An intrinsically stretchable blue-light-emitting polymer composite film and its electroluminescent device

Abstract

The present invention belongs to the technical field of OLED display, and particularly relates to an intrinsically stretchable blue-light polymer composite film and an electroluminescent device thereof. In the intrinsically stretchable blue-light polymer composite film prepared by the present invention, the light-emitting compound molecules have regular structures, good structural expandability, good solubility, and good luminous efficiency. The preferred matrix stretchable polymer material has a wide source and is easy to prepare. Therefore, it will have good application prospects in the field of OLED display.

Description

Technical Field

[0001] The invention belongs to the technical field of OLED display, and in particular relates to an intrinsically stretchable blue light polymer composite film and an electroluminescent device thereof. Background Art

[0002] Flexible light-emitting devices have broad application prospects in the fields of flexible displays and wearable electronics due to their advantages such as integrability, compatibility and reprocessability. Light-emitting polymers have the advantages of efficient luminescence, potential intrinsic flexibility and large-scale printable processing, and are important candidate materials for flexible displays and solid-state lighting. Compared with red and green light polymers, blue light polymers are prone to poor blue light color purity and low efficiency, poor device stability and obvious efficiency roll-off due to their wide bandgap structure (>3.0eV), high-energy exciton luminescence and low conductivity, which are important bottlenecks limiting the application of light-emitting polymers in full-color display and lighting. At the same time, the rigid condensed ring luminescent skeleton of the light-emitting polymer itself makes it difficult to form an energy dissipation structure of interchain entanglement, making the traditional rigid light-emitting polymer film brittle, resulting in failure and performance degradation of its flexible light-emitting devices under long-term or cyclic deformation. Based on this, establishing a universal and effective film preparation strategy, constructing an energy dissipation structure, combining intrinsic flexibility with efficient and stable blue light emitting, and realizing the controllable construction of intrinsically stretchable blue light polymer films and their flexible light-emitting devices are key issues that need to be urgently addressed in the field of flexible optoelectronics.

[0003] As mentioned above, in the blue light emitting molecular skeleton, the fluorenyl blue light molecule has complex electronic transition series, vibration relaxation, conformational transition and aggregation behavior, which produces wide-band, multi-peak, long baseline and long-wave emission, reducing the color purity and stability of blue light. Through steric hindrance and molecular encapsulation strategies, the π-electron coupling between conjugated skeletons can be suppressed, the excited state behavior of a single molecular state can be realized, the luminescence spectrum can be narrowed, and the color purity and efficiency can be improved. It is currently the blue light emitting skeleton molecule with the most application potential.

[0004] At present, the design strategies for achieving the intrinsic stretchability of polymer luminescent films mainly include supramolecular design, internal plasticization and blending plasticization strategies. The supramolecular design strategy mainly introduces dynamic non-covalent weak bond groups into the polymer chain to construct a dynamic reversible supramolecular network structure within / between the molecular chains to achieve intrinsic flexibility; while the internal plasticization strategy mainly introduces flexible segments into the main chain or side chain to reduce the activation energy of the molecular chain segments and the main chain while inhibiting the π-π interaction between the chains, reducing the crystallization ability, and improving the slip ability between the molecular chains to achieve the intrinsic stretchability of the film. However, both of the above strategies involve complex material synthesis processes and precise aggregation state regulation, which reduces the universality of the two types of molecular design strategies. In addition, the introduction of non-covalent groups or flexible segments between molecular chains can easily induce strong aggregation between the molecular chains of the luminescent polymer, leading to uncontrollable multi-level structural transformations, causing π-electron coupling between the luminescent skeletons, forming excimers and long-wavelength green band luminescence, reducing its luminescence efficiency and color purity, as well as device stability and efficiency. Therefore, in comparison, a simple blending strategy can effectively inhibit the interaction between conjugated skeletons, inhibit the orderly stacking and crystallization between chains, and improve the flexibility of the film. It is a simple design strategy to achieve the controllable preparation of intrinsically stretchable polymer semiconductor films and their flexible optoelectronic devices.

[0005] However, at present, the intrinsically stretchable blue light polymer composite film has low stretchability (<50%), poor deformation stability and low blue light color purity (CIEy>0.2, luminescence peak greater than 460 nm), which is an important challenge facing the field of flexible blue light polymer light-emitting diodes. At the same time, blue light conjugated polymers are currently mainly used as blue light emitting centers, which have complex synthesis, unstable luminescence, easy to produce green light bands, poor color purity, low efficiency and other problems. Therefore, the present invention adopts a simple blending strategy, a one-step design and synthesis of blue light small molecules, and a blue light polymer film with high stability, high blue light color purity and high stretchability is constructed for application in high-purity flexible light-emitting diodes. Summary of the invention

[0006] The object of the present invention is to provide a class of intrinsically stretchable blue light polymer composite films, which exhibits intrinsic stretchability and efficient luminescence, and has excellent and stable mechanical flexibility and blue light emitting characteristics. Another object of the present invention is to provide a method for preparing a class of intrinsically stretchable blue light polymer composite films. The last object of the present invention is to provide an electroluminescent device comprising the intrinsically stretchable blue light polymer composite film.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] An intrinsically stretchable blue light polymer composite film, comprising a luminescent compound I and a matrix polymer II;

[0009] Wherein, the structural formula of the luminescent compound I is:

[0010]

[0011] The matrix polymer II is selected from any one of PU (polyurethane) and PDMS (polydimethylsiloxane);

[0012] The structural formula of the PU is:

[0013] ;

[0014] The structural formula of the PDMS is:

[0015] ;

[0016] Where: R 1 is a hydrogen atom or a straight alkyl chain with 1 to 12 carbon atoms or a branched alkyl chain with 1 to 12 carbon atoms, Ar is a benzene ring or a biphenyl group; R 2 is a linear alkyl chain having 6 to 12 carbon atoms or a branched alkyl chain having 6 to 12 carbon atoms; R 3 It is a linear alkyl chain having 6 to 12 carbon atoms or a branched alkyl chain having 6 to 12 carbon atoms, and n represents the number of polymer repeating units.

[0017] Preferably, when the R 1 When is a hydrogen atom, the luminescent compound I is easier to obtain and prepare, and the matrix polymer II is selected from PU;

[0018] The PU is compounded with the luminescent compound I to prepare an intrinsically stretchable blue light polymer composite film.

[0019] Preferably, when the R 1 When is a hydrogen atom, the synthesis method of the luminescent compound I comprises:

[0020] Will and , sodium carbonate and tetrakistriphenylphosphine palladium are added into a reaction bottle, and then ethanol, water and an organic solvent are added, and the mixture is refluxed at 85° C. in a nitrogen atmosphere for 36 hours, and purified to obtain a luminescent compound I;

[0021] The organic solvent includes any one of DMF (N,N-dimethylformamide) and ethylene glycol dimethyl ether.

[0022] Preferably, the synthesis route of the luminescent compound I comprises:

[0023] .

[0024] Preferably, , The molar ratio of sodium carbonate and tetrakistriphenylphosphine palladium is 1:3:8:0.16, and the volume ratio of water, ethanol and organic solvent is 2:4:3. and The total molar concentration is 0.4-0.6mmol / mL.

[0025] A method for preparing the intrinsically stretchable blue light polymer composite film as described above comprises the following steps:

[0026] Dissolving the luminescent compound I and the matrix polymer II in chloroform to prepare a chloroform solution;

[0027] Wherein, in the chloroform solution, the total concentration of the luminescent compound I and the matrix polymer II is 10 mg / mL, and the mass ratio of the luminescent compound I to the matrix polymer II is 1:9 or 5:5;

[0028] The chloroform solution is spin-coated into a film, and the solvent is removed by vacuum drying at room temperature to obtain an intrinsically stretchable blue light polymer composite film.

[0029] The present invention also provides an electroluminescent device, which comprises an anode, a cathode and an organic light-emitting thin film layer located between the anode and the cathode;

[0030] The organic light-emitting film layer includes the intrinsic stretchable blue light polymer composite film as described above.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] (1) The present invention proposes to prepare an intrinsically stretchable blue light composite film by combining high-efficiency luminescent molecules with matrix polymers;

[0033] (2) The present invention prepares the highly efficient blue light fluorene-based luminescent molecule by a simple Suzuki reaction, which has the advantages of simple preparation, mild reaction conditions, high yield, high selectivity, and simple post-treatment;

[0034] (3) The intrinsically stretchable blue light-emitting polymer film prepared by the present invention has good mechanical stretchability and high-efficiency blue light-emitting properties, and will have good application prospects in the field of flexible blue light OLEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the nuclear magnetic resonance hydrogen spectrum of the luminescent compound TPFOH prepared in Example 1 of the present invention;

[0036] Figure 2 The absorption and luminescence spectra of the intrinsically stretchable blue light polymer composite film prepared in Example 2 of the present invention;

[0037] Figure 3 This is a stretching photograph of the intrinsically stretchable blue light polymer composite film prepared in Example 2 of the present invention;

[0038] Figure 4 is a stress-strain curve of the intrinsically stretchable blue light polymer composite film prepared in Example 2 of the present invention;

[0039] Figure 5 This is an atomic force microscope photograph of the intrinsically stretchable blue light polymer composite film prepared in Example 2 of the present invention;

[0040] Figure 6 This is an electroluminescent spectrum diagram of the electroluminescent device prepared in Example 3 of the present invention;

[0041] Figure 7 is a curve diagram of voltage and current density of the electroluminescent device prepared in Example 3 of the present invention;

[0042] Figure 8 is a curve diagram of voltage and efficiency of the electroluminescent device prepared in Example 3 of the present invention;

[0043] Fig. 9 The voltage and brightness curve of the electroluminescent device prepared in Example 3 of the present invention is shown in FIG. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with specific examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention.

[0045] The present invention discloses an intrinsically stretchable blue light polymer composite film, wherein the main blue light emitting skeleton is obtained by connecting two phenyl groups at positions 2 and 7 of fluorene, and then performing flexible chain modification on positions 9 of fluorene and positions 2 and 6 of benzene. The core feature of the film is that it has viscous flow behavior and exhibits semiconductor properties. The structural formula of the luminescent compound I is: ;

[0046] Where: R 1 is a hydrogen atom or a straight alkyl chain having 1 to 12 carbon atoms or a branched alkyl chain having 1 to 12 carbon atoms; Ar is a benzene ring or a biphenyl group.

[0047] Example 1

[0048] This embodiment discloses a luminescent compound TPFOH, whose structural formula is:

[0049]

[0050] The synthetic route of the luminescent compound TPFOH is as follows:

[0051] ;

[0052] The specific synthesis method of the luminescent compound TPFOH is:

[0053] 2,7-dibromo-9-phenylfluorenol (2.74 g, 5 mmol), 9-phenylfluorenol borate (2.73 g, 15 mmol), sodium carbonate (4.24 g, 40 mmol) and tetrakistriphenylphosphine palladium (0.92 g, 0.8 mmol) were added to the reaction flask, 2 mL of water, 20 mL of ethanol and 15 mL of DMF were added to the reaction flask, the temperature was raised to 85°C, and the reaction was refluxed at 85°C for 36 h in a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature and extracted with dichloromethane. The dichloromethane extracts of the organic phase were combined, dried over anhydrous sodium sulfate, the desiccant was filtered out, the solvent was removed, and the crude product was separated and purified by silica gel chromatography to obtain a viscous liquid, i.e., the luminescent compound TPFOH (2.1 g, 63%), whose hydrogen nuclear magnetic resonance spectrum is as follows: Figure 1 shown.

[0054] Example 2

[0055] This embodiment discloses an intrinsically stretchable blue light polymer composite film, the preparation method of which is as follows:

[0056] The luminescent compounds TPFOH and PU prepared in Example 1 were dissolved in chloroform to prepare a chloroform solution, wherein the total concentration of the luminescent compounds TPFOH and PU in the chloroform solution was 10 mg / mL, and the mass ratio of the luminescent compounds TPFOH and PU was 1:9. The chloroform solution was spin-coated at a rotation speed of 3000 r / min for 1 min to form a film, and the solvent was removed by vacuum drying at room temperature for 10 min to obtain an intrinsically stretchable blue light polymer composite film;

[0057] The thickness of the intrinsically stretchable blue light polymer composite film is 100 nm.

[0058] Material property test: The intrinsically stretchable blue light polymer composite film prepared in Example 2 was tested:

[0059] (1) Absorption and luminescence spectrum test:

[0060] The absorption and luminescence spectra of the intrinsically stretchable blue light polymer composite film were tested. The test results are as follows: Figure 2 As shown;

[0061] from Figure 2It can be seen that the intrinsic stretchable blue light polymer composite film exhibits maximum absorption and emission wavelengths of 380nm, 402nm and 420nm respectively, showing good blue light luminescence with a luminescence quantum efficiency of 60%.

[0062] (2) Stretch test:

[0063] The intrinsically stretchable blue light polymer composite film was subjected to a tensile test, and the test results are as follows Figure 3 and Figure 4 As shown;

[0064] Figure 3 This is a stretching photo of the intrinsically stretchable blue light polymer composite film. Figure 4 is the stress-strain curve of the intrinsically stretchable blue light polymer composite film. Figure 3 and Figure 4 It can be seen that the intrinsically stretchable blue light polymer composite film has excellent mechanical stretchability;

[0065] in, Figure 4 Here, 10% means that when preparing the intrinsic stretchable blue light polymer composite film, the mass ratio of the luminescent compound TPFOH and PU is 1:9, that is, the mass of the luminescent compound TPFOH accounts for 10% of the total mass of the luminescent compounds TPFOH and PU; 50% means that when preparing the intrinsic stretchable blue light polymer composite film, the mass ratio of the luminescent compound TPFOH and PU is 5:5, that is, the mass of the luminescent compound TPFOH accounts for 50% of the total mass of the luminescent compounds TPFOH and PU.

[0066] (3) Morphology test:

[0067] The morphology of the intrinsically stretchable blue light polymer composite film was tested. Figure 5 This is an atomic force microscope image of an intrinsically stretchable blue light polymer composite film. Figure 5 It can be seen that there is a small-scale phase separation in the film.

[0068] Example 3

[0069] This embodiment discloses an electroluminescent device, and the preparation method is as follows:

[0070] The ITO (indium tin oxide) substrate was ultrasonically cleaned with detergent, acetone, isopropanol, and deionized water in sequence, dried in an oven at 120°C for 2 hours, and subjected to ultraviolet ozone treatment for 10 minutes before spin coating: first, a 40 nm thick PEDOT:PSS (poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonic acid)) was prepared at a rotation speed of 1500 r / min and annealed at 120°C for 30 minutes; then the intrinsically stretchable blue light polymer composite film prepared in Example 2 was used as an OLED light-emitting layer; finally, at a temperature below Under a pressure of 200 ℃, 25 nm TPBI (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene), 0.8 nm LiF and 100 nm Al were prepared by thermal evaporation to obtain an electroluminescent device with an area of ​​2 mm × 2 mm.

[0071] The characteristics of the electroluminescent device prepared in Example 3 were measured, and all device parameter measurements were performed in an air environment.

[0072] Figure 6 is the electroluminescent spectrum of the electroluminescent device. Figure 7 is the voltage and current density curve of the electroluminescent device, Figure 8 is the voltage and efficiency curve of the electroluminescent device. Fig. 9 The voltage and brightness curve of the electroluminescent device. Figure 6 , Figure 7 , Figure 8 and Fig. 9 It can be seen that the intrinsically stretchable blue light polymer composite film prepared in the present invention is applied to an electroluminescent device to obtain good blue-violet light emission intensity.

[0073] The present invention has been disclosed above with preferred embodiments, but they are not intended to limit the present invention. Any technical solutions obtained by adopting equivalent replacement or equivalent transformation solutions fall within the protection scope of the present invention.

Claims

1. An intrinsically stretchable blue light polymer composite film, characterized in that: It comprises a light-emitting compound I and a matrix polymer II; Wherein, the structural formula of the luminescent compound I is: ； The matrix polymer II is selected from any one of PU and PDMS; The structural formula of the PU is: ； The structural formula of the PDMS is: ； In the formula: R1 is a hydrogen atom or a straight chain alkyl chain with 1 to 12 carbon atoms or a branched chain alkyl chain with 1 to 12 carbon atoms; Ar is a benzene ring or a biphenyl group; R2 is a straight chain alkyl chain with 6 to 12 carbon atoms or a branched chain alkyl chain with 6 to 12 carbon atoms; R3 is a straight chain alkyl chain with 6 to 12 carbon atoms or a branched chain alkyl chain with 6 to 12 carbon atoms; n represents the number of polymer repeating units; When the R1 is a hydrogen atom, the matrix polymer II is selected from PU; The PU is compounded with the luminescent compound I to prepare an intrinsically stretchable blue light polymer composite film; The synthesis method of the luminescent compound I comprises: Will and , sodium carbonate and tetrakistriphenylphosphine palladium are added into a reaction bottle, and then ethanol, water and an organic solvent are added, and the mixture is refluxed at 85° C. in a nitrogen atmosphere for 36 hours, and purified to obtain a luminescent compound I; The organic solvent includes any one of DMF and ethylene glycol dimethyl ether.

2. The intrinsically stretchable blue light polymer composite film according to claim 1, characterized in that: The synthesis route of the luminescent compound I includes: 。 3. The intrinsically stretchable blue light polymer composite film according to claim 1, characterized in that: , The molar ratio of sodium carbonate and tetrakistriphenylphosphine palladium is 1:3:8:0.16, and the volume ratio of water, ethanol and organic solvent is 2:4:

3. and The total molar concentration is 0.4-0.6mmol / mL.

4. A method for preparing an intrinsically stretchable blue light polymer composite film according to any one of claims 1 to 3, characterized in that: The following steps are involved: Dissolving the luminescent compound I and the matrix polymer II in chloroform to prepare a chloroform solution; Wherein, in the chloroform solution, the total concentration of the luminescent compound I and the matrix polymer II is 10 mg / mL, and the mass ratio of the luminescent compound I to the matrix polymer II is 1:9 or 5:5; The chloroform solution is spin-coated into a film, and the solvent is removed by vacuum drying at room temperature to obtain an intrinsically stretchable blue light polymer composite film.

5. An electroluminescent device, characterized in that: It includes an anode, a cathode and an organic light-emitting thin film layer located between the anode and the cathode; The organic light-emitting film layer includes the intrinsically stretchable blue light polymer composite film as described in any one of claims 1 to 3.

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