KR102351776B1 - Organic light-emitting device and method - Google Patents

Abstract

The present invention provides an organic light emitting device having an electron transport layer on the light emitting layer comprising a light emitting polymer and an electron transport material, the glass transition temperature (Tg(ETM)) of the electron transport material measured in degrees Celsius (° C.) and a glass transition temperature (Tg(LEP)) of the light emitting polymer satisfies the following inequality, and the glass transition temperature of the electron transport material exceeds 140°C:
Tg(ETM) + Tg(LEP) > 270.
The device may comprise a polymeric light emitting layer and a non-polymer (small molecule) electron transport layer deposited on the light emitting layer, wherein the electron transport layer comprises an electron transport material containing a small molecule host and an electron donating material containing a small molecule dopant. Including blends.

Description

Organic light emitting device and method {ORGANIC LIGHT-EMITTING DEVICE AND METHOD}

The present invention relates to an organic light emitting device and a method for manufacturing the same. More specifically, the present invention relates to organic light emitting devices comprising a polymer light emitting layer and a non-polymer (also known as "small molecule") electron transport layer. Such devices are often also known as "hybrid devices".

Electronic devices comprising active organic materials are of increasing interest for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (particularly organic photovoltaic devices and organic photosensors), organic transistors and memory devices. . Devices comprising organic materials offer advantages such as low weight, low power consumption and flexibility, and can also be used in the manufacture of displays or lighting devices. The use of soluble organic materials, such as polymers or small molecules, can be used in solution processing, such as inkjet printing, spin coating, to fabricate device layers. It enables the use of dip coating, slot die printing, nozzle printing, roll-to-roll printing, gravure printing and flexo printing. Furthermore, the use of non-soluble small molecules enables the fabrication of device layers by vacuum deposition. Examples of vacuum deposition methods include vacuum sublimation and co-deposition (or co-deposition) of many different small molecule materials.

An OLED may include a substrate having an anode, a cathode, one or more organic light emitting layers, and one or more charge injection and/or charge transport layers between the anode and the cathode.

During operation of the device, holes are injected into the device by the anode and electrons are injected by the cathode. The holes of the highest occupied molecular orbital (HOMO) and the electrons of the lowest unoccupied molecular orbital (LUMO) of the organic light emitting material combine to form an exciton, and the exciton emits its energy as light upon recombination.

The light emitting layer is made of, or includes, a light emitting material, which may include small molecule, polymer, and dendrimer materials. Suitable light emitting polymers include poly(arylene vinylene) (eg, poly(p-phenylene vinylene) disclosed in WO90/13148) and polyarylene (eg polyfluorene). In US Pat. No. 4,539,507 the luminescent material is (8-hydroxyquinoline)aluminum (“Alq3”, also referred to herein as ET3). WO99/21935 discloses a dendrimer light emitting material.

The light emitting layer may optionally consist of or include a semiconducting host material and a light emitting dopant, wherein energy is transferred from the host material to the light emitting dopant. See, for example, J. Appl. Phys. 65, 3610, 1989) disclose host materials doped with a fluorescent luminescent dopant (ie, a luminescent material that emits light by decay of singlet excitons), Appl. Phys. Lett., 2000, 77, 904] disclose host materials doped with a phosphorescent emissive dopant (ie, a light emitting material that emits light by decay of triplet excitons).

The charge transport layer consists of or comprises a material suitable for transporting holes and/or electrons, which may include small molecule, polymer and dendrimer materials. Suitable electron transport polymers include triazines and pyrimidines as disclosed in U.S. Patent No. 8,003,227. Suitable hole transport polymers include triarylamines as disclosed in Applicant's prior applications, International Publication Nos. WO02/066537 and WO2004/084260.

Advantageously, the electron transport layer comprises a semiconducting host material and a semiconducting dopant material. Typical examples of doped electron transport materials include fullerene C60 doped with acridine orange base (AOB); perylene-3,4,9,10-tetracarboxylic acid-3,4,9,10-dianhydride (PTCDA) doped with leuco crystal violet; Doping with tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II)(W ₂ (hpp) ₄ , ND1) 2,9-di(phenanthren-9-yl)-4,7-diphenyl-1,10-phenanthroline; naphthalenetetracarboxylic acid dianhydride doped with 3,6-bis-(dimethylamino)-acridine (NTCDA); and NTCDA doped with bis(ethylene-dithio)tetrathiofulvalene (BEDT-TTF).

The host material and dopant material may be simultaneously deposited by vapor deposition to form an electron transport layer comprising a mixture or blend of host material and dopant material.

In a typical OLED structure, an electron transport layer comprising a host-dopant small molecule material may be vapor deposited directly onto an emissive layer comprising a polymer and then capped with a thermally deposited metal layer. The metal layer typically forms the cathode metal contact of the device. However, these devices usually have very poor thermal stability after firing, which manifests as deterioration of device parameters such as PL (photoluminescence), operating voltage and external quantum efficiency. These parameters are usually measured at room temperature after firing the device at a predetermined temperature for a predetermined time, and then compared with values measured for the device before the firing step.

The thermal stability of OLEDs is a key parameter related to device performance, as deep degradation at the display operating temperature can significantly reduce the lifespan of the display. Therefore, there is a need to provide a thermally stable organic light emitting device, for example, an organic light emitting device in which light emission, operating voltage and external quantum efficiency do not change even when the device is fired.

According to a first aspect of the present invention, the present invention relates to an organic light emitting device having a light emitting layer comprising a light emitting polymer and an electron transport layer on the light emitting layer comprising an electron transport material, wherein the glass transition of the electron transport material measured in degrees Celsius The temperature (Tg(ETM)) and the glass transition temperature (Tg(LEP)) of the light emitting polymer satisfy the inequality, and the glass transition temperature of the electron transport material is greater than 140°C:

Tg(ETM) + Tg(LEP) > 270.

The glass transition temperature (Tg) of an electron transporting material (also known as a "host") above 140°C is indicative of the more bulky nature of such a material, so that even at temperatures close to the Tg of the light emitting polymer, it Reduces the diffusion of the material. Therefore, the size of the host molecule of the electron transport layer (ETL) can play an important role in determining the thermal stability of the OLED.

Preferably, the glass transition temperature of the electron transport material is greater than 155°C, more preferably greater than 175°C.

Preferably, the electron transport material is a non-polymeric molecular host, advantageously ET1. The chemical structures of the ET1 and ET2 molecular hosts (also known as "small molecule" hosts) are shown below:

.

.

Zirconium quinolinolate ET1 can be obtained, for example, by the method described in Zhurnal Neorganitcheskoi Khimii 1961, vol.6, p.1338-1341, and ET2 can be obtained, for example, by the method described in CS150747 .

In addition, the bulkier nature of the ET1 host is evident from the difference in Tg (179°C (ET1) versus 105°C (ET2)). Because of their larger physical dimensions, the more bulky small molecule hosts are less prone to diffusing into the light emitting polymer.

The electron transport layer may further include an electron donating material. Advantageously, the electron donating material is a non-polymeric molecular (also referred to as “small molecule”) dopant, preferably ND1. Small molecule dopants are highly reactive compounds that allow sufficient electrons to be generated for optimal charge transport within the electron transport layer.

According to a second aspect of the present invention, the present invention relates to an organic light emitting device having a light emitting layer comprising a light emitting polymer and an electron transport layer on the light emitting layer comprising an electron transport material, wherein the glass transition temperature (Tg ( ETM)) and the glass transition temperature (Tg(LEP)) of the light-emitting polymer satisfy the following inequality, provided that the glass transition temperature of the light-emitting polymer is greater than 180°C:

Tg(ETM) + Tg(LEP) > 280.

In general, the glass transition of an amorphous polymer is a reversible transition from a hard or solid state to a soft, viscous state by heating the polymer. This transition includes a gentle change in polymer viscosity without any appreciable change in polymer structure. Tg was determined using DSC (Differential Scanning Calorimetry).

The Tg values described herein were determined using a Perkin Elmer Pyris 1 differential scanning calorimetry. The Tg values described herein are extrapolated half Cp (specific heat capacity).

To determine Tg values, samples were weighed in aluminum pans and sealed with aluminum lids, weighed against empty pans and lids, heated and cooled using nitrogen purge gas.

The sample was heated from 30.00°C to 300.00°C at a rate of 40.00°C/min, held for 1.0 min, cooled from 300.00°C to 30.00°C at a rate of 40.00°C/min, and then held for an additional 1.0 min, process was repeated two or more times.

The Tg value is obtained after the second heating and checked against the value from the third heating.

A light emitting polymer having a glass transition temperature greater than 180° C. and calcined at about 80° C. to 120° C. may not undergo a change in viscosity. As a result, any small molecules (host molecules or dopant molecules) deposited directly on the light emitting layer may not diffuse into the light emitting polymer during the firing step and the integrity of the PL and operating voltage of the OLED measured after the firing step is maintained. can be

Preferably, the light emitting polymer is selected or adapted to have a Tg of greater than 200°C, more preferably greater than 220°C, even more preferably greater than 240°C and most preferably greater than 260°C.

The light emitting polymer may be a homopolymer or a copolymer comprising two or more different repeating units. Preferably, the light emitting polymer is a copolymer.

The light emitting polymer may be a conjugated polymer or a non-conjugated polymer. One exemplary non-conjugated polymer is polyvinylcarbazole (PVK).

The light-emitting polymer is preferably a conjugated polymer having a backbone comprising repeating units conjugated to adjacent repeating units.

The light emitting polymer preferably comprises arylene repeat units. Exemplary arylene repeat units include phenylene repeat units and fluorene repeat units.

An exemplary phenylene repeat unit is a 1,4-linked phenylene repeat unit that is unsubstituted or substituted with one or more substituents. Exemplary substituents are C _{1 -20} alkyl (wherein, C _{1 -20-alkyl} of one or more non-adjacent C atom is optionally substituted aryl or heteroaryl, more preferably unsubstituted phenyl ring or a C _{1 -10} alkyl group substituted phenyl, O, S, substituted by N, C = O, or including, but may be replaced) to -COO-, one or more H atoms of the C _{1 -20} alkyl may be replaced by F. If present, may be N-substituted dihydro-car is invoking, for example, C _{1 -10} alkyl, substituted phenyl group is unsubstituted phenyl, or one or more C _{1 -10} alkyl.

Exemplary fluorene repeat units have the structure of Formula I:

[Formula I]

In the above formula,

R ⁸ is the same or different substituent at each occurrence, two groups R ⁸ may be joined to form a ring;

R ⁷ is a substituent;

d is 0, 1, 2 or 3.

Preferably, each d is 0.

If more than one group d is 1, 2 or 3, each R ⁷ is optionally alkyl, such as C _{1 -20} alkyl (wherein one or more non-adjacent C atom is O, S, C = O and -COO-, optionally substituted aryl and optionally substituted heteroaryl). When present, R ⁷ is preferably selected from the C _{1 -20} alkyl and substituted or unsubstituted aryl, e.g., substituted with phenyl or one or more C _{1 -20} alkyl, unsubstituted phenyl.

each R ⁸ is independently selected from the group consisting of:

-Alkyl, optionally C _{1 -20} alkyl (wherein one or more non-adjacent C atom is optionally substituted aryl or heteroaryl, O, S, may be replaced by C = O or -COO-, one or more H atom may be replaced by F); and

- a group of formula -(Ar ⁷ ) _r , wherein each Ar ⁷ is independently an unsubstituted or substituted aryl or heteroaryl group, preferably unsubstituted or substituted phenyl, and r is 1 or more, optionally 1, 2 or 3. when one or more of Ar ⁷ group is substituted, the substituent or each substituent is a C _{1 -20} alkyl (wherein one or more non-adjacent C atom is replaced by O, S, C = O and -COO- may be made) can be a substituent group R ¹ is selected from the group. preferably, R ¹ is a C _{1 -10} alkyl group emitter, C _{1 -10} alkoxy or alkoxy group in the general formula of the emitter alkoxy is -O (CH ₂ O) _n -R may be ^2, wherein R ² is a C _{1 -5} alkyl group, n is 1, 2 or 3;

^{Substituent R 8} of one or more repeating units of Formula 1 One or both may be selected to provide a high glass transition temperature of the light emitting polymer, preferably greater than 180°C.

The high glass transition temperature polymer comprises at least 10 mol%, 20 mol%, 30 mol%, 40 mol% or 50 mol% of repeating units of formula 1, optionally wherein R ⁸ one or both are selected from the following groups:

- a group selected from the formula:

[In the above formula,

* represents a bonding position to the fluorene unit of formula (1);

R ¹ is as described above, preferably C _{1 -5} alkyl, or a C _{1 -5} emitter group to alkoxy group or an alkoxy group; and

- C _{1 -5} alkyl.

The light emitting polymer may include arylamine repeat units. Preferably, the repeating unit of the light emitting polymer comprises an arylene repeating unit, more preferably a fluorene repeating unit, and an arylamine repeating unit.

Optionally, the repeat units of the polymer consist of one or more arylene repeat units, preferably one or more fluorene repeat units, and one or more arylamine repeat units.

The arylamine repeat unit has the formula (II):

[Formula II]

In the above formula,

Ar ⁸ , Ar ⁹ and Ar ¹⁰ at each occurrence is independently selected from substituted or unsubstituted aryl or heteroaryl;

g is 0 or an integer, preferably 0 or 1;

R ¹³ is a substituent;

c, d and e are each independently 1, 2 or 3, preferably 1;

^{Any two of Ar 8} , Ar ⁹ , Ar ¹⁰ and R ¹³ that are directly bonded to the same N atom of Formula II may be bonded by a direct bond or a divalent group.

R ¹³ is 1, g is independently may be the same or different in each occurrence, alkyl, such as C _{1 -20} In the case of alkyl, Ar ^11, or Ar ¹¹ is a branched or straight chain group (wherein, Ar ¹¹ each not less than It is preferably selected from the group consisting of aryl or heteroaryl optionally substituted with Exemplary R ¹³ Group is a substituted phenyl group C _{1 -20} alkyl, phenyl and at least one C _{1 -20} alkyl.

Preferred repeating units of formula (II) have structures of formulas (1) to (3):

.

.

Preferably, Ar ⁸ , Ar ⁹ , Ar ¹⁰ and Ar ¹¹ are aromatic groups, wherein each group may be unsubstituted or substituted with one or more substituents.

Optionally, Ar ⁸ , Ar ^{10 of Formula 1} and Ar ¹¹ is phenyl, and each group may be independently unsubstituted or substituted with one or more substituents.

Optionally, Ar ⁹ of formula 1 is an unsubstituted or substituted phenyl or an unsubstituted or substituted polycyclic aromatic group, such as as described in International Publication Nos. WO2005/049546 and WO2013/108022, incorporated herein by reference .

^{Optionally, Ar 8} , Ar ⁹ and Ar ¹¹ in Formulas 2 and 3 are phenyl, and each group may be independently unsubstituted or substituted with one or more substituents.

The arylamine repeat unit may be provided in a molar amount ranging from about 0.5 mole % to about 50 mole %, optionally up to 40 mole %, optionally up to 30 mole %, optionally up to 10 mole %.

Ar ⁸ , Ar ⁹ , Ar ¹⁰ And preferred substituents of Ar ^11, when present, C _{1 -20} hydrocarbyl group, an optionally C _{1 -20} alkyl group.

Preferably, the electron transport material is a non-polymeric molecular host, advantageously ET1. Making bulky molecular hosts using light emitting polymers having a Tg greater than 180° C. can substantially reduce diffusion of small molecule host materials into the light emitting layer.

The electron transport layer may further include an electron donating material. It is preferred that the electron donating material is a non-polymer (also referred to as "small molecule") molecular dopant, preferably ND1.

According to a third aspect of the present invention, the present invention relates to a method for manufacturing an organic light emitting device, the method comprising: depositing a solution containing a light emitting polymer to form a light emitting layer; and co-depositing an electron transport material and an electron donor material by vapor deposition on the light emitting layer to form a mixed electron transport layer.

The combined use of solution deposition and vapor deposition methods to deposit the light emitting layer and the electron transport layer, respectively, increases the need to render the light emitting layer insoluble, for example by crosslinking the light emitting polymer.

Preferably, the deposition of the solution comprising the light emitting polymer is performed by spin coating, inkjet printing, dip coating, slot die printing, nozzle printing, roll-to-roll printing, gravure printing and flexor printing.

The present invention is described herein by way of example only and with reference to the accompanying drawings.
1A is a cross-sectional view of an OLED as a comparative example to the OLED of the first aspect of the present invention;
1B is a cross-sectional view of an embodiment of an OLED according to a first aspect of the present invention;
2A to 2C are graphs of the relative decrease in PL, ΔCIE-x and ΔCIE-y, respectively, measured after firing an OLED according to the first aspect of the present invention at 120° C. for 1 hour. The OLED contains a series of small molecule host materials.
3 is a graph of the relative PL reduction measured at different times (time window greater than 600 hours) after firing an OLED according to the first aspect of the present invention at 85° C. FIG.
4 is an OLED according to the first aspect of the present invention measured at different times (time window is greater than 600 hours) after firing _{at 85° C., in an inert N 2 atmosphere (black curve) and air (red curve).} It is a graph of one working voltage increase.
5 is a cross-sectional view of an embodiment of an OLED according to a second aspect of the present invention;
6 is a graph of the relative decrease in device PL as a function of the difference (Tg-Tb) between the glass transition temperature (Tg) and the device firing temperature (Tb) for a wide range of light emitting polymers.

1a schematically shows an OLED 100 as a comparative example to an OLED according to the first aspect of the invention, regardless of scale. The OLED 100 structure is deposited on a substrate 10, typically made of glass, and includes several layers provided on the substrate in the following order: an anode electrode 20, a hole injection layer (HIL) 30 ), an intermediate layer (IL) 40 , a light emitting polymer (LEP) layer 50 and a cathode electrode 60 .

The anode electrode 20, typically made of ITO (indium tin oxide), has a thickness of 45 nm and is deposited by physical vapor deposition such as vacuum or thermal evaporation. The HIL 30 has a thickness of 50 nm and is spin coated with a solution of a hole injection material referred to as Plexcore (registered trademark) OC AQ-1200 commercially available from Plextronics Inc. is deposited IL 40 is 22 nm thick and is deposited by spin coating a solution of hole transport polymer P10. Polymer P10 comprises monomers M11 to M14 in weight percent as follows: 50% M11, 30% M12, 12.5% M13 and 7.5% M14. The chemical structure of the monomer is shown below:

.

.

The LEP layer 50 is 60 nm thick and deposited by spin coating a solution of light emitting polymer P20 having a Tg of about 130°C. Polymer P20 comprises monomers M21 to M25 in weight percent as follows: 36% M21 (or P22), 14% M22 (or F8), 45% M23 (or P30), 4% M24 (or A061) and 1 % M25 (or POZ). The chemical structure of the monomer is shown below:

.

.

Polymers P10 and P20 were synthesized using the Suzuki polymerization method well known in the art. Monomer M11 in WO2005/092723, M12 in WO2005/074329, M13 in WO2002/092724, M14 in WO2005/038747, M21 International Publication No. WO2002/092724, M22 in US Patent Publication No. 6,593,450, M23 in International Publication No. WO2009/066061, M24 in International Publication No. WO2010/013723, and M25 in International Publication No. It is disclosed in Publication No. 2004/060970.

The cathode electrode 60 consists of three stacked layers of NaF (60a), Al (60b) and Ag (60c) having thicknesses of 5 nm, 20 nm and 200 nm, respectively. NaF is deposited by thermal evaporation on the LEP layer and then coated by a thermally deposited bilayer stack of Al and Ag.

During operation, holes injected from the anode electrode 20 and electrons injected from the cathode electrode 60 combine in the LEP layer 50 to form excitons that radiately decay upon recombination to provide light. Without wishing to be bound by theory, the presence of NaF at the interface between LEP P20 and Al cathode during vapor phase deposition of an aluminum cathode prevents the formation of carbon-aluminum covalent bonds resulting in the formation of an insulating interface, thereby conjugating in LEP P20. Avoid damage to the coupled π-system. Instead, in the presence of NaF at the interface, electron transfer to LEP P20 occurs and local n-doping of the polymer at the interface with the cathode occurs. It is believed that NaF does not diffuse into LEP P20 upon thermal annealing of OLED 100 , and therefore OLED 100 is called a thermally stable organic light emitting device. Because these complexes are formed, it is believed that NaF does not diffuse into LEP P20 upon thermal annealing of OLED 100 . Accordingly, the OLED 100 is called a thermally stable organic light emitting device.

1B schematically shows an aspect of an OLED 200 according to a first aspect of the present invention, irrespective of size. In FIG. 1B, the same reference numerals are used for parts corresponding to those of FIG. 1A. Instead of three stacked cathode layers of NaF, Al and Ag on the LEP layer 50 , the OLED 200 of the present invention has an electron transport layer (ETL) 62 and an Al encapsulating cathode layer 64 . ) with a double layer. Both layers are deposited by thermal evaporation to a thickness of 20 nm and 200 nm, respectively.

ETL 62 comprises an electron transport material containing any one of a small molecule host, such as ET1, ET2, ET3 and ET4. The chemical structures of ET3 and ET4 are shown below:

.

.

ET3 is commercially available. ET4 can be obtained, for example, by the method described in WO2010/057471. The ETL 62 further includes an electron donating material consisting of a small molecule dopant such as ND1.

The host and dopant materials of the hybrid small molecule-polymer OLED 200 of the present invention are simultaneously deposited (or co-deposited) by thermal evaporation, comprising a mixture or blend of the aforementioned host and dopant small molecule materials. A transport layer ETL 62 is formed.

In Example 1, ETL 62 comprises a blend of ET2 (host) and ND1 (dopant) on top of light emitting polymer P20. The hybrid OLED 200 of Example 1 typically exhibits typically greater than 50% reduction in device PL (photoluminescence) and ^{greater than 2 V (measured at 10 mA/cm 2} ) increase in device operating voltage. suffers from the problem of thermal stability after poor firing. The PL and voltage rise values are typically measured at room temperature after the OLED 200 is fired at 120° C. for 1 hour, and then compared with values measured for the device before the firing step. It is speculated that the mentioned thermal instability is caused by diffusion of the ETL host material ET2 into the light emitting polymer P20.

Example 2 shows the thermal stability of an OLED 200 of the present invention when replaced by ET1, an alternative ETL host material, in which ET2 is more bulky and prevents diffusion into polymer P20 even at calcination temperatures close to the Tg of polymer P20. This proves to be a significant improvement. The more bulky nature of host ET1 is evident from the difference in glass transition temperature (Tg) between ET2 (Tg at 105°C) and ET1 (Tg at 179°C). In addition, as summarized in Table 1 below, the physical properties of the thermally stable OLED 200 of Example 2 of the present invention are comparable to or similar to those of the Comparative Example OLED 100 prepared with a NaF/Al/Ag cathode.

[Table 1]

The main advantage of host ET1 of Example 2 over Host ET2 of Example 1 is that it enables the preparation of hybrid small molecule-polymer OLEDs 200 of the present invention using light emitting polymers with relatively low glass transition temperatures. These devices will meet the minimum thermal stability required for commercial OLED applications. In addition, OLEDs exhibiting the improved thermal stability described above can make the use of electron transport materials compatible with processes that require high temperature manufacturing conditions, such as thermal deposition of buffer layers in top-emitting devices. In addition, the use of ET1 as a host material enables direct experimental measurements of important device properties such as color, efficiency and lifetime at high annealing and/or operating temperatures.

2A-2C show the relative PL reduction (FIG. 2A) and ΔCIE coordinates (FIGS. 2B and 2C) measured for the OLED 200 of FIG. 1B. In addition to showing the PL and ΔCIE coordinate systems of the OLED 200 of Examples 1 and 2 above, the graph shows Example 3 (where ETL 62 includes a blend of ET4:ND1) and Example 4 (where: ETL 62 shows the same parameters for ET3:ND1). After the OLED 200 was fired at 120° C. for 1 hour, the PL, ΔCIE-x and ΔCIE-y parameters were measured at room temperature and compared with values measured for the device before the firing step.

Without wishing to be bound by theory, it is believed that the bulkier small molecule hosts have less tendency to diffuse into the polymer P20 upon firing. The Tg of a small molecule material may provide an indicator of the bulkiness of the material, and Table 2 below summarizes the glass transition temperatures of all hosts used for manufacturing the ETL 62 of the OLED 200 of the present invention.

[Table 2]

Referring to Figure 2a, from ET2 of Example 1, which exhibits the lowest Tg and highest PL reduction, through ET4 of Example 3, ET3 of Example 4, to ET1 of Example 2, which shows one of the highest Tg and lowest PL. case, the decrease in PL was inversely proportional to the increase in Tg. These results demonstrate that device thermal stability is greatly affected by the physical properties of the host used for the co-deposited electron transport layer ETL 62, and thus can be improved by the use of an appropriate host.

Since it was confirmed that ET1 was the most suitable host, the thermal stability of the OLED 200 of Example 1 (where the ETL 62 contained a blend of ET1:ND1) was evaluated, and the device was calcined at 85° C. for at least 600 hours. It was further investigated by The results of this investigation are shown in FIG. 3 showing the decrease in PL and FIG. 4 showing the change in device operating voltage (ΔV).

From the results of Figure 3, it can be readily seen that the device thermal stability after firing at 85° C. clearly exceeds the time window longer than 600 hours used in the experiment. These results for the OLED of Example 1 are comparable to experimentally measured results for a comparative device using a known NaF/Al/Ag cathode instead of the inventive ETL/Al/Ag structure.

Reasonable charge of globe (glove) of about 0.2V in the case of the firing of the box (10 mA / cm ² measured at a) - PL reduction look to be independent of the environment in which sintering is performed, only an inert N ₂ atmosphere, for example nitrogen element A voltage rise was observed in FIG. 4 (black curve in FIG. 4). A device fired in air (red curve in FIG. 4 ) shows a much larger voltage rise, often in excess of 0.7V.

According to a second aspect of the present invention, an alternative solution to using bulky hosts to improve the thermal stability of the OLED is to increase the glass transition temperature (Tg) of the light emitting polymer underlying the electron transport layer.

5 schematically shows an aspect of an OLED 300 according to a second aspect of the present invention, irrespective of size. In FIG. 5 , the same reference numerals are used for parts corresponding to those of FIG. 1B . Polymer P20 of LEP layer 50 of FIG. 1B was replaced with LEP layer 52 comprising polymers P22, P24, P26 and P28 with higher glass transition temperatures. The constituent monomers of each polymer are shown in Table 3 below, along with the glass transition temperature of the polymer and the corresponding weight percent of each monomer in the aforementioned polymers.

[Table 3]

The chemical structures of monomers M22 and M24 are shown above with respect to polymer P20, and the chemical structures of monomers M26 and M27 are shown below:

.

.

Polymers P22 to P28 were synthesized using the Suzuki polymerization method well known in the art. Monomer M26 is disclosed in WO2002/092723, and M27 is disclosed in WO2005/074329.

Hybrid fabricated using a co-deposited ETL 62 comprising a blend of ET2 (host) and ND1 (dopant) formed on top of an LEP layer 52 comprising polymers P22, P24, P26 and P28. The PL of the small molecule-polymer OLED 300 was measured at room temperature both before and after the OLED 300 was calcined at 120° C. for 1 hour. 6 shows a graph of the relative PL versus the temperature difference between the glass transition temperature (Tg) and the firing temperature (Tb) of polymers P22 to P28.

The relative PL reduction associated with the thermal instability of the OLED 300 is due to the diffusion of the small molecule host material ET2 into the underlying LEP layer 52 . It can be inferred from FIG. 6 that diffusion can occur at a temperature much lower (about 160° C.) than the Tg of the light-emitting polymer. That is, the onset of PL reduction is about 160° C., which is less than the Tg of the light-emitting polymers P22 to P28, which is independent of the firing temperature. These results demonstrate that it is necessary to use a light emitting polymer with a high Tg, such as P28 with a Tg of 266°C, to improve the thermal stability of the hybrid small molecule-polymer OLED.

Various modifications will be apparent to those skilled in the art. For example, the substrate 10 may be made of a plastic (eg, polyethylene naphthalate, PEN or polyethylene terephthalate, PET type). The HIL 30 may preferably have a thickness of 20 to 100 nm, more preferably 40 to 60 nm. The IL 40 may preferably have a thickness of 10 to 50 nm, more preferably 20 to 30 nm. The LEP layer 50 may preferably have a thickness of 10 to 150 nm, more preferably 50 to 70 nm.

Referring to FIG. 1A , the first layer of the cathode electrode 60 may be made of any halogenated alkali or alkaline earth metal salt, and the double layer encapsulation is such that the energy level for charge injection matches the LEP. It can be any metal pair.

Referring to FIG. 1B , if the LUMO (lowest unoccupied molecular orbital) level of the ETL 62 is adjusted to the LUMO level of the LEP, the vacuum deposited electron transporting and electron donating material of the ETL 62 can be of any vacuum deposited ratio. - may be a polymeric material. Energy level control is important to ensure electron injection from the cathode through the ETL to the emissive layer. By using vacuum deposition, ETL can be provided as a thick layer for improved production yield. The ETL 62 may preferably be between 5 and 50 nm thick. In addition, vacuum deposited ETL can be any metal, conductive oxide or metal alloy that can be deposited as a thick (100-300 nm), pin-hole-free layer, such as Ag, ITO, Au, Mg, Allows freedom of choice of the encapsulation material for the cathode layer 64, which may be an MgAg alloy or the like.

The present invention provides an organic light emitting device having an electron transport layer on the light emitting layer comprising a light emitting polymer and an electron transport material, the glass transition temperature (Tg(ETM)) of the electron transport material measured in degrees Celsius (° C.) and a glass transition temperature (Tg(LEP)) of the light emitting polymer satisfies the following inequality, and the glass transition temperature of the electron transport material exceeds 140°C:

Tg(ETM) + Tg(LEP) > 270.

The device may comprise a polymeric light emitting layer and a non-polymer (small molecule) electron transport layer deposited on the light emitting layer, wherein the electron transport layer comprises an electron transport material containing a small molecule host and an electron donating material containing a small molecule dopant. Including blends.

Claims (20)

delete delete delete delete delete delete delete delete a light emitting layer comprising a light emitting polymer;
an organic electron transport layer on the light emitting layer comprising an electron transport material that is a non-polymeric molecular host, and an electron donor material; and
a cathode in direct contact with the organic electron transport layer on the organic electron transport layer
As an organic light emitting device comprising a,
The glass transition temperature (Tg(ETM)) of the electron transport material and the glass transition temperature (Tg(LEP)) of the light-emitting polymer, measured in degrees Celsius (°C), satisfy the following inequality,
An organic light emitting device in which the glass transition temperature of the light emitting polymer exceeds 180° C.:
Tg(ETM) + Tg(LEP) > 280. 10. The method of claim 9,
An organic light emitting device having a glass transition temperature of the light emitting polymer exceeding 200°C. 10. The method of claim 9,
An organic light emitting device having a glass transition temperature of the light emitting polymer exceeding 220°C. 10. The method of claim 9,
An organic light emitting device having a glass transition temperature of the light emitting polymer exceeding 240°C. 10. The method of claim 9,
An organic light emitting device having a glass transition temperature of the light emitting polymer exceeding 260°C. delete 10. The method of claim 9,
An organic light emitting device wherein the molecular host is zirconium quinolinolate of the following formula ET1:
Formula ET1

. delete 10. The method of claim 9,
wherein the electron donating material is a non-polymeric molecular dopant. ◈Claim 18 was abandoned when paying the registration fee.◈ 18. The method of claim 17,
The organic light-emitting device wherein the molecular dopant is tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II). forming a light emitting layer with a solution containing a light emitting polymer;
co-depositing an electron transport material and an electron donor material on the light emitting layer by vapor deposition to form a mixed organic electron transport layer; and
forming a cathode on the organic electron transport layer in direct contact with the organic electron transport layer;
A method of manufacturing an organic light emitting device according to any one of claims 9 to 13, 15, 17 and 18, comprising:
The glass transition temperature (Tg(ETM)) of the electron transport material and the glass transition temperature (Tg(LEP)) of the light-emitting polymer, measured in degrees Celsius (°C), satisfy the following inequality,
wherein the glass transition temperature of the light emitting polymer is greater than 180°C:
Tg(ETM) + Tg(LEP) > 280. 20. The method of claim 19,
A manufacturing method in which the step of forming the light emitting layer with the solution containing the light emitting polymer is performed by spin coating, inkjet printing, dip coating, slot die printing, nozzle printing, roll-to-roll printing, gravure printing or flexo printing.

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