Preparation method of perovskite thin film and perovskite light-emitting diode

Abstract

The invention provides a preparation method of a perovskite thin film and a perovskite light-emitting diode. The method comprises the steps that lead iodide, lead bromide, a cesium iodide mixture and organic ammonium iodide salt are dissolved in a polar solvent, a perovskite precursor solution is obtained, and the cesium iodide mixture comprises cesium iodide and cesium triiodide; and dispensing the perovskite precursor solution on a substrate, enabling the substrate to rotate in an accelerated manner, and dropwise adding an anti-solvent in the rotation process to obtain the perovskite thin film. The perovskite thin film prepared by the invention is more compact and has fewer holes, meanwhile, the formation of a low-dimensional phase in the perovskite thin film is reduced, the defect density in the perovskite thin film is reduced, halogen movement is reduced, and better spectral stability and operation stability are realized while the efficiency and the brightness of a pure red light perovskite light-emitting diode are improved.

Description

Technical Field

[0001] The present disclosure relates to the field of semiconductor optoelectronic devices, and in particular to a method for preparing a perovskite film and a perovskite light-emitting diode. Background Art

[0002] As an electro-optical conversion semiconductor device, light-emitting diodes are widely used in the fields of display and lighting. As a new type of photoelectric conversion material, metal halide perovskite has the characteristics of high fluorescence yield, good luminescence purity, easy band gap adjustment, low cost, simple processing technology, etc. In recent years, it has been widely used in the field of light-emitting diodes and has attracted great attention.

[0003] External quantum efficiency and brightness are the main parameters for measuring the performance of light-emitting diode devices. Since the birth of perovskite light-emitting diodes, their efficiency and brightness have been greatly improved, but pure red perovskite light-emitting diodes used for display still have problems such as low efficiency and unstable spectrum.

[0004] The pure red perovskite LEDs currently prepared for display mainly adopt the strategy of mixed halogen or mixed large cation. The red light devices based on mixed halogen are generally of low efficiency and poor spectral stability. The efficiency and brightness of pure red light-emitting diodes based on mixed large cations are also not high, and need to be further improved. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of this, the present disclosure provides a method for preparing a perovskite film and a perovskite light-emitting diode, which are used to at least partially solve the current problems of insufficient density and large number of holes in the perovskite film, as well as technical problems such as low efficiency and brightness, and unstable spectrum of existing pure red light perovskite light-emitting diodes.

[0007] (II) Technical solution

[0008] In order to achieve the above-mentioned purpose, the first aspect of the present disclosure provides a method for preparing a perovskite film, comprising: dissolving lead iodide, lead bromide, a cesium iodide mixture and an organic ammonium iodide salt in a polar solvent to obtain a perovskite precursor solution, wherein the cesium iodide mixture includes cesium iodide and cesium triiodide; drop-coating the perovskite precursor solution onto a substrate, accelerating the rotation of the substrate, and drop-coating an anti-solvent during the rotation to obtain a perovskite film.

[0009] According to an embodiment of the present disclosure, the dissolution ratio of the lead iodide, lead bromide, cesium iodide mixture and the organic ammonium iodide salt is 1:1.11:a:b, wherein 1<a<2, 2<b<3.

[0010] According to an embodiment of the present disclosure, the ratio of the cesium triiodide in the cesium iodide mixture is 10% to 40%.

[0011] According to an embodiment of the present disclosure, the polar solvent is dimethyl sulfoxide and / or N,N-dimethylformamide.

[0012] According to an embodiment of the present disclosure, the anti-solvent is one of ethyl acetate, chlorobenzene and toluene.

[0013] According to an embodiment of the present disclosure, the material of the organic ammonium iodide salt is one or more of phenethylammonium iodide, 1-naphthylmethylammonium iodide, 2-naphthylmethylammonium iodide, 2-fluorophenethylammonium iodide, 3-fluorophenethylammonium iodide and 4-fluorophenethylammonium iodide.

[0014] A second aspect of the present disclosure provides a perovskite light-emitting diode, which comprises, from bottom to top, a substrate, a transparent conductive electrode, a first organic hole transport layer, a second organic hole transport layer, a perovskite light-emitting layer, an electron transport layer and a metal electrode, wherein the perovskite light-emitting layer is prepared according to the method for preparing a perovskite film according to any one of claims 1 to 6.

[0015] According to an embodiment of the present disclosure, the material of the first organic hole transport layer is polyethylenedioxythiophene-poly(styrene sulfonate).

[0016] According to an embodiment of the present disclosure, the material of the second organic hole transport layer is a combination of poly[bis(4-phenyl)(4-butylphenyl)amine] and poly(9-vinylcarbazole) or a combination of poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-n-butyl)phenyl)-diphenylamine)] and poly(9-vinylcarbazole).

[0017] According to an embodiment of the present disclosure, the material of the electron transport layer is a combination of tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane and lithium fluoride or a combination of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene and lithium fluoride.

[0018] (III) Beneficial effects

[0019] The present disclosure overcomes the deficiencies in the prior art and provides a method for preparing a perovskite film and a perovskite light-emitting diode. On the one hand, by adding cesium triiodide to a perovskite precursor solution, the crystallization process of the perovskite can be affected. The iodine triions in the cesium triiodide can combine with large cations to reduce the formation of a low-dimensional phase. Then the iodine triions are decomposed into iodine element and iodine ions. The process of iodine element sublimation can reduce holes and defects in the crystal to a certain extent, thereby obtaining a denser perovskite film with fewer defects. On the other hand, by using the above-mentioned perovskite film as the light-emitting layer of the perovskite light-emitting diode, the energy loss caused by the non-radiative recombination of carriers mediated by the low-dimensional phase and defects can be effectively reduced, and the fluorescence yield and carrier lifetime of the perovskite film can be improved, thereby improving the performance and stability of the perovskite light-emitting diode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The schematic diagram of the process of the method for preparing the perovskite film provided by the embodiment of the present disclosure is schematically shown;

[0021] Figure 2 The schematic diagram of the structure of the perovskite light-emitting diode provided by the embodiment of the present disclosure is shown;

[0022] Figure 3 A schematic diagram showing a comparison of the surface morphologies of the perovskite films prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure;

[0023] Figure 4 The following schematically shows a preparation flow chart of a perovskite light-emitting diode provided by an embodiment of the present disclosure;

[0024] Figure 5 A schematic diagram showing a comparison of the relationship between current density and voltage of a perovskite light-emitting diode prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure;

[0025] Figure 6 A schematic diagram showing a comparison of the relationship between brightness and voltage of a perovskite light-emitting diode prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure;

[0026] Figure 7 A schematic diagram showing a comparison of the relationship between the external quantum efficiency and the current density of the perovskite light-emitting diodes prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure;

[0027] Figure 8 A comparison curve of the relationship between the electroluminescence peak wavelength and the voltage of the perovskite light-emitting diodes prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0030] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0031] The present invention provides a method for preparing a perovskite film. Figure 1 , the method includes S11~S12.

[0032] In operation S11, lead iodide, lead bromide, cesium iodide mixture and organic ammonium iodide salt are dissolved in a polar solvent to obtain a perovskite precursor solution, wherein the concentration of Pb in the perovskite precursor solution is 0.4 mmol / mL, wherein the cesium iodide mixture includes cesium iodide and cesium triiodide, and the proportion of cesium triiodide in the cesium iodide mixture is 10% to 40%.

[0033] In operation S12, the perovskite precursor solution is drop-coated onto the substrate, the substrate is rotated at an accelerated speed, and an anti-solvent is drop-coated during the rotation process. The time for dropping the anti-solvent is 9 to 15 seconds of the spin coating to obtain a perovskite film.

[0034] Through the embodiments of the present disclosure, in the preparation of perovskite films, cesium triiodide is used as an additive to replace part of cesium iodide, which can affect the crystallization process of perovskite. The iodine triions in cesium triiodide can combine with large cations to reduce the formation of low-dimensional phases. Then the iodine triions decompose into iodine element and iodide ions. The process of iodine element sublimation can reduce the holes and defects in the crystal to a certain extent, thereby obtaining a denser perovskite film with fewer holes.

[0035] Further, the dissolution ratio of lead iodide, lead bromide, cesium iodide mixture and organic ammonium iodide salt is 1:1.11:a:b, wherein 1<a<2, 2<b<3. The material of the organic ammonium iodide salt is one or more of phenethylammonium iodide, 1-naphthylmethylammonium iodide, 2-naphthylmethylammonium iodide, 2-fluorophenethylammonium iodide, 3-fluorophenethylammonium iodide and 4-fluorophenethylammonium iodide.

[0036] In the disclosed embodiment, the polar solvent is dimethyl sulfoxide and / or N,N-dimethylformamide, and the anti-solvent is one of ethyl acetate, chlorobenzene and toluene.

[0037] Another aspect of the present disclosure provides a perovskite light emitting diode, Figure 2 The structural diagram of the perovskite light-emitting diode provided by the embodiment of the present disclosure is schematically shown.

[0038] like Figure 2 As shown, the perovskite light-emitting diode includes, from bottom to top, a substrate, a transparent conductive electrode, a first organic hole transport layer, a second organic hole transport layer, a perovskite light-emitting layer, an electron transport layer and a metal electrode, wherein the perovskite light-emitting layer is the above-mentioned perovskite film.

[0039] In the embodiments of the present disclosure, the use of the above-mentioned perovskite film as the perovskite light-emitting layer of the perovskite light-emitting diode can effectively reduce the energy loss caused by the non-radiative recombination of carriers mediated by low-dimensional phases and defects, and improve the fluorescence yield and carrier lifetime of the perovskite film, that is, improve the efficiency and brightness of the pure red light perovskite light-emitting diode while achieving better spectral stability and operational stability.

[0040] Furthermore, the materials used for the substrate and the transparent conductive electrode include glass and indium tin oxide, which play a supporting role and serve as the positive electrode of the device; the material of the first organic hole transport layer is polyethylene dioxythiophene-poly (styrene sulfonate), with a thickness of 20 to 50 nm, which is used to transport holes; due to the requirements of energy levels, it is necessary to transport holes layer by layer, so a second organic hole transport layer is set, which is also used to transport holes, and its material is a combination of poly [bis (4-phenyl) (4-butylphenyl) amine] and poly (9-vinyl carbazole) or poly [(9,9-di-n-octylfluorenyl-2,7-diyl) -alt- (4,4'- (N- (4-n-butyl) phenyl) - diphenylamine)] and poly ( The material of the electron transport layer is a combination of tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane and lithium fluoride or a combination of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene and lithium fluoride, with a thickness of 30 to 50 nm, and is used for transmitting electrons; the metal electrode material generally adopts aluminum with a thickness of 80 to 120 nm, which is used as the negative electrode of the device.

[0041] According to another aspect of the embodiments of the present disclosure, a method for preparing a perovskite light-emitting diode is provided, comprising S21 to S27.

[0042] In operation S21, a substrate is fabricated and cleaned.

[0043] In operation S22, an ITO thin film is deposited on the upper surface of the substrate by sputtering, evaporation or the like to manufacture a transparent conductive electrode.

[0044] In operation S23, a first organic hole transport layer is spin-coated on the upper surfaces of the substrate and the transparent conductive electrode and annealed.

[0045] In operation S24 , a second organic hole transport layer is spin-coated on an upper surface of the first organic hole transport layer and annealed.

[0046] In operation S25 , a perovskite film is spin-coated on an upper surface of the second organic hole transport layer and annealed to form a perovskite light-emitting layer, wherein the perovskite film is prepared according to a method for preparing a perovskite film.

[0047] In operation S26 , an electron transport layer is evaporated on an upper surface of the perovskite light emitting layer.

[0048] In operation S27 , a metal conductive electrode is evaporated on an upper surface of the electron transport layer.

[0049] In the disclosed embodiment, the substrate and the transparent conductive electrode in operation S23 are treated with ultraviolet ozone for 40 minutes. In operations S23 to S25, the rotation speed of the spin coating is 2000 to 8000 rpm, the acceleration of the spin coating is 2000 to 9000 rpm / s, the total spin coating time is 40 to 70 s, the annealing temperature is 80 to 160° C., and the time is 5 to 20 minutes. Operations S24 to S27 are performed in a glove box filled with high-purity nitrogen, and the water and oxygen content in the glove box is less than 0.1 ppm.

[0050] In the disclosed embodiment, by adding cesium triiodide to the perovskite precursor solution, the formation of low-dimensional phases in the perovskite film is reduced, the defect density therein is reduced, and the halogen movement is reduced, thereby obtaining a denser perovskite film with fewer holes. The perovskite film to which cesium triiodide is added is used as a perovskite light-emitting layer to prepare a perovskite light-emitting diode, which can effectively improve the efficiency and brightness of a pure red light perovskite light-emitting diode, while improving the performance of the perovskite light-emitting diode, and achieving better spectral stability and operational stability.

[0051] Embodiment 1

[0052] The preparation of perovskite film is as follows:

[0053] (1) Lead iodide, lead bromide, cesium iodide, cesium triiodide, phenethylammonium iodide and 1-naphthylmethylammonium iodide were mixed at concentrations of 0.19 mol / L, 0.21 mol / L, 0.24 mol / L, 0.06 mol / L, 0.32 mol / L and 0.08 mol / L, respectively, and dissolved in a polar solvent of dimethyl sulfoxide, stirred for 2 hours, and filtered with a 0.45 μm filter to obtain a perovskite precursor solution, in which the proportion of cesium triiodide was 20%.

[0054] (2) A control group was set up, and lead iodide, lead bromide, cesium iodide, phenethylammonium iodide and 1-naphthylmethylammonium iodide were mixed at concentrations of 0.19 mol / L, 0.21 mol / L, 0.3 mol / L, 0.32 mol / L and 0.08 mol / L, respectively, and dissolved in a polar solvent dimethyl sulfoxide, stirred for 2 hours, and filtered with a 0.45 μm filter to obtain a perovskite precursor solution (without adding cesium triiodide, that is, the proportion of the additive cesium triiodide in the perovskite precursor solution was 0%).

[0055] (3) The perovskite precursor solution was statically drop-coated onto the substrate, and the substrate was accelerated to rotate at a speed of 8000 rpm. The total spin coating time was 70 s.

[0056] (4) At 12 seconds into the rotation process, ethyl acetate was dynamically drop-coated on the perovskite.

[0057] (5) After spin coating, annealing was performed at 80°C for 10 minutes to obtain the perovskite film.

[0058] Figure 3 A schematic diagram showing a comparison of the surface morphologies of perovskite films prepared without adding cesium triiodide and with adding cesium triiodide provided in an embodiment of the present disclosure is shown.

[0059] like Figure 3 As shown, Figure 3 (a) is the surface morphology of the perovskite film prepared from the perovskite precursor solution (without cesium triiodide added) used for comparison. Figure 3 (b) is the surface morphology of the perovskite film prepared after adding cesium triiodide to the perovskite precursor solution. It can be seen that the addition of cesium triiodide can significantly change the morphology of the perovskite film. There are many holes in the perovskite film without the addition of cesium triiodide. The perovskite film with the addition of cesium triiodide has fewer holes, and the perovskite grains obtained are smaller and the crystallization quality is better.

[0060] Embodiment 2

[0061] The structure of the perovskite light-emitting diode is as follows:

[0062] The glass substrate and the anode are a glass substrate and indium tin oxide thereon; the first organic hole transport layer is polyethylene dioxythiophene-poly(styrene sulfonate); the second organic hole transport layer is a combination of poly[bis(4-phenyl)(4-butylphenyl)amine] and poly(9-vinylcarbazole); the perovskite light-emitting layer includes two perovskite films prepared in Example 1, the difference being whether cesium triiodide is added to the perovskite precursor solution; the electron transport layer is tri[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane and lithium fluoride; and the metal electrode is an aluminum electrode.

[0063] Embodiment 3

[0064] Based on the structure of the perovskite light-emitting diode in Example 2, the preparation flow chart of the perovskite light-emitting diode in this example is as follows: Figure 4 As shown, the following steps are included:

[0065] (1) A glass substrate and indium tin oxide with a size of 1.5 cm × 1.5 cm and an effective area of ​​0.1 square centimeters were used. The glass substrate and indium tin oxide were ultrasonically cleaned in sequence using cleaning fluid, acetone, isopropanol, and ethanol.

[0066] (2) After the glass substrate and indium tin oxide cleaned in step (1) are treated in an ultraviolet ozone cleaning mechanism for 40 minutes, a polyethylene dioxythiophene-poly (styrene sulfonate) aqueous solution is filtered and spin-coated thereon at a speed of 7000 rpm for 40 seconds, and then annealed at 160° C. for 15 minutes to obtain a first organic hole transport layer with a thickness of about 20 nm.

[0067] (3) The glass substrate, indium tin oxide and the first organic hole transport layer obtained in step (2) were transferred to a glove box filled with nitrogen, and the device preparation was continued. The above-mentioned 10 mg / mL poly[bis(4-phenyl)(4-butylphenyl)amine] and 2.5 mg / mL poly(9-vinylcarbazole) were spin-coated on the first organic hole transport layer at a speed of 2000 rpm in sequence, the spin coating time was 40 s, and annealed at 150° C. for 20 minutes to obtain a second organic hole transport layer with a thickness of about 30 nm.

[0068] (4) Spin coating the above-mentioned perovskite precursor solution containing cesium triiodide and the perovskite precursor solution not containing cesium triiodide for control on the second organic hole transport layer at a speed of 8000 rpm, the spin coating time is 70 seconds, and ethyl acetate anti-solvent is quickly added dropwise for extraction at 12 seconds after the start of spin coating. After spin coating, annealing is performed at 80° C. for 10 minutes to obtain a perovskite light-emitting layer with a thickness of about 50 nm;

[0069] (5) Place the spin-coated perovskite light-emitting layer in a thermal evaporation chamber at 2×10 -4 At a pressure below 200 Pa, 40 nm of tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane was evaporated using a full-area mask. The mask was replaced and placed back in the evaporation chamber, and 1 nm of lithium fluoride was evaporated on top to obtain an electron transport layer.

[0070] (6) On the electron transport layer, a 100 nm thick aluminum electrode was evaporated to obtain the cathode of the device.

[0071] The electroluminescent properties of the perovskite light-emitting diodes prepared using different perovskite light-emitting layers in this embodiment were tested, including the relationship curves between current density and voltage, the relationship curves between brightness and voltage, the relationship curves between external quantum efficiency and current density, and the relationship curves between electroluminescence peak wavelength and voltage, as shown in FIG. Figures 5 to 8 shown.

[0072] from Figures 5 to 8 It can be seen that the device with the addition of cesium triiodide has better current injection, higher efficiency and brightness, and better spectral stability. This shows that the addition of cesium triiodide can reduce the formation of low-dimensional phases in the perovskite film and reduce defects, thereby improving the performance and stability of the prepared device.

[0073] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0074] Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims

1. A method for preparing a perovskite film, characterized in that: include: Dissolving lead iodide, lead bromide, a cesium iodide mixture and an organic ammonium iodide salt in a polar solvent to obtain a perovskite precursor solution, wherein the cesium iodide mixture includes cesium iodide and cesium triiodide; The perovskite precursor solution is dripped onto a substrate, the substrate is rotated at an accelerated speed, and an anti-solvent is dripped during the rotation process to obtain a perovskite film.

2. The method for preparing a perovskite thin film according to claim 1, characterized in that: The dissolution ratio of the lead iodide, lead bromide, cesium iodide mixture and the organic ammonium iodide salt is 1:1.11:a:b, wherein 1<a<2, 2<b<3.

3. The method for preparing a perovskite thin film according to claim 1, characterized in that: The proportion of the cesium triiodide in the cesium iodide mixture is 10% to 40%.

4. The method for preparing a perovskite thin film according to claim 1, characterized in that: The polar solvent is dimethyl sulfoxide and / or N,N-dimethylformamide.

5. The method for preparing a perovskite thin film according to claim 1, characterized in that: The anti-solvent is one of ethyl acetate, chlorobenzene and toluene.

6. The method for preparing a perovskite thin film according to claim 1, characterized in that: The material of the organic ammonium iodide salt is one or more of phenethylammonium iodide, 1-naphthylmethylammonium iodide, 2-naphthylmethylammonium iodide, 2-fluorophenethylammonium iodide, 3-fluorophenethylammonium iodide and 4-fluorophenethylammonium iodide.

7. A perovskite light-emitting diode, characterized in that: From bottom to top, they include: A substrate, a transparent conductive electrode, a first organic hole transport layer, a second organic hole transport layer, a perovskite light-emitting layer, an electron transport layer and a metal electrode, wherein the perovskite light-emitting layer is prepared according to the method for preparing a perovskite thin film according to any one of claims 1-6.

8. The perovskite light-emitting diode according to claim 7, characterized in that: The material of the first organic hole transport layer is polyethylenedioxythiophene-poly(styrene sulfonate).

9. The perovskite light-emitting diode according to claim 7, characterized in that: The material of the second organic hole transport layer is a combination of poly[bis(4-phenyl)(4-butylphenyl)amine] and poly(9-vinylcarbazole) or a combination of poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-n-butyl)phenyl)-diphenylamine)] and poly(9-vinylcarbazole).

10. The perovskite light-emitting diode according to claim 7, characterized in that: The material of the electron transport layer is a combination of tris[2,4,6-trimethyl-3-(3-pyridyl)phenyl]borane and lithium fluoride or a combination of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene and lithium fluoride.

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