TW201526327A - Organic light-emitting device and method - Google Patents

Abstract

An organic light-emitting device having a light-emitting layer comprising a light-emitting polymer, and an electron-transporting layer on the light-emitting layer and comprising an electron-transporting material, wherein the glass transition temperatures, measured in degrees Celsius, of the electron-transporting material (Tg(ETM)) and the light-emitting polymer (Tg(LEP)) satisfy the following inequality: Tg(ETM)+Tg(LEP) > 270 and wherein the glass transition temperature of the electron-transporting material is greater than 140 degrees Celsius. The device may comprise a polymer light-emitting layer and a non-polymeric (small-molecule) electron-transporting layer deposited on the light-emitting layer, the electron-transporting layer comprising a blend of electron-transporting materials containing small-molecule hosts and electron-donating materials containing small-molecule dopants.

Description

Organic light emitting device and method

The present invention relates to an organic light-emitting device and a method of fabricating the same. More particularly, the present invention relates to organic light-emitting devices comprising a polymeric light-emitting layer and a non-polymer (also referred to as "small molecule") electron transport layer. These devices are sometimes referred to as "mixing devices."

Electronic devices containing active organic materials are attracting increasing attention due to their use in devices such as organic light-emitting diodes (OLEDs), organic light-responsive devices (specifically, organic photovoltaic devices and organic light sensing). , organic transistors and memory devices. Devices containing organic materials offer a variety of benefits (eg, low weight, low power consumption, and flexibility) and can be used in the manufacture of displays or lighting fixtures. The use of soluble organic material polymers or small molecules allows solution processing in the fabrication of device layers, such as inkjet printing, spin coating, dip coating, slot die printing, nozzle printing, roll-to-roll Printing, gravure and flexographic printing. Moreover, the use of insoluble small molecules enables the fabrication of device layers by vacuum deposition. Examples of vacuum deposition methods are vacuum sublimation and co-evaporation (or simultaneous evaporation) of a plurality of different small molecule materials.

The OLED can comprise a substrate carrying 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 through the anode and electrons are injected through the cathode. The hole in the highest occupied molecular orbital (HOMO) of the luminescent material is combined with the electrons in the lowest unoccupied molecular orbital (LUMO) to form a light-releasing energy during recombination. child.

The luminescent layer is comprised of or includes luminescent materials that can include small molecules, polymers, and dendritic polymeric materials. Suitable luminescent polymers include poly(arylene extended vinyl) (e.g., poly(p-phenylene vinyl) as disclosed in WO 90/13148) and polyaryl (e.g., polyfluorene). In US 4,539,507, the luminescent material is (8-hydroxyquinoline)aluminum ("Alq3", also referred to herein as ET3). WO 99/21935 discloses dendrimer luminescent materials.

The luminescent layer can alternatively consist of or include a semiconductor host material and an luminescent dopant, wherein energy is transferred from the host material to the luminescent dopant. For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent dopant (ie, a luminescent material that emits light via decay of singlet excitons), and Appl. Phys .Lett., 2000, 77, 904 discloses a host material doped with a phosphorescent luminescent dopant (i.e., a luminescent material that emits light via decay of triplet excitons).

The charge transport layer is comprised of or includes materials suitable for transporting holes and/or electrons, which may include small molecules, polymers, and dendrimer materials. Suitable electron transport polymers include triazines and pyrimidines, such as those disclosed in U.S. Patent No. 8,003,227. Suitable hole transport polymers include triarylamines such as those disclosed in the applicant's earlier applications WO 02/066537 and WO 2004/084260.

Advantageously, the electron transport layer comprises a semiconductor host material and a semiconductor dopant material. Typical examples of doped electron transport materials are: fullerene C60 doped with acridine orange base (AOB); 苝-3,4,9,10-tetracarboxylic acid doped with leuco crystal violet -3,4,9,10-dianhydride (PTCDA); tetra-tungsten by tetrakis (1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) (II) (W ₂ (hpp) ₄ , (ND1)) doped 2,9-di(phenanthrene-9-yl)-4,7-diphenyl-1,10-phenanthroline; 6-bis-(dimethylamino)-acridine-doped naphthalenetetracarboxylic acid dianhydride (NTCDA); bisvalyl-dithio) tetravalefulvalene (BEDT-TTF) ) doped NTCDA.

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

In a typical OLED structure, an electron transport layer comprising a host-dopant small molecule material can be directly vapor deposited onto a light-emitting layer comprising a polymer and then covered with a layer of thermally evaporated metal. The metal layer will typically form the cathode metal contacts of the device. However, such devices typically suffer from very poor thermal stability after baking, which manifest themselves as poor device parameters such as PL (photoluminescence), operating voltage, and external quantum efficiency. These parameters are typically measured at room temperature after the device has been baked at a predetermined temperature for a predetermined period of time and then compared to the values measured on the device prior to the baking step.

The thermal stability of an OLED is a critical parameter with respect to device performance because accelerated degradation at the operating temperature of the display significantly reduces the useful life of the display. Accordingly, there is a need in the art to provide thermally stable organic light-emitting devices that are, for example, photoluminescent, operating voltage, and external quantum efficiency that are not altered by the baking apparatus.

According to a first aspect of the present invention, there is provided 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 and comprising an electron transport material, wherein the electron transport material (Tg(ETM)) and the light-emitting layer The glass transition temperature (measured in °C) of the polymer (Tg(LEP)) satisfies the following inequality: Tg(ETM)+Tg(LEP)>270

And wherein the glass transition temperature of the electron transporting material is higher than 140 °C.

The glass transition temperature (Tg) of an electron transporting material (also referred to as "host") is greater than 140 ° C as an indication of the relatively bulky nature of the material, thereby reducing its temperature to the luminescent polymer even at temperatures near the Tg of the luminescent polymer. The spread of it. Therefore, the size of the host molecule of the electron transport layer (ETL) plays an important role in determining the thermal stability of the OLED.

Preferably, the electron transporting material has a glass transition temperature of higher than 155 ° C, and more preferably higher than 175 ° C.

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

Quinolinium zirconium ET1 can be obtained, for example, by the procedure set forth in Zhurnal Neorganitcheskoi Khimii 1961, Vol. 6, pp. 1338-1341, which can be obtained by, for example, the procedure set forth in CS150747.

The larger nature of the ET1 body is also evident from the difference in Tg (179 ° C for ET1 compared to 105 ° C for ET 2). It is believed that due to its larger physical size, larger bulky molecules are less likely to diffuse into the luminescent polymer.

The electron transport layer may further comprise an electron donating material. Advantageously, the electron donating material is a non-polymeric molecule (also referred to as a "small molecule") dopant, preferably ND1. Small molecule dopants are highly reactive compounds that ensure the formation of sufficient electrons for optimal charge transport within the electron transport layer.

According to a second aspect of the present invention, there is provided 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 and comprising an electron transport material, wherein the electron transport material (Tg(ETM)) and the light-emitting layer The glass transition temperature of the polymer (Tg(LEP)) satisfies the following inequality: Tg(ETM)+Tg(LEP)>280

And wherein the luminescent polymer has a glass transition temperature higher than 180 °C.

Generally, the glass transition of an amorphous polymer is a reversible conversion from a hard or solid state to a softened, viscous state when the polymer is heated. This conversion involves a smooth change in the viscosity of the polymer without any significant change in the polymer structure. The Tg was measured using DSC (differential scanning calorimetry).

The Tg values provided herein were as measured using a Perkin Elmer Pyris 1 differential scanning calorimeter. The Tg values given herein are extrapolated half-Cp (specific heat capacity).

To measure the Tg value, the samples were weighed in an aluminum pan and sealed with an aluminum lid and measured for the empty pan and lid, and heated and cooled using a nitrogen purge gas.

The sample was heated from 30.00 ° C to 300.00 ° C at a rate of 40.00 ° C / min for 1.0 min, cooled from 300.00 ° C to 30.00 ° C at a rate of 40.00 ° C / min and held for another 1.0 min, then this process was repeated twice.

The Tg value is given after the second heating and is verified against the value from the third heating.

Luminescent polymers having a glass transition temperature in excess of 180 ° C and baked at about 80 ° C to 120 ° C may not undergo a change in viscosity. Therefore, any small molecules (host or dopant molecules) deposited directly on the luminescent layer do not diffuse into the luminescent polymer during the baking step, and can preserve the integrity of the PL and operating voltage of the OLED, such as during baking. Measured after the baking step.

Preferably, the luminescent polymer is selected or adapted such that the Tg is above 200 °C, more preferably above 220 °C, still more preferably above 240 °C and even more preferably above 260 °C.

The luminescent polymer can be a homopolymer or a copolymer comprising two or more different repeating units. Preferably, the luminescent polymer is a copolymer.

The luminescent polymer can be a conjugated or non-conjugated polymer. An exemplary non-conjugated polymer is polyvinyl carbazole (PVK).

The luminescent polymer preferably has a conjugated polymer comprising a backbone conjugated to repeating units adjacent to the repeating unit.

The luminescent polymer preferably comprises an extended aryl repeating unit. Exemplary extended aryl repeat units include a phenyl extended repeat unit and a fluorene repeat unit.

An exemplary phenyl extended repeat unit is a 1,4-linked phenyl repeating unit which is unsubstituted or substituted with one or more substituents. Exemplary substituents include a C _1-20 alkyl group wherein one or more non-adjacent C atoms of the C _1-20 alkyl group may be optionally substituted aryl or heteroaryl, preferably unsubstituted benzene a phenyl group substituted with one or more C1-10 alkyl groups; O; S; substituted N; C=O; or -COO-substituted, and wherein one or more of C _1-20 alkyl groups Atoms can be replaced by F. The substituted N, when present, can be a hydrocarbyl group such as a C _1-10 alkyl group, an unsubstituted phenyl group or a phenyl group substituted with one or more C _1-10 alkyl groups.

An exemplary 茀 repeating unit has the formula (I):

Wherein R ⁸ is the same or different and is a substituent at each occurrence, wherein two groups R ⁸ may be linked to form a ring; R ⁷ is a substituent; and d is 0, 1, 2 or 3.

Preferably, each d is 0.

In the case of at least one of the groups d, 1, 2 or 3, each R ⁷ is optionally selected from the group consisting of alkyl groups, such as C _1-20 alkyl groups, wherein one or more non-adjacent C atoms Substituting O, S, C=O and -COO-; optionally substituted aryl; and optionally substituted heteroaryl. When present, R ^{7 is} preferably selected from C _1-20 alkyl and substituted or unsubstituted aryl such as unsubstituted phenyl or phenyl substituted by one or more C _1-20 alkyl groups. .

Each R ⁸ may be independently selected from the group consisting of: -alkyl, optionally C _1-20 alkyl, wherein one or more non-adjacent C atoms may be optionally substituted aryl or heteroaryl, O, S, C=O or -COO-substitution, and one or more H atoms may be replaced by F; and a group of the formula -(Ar ⁷ ) _r wherein each Ar ^{7 is} independently unsubstituted or Substituted aryl or heteroaryl, preferably unsubstituted or substituted phenyl, and r is at least 1, optionally 1, 2 or 3. If one or more Ar ⁷ groups are substituted, the or each substituent may be substituted with a substituent R ¹ selected from the group consisting of C _1-20 alkyl groups, wherein one or more non-adjacent C atoms may pass through O, S, C=O and -COO- substitutions. Preferably, R ¹ is a C _1-10 alkyl, C _1-10 alkoxy or alkoxy ether group. The alkoxy ether group can have the formula -O(CH ₂ O) _n -R ² wherein R ² is C _1-5 alkyl and n is 1, 2 or 3.

One or both substituents R ⁸ of one or more repeating units of formula (I) may be selected from a high glass transition temperature selected to provide a luminescent polymer, preferably at a glass transition temperature above 180 °C.

The high glass transition temperature polymer comprises a repeating unit of formula (I), optionally at least 10 mol%, 20 mol%, 30 mol%, 40 mol% or 50 mol% of repeating units of formula (I), wherein one or two groups R ⁸ are A group selected from the group consisting of: - a group selected from the group consisting of:

Wherein * represents an attachment point to a unit of formula (I), and R ¹ is as described above, preferably a C _1-5 alkyl or C _1-5 alkoxy or alkoxy ether group; C _1-5 alkyl.

The luminescent polymer can comprise an arylamine repeating unit. Preferably, the repeating unit of the luminescent polymer comprises an extended aryl repeating unit, more preferably a fluorene repeating unit, and an arylamine repeating unit.

Optionally, the repeating unit of the polymer consists of one or more extended aryl repeating units, preferably one or more fluorene repeating units, and one or more arylamine repeating units.

The arylamine repeating unit may have the formula (II):

Wherein Ar ⁸ , Ar ⁹ and Ar ¹⁰ are independently selected, at each occurrence, from substituted or unsubstituted aryl or heteroaryl, g is 0 or an integer, preferably 0 or 1, R ¹³ substituent , c, d and e are each independently 1, 2 or 3, preferably 1, and are directly linked to either of Ar ⁸ , Ar ⁹ , Ar ¹⁰ and R ¹³ of the same N atom of formula (II) It can be linked by a direct bond or a divalent group.

R ¹³ which may be the same or different at each occurrence when g is at least 1, is preferably selected from the group consisting of an alkyl group (for example, C _1-20 alkyl group), Ar ¹¹ or a branched or linear Ar ¹¹ group. Wherein Ar ¹¹ independently, upon each occurrence, is optionally substituted with an aryl or heteroaryl group. Exemplary groups R ¹³ are C _1-20 alkyl, phenyl, and phenyl substituted with one or more C _1-20 alkyl groups.

Preferred repeating units of formula (II) have subformulas 1-3:

Preferably, the Ar ⁸ , Ar ⁹ , Ar ¹⁰ and Ar ¹¹ -based aromatic groups, each of which may be unsubstituted or substituted with one or more substituents.

Depending on the case, the Ar ⁸ , Ar ¹⁰ and Ar ¹¹ phenyl groups of the formula 1 may each independently be unsubstituted or substituted with one or more substituents.

Depending on the case, the Ar ⁹ of the formula 1 is an unsubstituted or substituted phenyl group or an unsubstituted or substituted polycyclic aromatic group, as described, for example, in WO 2005/049546 and WO 2013/108022. This is incorporated herein by reference.

Optionally, Ar ⁸ , Ar ⁹ and Ar ¹¹ phenyl groups of the formulae 2 and 3, each of which may be independently unsubstituted or substituted with one or more substituents.

The arylamine repeating unit can be provided in an amount of from about 0.5 mol% up to about 50 mol%, optionally up to 40 mol%, optionally up to 30 mol%, and optionally up to 10 mol%.

Preferred substituents (if present) of Ar ⁸ , Ar ⁹ , Ar ¹⁰ and Ar ¹¹ are C _1-20 hydrocarbyl groups, optionally C _1-20 alkyl groups.

Preferably, the electron transporting material is a non-polymeric molecular host, advantageously ET1. Adjusting the bulky molecular host with a luminescent polymer having a Tg in excess of 180 °C can substantially reduce the diffusion of the small molecule host material into the luminescent layer.

The electron transport layer may further comprise an electron donating material. Advantageously, the electron donating material is a non-polymeric (also referred to as "small molecule") molecular dopant, preferably ND1.

According to a third aspect of the present invention, there is provided a method of forming an organic light-emitting device, the method comprising depositing a solution comprising a light-emitting polymer to form a light-emitting layer; and co-depositing an electron transport material and an electron supply by vapor deposition on the light-emitting layer Materials to form a hybrid electron transport layer.

The use of a combination of solution and vapor deposition methods to separately deposit the luminescent layer and the electron transport layer mitigates the need to render the luminescent layer insoluble, for example, by crosslinking the luminescent polymer.

Preferably, the deposition of the solution containing the luminescent polymer is carried out by spin coating, ink jet printing, dip coating, slit type extrusion printing, nozzle printing, roll-to-roll printing, gravure printing, and flexographic printing. .

10‧‧‧Substrate

20‧‧‧Anode electrode

30‧‧‧ Hole Injection Layer (HIL)

40‧‧‧Intermediate (IL)

50‧‧‧Light Emitting Polymer (LEP) layer

52‧‧‧Lighting polymer layer

60‧‧‧Cathode electrode

60a‧‧‧NaF

60b‧‧‧Al

60c‧‧‧Ag

62‧‧‧Electronic Transport Layer (ETL)

64‧‧‧Al encapsulated cathode layer

100‧‧‧Organic Luminescent Diodes

200‧‧‧Organic Luminescent Diodes

300‧‧‧Organic Luminescent Diodes

The invention will now be described by way of example only with reference to the accompanying drawings in which: FIG. 1a is a cross-sectional view of an OLED as a comparative example of the OLED of the first aspect of the invention; FIG. 1b is an OLED according to a first aspect of the invention A cross-sectional view of an embodiment; FIGS. 2a to 2c are graphs of relative PL drop, ΔCIE-x, and ΔCIE-y, respectively, measured after baking the 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; Figure 3 is a plot of relative PL drop measured at different times (time window over 600 hours) after baking the OLED according to the first aspect of the invention at 85 °C; Figure 4 is a graph showing the increase in operating voltage measured at different times (time window over 600 hours) after baking the OLED according to the first aspect of the present invention at 85 ° C in an inert N 2 atmosphere and air; Figure 5 is a cross-sectional view of an embodiment of an OLED according to a second aspect of the present invention; Figure 6 is a graph showing the difference between the relative drop of the device PL and the glass transition temperature Tg of the wide range of light-emitting polymers and the device baking temperature Tb. Diagram of change.

Figure 1a (which is not drawn to any scale) schematically illustrates an OLED 100 as a comparative example of an OLED according to a first aspect of the present invention. 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: anode electrode 20, hole injection layer (HIL) 30, intermediate layer (IL) 40, luminescence Polymer (LEP) layer 50 and cathode electrode 60.

The anode electrode 20, typically made of ITO (indium tin oxide), is 45 nm thick and is deposited by physical vapor deposition (e.g., vacuum or thermal evaporation). HIL 30 is 50 nm thick and is deposited by spin coating a solution known as Plexcore © OC AQ-1200 from Plextronics Corporation. The IL 40 is 22 nm thick and is deposited by a solution of a spin-coated hole transporting polymer P10. The polymer P10 contained the monomers M11 to M14 in the following weight %: 50% M11, 30% M12, 12.5% M13 and 7.5% M14. The chemical structure of these monomers is shown below:

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

Polymers P10 and P20 are synthesized using Suzuki polymerization, as is well known in the art. Monomer M11 is described in WO2002/092723, M12 is described in WO2005/074329, M13 is described in WO2002/092724, M14 is described in WO2005/038747, M21 is described in WO2002/092724, and M22 is described in US 6,593,450. M23 is described in WO2009/066061, and M24 is described in WO2010/013723, and M25 is set forth in WO2004/060970.

The cathode electrode 60 is composed of three stacked layers of NaF 60a, Al 60b, and Ag 60c having thicknesses of 5 nm, 20 nm, and 200 nm, respectively. The NaF is deposited by thermal evaporation on the LEP layer 50 and then by thermal evaporation of a double layer stack of Al and Ag.

In operation, the holes injected from the anode electrode 20 and the electrons injected from the cathode electrode 60 are combined in the LEP layer 50 to form excitons that can be attenuated upon recombination to provide light upon recombination. Without wishing to be bound by theory, it is believed that the NaF present at the interface between the LEP P20 and the Al cathode during vapor deposition of the aluminum cathode prevents the formation of a covalent carbon-aluminum bond that would result in the formation of an insulating interface against LEP. Destruction of the conjugated π-system in P20. Conversely, the presence of NaF at the interface occurs with electron transfer to LEP P20 and results in local n-doping of the polymer at the interface with the cathode. It is assumed that NaF does not diffuse into the LEP P20 when the OLED 100 is thermally annealed, and thus the OLED 100 is referred to as a thermally stable organic light-emitting device. It is assumed that due to the formation of this composite, NaF does not diffuse into the LEP P20 when the OLED 100 is thermally annealed. Therefore, the OLED 100 is referred to as a thermally stable organic light-emitting device.

Figure 1b (which is not drawn to any scale) schematically illustrates an embodiment of an OLED 200 in accordance with a first aspect of the present invention. In Figure 1b, the same reference numerals are used for the corresponding parts of Figure 1a. In contrast to the three stacked cathode layers having NaF, Al, and Ag on the LEP layer 50, the OLED 200 of the present invention comprises a double layer having an electron transport layer (ETL) 62 and an Al encapsulated cathode layer 64. Both layers were deposited by thermal evaporation at thicknesses of 20 nm and 200 nm, respectively.

ETL 62 comprises an electron transport material comprising any of a small molecule host (eg, ET1, ET2, ET3, and ET4). The chemical structure of ET3 and ET4 is illustrated as follows:

ET3 is commercially available, and ET4 can be as described, for example, in WO 2010/057471 The program is obtained. The ETL 62 further comprises an electron donating material consisting of a small molecule dopant (e.g., ND1).

The host and dopant material of the hybrid small molecule-polymer OLED 200 of the present invention have been simultaneously evaporated (or co-evaporated) by thermal evaporation to form an electron transport layer ETL comprising a blend of the above host and dopant small molecule materials. 62.

In Example 1, ETL 62 comprises a blend of ET2 (host) and ND1 (dopant) on top of luminescent polymer P20. The hybrid OLED 200 of Example 1 typically experienced poor thermal stability after baking, which manifest itself as a drop of more than 50% in the device PL (photoluminescence) and an increase in device operating voltage of more than 2V (eg, at 10 mA/ Measured under cm ² ). The PL and voltage rise values are typically measured at room temperature after baking the OLED 200 at 120 ° C for 1 hour and then compared to the values measured on the device prior to the baking step. It is assumed that the above thermal instability is caused by the diffusion of the ETL host material ET2 into the luminescent polymer P20.

Example 2 demonstrates that the thermal stability of the inventive OLED 200 when ET2 is replaced by a replacement ETL host material ET1 having a relatively large nature, thereby preventing its diffusion into the polymer P20 even at a baking temperature close to the Tg of the polymer P20. Sex has been greatly improved. The bulky nature of the bulk ET1 is evident from the difference in glass transition temperature Tg between ET2 (Tg at 105 °C) and ET1 (Tg at 179 °C). Moreover, the thermally stable OLED 200 of Example 2 of the present invention is comparable or similar to the comparative example OLED 100 fabricated using a NaF/Al/Ag cathode, as summarized in Table 1 below.

The main advantage of the main body ET1 of the example 2 over the main body ET2 of the example 1 is that it allows The hybrid small molecule-polymer OLED 200 of the present invention is fabricated from a luminescent polymer having a relatively low glass transition temperature. These devices will therefore meet the minimum thermal stability required for commercially available OLED applications. Additionally, OLEDs exhibiting improved thermal stability are shown to utilize electron transport materials that are compatible with processes that require high temperature manufacturing conditions, such as thermal evaporation buffer layers in top emitting devices. Moreover, the use of ET1 as the host material allows direct testing to determine important device properties such as color, efficiency, and lifetime at high annealing and/or operating temperatures.

Figures 2a through 2c show the relative PL drop (Figure 2a) and ΔCIE coordinates (Figures 2b and 2c) measured for the OLED 200 of Figure 1b. In addition to the PL and ΔCIE coordinates of the OLED 200 of Examples 1 and 2 above, the graph shows Example 3 (where ETL 62 contains blend ET4: ND1) and Example 4 (where ETL 62 contains blend ET3: ND1) The same parameters. The PL, ΔCIE-x and ΔCIE-y parameters were measured at room temperature after baking at 120 ° C for 1 hour and then compared to the parameters measured on the device prior to the baking step.

Without wishing to be bound by theory, it is assumed that a relatively large small molecule body is less likely to diffuse into the polymer P20 during baking. It also assumes that the Tg of the small molecule material provides an indication of the bulkiness of the material and Table 2 below summarizes the glass transition temperatures of all of the bodies of the ETL 62 used to make the OLED 200 of the present invention.

Referring to Figure 2a, when ET2 from Example 1 (which has the lowest Tg and the highest PL drop) to ET4 of Example 3, ET3 of Example 4, and ET1 of Example 2 (which has the highest Tg and lowest PL drop), the PL drop display It is inversely proportional to the increase in Tg. These results demonstrate that the thermal stability of the device is strictly affected by the nature of the host used in the co-evaporated electron transport layer ELT 62 and can therefore be improved by the use of a suitable host.

The most suitable host of the ET1 system has been identified, the thermal stability of the OLED 200 of Example 1 (where ETL 62 comprises the blend ET1: ND1) is further baked by the device at 85 ° C over 600 Hours to study. The results of this study are plotted in Figure 3 (which shows a decrease in PL) and Figure 4 (which shows the change in device operating voltage ΔV).

As can be readily seen from the results of Figure 3, the thermal stability of the apparatus after baking at 85 °C significantly exceeded the time window of more than 600 hours used in the test. The results of Example 1 OLEDs were comparable to those observed for comparison devices using known NaF/Al/Ag cathodes rather than the ETL/Al/Ag structures of the present invention.

Although the PL drop appears to be independent of the baking environment, only about 0.2 V (at 10 mA/cm ² ) is observed in Figure 4 when the device is baked in an inert N ₂ atmosphere (such as a nitrogen-filled glove box). The reasonable voltage rise of the test). Devices that are baked in air exhibit much greater voltage rises, sometimes exceeding 0.7V.

According to a second aspect of the invention, an alternative to using a bulky body to improve the thermal stability of the OLED is to increase the glass transition temperature Tg of the luminescent polymer located below the electron transport layer.

Figure 5, which is not drawn to any scale, schematically illustrates an embodiment of an OLED 300 in accordance with a second aspect of the present invention. In Figure 5, the same reference numerals are used for the corresponding parts of Figure 1b. The polymer P20 of the LEP layer 50 of Figure 1b has been replaced by an LEP layer 52 comprising polymers P22, P24, P26 and P28 having a higher glass transition temperature. The constituent monomers of each of the polymers are shown in Table 3 below along with the corresponding weight percent of each of the above polymers and the glass transition temperature of the polymer.

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

The polymers of P22 to P28 are synthesized using Suzuki polymerization, as is well known in the art. Monomeric M26 is disclosed in WO2002/092723 and M27 is disclosed in WO2005/074329.

Mixed small molecule-polymer OLED 300 fabricated on top of LEP layer 52 comprising polymers P22, P24, P26 and P28 by co-evaporation of ETL 62 comprising a blend of ET2 (host) and ND1 (dopant) The PL was measured at room temperature before baking and after OLED 300 was baked at 120 ° C for 1 hour. Figure 6 is a graph showing the temperature difference between the glass transition temperature Tg and the baking temperature Tb of the polymer P22 to P28 with respect to PL.

It is believed that the relative PL drop associated with the thermal instability of OLED 300 is due to the diffusion of small molecule host material ET2 into the underlying LEP layer 52. As can be derived from Figure 6, the diffusion process can be carried out at temperatures well below the Tg of the luminescent polymer (about 160 ° C). In other words, the starting point of the PL drop is lower than the Tg of the light-emitting polymers P22 to P28 by about 160 ° C and is independent of the baking temperature. These results demonstrate that the thermal stability of the modified hybrid small molecule-polymer OLED requires the use of a high Tg luminescent polymer, such as P28 with a Tg of 266 °C.

Various changes will be apparent to those skilled in the art. For example, the substrate 10 can be made of a plastic such as polyethylene naphthalate PEN or polyethylene terephthalate PET type. The HIL 30 may preferably be 20 nm to 100 nm thick and more preferably 40 nm to 60 nm thick. The IL 40 may preferably be 10 nm to 50 nm thick and more preferably 20 nm to 30 nm thick. LEP layer 50 is preferred It may be 10 nm to 150 nm thick and more preferably 50 nm to 70 nm thick.

Referring to Figure 1a, the first layer of cathode electrode 60 can be made of any halogenated alkali or alkaline earth metal salt, and the double layer encapsulation can be any metal pair that matches the energy level of the charge injection to the energy level of the LEP.

Referring to Figure 1b, the vacuum deposited electron transport and electron donating material of ETL 62 can be any vapor deposited non-polymeric material, with the condition that the LUMO (lowest unoccupied molecular orbital) level of the ETL is adjusted to the LUMO level of the LEP. This level adjustment is critical to ensure that electrons pass through the ETL from the cathode and into the luminescent layer. By using a vacuum deposition method, ETL can be provided as a thick layer for improving production yield. The ETL 62 preferably has a thickness of 5 nm to 50 nm. In addition, the vacuum deposited ETL can be freely selected for the encapsulating material for the cathode layer 64, which can be any metal, conductive oxide or metal alloy capable of evaporating into a pinhole free layer (100 nm to 300 nm), such as Ag, ITO, Au, Mg, MgAg alloy, and the like.

The present invention provides 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 and comprising an electron transport material, wherein the electron transport material (Tg(ETM)) and the light-emitting polymer (Tg (LEP)) The glass transition temperature (measured in °C) satisfies the following inequality: Tg(ETM)+Tg(LEP)>270

And wherein the glass transition temperature of the electron transporting material is higher than 140 °C. The device may comprise a polymer light-emitting layer and a non-polymer (small molecule) electron transport layer deposited on the light-emitting layer, the electron transport layer comprising an electron transport material containing a small molecule body and an electron donating material containing a small molecule dopant Blend.

10‧‧‧Substrate

20‧‧‧Anode electrode

30‧‧‧ Hole Injection Layer (HIL)

40‧‧‧Intermediate

50‧‧‧Light Emitting Polymer (LEP) layer

62‧‧‧Electronic Transport Layer (ETL)

64‧‧‧Al encapsulated cathode layer

200‧‧‧Organic Luminescent Diodes

Claims (20)

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 and comprising an electron transport material, wherein the electron transport material (Tg(ETM)) and the light-emitting polymer (Tg ( The glass transition temperature (measured in ° C) of LEP)) satisfies the following inequality: Tg(ETM) + Tg(LEP) > 270 and wherein the glass transition temperature of the electron transporting material is higher than 140 °C. The device of claim 1, wherein the glass transition temperature of the electron transporting material is higher than 155 °C. The device of claim 1, wherein the glass transition temperature of the electron transporting material is higher than 175 °C. The device of any one of claims 1 to 3, wherein the electron transporting material is a non-polymeric molecular host. The device of claim 4, wherein the molecular main system has a quinoline zirconium of the formula The device of any one of claims 1 to 3, wherein the electron transport layer further comprises an electron donating material. The device of claim 6, wherein the electron donating material is a non-polymeric molecular dopant. The device of claim 7, wherein the molecular dopant is tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinyl)di-tungsten (II) ). 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 and comprising an electron transporting material, wherein a glass transition temperature of the electron transporting material (Tg(ETM)) and the light-emitting polymer (Tg(LEP)) satisfies the following inequality: Tg(ETM)+ Tg(LEP) > 280 and wherein the glass transition temperature of the luminescent polymer is above 180 °C. The device of claim 9, wherein the luminescent polymer has a glass transition temperature of greater than 200 °C. The device of claim 9, wherein the luminescent polymer has a glass transition temperature of greater than 220 °C. The device of claim 9, wherein the luminescent polymer has a glass transition temperature of greater than 240 °C. The device of claim 9, wherein the luminescent polymer has a glass transition temperature of greater than 260 °C. The device of any one of claims 9 to 13, wherein the electron transporting material is a non-polymeric molecular host. The device of claim 14, wherein the molecular main system has a quinoline zirconium of the formula The device of any one of claims 9 to 13, wherein the electron transport layer further comprises an electron donating material. The device of claim 16, wherein the electron donating material is a non-polymeric molecular dopant. The device of claim 17, wherein the molecular dopant is tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinyl)di-tungsten (II) ). A method of forming an organic light-emitting device according to any one of claims 1 to 18, comprising depositing a solution containing a light-emitting polymer to form a light-emitting layer; and co-depositing an electron-transport material on the light-emitting layer by vapor deposition And supplying an electronic material to form a mixed electron transport layer. The method of claim 19, wherein depositing the solution comprising the luminescent polymer is by spin coating, inkjet printing, dip coating, slot die printing, nozzle printing, roll-to-roll Printing, gravure and flexographic printing.