layer350may be patterned to cover edges of the first subsidiary electrodes322and332, and also completely cover the first electrode protection unit342.

An HIL361and an HTL363may be formed on the pixel defining layer350, the first electrode341, and the first subsidiary electrode322and332. The HIL361and the HTL363may be formed to cover all of the respective pixel units320,330, and340.

A subsidiary HIL362may be formed to a predetermined thickness, in an opening of the first pixel unit320. The subsidiary HIL362may be formed of the same material as the HIL361.

The HTL363may be formed to cover both the HIL361and the subsidiary HIL362. Organic EMLs323,333, and343, capable of respectively forming R, G, and B colors, may be formed on the HTL363, in the pixel units320,330, and340, respectively.

An ETL365and an EIL367may be sequentially formed on the organic EMLs323,333, and343. A second electrode370(common electrode) may be formed on the EIL367. The second electrode370may be formed of a semitransparent metal. Collectively, the organic EMLs323,333, and343; the HIL361, the HTL363, the ETL365, the EIL367, and the subsidiary HIL362may be referred to as a light emission layer360, however the present invention is not limited thereto. In particular, various layers may be added to, or omitted from, the light emission layer360.

An optical distance L32of the second pixel unit330may be less than an optical distance L31of the first pixel unit320, and may be greater than an optical distance L33of the third pixel unit340, thereby increasing the optical efficiency of the OLED300. Also, since a fine metal mask is used only once, to form the subsidiary HIL362, a failure rate, due to stains and dim spots, is reduced. In addition, the first electrode protection unit342may prevent damage to the edges of the first electrode341, during the etching of a PR.

FIG. 9is a cross-sectional view of an OLED400, according to still another exemplary embodiment of the present invention. Hereinafter differences between the OLED100and the OLED400will be described in detail. Referring toFIG. 9, the OLED400may include first through third pixel units420,430, and440disposed on a substrate410. Like in the previous exemplary embodiments, the first pixel unit320may produce an R color, the second pixel unit330may produce a G color, and the third pixel unit340may produce a B color.

First electrodes421,431, and441(reflective electrodes) may be formed in the pixel units420,430, and440, respectively. First and second subsidiary electrodes422and432may be formed on the first electrodes421and431, respectively, while a first electrode protection unit442may be formed on edges of the first electrode441. The first subsidiary electrode422may be thicker than the second subsidiary electrode432.

A pixel defining layer450may be patterned to expose the first and second subsidiary electrodes422and432, and the first electrode441. Also, the pixel defining layer450may be patterned to cover edges of the first electrodes421and431, and the first and second subsidiary electrodes422and432, and also completely cover the first electrode protection unit442.

An HIL461and an HTL463may be formed on the pixel defining layer450, the first electrode441, and the first subsidiary and second electrodes422and432. The HIL461and the HTL463may be formed to cover all of the pixel units420,430, and440. The HTL463may be formed on the HIL461.

Organic EMLs423,433, and443, capable of producing R, G, and B colors, may be formed on the HTL463, in the pixel units420,430, and440, respectively. An ETL465and an EIL467may be sequentially formed as common layers, on the organic EMLs423,433, and443. A second electrode470(common electrode) may be formed on the EIL467. The second electrode470may be formed of a semitransparent metal.

Collectively, the organic EMLs423,433, and443; the HIL461, the HTL463, the ETL465, and the EIL467, may be referred to as a light emission layer460, however the present invention is not limited thereto. In particular, various layers may be added to, or omitted from, the light emission layer460. The light emission layer460is different from the previous embodiments, in that it does not include a subsidiary HIL. As a result, an optical distance L42of the second pixel unit430may be less than an optical distance L41of the first pixel unit420, and may be greater than an optical distance L43of the third pixel unit440, thereby increasing the optical efficiency of the OLED400. Also, a fine metal mask for forming a subsidiary thin layer is not used, thereby reducing a failure rate due to stains and dim spots. In addition, the first electrode protection unit442may prevent damage to the edges of the first electrode441, during the etching of a PR.

In the above-described exemplary embodiments and drawings, a subsidiary HIL is formed of the same material as an HIL, adjacent to the HIL, and is used as a subsidiary thin layer, but the present invention is not limited thereto. A layer formed of the same material as any one thin layer selected out of an HTL, an HBL, an ETL, and an EIL, adjacent to the selected thin layer, may replace the subsidiary HIL, irrespective of its name. Also, although not shown in the drawings, the above-described OLEDs may further include a sealing member bonded to the substrates.

According to an OLED of the present invention, an optical distance of each pixel unit is optimized to increase optical efficiency, and a protection unit is formed on edges of a first electrode, to protect etching damage to the edges of the first electrode. Also, the use of a fine metal mask is reduced, thereby decreasing failure rates.