Organic light emitting diode display

An organic light emitting diode (OLED) display is provided. An OLED display in accordance with an exemplary embodiment may include a substrate including a first subpixel, a second subpixel, and a third subpixel, a first electrode disposed on each of the first subpixel, the second subpixel, and the third subpixel, a second electrode facing the first electrode, a first common layer disposed on the first subpixel and the second subpixel, a first emission layer and a second emission layer disposed on the first common layer, a second common layer disposed on the third subpixel, and a third emission layer disposed on the second common layer. The first common layer may include a first doping layer and a second doping layer disposed on the first doping layer. Each of the doping layers may including a p-type dopant, and the second common layer may be formed as a single layer.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2013-0096834 filed on Aug. 14, 2013, in the Korean Intellectual Property Office, and entitled: “ORGANIC LIGHT EMITTING DIODE DISPLAY,” is incorporated by reference herein in its entirety.

BACKGROUND

Embodiments relate to an organic light emitting device.

2. Description of the Related Art

Recent trends toward lightweight and thin personal computers and televisions sets also require lightweight and thin display devices, and flat panel displays satisfying such requirements are being substituted for conventional cathode ray tubes (CRTs). However, since the LCD is a passive display device, an additional back-light as a light source is needed, and the LCD has various problems such as a slow response time and a narrow viewing angle. In this connection, an organic light emitting diode (OLED) display has recently been spotlighted as a display device that has merits such as a wide viewing angle, outstanding contrast, and a fast response time. In the organic light emitting diode device, electrons injected from one electrode and holes injected from another electrode are combined with each other in an emission layer, thereby generating excitons, and energy is outputted from the excitons to thereby emit light. The above information disclosed in this Background section is only for enhancement of understanding of the background and therefore it may include information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY

An organic light emitting diode (OLED) display may include a substrate including a first subpixel, a second subpixel, and a third subpixel, a first electrode on each of the first subpixel, the second subpixel, and the third subpixel. A second electrode may face the first electrode, and a first common layer may be disposed on the first subpixel and the second subpixel. A first emission layer and a second emission layer may be disposed on the first common layer, and a second common layer may be disposed on the third subpixel. A third emission layer may be disposed on the second common layer. The first common layer may include a first doping layer and a second doping layer on the first doping layer, each of the doping layers may include a p-type dopant, and the second common layer may be formed as a single layer.

The second common layer may include a p-type dopant. Each of the first common layer and the second common layer may include a hole injection material and a hole transport material.

The first emission layer may be a red emission layer, the second emission layer may be a green emission layer, and the third emission layer may be a blue emission layer.

The first electrode may include at least one of silver (Ag) and indium-tin oxide (ITO), and the second electrode may include at least one of silver (Ag), a silver alloy, aluminum (Al), an aluminum alloy, magnesium (Mg), and a magnesium alloy.

Exemplary embodiments may include a first auxiliary layer between the first common layer and the first emission layer; and a second auxiliary layer between the first common layer and the second emission layer.

The first doping layer and the second doping layer may include the same components.

DETAILED DESCRIPTION

FIG. 1is a cross-sectional view showing an organic light emitting diode (OLED) display in accordance with an exemplary embodiment.

Referring toFIG. 1, the OLED display of an exemplary embodiment includes a red pixel area R, a green pixel area G, and a blue pixel area B. A first electrode191may be disposed on a substrate110in the red pixel area R, the green pixel area G, and the blue pixel area B.

The substrate110may be a typical substrate used in OLED displays, e.g., a glass substrate or a transparent plastic substrate, with excellent mechanical strength, thermal stability, transparency, surface smoothness, and water-resistance.

The first electrode191may be an anode, may be formed of silver (Ag) or a transparent conductive oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZNO), and aluminum-doped zinc oxide (AZO), and may be formed of a plurality of layers including the aforementioned materials instead of a single layer.

First common layers131aand131bare disposed on the first electrode191in the red pixel area R and the green pixel area G, and a second common layer132is disposed on the first electrode191in the blue pixel area B. Each of the first common layers131aand131band the second common layer132may include both a hole injection material and a hole transport material to serve as a functional layer simultaneously having a hole injection function and a hole transport function. The first common layers131aand131band the second common layer132may be formed by co-deposition of the hole injection material and the hole transport material or by allowing the hole injection material and the hole transport material to form a concentration gradient.

The first common layers131aand131binclude a first doping layer131adisposed at a lower side, and a second doping layer131bdisposed on the first doping layer131a. Each of the first doping layer131aand the second doping layer131bmay include a p-type dopant and have a structure in which two layers are stacked. The first doping layer and the second doping layer may include the same components. Each of the first doping layer131aand the second doping layer131bmay serve as an electrode by increasing mobility of holes so that a distance between the electrodes is shortened, thereby increasing the possibility of a short circuit between the first electrode191and a second electrode270caused by particles to be described later.

Accordingly, in an exemplary embodiment, the second common layer132may include the p-type dopant similar to the first common layers131aand131b, but may have a single-layer structure unlike the first common layers131aand131b. Alternatively, the second common layer132may include only the hole transport material and the hole injection material without including the p-type dopant. In a case of the blue pixel area B, the distance between the second common layer132and the second electrode270may be substantially increased. Accordingly, it may be possible to reduce the likelihood of a short circuit being generated between the first electrode191and the second electrode270. As a result, the distance between the electrodes may be smaller, and thus the incidence of dark points caused by particles may be reduced.

A red emission layer135amay be formed in the red pixel area R, and a green emission layer135bmay be formed in the green pixel area G. An auxiliary layer133may be provided between the second doping layer131band the red emission layer135aand between the second doping layer131band the green emission layer135b. The auxiliary layer133may serve to adjust an optical resonance distance for a color of each pixel area. The auxiliary layer133may include a well-known hole injection material or hole transport material, or a material simultaneously having a hole injection function and a hole transport function. The auxiliary layer133may include, e.g., a carbazole derivative such as N-phenylcarbazole, polyvinylcarbazole, N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD), or the like, but is not limited thereto.

In the blue pixel area B, no additional auxiliary layer may be formed between the second common layer132and a blue emission layer135c.

The blue emission layer135cmay include a blue light emitting material or a mixture of a blue host and a blue dopant. The blue host may include Alq3, CBP (4,4′-N,N′-dicarbazole-biphenyl), or PVK (poly(n-vinylcarbazole)), but is not limited thereto.

The blue host material may have a hole transport characteristic. For example, a material such as ADN, which is shown below, may be employed as the blue host material.

An example of a blue dopant may include F2Irpic, (F2ppy)2Ir(tmd), terfluorene, or the like, but is not limited thereto.

The red emission layer135amay include a red light emitting material or a mixture of a red host and a red dopant. The red host may include Alq3, CBP (4,4′-N,N′-dicarbazole-biphenyl), or PVK (poly(n-vinylcarbazole)), like the blue host. A material having an electron transport characteristic may be employed as the red host.

An example of a red dopant may include PtOEP, Ir(piq)3, Btp2Ir(acac), or the like, but is not limited thereto.

The green emission layer135bmay include a green light emitting material or a mixture of a green host and a green dopant. The green host may include Alq3, CBP (4,4′-N,N′-dicarbazole-biphenyl), or PVK (poly(n-vinylcarbazole)), like the blue host. A material having an electron transport characteristic may be employed as the green host. An electron transport layer (ETL) to be described later may be omitted in a case where the material having an electron transport characteristic is the green host of the green emission layer135band the red host of the red emission layer135a.

As a green dopant, Ir(ppy)3, Ir(ppy)2(acac), Ir(mpyp)3, or the like may be employed, but is not limited thereto.

An ETL140may be provided on the emission layers135a,135b, and135c. As the ETL140, a well-known electron transport material may be employed. An example of the electron transport material may include Bphen (4,7-diphenyl-1,10-phenanthroline) or BAlq (bis(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminum).

An electron injection layer (EIL)150may be disposed on the ETL140. The EIL150may be formed of, e.g., LiQ, LiF, Li2O, NaCl, NaF, KF, RbF, CsF, or BaO, but is not limited thereto.

The second electrode270may be disposed on the EIL150. The second electrode270may be a cathode, and may include at least one of silver (Ag), a silver alloy, aluminum (Al), an aluminum alloy, magnesium (Mg), and a magnesium alloy.

A capping layer290may be disposed on the second electrode270, and the capping layer290may serve to protect the OLED display against external moisture or impurities.

By way of summation and review, embodiments provide an organic light emitting diode (OLED) display having an advantage of being capable of reducing incidence of dark points.

In accordance with exemplary embodiments, a high-efficiency OLED display may be provided that is capable of reducing incidence of dark points by forming an HITL layer (a functional layer simultaneously serving to perform a hole injection function and a hole transport function) as a single layer in a blue subpixel unlike other subpixels.

DESCRIPTION OF SYMBOLS