Organic light emitter indicator device

Abstract

Organic light emitter indicator device comprising: a first electrode (102) and a second electrode (104) facing each other on a substrate (101); at least one emission layer (126) formed between the first (102) and the second electrode (104); at least one hole transport layer (124b) formed between the first electrode (102) and the emission layer (126); and an electron transport layer (128) formed between the second electrode (104) and the emission layer (126), the emission layer contains (126): a first emission mixed layer (126a) formed on the hole transport layer (124b), wherein the first emission mixed layer (126a) contains a first hole-type host (host_h, host_h1) and a first phosphorescent dopant; and a second emission mixing layer (126b) which is formed on the first emission mixing layer (126a) such that an interface is present between the second emission mixing layer (126b) and the first emission mixing layer (126a), is arranged between the first emission mixing layer (126a) and the electron transport layer (128) and is in contact with the electron transport layer (128), wherein the second emission mixing layer (126b) contains a first electron-type host (host_e, host_e1) and a second phosphorescent dopant, and the first emission mixed layer (126a) further contains a second hole-type host (host_h2), and / or the second emission mixing layer (126b) further contains a second electron-type host (host_e2).

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to an organic light emitting display device which can prevent the deterioration of luminous efficiency and lifetime. Discussion of the state of the art

[0002] The recent transition to an information-oriented society has caused rapid development in the field of displays to visually represent electrical information signals, and accordingly, various flat panel display devices have been developed that have excellent characteristics such as being both thin and lightweight and requiring low power consumption.

[0003] Representative examples of these flat panel display devices may include liquid crystal display devices (LCD devices), plasma display device (PDP device), field emission display device (FED device), and organic light emitting diode (OLED) display devices.

[0004] In particular, organic light emitting display devices are self-luminous devices, and they have faster response speed, higher luminous efficiency, higher brightness, and wider viewing angle than other flat panel display devices.

[0005] Typically, such an organic light emitting display device includes an anode and a cathode arranged to face each other with a light emitting layer interposed therebetween, so that an electron-hole pair, i.e., an exciton, is generated within the emitting layer via recombination of a hole injected from the anode and an electron injected from the cathode, and light is again emitted by the transition of the exciton to the equilibrium state.However, in the typical OLED device, the exciton generated in the emission layer propagates through the emission layer to the interfaces with an electron transport layer and a hole transport layer adjacent to the emission layer, which reduces the luminous efficiency and causes rapid deterioration of the electron transport layer and the hole transport layer adjacent to the emission layer, resulting in a reduction in lifetime.

[0006] Organic light emitting display devices are disclosed, for example, in the documents CN 102 694 131 A, DE 10 2010 020 044 A1, DE 10 2008 054 234 A1, DE 10 2007 053 396 A1 and DE 10 2011 054 644 A1. SUMMARY OF THE INVENTION

[0007] Accordingly, the present invention is directed to an organic light emitting display device that substantially obviates one or more problems due to the limitations and disadvantages of the related art.

[0008] It is an object of the present invention to provide an organic light emitting display device which can prevent the deterioration of luminous efficiency and lifetime.

[0009] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and in part will become apparent to those of ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof, as well as the appended drawings.

[0010] To achieve these objects and other advantages, and in accordance with the purpose of the disclosure as embodied and broadly described herein, an organic light emitting display device includes first and second electrodes arranged on a substrate to face each other, at least one emission layer formed between the first and second electrodes, a hole transport layer formed between the first electrode and the emission layer, and an electron transport layer formed between the second electrode and the emission layer, wherein the emission layer includes a first emission mixture layer formed on the hole transport layer, wherein the first emission mixture layer comprises a first hole-type host and a first phosphorescent dopant,and a second emission mixture layer formed between the first emission mixture layer and the electron transport layer, wherein the second emission mixture layer contains a first electron-type host and a second phosphorescent dopant material.

[0011] Furthermore, at least one of the following conditions (i) and (ii) is satisfied in the organic light emitting display device according to the present invention: (i) The first mixed emission layer further includes a second hole-type host. (ii) The second mixed emission layer further includes a second electron-type host.

[0012] A difference between the level of the lowest unoccupied orbital of a molecule (LUMO) of both the first and second electron-type hosts and the LUMO level of the electron-transport layer may be ±0.5 eV or less, and a difference between the level of the highest occupied orbital of a molecule (HOMO) of both the first and second hole-type hosts and the HOMO level of the hole-transport layer may be ±0.5 eV or less.

[0013] The first and second hole-type hosts can achieve a hole mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 have.

[0014] The first and second electron-type hosts can have an electron mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 have.

[0015] The organic light emitting display device may include two emission layers, and may further include an N-type charge generation layer and a P-type charge generation layer sequentially stacked between the emission layers.

[0016] The first and second phosphorescent dopant materials may be formed from the same material or from different materials.

[0017] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate one embodiment(s) of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: Fig. 1 is a sectional view showing an organic light emitting display device according to a first reference embodiment; Fig. 2 a band diagram of the Fig. 1 shown organic light emitting display device; Fig. 3A to 3C are explanatory views of the electro-optical characteristics of an organic light emitting display device of the prior art and the organic light emitting display device according to the first reference embodiment; Fig.4 is a sectional view showing an organic light emitting display device according to a first embodiment of the present invention; Fig. 5A to 5C are explanatory views of the electro-optical characteristics of a prior art organic light emitting display device and the organic light emitting display device according to the first embodiment of the present invention; Fig. 6 is a sectional view showing an organic light emitting display device according to a second reference embodiment; Fig. 7 is a sectional view showing an alternative configuration of the Fig. 6 shows the organic light emitting display device; Fig. 8 is a sectional view showing an organic light emitting display device according to a second embodiment of the present invention; Fig.9 is a sectional view showing an organic light emitting display device according to a third embodiment of the present invention; Fig. 10 is a sectional view showing an organic light emitting display device including three light emitting units; and Fig. 11 is a sectional view showing an organic light emitting display device including color filters according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] Fig. 1 is a sectional view showing an organic light emitting display device according to a first reference embodiment.

[0021] The organic light emitting display device used in Fig.1, includes first and second electrodes 102 and 104 arranged to face each other, first and second light emitting units 110 and 120 formed between the first and second electrodes 102 and 104, and a charge generation layer 130 located between the first and second light emitting units 110 and 120.

[0022] At least one of the first and second electrodes 102 and 104 takes the form of a transparent electrode. If the first electrode 102 is a transparent electrode and the second electrode 104 is an opaque electrode, a bottom emission configuration is achieved to emit light downwards. If the second electrode 104 is a transparent electrode and the first electrode 102 is an opaque electrode, a top emission configuration is achieved to emit light upwards. If both the first and second electrodes 102 and 104 are transparent electrodes, a double-sided emission configuration is achieved to emit light upwards and downwards.

[0023] The transparent electrode may include, for example, an indium tin oxide (ITO) or an indium zinc oxide (IZO) electrode. The opaque electrode may be formed of a reflective metal material such as aluminum (Al), gold (Au), molybdenum (Mo), chromium (Cr), copper (Cu), lithium fluoride (LiF), or the like, or may take the form of a bilayer using the same.

[0024] A configuration in which the first electrode 102 is an anode in the form of a transparent electrode and the second electrode 104 is a cathode in the form of an opaque electrode will be described below by way of example.

[0025] The first light-emitting unit 110 is formed between the first electrode 102 and an N-type charge generation layer (N-CGL) 132. The first light-emitting unit 110 includes a hole-injection layer (HIL) 112, at least a first hole-transport layer (HTL) 114, a first emission layer (EML) 116, and a first electron-transport layer (ETL) 118, which are sequentially formed on the first electrode 102. The first hole-transport layer 114 supplies a hole from the first electrode 102 to the first emission layer 116, and the first electron-transport layer 118 supplies an electron from the N-type charge generation layer 132 to the first emission layer 116. The first emission layer 116 generates light via the recombination of the hole supplied through the first hole transport layer 114 and the electron supplied through the first electron transport layer 118.

[0026] The second light-emitting unit 120 is formed between the second electrode 104 and a P-type charge generation layer (P-CGL) 134. The second light-emitting unit 120 includes a second hole-transport layer (HTL) 124a, a third hole-transport layer (HTL) 124b, a second emission layer (EML) 126, and a second electron-transport layer (ETL) 128 sequentially formed on the P-type charge generation layer 134. The second and third hole-transport layers 124a and 124b supply a hole from the P-type charge generation layer 134 to the second emission layer 126, while the second electron-transport layer 128 supplies an electron from the second electrode 104 to the second emission layer 126. The second emission layer 126 generates light through the recombination of the hole supplied through the second and third hole transport layers 124a and 124b and the electron supplied through the second electron transport layer 128.

[0027] The charge generation layer 130 includes the N-type charge generation layer 132 and the P-type charge generation layer 134 stacked on top of each other.

[0028] The N-type charge generation layer 132 is located closer to the first electrode 102 than the P-type charge generation layer 134. The N-type charge generation layer 132 serves to attract an electron as an n-type charge carrier separated from an interface between the P-type charge generation layer 134 and the second hole-transport layer 124a. The N-type charge generation layer 132 is formed by doping an organic material with alkali metal particles.

[0029] The P-type charge generation layer 134 is located closer to the second electrode 104 than the N-type charge generation layer 132. The generation and separation of an electron as an n-type charge carrier and a hole as a p-type charge carrier are achieved at an interface between the P-type charge generation layer 134 and the second hole transport layer 124a.

[0030] The separated electron moves through the N-type charge generation layer 132 to the first light-emitting unit 110 and binds with the hole that has moved from the first electrode 102 into the first emission layer 116 of the first light-emitting unit 110 to generate an exciton. Thus, visible light emission is achieved by discharging the energy from the exciton.

[0031] The separated hole moves to the second light-emitting unit 120 and binds with the electron that has moved from the second electrode 104 into the second emission layer 126 to generate an exciton. This achieves visible light emission by discharging the energy from the exciton.

[0032] Here, the first emission layer 116 may be an emission layer containing a blue fluorescent dopant and a host for emitting blue light, while the second emission layer 126 may be an emission layer containing a red-green phosphorescent dopant and a host for emitting orange light, resulting in the emission of white light. Various other fluorescent and phosphorescent dopant materials may be used to achieve the emission of white light.

[0033] In particular, the second emission layer 126 containing the phosphorescent dopant includes first and second emission mixture layers (ML1 and M2) 126a and 126b.

[0034] The first mixed emission layer 126a is formed on the third hole-transport layer 124b so as to contact the third hole-transport layer 124b. The first mixed emission layer 126a is formed by mixing a hole-type host (host_h) that is excellent in transporting a hole into the second emission layer 126 and a phosphorescent dopant. The phosphorescent dopant is a phosphorescent yellow-green dopant formed of, for example, tris(2-phenylpyridine)iridium. The phosphorescent dopant occupies approximately 5 to 15% of the first mixed emission layer 126a. A difference between the HOMO level of the hole-type host (host_h) and the HOMO level of the third hole-transport layer 124b is ±0.5 eV or less. The hole-type host host_ h is made of a material that has a hole mobility of 1.0 × 10 -6 Vs / cm 2up to 5.0 × 10 -3 Vs / cm 2 For this purpose, the hole-type host host_h is formed from a material that is different from or identical to that of the third hole-transport layer 124b. The hole-type host host_h is formed, for example, from TCTA (4,4',4"-tris(N-carbazolyl)triphenylamine) or CBP (4,4'-bis(carbazol-9-yl)biphenyl).

[0035] The second emission mixture layer 126b is formed on the first emission mixture layer 126a to contact the second electron-transport layer 128. The second emission mixture layer 126b is formed by mixing an electron-type host (host_e) that excels in electron transport into the second emission layer 126 and a phosphorescent dopant. The phosphorescent dopant is a yellow-green phosphorescent dopant of the same type as in the first emission mixture layer 126a and occupies approximately 5 to 15% of the second emission mixture layer 126b. A difference between the lowest unoccupied orbital level of a molecule (LUMO) of the electron-type host (host_e) and the LUMO level of the second electron-transport layer 128 is ±0.5 eV or less.The electron-type host host_e is made of a material that has an electron mobility of 1.0 × 10. -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 For this purpose, the electron-type host host_e is formed from a material that is different from or identical to that of the second electron-transport layer 128. The electron-type host host_e is formed, for example, from UGH3 (m-bis(triphenylsilyl)benzene) or TAZ (3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole).

[0036] As such, the organic light-emitting display device according to the first reference embodiment ensures easy hole and electron injection into the first and second mixed emission layers 126a and 126b via the electron-type host host_e and the hole-type host host_h, achieving a reduction in voltage compared to the prior art. Furthermore, in the organic light-emitting display device according to the first reference embodiment, the hole and electron injected through the hole-transport layer and the electron-transport layer move to an interface between the first and second mixed emission layers 126a and 126b, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent deterioration of the luminous efficiency.Furthermore, limiting the hole-electron recombination area to the emission layer 126 can increase lifetime and stability. Furthermore, reducing the content of the phosphorescent dopant material can reduce the price.

[0037] Table 1 represents the electro-optical characteristics of a prior art organic light emitting display device and the white organic light emitting display device according to the first reference embodiment. Table 1 Condition T95 (50 mA / cm 2 ) 10 mA / cm 2 Volts (V) CD / A Efficiency ratio State of the art 137 hours 3,6 76,5 0,73 first reference embodiment 182 hours 3,2 79,4 0,77

[0038] In Table 1, a prior art configuration includes a single emission layer in which two hosts and a dopant are mixed together, where T95 represents the time required for the lifetime of a white organic light emitting display device to reach approximately 95%. As shown in Table 1 and in Fig.3A, the white organic light emitting display device of the prior art (curve A) requires 137 hours until its lifetime reaches 95%, whereas the white organic light emitting display device according to the first reference embodiment (curve B) requires 182 hours until its lifetime reaches 95%. In addition, as shown in Fig. 3B, it is recognized that the organic light emitting display device according to the first reference embodiment (curve B) has a higher current density than that of the prior art (curve A) as a function of voltage and consequently a current density lower by about 0.4 V per 10 mA / cm 2lower voltage is required to achieve the same current density as that of the prior art. In particular, as shown in Table 1, it is recognized that the drive voltage in the first reference embodiment is lower than that of the prior art. In addition, as shown in Fig. 3C, it is recognized that the organic light emitting display device according to the first reference embodiment (curve B) has a higher brightness and consequently a lower deterioration in efficiency than that of the prior art (curve A). Accordingly, it is recognized that the efficiency ratio at 50 mA / cm 2 on efficiency at 10 mA / cm 2 in the first reference embodiment is higher than in the prior art, thus achieving a reduced drop in efficiency as a function of an increase in brightness.

[0039] As described above, it is recognized that the organic light emitting display device according to the first reference embodiment is superior to the prior art organic light emitting display device in terms of lifetime, driving voltage (V) and luminance (cd / A), as shown in Table 1 and the Fig. 3A to 3C is shown as an example.

[0040] Although it has been described by way of example that the organic light emitting display device according to the first reference embodiment has a tandem configuration using a plurality of light emitting units, the organic light emitting display device can be applied to a configuration using a single light emitting unit.

[0041] Fig. 4 is a sectional view showing an organic light emitting display device according to a first embodiment of the present invention.

[0042] The organic light emitting display device used in Fig. 4, contains the same components as those of the organic light emitting display device shown in Fig. 1 is shown by way of example, except for the second emission layer 126. Consequently, a detailed description of the same components will be omitted below.

[0043] The second emission layer 126 includes the first and second emission mixing layers (ML1 and ML2) 126a and 126b.

[0044] The first mixed emission layer 126a is formed on the third hole-transport layer 124b to contact the third hole-transport layer 124b. The first mixed emission layer 126a is formed by mixing first and second hole-type hosts (host_h1 and host_h2) and a first phosphorescent dopant. The first phosphorescent dopant is a phosphorescent yellow-green dopant and is formed, for example, from tris(2-phenylpyridine)iridium. The first phosphorescent dopant occupies approximately 5 to 15% of the first mixed emission layer 126a. A difference between the HOMO level of each of the first and second hole-type hosts (host_h1 and host_h2) and the HOMO level of the third hole-transport layer 124b is ±0.5 eV or less.For this purpose, the first and second hole-type hosts host_h1 and host_h2 are formed from a material that is different from or the same as that of the third hole-transport layer 124b, and the first and second hole-type hosts host_h1 and host_h2 are formed from the same material or from different materials. The first and second hole-type hosts host_h1 and host_h2 are formed from a material having a hole mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2Specifically, any one hole-type host among the first and second hole-type hosts host_h1 and host_h2 is formed of a material that exhibits excellent transport of a hole into the second emission layer 126, while the other hole-type host is formed of a material that exhibits excellent energy transfer to the dopant material. The first and second hole-type hosts host_h1 and host_h2 are formed, for example, of TCTA (4,4',4"-tris(N-carbazolyl)triphenylamine) or CBP (4,4'-bis(carbazol-9-yl)biphenyl).

[0045] The second emission mixture layer 126b is formed on the first emission mixture layer 126a to contact the second electron-transport layer 128. The second emission mixture layer 126b is formed by mixing an electron-type host (host_e) that excels in electron transport into the second emission layer 126 and a second phosphorescent dopant. The second phosphorescent dopant is a yellow-green phosphorescent dopant of the same type as in the first emission mixture layer 126a and occupies approximately 5 to 15% of the second emission mixture layer 126b. A difference between the LUMO level of the electron-type host (host_e) and the LUMO level of the second electron-transport layer 128 is ±0.5 eV or less. The electron-type host host_e is made of a material that has an electron mobility of 1.0 × 10 -6 Vs / cm 2up to 5.0 × 10 -3 Vs / cm 2 For this purpose, the electron-type host host_e is formed from a material that is different from or identical to that of the second electron-transport layer 128. The electron-type host host_e is formed, for example, from UGH3 (m-bis(triphenylsilyl)benzene) or TAZ (3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole).

[0046] As such, the organic light-emitting display device according to the present invention ensures easy hole and electron injection into the first and second emission mixture layers 126a and 126b, achieving a reduction in voltage compared to the prior art. Furthermore, in the organic light-emitting display device according to the present invention, the hole and electron injected through the hole-transport layer and the electron-transport layer move to an interface between the first and second emission mixture layers 126a and 126b, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent the deterioration of the luminous efficiency.In addition, limiting a region for the recombination of the hole and the electron to the emission layer 126 can prevent the deterioration of the electron transport layer 128 and the hole transport layer 124b immediately adjacent to the emission layer 126, thereby achieving an extended lifetime and increased stability.

[0047] Table 2 represents the electro-optical characteristics of a prior art organic light emitting display device and the white organic light emitting display device according to the first embodiment of the present invention. Table 2 Condition T95 (50 mA / cm 2 ) 10 mA / cm 2 Volts (V) CD / A Efficiency ratio State of the art 137 hours 3,6 76,5 0,73 first embodiment 212 hours 3,3 80,1 0,78

[0048] In Table 2, a prior art configuration includes a single emission layer in which two hosts and a dopant are mixed together, where T95 represents the time required until the lifetime of the white organic light emitting display device reaches approximately 95%. As shown in Table 2 and in Fig. As shown by way of example in Figure 5A, the white organic light emitting display device of the prior art (curve A) requires 137 hours until its lifetime reaches 95%, whereas the white organic light emitting display device according to the present invention (curve C) requires 212 hours until its lifetime reaches 95%, thus recognizing that the present invention has a longer lifetime than the prior art. In addition, as shown in Fig.5B, it is recognized that the organic light emitting display device according to the present invention (curve C) has a higher current density as a function of voltage than that of the prior art (curve A) and consequently a current density lower by about 0.3 V per 10 mA / cm 2 lower voltage is required to achieve the same current density as that of the prior art. In particular, as shown in Table 2, it is recognized that the drive voltage in the first embodiment of the present invention is lower than that of the prior art. In addition, as shown in Fig. 5C, it is recognized that the organic light emitting display device according to the present invention (curve C) has a higher brightness and consequently a lower deterioration in efficiency than that of the prior art (curve A). Accordingly, it is recognized that the efficiency ratio at 50 mA / cm2 on efficiency at 10 mA / cm 2 in the present invention is higher than in the prior art, thus achieving a reduced drop in efficiency as a function of an increase in brightness.

[0049] As described above, it is recognized that the organic light emitting display device according to the first embodiment of the present invention is superior to the prior art organic light emitting display device in terms of lifetime, driving voltage (V) and luminance (cd / A), as shown in Table 2 and the Fig. 5A to 5C is shown as an example.

[0050] Although it has been described by way of example that the organic light emitting display device according to the first embodiment of the present invention has a tandem configuration using a plurality of light emitting units, the organic light emitting display device can be applied to a configuration using a single light emitting unit.

[0051] Fig. 6 is a sectional view showing an organic light emitting display device according to a second reference embodiment.

[0052] The organic light emitting display device used in Fig.6, includes the first and second electrodes 102 and 104 arranged to face each other, as well as a hole injection layer 142, a hole transport layer 144, an emission layer 126, and an electron transport layer 148 formed between the first and second electrodes 102 and 104. Here, the other components except for the emission layer 126 have been described above in the first reference embodiment; therefore, a detailed description of these components will be omitted below.

[0053] The emission layer 126 includes the first and second emission mixing layers (ML1 and ML2) 126a and 126b.

[0054] The first mixed emission layer 126a is formed on the hole-transport layer 144 to contact the third hole-transport layer 144. The first mixed emission layer 126a is formed by mixing a first hole-type host host_h1, a second electron-type host host_e2, and a first phosphorescent dopant.

[0055] The second mixed emission layer 126b is formed on the first mixed emission layer 126a to contact the electron-transport layer 148. The second mixed emission layer 126a is formed by mixing a first electron-type host host_e1, a second hole-type host host_h2, and a second phosphorescent dopant.

[0056] Both the first and second phosphorescent dopant materials occupy approximately 5 to 15% of each of the first and second mixed emission layers 126a and 126b. A material of the first phosphorescent dopant material contained in the first mixed emission layer 126a is the same as or different from a material of the second phosphorescent dopant material contained in the second mixed emission layer 126b.

[0057] A difference between the LUMO level of each of the first and second electron-type hosts host_e1 and host_e2 and the LUMO level of the electron-transport layer 148 is ±0.5 eV or less. Both the first and second electron-type hosts host_e1 and host_e2 are formed of a material having an electron mobility of 1.0 × 10 -6 Vs / cm2 up to 5.0 × 10 -3 Vs / cm 2 For this purpose, both the first and second electron-type hosts host_e1 and host_e2 are formed from a material that is the same as or different from the electron-transport layer 148. The first and second electron-type hosts host_e1 and host_e2 are formed, for example, from UGH3 (m-bis(triphenylsilyl)benzene) or TAZ (3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole). Here, the second electron-type host host_e2 in the first mixed emission layer 126a and the first electron-type host host_e1 in the second mixed emission layer 126b are formed from the same material or from different materials.

[0058] A difference between the HOMO level of each of the first and second hole-type hosts host_h1 and host_h2 and the HOMO level of the hole-transport layer 144 is ±0.5 eV or less. Both the first and second hole-type hosts host_h1 and host_h2 are formed of a material having a hole mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2For this purpose, both the first and second hole-type hosts host_h1 and host_h2 are formed from a material that is the same as or different from the hole-transport layer 144. The first and second hole-type hosts host_e1 and host_e2 are formed, for example, from TCTA (4,4',4"-tris(N-carbazolyl)triphenylamine) or CBP (4,4'-bis(carbazol-9-yl)biphenyl). Here, the first hole-type host host_h2 in the first emission mixing layer 126a and the second hole-type host host_h2 in the second emission mixing layer 126b are formed from the same material or from different materials.

[0059] The rate of the electron-type host host_e1 in the second mixed emission layer 126b adjacent to the electron-transport layer 148 is higher than the rate of the electron-type host host_e2 in the first mixed emission layer 126a, and the rate of the hole-type host host_h1 in the first mixed emission layer 126a adjacent to the hole-transport layer 144 is higher than the rate of the hole-type host host_h2 in the second mixed emission layer 126b. The ratio of the first hole-type host host_h1 to the second electron-type host host_e2 in the first mixed emission layer 126a adjacent to the hole-transport layer 144 is 4-7:3-6. Furthermore, the ratio of the first electron-type host host_e1 to the second hole-type host host_h2 in the second mixed emission layer 126b adjacent to the electron-transport layer 148 is 6-9:1-4.

[0060] As such, the organic light-emitting display device according to the second reference embodiment ensures easy hole and electron injection into the first and second emission mixture layers 126a and 126b, achieving a reduction in voltage compared to the prior art. Furthermore, in the organic light-emitting display device according to the second reference embodiment, the hole and electron injected through the hole-transport layer and electron-transport layer move to an interface between the first and second emission mixture layers 126a and 126b, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent deterioration in luminous efficiency.In addition, limiting a region for the recombination of the hole and the electron to the emission layer 126 can prevent the deterioration of the electron transport layer 148 and the hole transport layer 144 adjacent to the emission layer 126, thereby achieving an extended lifetime and increased stability.

[0061] Table 3 represents the electro-optical characteristics of a prior art organic light emitting display device and the white organic light emitting display device according to the second reference embodiment. Table 3 Condition 10 mA / cm 2 Volts (V) CD / A CIEx CIEy State of the art 7,2 62,6 0,301 0,337 second reference embodiment 7,1 67,8 0,300 0,351

[0062] In Table 3, a prior art configuration includes a single emission layer in which two hosts and a dopant are mixed together. In the second reference embodiment of the present invention, the ratio of the first hole-type host host_h1 to the second electron-type host host_e2 in the first mixed emission layer 126a is 5.5:4.5, and the ratio of the second hole-type host host_h2 to the first electron-type host host_e1 in the second mixed emission layer 126b is 3:7. As exemplified in Table 3, it is recognized that the third embodiment of the present invention is superior to the prior art organic light emitting display device in terms of drive voltage (V), luminance (cd / A), and chromaticity coordinates (CIEx and CIEy).

[0063] Although it has been described by way of example that the organic light emitting display device according to the second reference embodiment of the present invention includes a single light emitting unit, the organic light emitting display device can be applied to a tandem configuration including a plurality of light emitting units 110 and 130 as shown in Fig. 7 is shown as an example.

[0064] Fig. 8 is a sectional view showing an organic light emitting display device according to a second embodiment of the present invention.

[0065] The organic light emitting display device used in Fig. 8, contains the same components as those of the organic light emitting display device shown in Fig.1, except for the second mixed emission layer, which contains two electron-type hosts. Consequently, a detailed description of these same components is omitted below.

[0066] The second emission layer 126, which is Fig. 8, the first and second emission mixing layers (ML1 and ML2) include 126a and 126b.

[0067] The first mixed emission layer 126a is formed on the third hole-transport layer 124b to contact the third hole-transport layer 124b. The first mixed emission layer 126a is formed by mixing a hole-type host host_h, which has excellent hole transport into the second emission layer 126, and a first phosphorescent dopant. The first phosphorescent dopant is a phosphorescent yellow-green dopant formed of, for example, tris(2-phenylpyridine)iridium. The first phosphorescent dopant occupies approximately 5 to 15% of the first mixed emission layer 126a. A difference between the HOMO level of the hole-type host host_h and the HOMO level of the third hole-transport layer 124b is ±0.5 eV or less.For this purpose, the hole-type host host_h is formed from a material that is different from or the same as that of the third hole-transport layer 124b. The hole-type host host_h is formed from a material that has a hole mobility of 1.0 × 10. -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 The hole-type host host_h is formed, for example, from TCTA (4,4',4"-tris(N-carbazolyl)-triphenylamine) or CBP (4,4'-bis(carbazol-9-yl)biphenyl). Although the first emission mixing layer 126a containing a single hole-type host has been described by way of example, the first emission mixing layer 126a may contain a plurality of different hole-type hosts, as shown in Fig. 4 is shown as an example.

[0068] The second emission mixture layer 126b is formed on the first emission mixture layer 126a to contact the second electron-transport layer 128. The second emission mixture layer 126b is formed by mixing first and second electron-type hosts (host_e1 and host_e2) and a second phosphorescent dopant. The second phosphorescent dopant is a yellow-green phosphorescent dopant and is the same as that of the first emission mixture layer 126a, occupying approximately 5 to 15% of the second emission mixture layer 126a. A difference between the LUMO level of each of the first and second electron-type hosts (host_e1 and host_e2) and the LUMO level of the second electron-transport layer 128 is ±0.5 eV or less. The electron-type host host_e is made of a material that has an electron mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10-3 Vs / cm 2For this purpose, both the first and second electron-type hosts host_e1 and host_e2 are formed from a material that is different from or the same as that of the second electron-transport layer 128, wherein the first and second electron-type hosts host_e1 and host_e2 are formed from the same material or from different materials. In particular, any one electron-type host among the first and second electron-type hosts host_e1 and host_e2 is formed from a material that has excellent transport of an electron into the second emission layer 126, while the other electron-type host is formed from a material that has excellent energy transfer to the second phosphorescent dopant. The first and second electron-type hosts host_e1 and host_e2 are, for example,from UGH3 (m-bis-(triphenylsilyl)benzene) or TAZ (3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole).

[0069] As such, the organic light-emitting display device according to the present invention ensures easy hole and electron injection into the first and second emission mixture layers 126a and 126b, achieving a reduction in voltage compared to the prior art. Furthermore, in the organic light-emitting display device according to the present invention, the hole and electron injected through the hole-transport layer and the electron-transport layer move to an interface between the first and second emission mixture layers 126a and 126b, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent the deterioration of the luminous efficiency.In addition, limiting a region for the recombination of the hole and the electron to the emission layer 126 can prevent the deterioration of the electron transport layer 128 and the hole transport layer 124b adjacent to the emission layer 126, thereby achieving an extended lifetime and increased stability.

[0070] Fig. 9 is a sectional view showing an organic light emitting display device according to a third embodiment of the present invention.

[0071] The organic light emitting display device used in Fig. 9, contains the same components as those of the organic light emitting display device shown by way of example in Fig. 8, except for the first mixed emission layer, which further contains an electron-type host. Therefore, a detailed description of these same components will be omitted below.

[0072] The first emission mixing layer 126a, which is Fig. 9, is formed on the third hole-transport layer 124b to contact the third hole-transport layer 124b. The first mixed emission layer 126a is formed by mixing a hole-type host host_h that exhibits excellent hole transport into the second emission layer 126, an electron-type host host_e, and a first phosphorescent dopant.

[0073] The first phosphorescent dopant is a phosphorescent yellow-green dopant and is formed, for example, from tris(2-phenylpyridine)iridium. The first phosphorescent dopant occupies approximately 5 to 15% of the first emission mixture layer 126a.

[0074] A difference between the HOMO level of the hole-type host host_h and the HOMO level of the third hole-transport layer 124b is ±0.5 eV or less. For this purpose, the hole-type host host_h is formed from a material that is different from or the same as the third hole-transport layer 124b. The hole-type host host_h is formed from a material that has a hole mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 The hole-type host host_h is formed, for example, from TCTA (4,4',4"-tris(N-carbazolyl)-triphenylamine) or CBP (4,4'-bis(carbazol-9-yl)biphenyl).

[0075] The difference between the LUMO level of the electron-type host host_e and the LUMO level of the electron-transport layer 128 is ±0.5 eV or less. The electron-type host host_e is formed of a material having an electron mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 For this purpose, the electron-type host host_e is formed from a material that is the same as a material of any of the first and second electron-type hosts host_e1 and host_e2 or a material of the electron-transport layer 128, or different from a material of any of the first and second electron-type hosts host_e1 and host_e2 or a material of the electron-transport layer 128. The electron-type host host_e is formed, for example, from UGH3 (m-bis(triphenylsilyl)benzene) or TAZ (3-phenyl-4-(1'-naphthyl)-5-phenyl-1,2,4-triazole).

[0076] The rate of the electron-type host host_e in the second mixed emission layer 126b adjacent to the electron-transport layer 128b is higher than the rate of the electron-type host host_e in the first mixed emission layer 126a. The ratio of the hole-type host host_h to the electron-type host host_e in the first mixed emission layer 126a adjacent to the hole-transport layer 124b is 4-7:3-6.

[0077] As such, the organic light-emitting display device according to the present invention ensures easy hole and electron injection into the first and second emission mixture layers 126a and 126b, achieving a reduction in voltage compared to the prior art. Furthermore, in the organic light-emitting display device according to the present invention, the hole and electron injected through the hole-transport layer and the electron-transport layer move to an interface between the first and second emission mixture layers 126a and 126b, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent the deterioration of the luminous efficiency.In addition, limiting a region for the recombination of the hole and the electron to the emission layer 126 can prevent the deterioration of the electron transport layer 128 and the hole transport layer 124b immediately adjacent to the emission layer 126, thereby achieving an extended lifetime and increased stability.

[0078] Although it has been described by way of example that the organic light-emitting display device according to the present invention includes two emission mixture layers, the organic light-emitting display device may include three or more emission mixture layers. In this case, the content of the hole-type host host_h gradually increases with the decreasing distance from the hole-transport layer 124b, while the content of the electron-type host host_e gradually increases with the decreasing distance from the electron-transport layer 128.

[0079] Although it has been described by way of example that the organic light emitting display device according to the present invention includes two light emitting units, the organic light emitting display device may include three or more light emitting units. For example, three light emitting units 110, 120, and 140 may be provided, as shown in Fig. 10 is shown as an example.

[0080] In particular, it is recognized from the following Table 4 that a configuration of the present invention as shown in Fig. 10, in which the first mixed emission layer 126a contains the first and second hole-type hosts and the phosphorescent dopant material, and the second mixed emission layer 126b contains the electron-type host and the phosphorescent dopant material, as shown in Fig.4 by way of example, has both a longer lifetime and a higher luminance as well as a lower operating voltage than a prior art configuration including a single emission layer in which two hosts and a dopant are mixed. Table 4 Condition T95 (50 mA / cm 2 ) 50 mA / cm 2 Volts (V) CD / A State of the art 100 % 100 % 100 % Embodiment (configuration according to Fig. 10) 120 % 96% 103 %

[0081] It will be appreciated from the following Table 5 that a configuration of the present invention as exemplified in Fig.10, in which the first mixed emission layer 126a includes the first and second hole-type hosts and the phosphorescent dopant, and the second mixed emission layer 126b includes the first and second electron-type hosts and the phosphorescent dopant, has a longer lifetime and a lower operating voltage than a prior art configuration including a single emission layer in which two hosts and one dopant are mixed. Table 5 Condition T95 (50 mA / cm 2 ) 50 mA / cm 2 Volts (V) CD / A State of the art 100 % 100 % 100 % Embodiment (configuration according to Fig. 10) 120 % 99% 100 %

[0082] The organic light emitting display device according to the present invention as described in Fig. 11 can be applied to a configuration including red, green and blue color filters 150R, 150G and 150B. That is, in the emission layers 116 and 126, which are shown in the Fig.1, 4, 6 and 7 to 10 are shown by way of example, the white light generated is converted into red light while passing through a sub-pixel region provided with the red color filter 150R, converted into green light while passing through a sub-pixel region provided with the green color filter 150G, and converted into blue light while passing through a sub-pixel region provided with the blue color filter 150B, and directly passes through a sub-pixel region not provided with any color image.

[0083] As is clear from the above description, an organic light-emitting display device according to the present invention ensures easy hole and electron injection into the first and second emission mixture layers, achieving a voltage reduction compared to the prior art. Furthermore, in the organic light-emitting display device according to the present invention, a hole and an electron injected through a hole-transport layer and an electron-transport layer move to an interface between the first and second emission mixture layers, which can prevent the loss of an exciton (i.e., an electron-hole pair) and thus prevent the deterioration of luminous efficiency. Furthermore, limiting a region for recombination of the hole and the electron to the emission layer can achieve extended lifetime and increased stability.In addition, a price reduction is achieved by reducing the content of a phosphorescent dopant.

Claims

[1] Organic light emitting display device comprising: a first (102) and a second electrode (104) facing each other on a substrate (101); at least one emission layer (126) formed between the first (102) and second electrodes (104); at least one hole transport layer (124b) formed between the first electrode (102) and the emission layer (126); and an electron transport layer (128) formed between the second electrode (104) and the emission layer (126), wherein the emission layer (126) contains: a first emission mixture layer (126a) formed on the hole transport layer (124b), the first emission mixture layer (126a) containing a first hole-type host (host_h, host_h1) and a first phosphorescent dopant; and a second emission mixture layer (126b) formed on the first emission mixture layer (126a) such that an interface is present between the second emission mixture layer (126b) and the first emission mixture layer (126a), arranged between the first emission mixture layer (126a) and the electron transport layer (128) and in contact with the electron transport layer (128), wherein the second emission mixture layer (126b) contains a first electron-type host (host_e, host_e1) and a second phosphorescent dopant, and the first emission mixing layer (126a) further contains a second hole-type host (host_h2), and / or the second emission mixture layer (126b) further contains a second electron-type host (host_e2). [2] The device according to claim 1, wherein a difference between the level of the lowest unoccupied orbital of a molecule (LUMO) of each of the first (host_e1) and the second electron-type host (host_e2) and the LUMO level of the electron-transport layer (128) is ±0.5 eV or less, and wherein a difference between the level of the highest occupied orbital of a molecule (HOMO) of each of the first (host_h1) and the second hole-type host (host_h2) and the HOMO level of the hole-transport layer (124b) is ±0.5 eV or less. [3] The device according to claim 2, wherein the first (host_h1) and the second (host_h2) hole type hosts have a hole mobility of 1.0 × 10 -6 Vs / cm 2 up to 5.0 × 10 -3 Vs / cm 2 have. [4] The device according to claim 3, wherein the first (host_e1) and the second electron-type host (host_e2) have an electron mobility of 1.0 × 10 -6 Vs / cm 2up to 5.0 × 10 -3 Vs / cm 2 have. [5] A device according to any one of the preceding claims, comprising at least two emission layers (116, 126), wherein the organic light emitting display device further comprises an N-type charge generation layer (132) and a P-type charge generation layer (134) sequentially stacked between the emission layers (116, 126). [6] A device according to any one of the preceding claims, wherein the first and second phosphorescent dopant materials are formed from the same material or from different materials.

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