TWI500653B - Polymer, electron hole transferring material using the same and organic light emitting element comprising the electron hole transferring material - Google Patents

Description

Polymer, hole transfer material and organic light emitting diode element

The present invention relates to a hole transfer material, and more particularly to a polymer comprising a conjugated polymer backbone structure having excellent hole transport properties and a side chain structure of a crosslinkable functional group, by physics The hole-transferring material formed by cross-linking greatly increases the ability to transmit holes and can be applied to organic light-emitting diode elements.

Organic Light Emitting Diode (OLED) was first developed in 1987 by Kodak's CWTang and SAVanSlyk, etc., using vacuum evaporation to separate the hole transport material and electron transport. The material is plated on transparent indium tin oxide (ITO) glass, and then vapor-deposited a metal electrode to form a self-luminous OLED element, which has high brightness, fast reaction speed, light weight and shortness, Full color, no viewing angle difference, no need for liquid crystal display backlight board, saving lamp source and power consumption, it is widely used in the production of large area, high brightness, full color flat panel display.

Generally, the structure of the OLED device includes a transparent substrate, a transparent anode, a hole transfer layer, an organic light-emitting layer, an electron transport layer, and a metal cathode from bottom to top, when a forward bias is applied. At voltage, the hole is injected by the anode and electrons are injected from the cathode, and the potential difference caused by the externally applied electric field causes the electrons and holes to move in the film, thereby causing recombination in the organic light-emitting layer; The energy released by the combination of electrons and holes will excite the luminescent molecules of the organic luminescent layer to form an excited state, and when the luminescent molecules decay from the excited state to the ground state, a certain proportion of them The energy will be released in the form of photons.

Among the existing organic materials, poly(3,4-extended ethyldioxythiophene) (PEDOT)/poly-p-styrenesulfonic acid (PSS) is commonly used in the industry, and there is no other market available on the market. Replaces PEDOT/PSS organic materials. However, PEDOT/PSS is water-soluble, so it is easy to disperse in water, and since it is acidic on PSS, it will corrode the anode surface after being dissolved in water. Moreover, since PSS itself is easy to absorb water, it will lead to the efficiency of OLED components. The service life is reduced.

In addition, the prior art discloses an organic material of a hole transport layer, mainly using a thermosetting polymer, but the polymerization process needs to be baked for 45 to 60 minutes in an environment having nitrogen gas and high temperature (about 225 ° C). Such a molding method is actually difficult to handle, resulting in failure to mass production. In addition, the hole transfer layer can also use thermal cross-linking materials, in addition to improving the solvent resistance of the molecules, and greatly improving the thermal properties of the molecules and the ability to transport holes, but such thermal cross-linking molecules need to rely on Cross-linking occurs at high temperatures. Such harsh conditions tend to damage other materials in the OLED component, and it requires an additional heating step to make the fabrication process more cumbersome, resulting in the application of such thermally crosslinked materials. And difficulties.

In view of this, the present inventors have finally obtained a practical invention based on years of experience in manufacturing development and research of related materials, and after many experiments and prudent evaluation.

In order to provide a good hole injection/transport material, the present invention first discloses a polymer having a main chain structure and a side chain structure. Characterized in that the main chain structure is selected from the group consisting of a monocyclic aromatic group, a bicyclic aromatic group, a polycyclic aromatic group, a heterocyclic aromatic group, a substituted aromatic group, and a substituted heterocyclic aromatic group. a group consisting of; the side chain structure comprises a functional group having an electron affinity with respect to the main chain structure, and the functional group is selected from one of a pyrimidine derivative and an anthracene derivative.

Furthermore, the present invention further discloses a hole transporting material which is obtained by crosslinking and polymerizing the above-mentioned polymers by functional groups.

In addition, the present invention further discloses an organic light emitting diode device comprising a substrate, a first conductive layer, a hole transfer layer, a light emitting layer, an electron transport layer and a second conductive layer. The first conductive layer is located on the substrate, the hole transfer layer is located on the first conductive layer, and the hole transfer layer comprises the above-mentioned hole transfer material, and the light emitting layer is located on the hole transfer layer. The electron transport layer is on the light emitting layer, and the second conductive layer is on the electron transport layer.

The invention has the following beneficial effects:

The present invention utilizes a thermoplastic and electron-affinitive polymer which itself has better thermal stability, so that cracking is less likely to occur in a high-temperature environment, and it is possible to improve thermosetting polymer production, and to improve PEDOT/PSS-containing The hole transfer material is susceptible to moisture. Furthermore, the polymer can pass physical crosslinking to reduce the energy barrier of the hole injection, thereby improving the ability of the hole to be transferred. In addition, the hole transfer material of the present invention can utilize the characteristics of the supramolecular, that is, the polymer. The segments will be dispersed at high temperatures, and will re-aggregate at low temperatures to form a network-like structure, which is advantageous for mass production and industrial utilization.

In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, the drawings are only for reference and explanation, and are not intended to limit the creation.

A specific embodiment of the present invention provides a thermoplastic polymer, a hole transporting material formed by polymerizing the polymer through physical crosslinking, and an organic light-emitting device using the hole transporting material.

It is characterized in that the thermoplastic polymer has a conjugated main chain structure and a side chain structure. Wherein, the conjugated main chain structure may be polymerized by a (homopolymer) or a plurality of (copolymer) conjugated polymers; and the side chain structure comprises an electron affinity with respect to the main chain structure. A functional group, and the functional group can be a variety of biomimetic or non-mimetic modified functional groups.

Specifically, the main chain structure may be selected from a monocyclic aromatic group, a bicyclic aromatic group, a polycyclic aromatic group, a heterocyclic aromatic group, a substituted aromatic group, and a substituted heterocyclic aromatic group. The group formed, in other words, a polymer monomer having a conjugated main chain can be used as a conjugated main chain structure of the polymer of the present invention, such as polyacetylene, polyfluorene, polythiophene. (polythiophene), polyphenylamine (triphenylamine) or polycarbazole (carbazol), etc., but different conjugated polymer monomers have different hole transfer effects.

In more detail, the conjugated backbone structure of the present invention may comprise one or more of the following configurations:

Further, in a specific embodiment of the present invention, the functional group contained in the side chain structure may be a base pair of DNA and RNA or an artificial multi-point hydrogen bond supramolecule. For example, the pyrimidine derivative may be uracil, cytosine or thymine, and the purine derivative may be adenine or guanine, but pyrimidine derived The kind of the substance and the anthracene derivative is not limited to the above.

Base pairs of DNA and RNA:

Artificial multi-point hydrogen bonding supramolecular:

In a preferred embodiment of the present invention, the conjugated main chain structure is selected from the group consisting of poly(triphenylamine-carbazole) (PTC) obtained by polymerizing triphenylamine and carbazole having better hole transport properties. Its structural formula is represented by the formula (I), wherein Rx is a functional group contained in the side chain structure, and the PTC itself has better thermal stability, so that cracking is less likely to occur in a high temperature environment.

Further, in a representative embodiment of the present invention, the conjugated main chain structure is selected from the group consisting of poly(triphenylamine-carbazole) (PTC), and the side chain structure is introduced with uracil ( A functional group of uracil, U), and a long carbon chain added between the conjugated main chain and the functional group to regulate the intermolecular UU force to form poly(triphenylamine-carbazole-uracil) (PTC-U), the structural formula is as shown in formula (II), PTC-U has suitable glass transition temperature, and can also be dissolved in high In a polar solvent.

Please refer to FIG. 1A, which shows a schematic diagram of a network cross-linked structure of a hole transfer material of the present invention. The above-mentioned poly(triphenylamine-carbazole-uracil) (PTC-U) provides an electric power. The hole transporting material is formed by the self-assembly behavior of the complex PTC-U through the functional groups (ie, uracil) on the respective side chain structures (ie, physically cross-linking, as shown in part A of FIG. 1A). . Hereinafter, a method for producing the polymer (PTC-U) of the present invention will be described: see Fig. 1B, which shows the synthetic reaction formula of PTC-U. First, 4-butyl-N,N-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-4-phenyl)-aniline (0.2 g, 0.36 mmol), 4-uracilbutyl-9 was mixed. (3,6-dicarbazole) (0.178 g, 0.36 mmol) and a metal catalyst Pd(0)(PPh3)4 (0.18 g); then, the mixture was dissolved in a deoxygenated mixed solvent THF (6 mL), DMF (6mL) and 2M K ₂ CO ₃ solution (8mL), and stirred vigorously for 48-72 hours at a temperature of 85-90 ° C.

Subsequently, the obtained solution was cooled and slowly added to methanol/deionized water (volume ratio 10/1). After filtration, the polymer product was collected and washed with methanol, and the solid was subjected to soxhlet extraction with acetone for 24 hours to further remove low. The polymer and the catalytic metal residual solid; finally, the obtained high molecular polymer is further redissolved in DMF and purified again, and precipitated again with ice methanol, and then dried under high vacuum at room temperature to obtain the PTC-U of the present invention. . In addition, the resulting plurality of PTC-Us can undergo self-assembly behavior through functional groups (ie, uracil) on their respective side chain structures (as shown in Part A of Figure 1B, or in part A of Figure 1A), Further explaining the advantages of introducing a functional group containing uracil to the side chain structure: Please refer to FIG. 2A and FIG. 2B, wherein FIG. 2A is the heat of using PTC and PTC-U as the material for the hole transfer, respectively. The Heavy Gravimetric Analyzer (TGA) map, and FIG. 2B is a Differential Scanning Calorimeter (DSC) using PTC and PTC-U as the hole transfer materials, respectively. It can be seen from Fig. 2A that the thermal decompose temperature (T _d ) of both materials can be greater than 350 ° C, indicating that both materials can withstand higher operating temperatures without decomposition. 2B, PTC-U enhances the physical cross-linking between molecules due to hydrogen bonding, so that its Tg is 20 °C higher than that of PTC, thereby improving the thermal stability of the hole transfer material.

Please refer to FIG. 3A and FIG. 3B, wherein FIG. 3A shows the package first. The PTC-containing cavity transfer material was spin-coated on quartz glass to form a film and UV-vis was measured. A few drops of toluene were dropped and uniformly distributed on the glass surface by spin coating, and the UV-vis was again measured. The resulting map. As can be seen from Fig. 3A, the absorbance of the hole-transporting material containing the PTC is remarkably lowered after the toluene treatment.

In addition, FIG. 3B shows that the hole transfer material containing PTC-U is first spin-coated on quartz glass to form a film, and after measuring UV-vis, a few drops of toluene are dropped and uniformly distributed by spin coating. The glass surface was measured again and the spectrum obtained by UV-vis was measured again. As can be seen from Fig. 3B, the absorbance of the hole-transporting material containing PTC-U hardly changed after the toluene treatment. Representing that the side chain structure of the polymer, after introduction of a functional group having uracil, and a network crosslinked structure formed by self-assembly behavior, can make the hole transfer material less soluble in a common organic solvent, thereby including The hole transport layer of the hole transfer material of the present invention is not damaged by the organic solvent in the wet process to cause breakage of the film.

Please refer to FIG. 4, which shows an I-V map of the hole transfer capability of the hole transfer layer of the PTC and PTC-U, respectively. It can be seen that the hole transfer layer including the PTC-U has better hole transmission/injection capability when the voltage is greater than 12 (V). Accordingly, the side chain structure of the polymer, after introducing a functional group having uracil, a network crosslinked structure formed by self-assembly behavior can serve as a bridge for the transmission of holes, thereby enhancing hole jumping to the vicinity. The possibility of a main chain structure.

Referring to Figure 5A, a light emitting diode component 100 of a particular embodiment of a hole transfer material of the present invention is shown. The LED component 100 includes a substrate 110 and a first conductive layer on the substrate 110. The layer 120, a hole transmission layer 130 on the first conductive layer 120, a light-emitting layer 140 on the hole-transport layer 130, an electron-transport layer 150 on the light-emitting layer 140, and a layer on the electron-transport layer 150 The second conductive layer 160.

Specifically, the substrate 110 may be a glass substrate, a plastic substrate or a metal substrate. The material of the first conductive layer 120 may be indium tin oxide (ITO) or indium zinc oxide (IZO). The material of the transfer layer 130 may be formed by the above-mentioned polymer (PTC-U) being functionalized by self-assembly behavior (ie, physical cross-linking) of the functional group of the side chain structure, and the material of the electron transport layer 150 may be tris (8-hydroxyquinoline) aluminum (ie, Alq3), and the material of the second conductive layer 160 may be aluminum (Al).

In addition, please refer to FIG. 5B, which shows a light emitting diode element 100 employing a variation of the embodiment of the hole transfer material of the present invention. In order to adjust the energy barrier between the first conductive layer 120, the hole transfer layer 130, the electron transport layer 150 and the second conductive layer 160, the hole transfer layer 130 may be further divided into a hole injection layer 131 and a The hole transport layer 132 on the hole injection layer 131, and the electron transport layer 150 are further divided into an electron transport layer 151 and an electron injection layer 152 on the electron transport layer 151.

In this variant embodiment, the material of the hole injection layer 131 may be formed by the above-mentioned polymer (PTC-U) being subjected to self-assembly behavior (ie, physical crosslinking) by the functional group of the side chain structure. The material of the hole transport layer 132 may be N, N'-bis-(1-naphthy)-N, N'-diphenyl-1, 1'-biphenyl-4, 4'-diamine (ie NPB); The material of the transport layer 151 may be tris (8-hydroxyquinoline) Aluminum (ie, Alq3), the material of the electron injecting layer 152 is lithium fluoride (LiF). Accordingly, it contributes to the injection and transmission of electrons and holes, thereby increasing the luminous efficiency of the light-emitting diode element 100'.

Furthermore, please refer to Table 1 below, which shows a comparison of a light-emitting diode element including a PTC as a hole transfer layer and a PTC-U as a hole transfer layer. As can be seen from Table 1, the maximum luminance of the light-emitting diode element including the PTC-U as the hole-transporting layer is 8828 cd/m ² , the luminous efficiency is 1.5 cd/A, the external quantum efficiency is 0.46%, and the driving voltage is only 3.7V. Compared with a light-emitting diode element including a PTC as a hole transfer layer, the light-emitting luminance maximum value is 3375 cd/m ² , the light-emitting efficiency is 0.8 cd/A, the external quantum efficiency is 0.25%, and the driving voltage is 4.8V. Accordingly, a light-emitting diode element including a hole transfer layer formed by self-assembly of PTC-U can produce higher brightness at a lower driving voltage.

Please refer to FIG. 6 to FIG. 9 , which respectively show the light emitting diode component including the hole transport layer of NPB material and the hole transport layer of PTC-U material, compared with the hole transport layer of NPB material and PEDOT: The component efficiency of the light-emitting diode component of the PSS material hole transmission layer, it should be noted that the hole transmission layer of the PEDOT:PSS material may affect the hole transmission efficiency due to the thickness change. It can be seen that the inclusion of NPB material The light-emitting diode layer of the quality hole transmission layer and the hole transmission layer of the PTC-U material has higher luminous power, maximum luminous brightness and external quantum effect at the same current or voltage than the hole transmission layer including the NPB material. And the light-emitting diode component of the PEDOT: PSS material hole transmission layer.

The invention has the following beneficial effects:

The invention successfully synthesizes a novel supramolecular polymer, and a functional group containing uracil is introduced into the side chain structure, which can obviously improve the properties of the conjugated main chain structure, such as thermal stability, electrical stability, etc., and is improved. The amplitude has a great correlation with the hydrogen bonding force, so the polymer is less prone to cracking in a high temperature environment, thereby improving the problem that the thermosetting polymer is not easily quantified.

Furthermore, the hole transporting material of the present invention is formed by the self-assembly behavior (physical crosslinking) of the functional group contained in the side chain structure of the polymer, which is not easily soluble in a general organic solvent, and thus can Improving the problem of film breakage caused by the wet process; further, the mesh cross-linked structure of the hole transfer material can serve as a bridge for the transmission of the hole, thereby increasing the possibility of the hole jumping to the adjacent main chain structure, thereby The ability to transfer holes is improved, and the hole transfer material can be characterized by super-molecules, that is, the polymer segments are dispersed at a high temperature, and at a low temperature, they are re-aggregated to form a network structure, which is advantageous. Mass production and industrial utilization.

In addition, the light-emitting diode element using the hole-transporting material of the present invention has better luminous power, maximum light-emitting brightness and external quantum effect at the same current or voltage than the light-emitting diode element including the commercially available PEDOT:PSS. Therefore, the polymer of the present invention has potential as a hole transfer material for the next generation of high performance light-emitting diode elements.

100, 100'‧‧‧Lighting diode components

110‧‧‧Substrate

120‧‧‧First conductive layer

130‧‧‧ hole transfer layer

131‧‧‧ hole injection layer

132‧‧‧ hole transport layer

140‧‧‧Lighting layer

150‧‧‧Electronic transmission layer

151‧‧‧ hole transport layer

152‧‧‧ hole injection layer

160‧‧‧Second conductive layer

1A is a schematic view showing a mesh cross-linking structure of a hole transfer material of the present invention; FIG. 1B is a flow chart of synthesizing a hole transfer material of the present invention; FIG. 2A is a hole transfer material comprising the PTC of the present invention and comprising FIG. 2B is a heat flow analysis diagram of a PTC-containing hole transfer material and a PTC-U-containing hole transfer material according to the present invention; FIG. 3A is included in the present invention; FIG. 3B is a light absorption analysis diagram of a hole transfer material including a PTC-U according to the present invention; FIG. 4 is a hole transfer material including a PTC of the present invention and includes a PTC- FIG. 5A is a schematic structural view of a light-emitting diode component according to a specific embodiment of the present invention; FIG. 5B is a schematic diagram of a light-emitting diode component according to a modified embodiment of the present invention; FIG. 6 is a diagram showing brightness analysis of a PTC-U-containing light-emitting diode element and a PEDOT-containing light-emitting diode element at the same voltage; FIG. 7 is a PTC-U-containing luminescence of the present invention; Diode components and including PEDOT Luminous power analysis diagram of the photodiode element at the same current density; FIG. 8 is an external quantum efficiency analysis of the PTC-U-containing LED component of the present invention and the PEDOT-containing LED component at the same current density Figure; Fig. 9 is a graph showing the analysis of the luminous power of the PTC-U-containing light-emitting diode element and the PEDOT-containing light-emitting diode element at the same voltage.

Claims (7)

A polymer having a main chain structure and a side chain structure, wherein the main chain structure is triphenylamine linked carbazole, and the main chain structure is as follows: Characterized in that the Rx on the side chain structure is cytosine or thymine. A polymer having a main chain structure and a side chain structure, wherein the main chain structure is triphenylamine linked carbazole, and the main chain structure is as follows: It is characterized in that Rx on the side chain structure is adenine or guanine. A hole transfer material obtained by cross-linking a plurality of polymers as described in claim 1 or 2 to each other. An organic light emitting diode element comprising: a substrate; a first conductive layer on the substrate; a hole transfer layer on the first conductive layer, and the hole transfer layer includes the hole transfer as described in claim 3 a material; a light-emitting layer on the hole transport layer; an electron transport layer on the light-emitting layer; and a second conductive layer on the electron transport layer. The OLED device of claim 4, wherein the hole transfer layer comprises a hole injection layer and a hole transport layer on the hole injection layer, the hole injection layer The material is a hole transfer material as described in claim 3, and the material of the hole transport layer is N, N'-bis-(1-naphthy)-N, N'-diphenyl-1, 1'- Biphenyl-4,4'-diamine (ie NPB). The organic light emitting diode device of claim 4, wherein the electron transport layer comprises an electron transport layer and an electron injection layer on the electron transport layer, the electron transport layer is made of tris (8) -hydroxyquinoline)aluminum (Alq3), the electron injecting layer is made of lithium fluoride (LiF). The OLED device of claim 4, wherein the substrate is a glass substrate, a plastic substrate or a metal substrate, and the first conductive layer is made of indium tin oxide (ITO) or oxidized. Indium zinc oxide (IZO), the second conductive layer is made of aluminum.