Vapor deposition in-situ synthesis perovskite quantum dot and preparation method of electroluminescent blue light device

Abstract

The invention belongs to the field of photoelectric devices, and discloses a vapor deposition in-situ synthesis perovskite quantum dot and a preparation method of an electroluminescent blue light device.A light-emitting layer of the perovskite electroluminescent blue light device is based on a CsPbBr3 quantum dot light-emitting system, CsBr, PbBr2 and MBABr are independently used as evaporation sources, and the light-emitting layer is obtained through a three-source co-vapor deposition process; the deposition rate of PbBr2 does not exceed 0.020 nm / s, and the molar ratio of CsBr to PbBr2 to MBABr is 1.10: 1: (0.2-1). According to the invention, the synthesis process of CsPbBr3 quantum dots is improved, a vapor deposition in-situ synthesis strategy is adopted, the CsPbBr3 quantum dot material composed of three components of CsBr, PbBr2 and MBABr is used as the luminescent layer, the molar ratio of the three components is strictly controlled, deposition is carried out at a low deposition rate, and compared with a mixed halogen luminescent layer material, the obtained luminescent layer has the advantages that the light emitting efficiency is improved, and the light emitting efficiency is improved. The LED lamp is good in spectral stability, high in brightness and long in service life.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic devices, and more specifically, relates to a method for preparing a perovskite quantum dot and an electroluminescent blue light device by in-situ synthesis of perovskite quantum dots by vapor deposition. The obtained CsPbBr3 quantum dot electroluminescent device is particularly suitable for blue light electroluminescence in the wavelength range of 470nm-490nm. Background Art

[0002] As the core technology in the display field, light-emitting diodes (LEDs) have always been the research focus of the industry and scientific research community. In recent years, metal halide perovskite materials with high fluorescence quantum yield (PLQY) and high color purity have shown good application prospects in the display field due to their unique advantages such as low cost, high mobility, and flexible preparation methods. However, the development of perovskite blue light devices has long been limited by the mixed halogen system (such as CsPbBr x Cl 3-x )'s spectral instability problem - under electric field or thermal stress, halogen phase separation will cause the emission peak position to drift and efficiency to decay, which seriously restricts practical applications. In comparison, single halogen CsPbBr3 quantum dots, due to their uniform crystal structure and halogen composition, exhibit better spectral stability, and by regulating the size of CsPbBr3 quantum dots, the emission wavelength can be blue-shifted to 470-490nm, achieving efficient blue light emission while maintaining the intrinsic stability of the material. Traditional solution methods (such as hot injection and ligand-assisted reprecipitation) face significant challenges in the preparation of blue-light CsPbBr3 quantum dots: the introduction of solvents can easily lead to surface defects of quantum dots and agglomeration problems during the film formation process, and it is difficult to be effectively compatible with the vacuum-deposited charge transport layer. For mixed halogen systems, post-treatment processes (such as annealing and surface passivation) may also aggravate halogen migration and further reduce spectral stability.

[0003] Taking the solution-based synthesis of blue-emitting CsPbBr3 quantum dots as an example, the synthesis of CsPbBr3 quantum dots requires the addition of long-chain organic ligands (such as oleylamine, octadecylamine, and dodecanethiol) to maintain the stability of the quantum dots in solution. However, long-chain organic materials have poor conductivity, hindering carrier injection. Furthermore, traditional CsPbBr3 quantum dot preparation strategies face challenges such as ligand detachment and excessive ligands leading to poor optical performance and conductivity.

[0004] Therefore, if we can find a way to further form a light-emitting layer with higher carrier injection ability based on the blue light CsPbBr3 quantum dots, it will undoubtedly further promote the application of electroluminescent blue light devices. Summary of the Invention

[0005] In response to the above defects or improvement needs of the prior art, the purpose of the present invention is to provide a method for preparing perovskite quantum dots and electroluminescent blue light devices by vapor deposition in situ synthesis, by improving the synthesis process of CsPbBr3 quantum dots, adopting the strategy of vapor deposition in situ synthesis, using CsPbBr3 quantum dot material composed of three components, CsBr, PbBr2 and MBABr, as the light-emitting layer, strictly controlling the molar ratio of CsBr: PbBr2: MBABr to 1.10: 1: 0.2-1, and depositing at a low deposition rate (wherein the deposition rate of PbBr2 material does not exceed 0.020nm / s), to obtain a CsPbBr3 quantum dot light-emitting layer, which has good spectral stability, high brightness and long life compared to mixed halogen light-emitting layer materials. In addition, the device structure can be prepared in particular using a full vacuum process, which is simple in process, low in equipment investment, compatible with existing OLED production processes, and has application value in display integration.

[0006] To achieve the above object, according to one aspect of the present invention, a perovskite blue light electroluminescent device is provided, characterized in that it comprises, from top to bottom, a top electrode, an electron transport layer, a light-emitting layer, a hole transport layer and a bottom electrode;

[0007] Among them, the light-emitting layer is based on the CsPbBr3 quantum dot light-emitting system, specifically, CsBr material, PbBr2 material and MBABr material are independently used as evaporation sources, and are deposited through a three-source co-vapor phase deposition process, wherein the deposition rate of PbBr2 material does not exceed 0.020nm / s; and the molar ratio of CsBr:PbBr2:MBABr corresponding to the light-emitting layer is 1.10:1:0.2~1.

[0008] As a further preferred embodiment of the present invention, the electron transport layer is made of organic electron transport material.

[0009] As a further preferred embodiment of the present invention, the electron transport layer preferably adopts a stack of TPBi and Bphen.

[0010] As a further preferred embodiment of the present invention, the hole transport layer is made of organic or inorganic doped hole transport layer materials.

[0011] As a further preferred embodiment of the present invention, the hole transport layer is preferably a stack of TAPC and TCTA doped with MoO3.

[0012] As a further preferred embodiment of the present invention, the top electrode is a LiF-modified Al electrode, and the work function of the top electrode is 3.2 eV;

[0013] The bottom electrode is an ITO electrode.

[0014] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned perovskite blue electroluminescent device, characterized in that the preparation process of the light-emitting layer is as follows: based on a three-source co-evaporation vapor deposition process, three independent raw materials of CsBr, PbBr2 and MBABr are used as three evaporation sources, and these three raw materials are respectively placed in three independent evaporation boats, and then the vapor deposition chamber is evacuated, and the three evaporation boats are heated to co-deposit to obtain the light-emitting layer; wherein, the deposition rate of the PbBr2 material does not exceed 0.020nm / s.

[0015] As a further preferred embodiment of the present invention, the vacuuming is to make the vacuum degree ≤1×10 -4 Pa;

[0016] The deposition rate of PbBr2 material is 0.020~0.001nm / s.

[0017] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned perovskite blue light electroluminescent device, characterized in that the preparation method is based on a full vacuum deposition process, comprising the following steps:

[0018] (1) Prepare a clean and dry ITO glass substrate and place it in a vapor deposition chamber under a vacuum of ≤1×10 -4 Under the conditions of Pa, TCTA and MoO3 were simultaneously evaporated by dual-source co-evaporation, and then TAPC was evaporated separately to form a hole transport layer on the ITO glass substrate;

[0019] (2) Using the substrate obtained in step (1) as the base, a three-source co-evaporation vapor deposition process is performed, using three independent raw materials, CsBr, PbBr2 and MBABr, as three evaporation sources. These three raw materials are placed in three independent evaporation boats, and then the vapor deposition chamber is evacuated to a vacuum degree of ≤1×10 -4 Pa, and heating the three evaporation boats to co-deposit a light-emitting layer formed on the hole transport layer; wherein the deposition rate of the PbBr2 material does not exceed 0.020 nm / s;

[0020] (3) The substrate obtained in step (2) was placed in a vapor deposition chamber under a vacuum of ≤1×10 -4 Pa, first evaporating TPBi and then evaporating Bphen to form an electron transport layer on the light-emitting layer;

[0021] (4) The substrate obtained in step (3) was placed in a vapor deposition chamber under a vacuum of ≤1×10 -4 Under the condition of Pa, a LiF thin film is first evaporated, and then an Al film is evaporated, thereby forming a top electrode on the electron transport layer.

[0022] According to another aspect of the present invention, the present invention provides the use of the above-mentioned perovskite blue light electroluminescent device in a display screen.

[0023] Through the above technical solution conceived by the present invention, compared with the existing technology, the present invention utilizes multi-source co-evaporation technology, uses MBABr as a ligand, and uses CsBr material, PbBr2 material and MBABr material as independent evaporation sources to perform three-source co-evaporation, and adjusts the molar ratio of CsBr:PbBr2:MBABr in the light-emitting layer to 1.10:1:0.2~1. In this way, the content of the ligand material MBABr is precisely controlled, and deposition is performed at a relatively low deposition rate (wherein the deposition rate of the PbBr2 material does not exceed 0.020nm / s), thereby achieving precise control of the CsPbBr3 grain size (taking Examples 1 and 2 below as examples, CsPbBr3 quantum dots with a grain size of 4-6nm can be formed), thereby ensuring the formation of a CsPbBr3 quantum dot light-emitting layer.

[0024] The present invention uses vapor deposition to in-situ synthesize CsPbBr3 quantum dots, depositing CsBr, PbBr2, and organic ligands on the substrate surface. A uniformly sized quantum dot film is directly generated during the reactive crystallization process. The size of the perovskite quantum dots is precisely controlled by selecting ligand materials and adjusting evaporation parameters. This passivates surface defects in the quantum dots, improving the film's PLQY. The fully vapor-deposited device structure is rationally designed to produce a highly efficient and stable blue-light PeLED device. Furthermore, by utilizing a fully vacuum process (compatible with OLED production lines) and optimizing the device structure (such as the design of a combination of multiple transport layer materials), the present technology is expected to accelerate the industrialization of highly stable blue-light perovskite LEDs in the display field.

[0025] The present invention synthesizes perovskite quantum dots in situ through a vapor deposition process, and uses a strong ligand material MBABr to regulate the grain size of the CsPbBr3 perovskite light-emitting layer, which can realize a spectrum-tunable blue light perovskite electroluminescent device. Compared with the commonly used CsPbBr x Cl 1-x The light-emitting layer material has good spectral stability, high brightness and long life.

[0026] Specifically, the present invention can achieve the following beneficial effects:

[0027] 1. The present invention provides a vapor-deposited perovskite blue light-emitting device, the light-emitting layer of which is a CsPbBr3 quantum dot system material (which can be produced by co-evaporation of CsBr, PbBr2, and MBABr). This material is a single halogen perovskite material with excellent spectral stability and high fluorescence quantum yield. Furthermore, this material has high mobility, making it suitable for use as the light-emitting layer of an electroluminescent material. The corresponding device emits blue electroluminescence in the wavelength range of 470-490nm. The present invention can utilize vapor deposition three-source co-evaporation to prepare the light-emitting layer material, and in particular, can use the light-emitting material of the CsPbBr3 quantum dot system to produce a thin-film electroluminescent device.

[0028] The present invention uses a vapor deposition process to in situ synthesize a CsPbBr3 quantum dot system material composed of three components: CsBr, PbBr2, and MBABr, effectively expanding the preparation process of the perovskite blue light emitting system. CsBr material and PbBr2 material form the CsPbBr3 light emitting system, and the film co-evaporated by the two exhibits green fluorescence. The present invention found that when an appropriate amount of MBABr was added, the film emitted a blue fluorescence. It is speculated that the addition of MBABr material may form a good coating on the CsPbBr3 crystals, while inhibiting the growth of CsPbBr3 crystals, forming a CsPbBr3 quantum dot film with strong quantum confinement, causing the emitted fluorescence to blue-shift. The present invention adopts a vapor deposition in situ synthesis strategy of CsPbBr3 quantum dots, effectively avoiding the short board of mixed halogen preparation of blue light perovskite light-emitting devices, while the short-chain ligand MBABr effectively increases charge injection, obtaining a spectrally stable and bright blue light emission. The light-emitting layer in the present invention is obtained by three-source co-vapor phase deposition using CsBr material, PbBr2 material and MBABr material as independent evaporation sources. The light-emitting spectrum can be regulated by the ratio of the three components of the light-emitting layer; when the molar ratio of CsBr, PbBr2 and MBABr corresponding to the light-emitting layer is CsBr:PbBr2:MBABr=1.10:1:0.2~1, the emission spectrum of the light-emitting layer can be tuned within the range of 470-490nm, and an electroluminescent blue light device is obtained.

[0029] The present invention can realize wavelength-tunable perovskite blue light electroluminescent devices, and can solve the technical problems of poor spectral stability, low brightness, and difficulty in integrating with driving circuits of solution-processed mixed halogen blue light perovskite devices. The present invention has a higher carrier injection capability than the solution-processed CsPbBr3 quantum dot light-emitting system. In the process of synthesizing CsPbBr3 quantum dot materials by solution method, long-chain organic ligands need to be added to maintain the stability of quantum dots in solution. However, long-chain organic materials have poor conductivity and are not conducive to carrier injection. Therefore, it is necessary to find a way to improve the carrier injection capability. The traditional CsPbBr3 quantum dot preparation strategy also faces problems such as easy ligand shedding and excessive ligands resulting in poor optical performance and conductivity. However, the present invention uses a vapor deposition in-situ synthesis process and selects MBABr as a ligand material to in-situ coat and size-control CsPbBr3 crystals, avoiding the use of long-chain ligands, achieving greater charge injection, and obtaining spectrally stable and bright blue light emission.

[0030] 2. The vapor-deposited perovskite blue light device provided by the present invention has a light-emitting layer material with better electroluminescence spectrum stability than the mixed halogen blue light perovskite system, and is expected to realize a spectrally stable blue light device. Our research group has previously conducted research on mixed halogen blue light perovskite light-emitting devices [Zhu, J. et al. All-Thermally Evaporated Blue Perovskite Light-Emitting Diodes for Active Matrix Displays. Small Methods 8, 2300712 (2024).], taking the bromine-chlorine mixed perovskite blue light film as an example, the blue light perovskite system is achieved by doping Cl elements into CsPbBr3 as the light-emitting layer. Although it can achieve blue light emission, the spectral stability of the device is poor (it is speculated that the reason should be that the halogen phase separation under the action of the electric field will cause the luminescence peak position to drift); and the device using a single halogen CsPbBr3 quantum dot material in the present invention can achieve electroluminescence spectrum stability (as shown later). Figure 6 ), the improvement is obvious.

[0031] 3. The present invention also preferably utilizes appropriate hole transport layers and electron transport layers to obtain efficient electroluminescent devices. The CsPbBr3 quantum dot blue perovskite light-emitting device provided by the present invention preferably utilizes a stack of TCTA and TAPC doped with MoO3 as the hole transport layer, and a stack of TPBi and Bphen as the electron transport layer, which can effectively adjust the injection balance and improve efficiency.

[0032] 4. The light-emitting layer of the present invention can be obtained by co-evaporation deposition of three sources of CsBr, PbBr2, and MBABr, without the need for complex chemical synthesis, and the raw materials are non-toxic and environmentally friendly.

[0033] 5. The light-emitting layer film and all parts of the device in the present invention can be processed at room temperature by vapor deposition (as illustrated in the examples below). The process is simple, the reaction temperature is low, and it is compatible with various substrates. It has significant advantages in large-area, flexible, silicon-based micro-displays.

[0034] 6. The CsPbBr3 quantum dot blue light perovskite light-emitting device provided by the present invention can be prepared by vapor deposition, and by combining it with the existing OLED industry chain, a light-emitting layer with high fluorescence yield can be effectively and controllably prepared.

[0035] In summary, the present invention provides a novel CsPbBr3 quantum dot blue electroluminescent device. By regulating the proportion of the light-emitting layer, the size of the CsPbBr3 quantum dots can be regulated, the emission spectrum of the film can be changed, and spectrally stable electroluminescent blue light can be achieved. The present invention can further optimize the device structure, ultimately achieving spectrally stable, high-brightness, and high-efficiency electroluminescent blue light. At the same time, the CsPbBr3 quantum dot blue light film is processed by vapor deposition, which is simple and convenient. Its room temperature process not only has low equipment requirements and low equipment investment, but also enables it to be directly produced on various substrates, realizing large-area, flexible devices. At the same time, the device structure is simple and compatible with existing integrated circuits, making pixelated display possible. The new technical solution provided by the present invention integrates material advantages and process advantages, has certain advantages over existing technical solutions, and provides a reliable new approach for the realization of perovskite electroluminescent blue light. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A diagram illustrating the structure of a CsPbBr3 quantum dot blue electroluminescent device according to an embodiment of the present invention. The " / " in the diagram indicates a stacked structure; for example, Al / LiF represents a stacked structure of Al and LiF films. The ":" in the diagram indicates doping; for example, TCTA:MoO3 represents TCTA doped with MoO3.

[0037] Figure 2 Schematic diagram of the three-source co-evaporation of CsBr, PbBr2, and MBABr provided in an embodiment of the present invention.

[0038] Figure 3 The blue electroluminescence spectra of CsPbBr3 quantum dots from devices produced in Examples 1 and 2 of the present invention are shown. The ratio of CsBr, PbBr2, and MBABr shown in the legend is the molar ratio of CsBr, PbBr2, and MBABr in the light-emitting layer (which is equivalent to the ratio of the evaporation rates of the three evaporation sources during the co-evaporation process).

[0039] Figure 4This is a performance diagram of the electroluminescent blue light device obtained in Example 1 of the present invention; wherein, Figure 4 The a in the equation corresponds to the current density, Figure 4 The b in the equation corresponds to brightness, Figure 4 The c in the equation corresponds to efficiency.

[0040] Figure 5 The following is a CIE coordinate diagram of the electroluminescence spectra of the devices obtained in Example 1 and Example 2 of the present invention.

[0041] Figure 6 The electroluminescence spectra of the device prepared in Example 1 of the present invention at different voltages are shown.

[0042] Figure 7 This is the electroluminescence spectrum of the device obtained in Comparative Example 1 of the present invention at a voltage of 6.0 V (the inset in the figure is a photo of the device in operation).

[0043] Figure 8 TEM images of the light-emitting layer thin films of the blue light devices obtained in Example 1 and Example 2 of the present invention and the green light device obtained in Comparative Example 1; wherein, Figure 8 A in corresponds to the sample of Example 1, Figure 8 B in corresponds to the sample of Example 2, Figure 8 C in the figure corresponds to sample 1 of the corresponding example.

[0044] Figure 9 The following are fluorescent photos of the light-emitting layer thin films of the blue light devices obtained in Example 1 and Example 2 of the present invention and the green light device obtained in Comparative Example 1; wherein, Figure 9 A in corresponds to the sample of Example 1, Figure 9 B in corresponds to the sample of Example 2, Figure 9 C in the figure corresponds to sample 1 of the corresponding example. DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0046] The CsPbBr3 quantum dot blue light electroluminescent device in the following examples is as follows Figure 1 As shown, it includes: a top electrode, an electron transport layer, a light-emitting layer and a hole transport layer, and a bottom electrode; wherein,

[0047] The top electrode material can be a LiF-modified Al electrode with a work function of 3.2 eV; of course, other electrode materials known in the prior art can also be used;

[0048] The material of the light-emitting layer is a CsPbBr3 quantum dot light-emitting system formed by co-evaporation of CsBr, PbBr2 and MBABr;

[0049] Similar to the prior art, the electron transport layer and the hole transport layer are both used to localize electrons or holes in the light-emitting layer and adjust the injection balance of electrons and holes; of course, in addition to TPBi, Bphen, TAPC, TCTA, and MoO3 materials, other electron transport materials and other hole transport materials known in the prior art can also be used to construct the electron transport layer and the hole transport layer respectively;

[0050] The bottom electrode is an ITO electrode, which can be a substrate obtained by etching an ITO substrate; of course, other transparent conductive substrates known in the prior art can also be used.

[0051] The deposition method of the light-emitting layer in the following text draws on the existing technology and adopts the method of three-source co-evaporation (on three-source co-evaporation, the inventor's research group has reported many reports in the early stage), and the target material is obtained through in-situ synthesis reaction on the substrate. The principle diagram of three-source co-evaporation is shown in the figure below. Figure 2 shown.

[0052] The following describes the present invention in detail using a Fangsheng FS-300 instrument for three-source co-evaporation as an example. (During three-source co-evaporation, the substrate temperature is room temperature, i.e., 25°C; of course, depending on the actual situation, the substrate temperature can also be actively controlled between -10°C and 50°C, as long as the CsBr, PbBr2, and MBABr can be successfully co-evaporated.) The MBABr material (Chinese name: α-methylbenzylamine bromide; CAS number: 48104-35-4) used in the examples below was purchased from Biolight.

[0053] The following text takes the preparation of devices using the full vapor deposition process as an example. Of course, except for the CsPbBr3 quantum dot light-emitting layer which requires the three-source co-evaporation method, other layer structures of the device can also be prepared using other processes.

[0054] Example 1

[0055] This embodiment takes an electroluminescent blue light emitting device whose light emitting layer material is a CsPbBr3 quantum dot light emitting system material (CsBr, PbBr2, MBABr three-source co-evaporation) as an example, and its specific preparation method includes the following steps:

[0056] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0057] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TCTA was first co-evaporated at a rate of 0.100-0.110 nm / s, and MoO3 was evaporated at a rate of 0.010-0.011 nm / s, with a total thickness of 40 nm. TAPC was then evaporated at a rate of 0.035-0.040 nm / s, with a film thickness of 5 nm. CsBr was evaporated at a rate of 0.011 nm / s, PbBr2 was evaporated at a rate of 0.010 nm / s, and MBABr was evaporated at a rate of 0.010 nm / s, with a total thickness of 20 nm. TPBi was then evaporated at a rate of 0.020-0.030 nm / s to a thickness of 10 nm, and Bphen was evaporated at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0058] To verify the microscopic quantum dot morphology of the light-emitting layer formed by the three-source co-evaporation in step b), a TEM copper mesh was placed in the vapor deposition chamber as a secondary substrate, in addition to the device substrate, from the start of TAPC deposition to the end of the three-source co-evaporation. TAPC was first deposited on the copper mesh at a rate of 0.035-0.040 nm / s to a film thickness of 5 nm. Then, using the three-source co-evaporation method, CsBr was deposited at a rate of 0.011 nm / s, PbBr2 at a rate of 0.010 nm / s, and MBABr at a rate of 0.010 nm / s, for a total thickness of 20 nm. The sample prepared on the copper mesh was directly subjected to TEM examination.

[0059] In this Example 1, the deposited layer formed by the co-evaporation of three sources corresponds to a molar ratio of CsBr:PbBr2:MBABr of 1.10:1:1, which is recorded as "MBABr-1".

[0060] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0061] The performance test results of the obtained device are as follows:

[0062] Figure 4 Shown are the efficiency, brightness, and current density curves of the device. It is not difficult to see that the device can work well.

[0063] like Figure 5 As shown, the color coordinates of the device (0.13, 0.08) reach standard blue light.

[0064] like Figure 3As shown, its luminescence peak is at 470nm. Figure 6 The spectra of the device at different voltages are shown. It can be seen that the spectra at different voltages do not shift, showing standard blue light emission with good spectral stability (commonly used CsPbBr x Cl 1-x The emission peak of the luminescent layer material has a significant red shift as the voltage increases, and the spectral stability is poor).

[0065] Example 2

[0066] This embodiment takes an electroluminescent blue light emitting device whose light emitting layer material is a CsPbBr3 quantum dot light emitting system material (CsBr, PbBr2, MBABr three-source co-evaporation) as an example, and its specific preparation method includes the following steps:

[0067] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0068] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TCTA was first deposited at a rate of 0.100-0.110 nm / s and MoO3 was deposited at a rate of 0.010-0.011 nm / s by co-evaporation, with a total thickness of 40 nm. TAPC was then deposited at a rate of 0.035-0.040 nm / s to a film thickness of 5 nm. CsBr was then deposited at a rate of 0.011 nm / s, PbBr2 was deposited at a rate of 0.010 nm / s, and MBABr was deposited at a rate of 0.002 nm / s by three-source co-evaporation, with a total thickness of 20 nm. TPBi was then deposited at a rate of 0.02-0.03 nm / s to a thickness of 10 nm, and Bphen was deposited at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0069] Similarly, to verify the microscopic quantum dot morphology of the light-emitting layer formed by the three-source co-evaporation in step b), a TEM copper mesh was also present in the vapor deposition chamber as a secondary substrate, in addition to the device substrate, from the start to the end of the TAPC deposition. TAPC was first deposited on the copper mesh at a rate of 0.035-0.040 nm / s to a thickness of 5 nm. Then, using the three-source co-evaporation method, CsBr was deposited at a rate of 0.011 nm / s, PbBr2 at a rate of 0.010 nm / s, and MBABr at a rate of 0.002 nm / s, for a total thickness of 20 nm. The sample prepared on the copper mesh was directly subjected to TEM examination.

[0070] In this Example 2, the molar ratio of CsBr:PbBr2:MBABr corresponding to the deposited layer formed by three-source co-evaporation is 1.10:1:0.2, which is recorded as "MBABr-0.2".

[0071] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0072] The performance test results of the obtained device are as follows:

[0073] like Figure 3 As shown, its emission peak is at 490nm.

[0074] like Figure 5 As shown, the color coordinates (0.08, 0.29) of the device are sky blue light.

[0075] Example 3

[0076] This embodiment takes an electroluminescent blue light emitting device whose light emitting layer material is a CsPbBr3 quantum dot light emitting system material (CsBr, PbBr2, MBABr three-source co-evaporation) as an example, and its specific preparation method includes the following steps:

[0077] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0078] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TCTA was first deposited at a rate of 0.100-0.110 nm / s and MoO3 was deposited at a rate of 0.010-0.011 nm / s by co-evaporation, with a total thickness of 40 nm. TAPC was then deposited at a rate of 0.035-0.040 nm / s to a film thickness of 5 nm. CsBr was then deposited at a rate of 0.022 nm / s, PbBr2 was deposited at a rate of 0.020 nm / s, and MBABr was deposited at a rate of 0.020 nm / s by three-source co-evaporation, with a total thickness of 20 nm. TPBi was then deposited at a rate of 0.02-0.03 nm / s to a thickness of 10 nm, and Bphen was deposited at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0079] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0080] The performance test results of the obtained device are as follows: the CsPbBr3 quantum dot film is blue fluorescence under ultraviolet light; and the electroluminescent device emits blue light.

[0081] Example 4

[0082] This embodiment takes a film whose light-emitting layer material is a CsPbBr3 quantum dot light-emitting system material (CsBr, PbBr2, MBABr three-source co-evaporation) as an example, and its specific preparation method includes the following steps:

[0083] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0084] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TAPC was evaporated at a rate of 0.035-0.040 nm / s, and the film thickness was 5 nm. Using the three-source co-evaporation method, CsBr was evaporated at a rate of 0.0011 nm / s, PbBr2 was evaporated at a rate of 0.001 nm / s, and MBABr was evaporated at a rate of 0.001 nm / s, with a total deposition thickness of 20 nm.

[0085] The CsPbBr3 quantum dot film exhibits blue fluorescence under ultraviolet light.

[0086] Comparative Example 1

[0087] This comparative example takes an electroluminescent green light device whose light-emitting layer material is a binary light-emitting system material of CsBr and PbBr2 as an example, and its specific preparation method includes the following steps:

[0088] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0089] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4Under the conditions of Pa, TCTA was first co-evaporated at a rate of 0.100-0.110 nm / s and MoO3 was evaporated at a rate of 0.010-0.011 nm / s, with a total thickness of 40 nm. TAPC was then evaporated at a rate of 0.035-0.040 nm / s to a film thickness of 5 nm. CsBr was evaporated at a rate of 0.011 nm / s and PbBr2 was evaporated at a rate of 0.010 nm / s to a total thickness of 20 nm using a dual-source co-evaporation method. TPBi was then evaporated at a rate of 0.02-0.03 nm / s to a thickness of 10 nm and Bphen was evaporated at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0090] Similarly, to verify the micromorphology of the light-emitting layer formed by dual-source co-evaporation in step b), a TEM copper mesh was present in the vapor deposition chamber as a secondary substrate, in addition to the device substrate, from the start to the end of TAPC deposition. TAPC was first deposited on the copper mesh at a rate of 0.035-0.040 nm / s to a thickness of 5 nm. Then, using dual-source co-evaporation, CsBr was deposited at a rate of 0.011 nm / s and PbBr2 at a rate of 0.010 nm / s, for a total thickness of 20 nm. The resulting sample on the copper mesh was directly subjected to TEM examination.

[0091] In this comparative example 1, MBABr was not involved in the dual-source co-distillation, which was recorded as "MBABr-0".

[0092] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0093] The performance test results of the obtained device are as follows:

[0094] like Figure 7 As shown, the luminescence peak of the device is at 520nm, and the inset is a real photo of the electroluminescent device, showing green emission.

[0095] In addition, the TEM test results of the "MBABr-1" sample in Example 1, the "MBABr-0.2" sample in Example 2, and the "MBABr-0" sample in Comparative Example 1 are as follows: Figure 8As shown in the figure, it is not difficult to see that the grain size of the light-emitting layer thin film of Example 1 is about 4nm, the grain size of the light-emitting layer thin film of Example 2 is about 6nm, and the grain size of the light-emitting layer thin film of Comparative Example 1 is about 30nm, which is much larger than that of Examples 1 and 2. The fluorescence photographs of the "MBABr-1" sample in Example 1, the "MBABr-0.2" sample in Example 2, and the "MBABr-0" sample in Comparative Example 1 are shown in the figure. Figure 9 As shown in the figure, it can be seen that the light-emitting layer film of Example 1 emits blue fluorescence, the light-emitting layer film of Example 2 emits sky blue fluorescence, and the light-emitting layer film of Comparative Example 1 emits green fluorescence.

[0096] Comparative Example 2

[0097] This comparative example takes an electroluminescent device whose light-emitting layer material is a CsPbBr3 quantum dot light-emitting system material (CsBr, PbBr2, MBABr three-source co-evaporation) as an example, and its specific preparation method includes the following steps:

[0098] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0099] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TCTA was first co-evaporated at a rate of 0.100-0.110 nm / s, and MoO3 was evaporated at a rate of 0.010-0.011 nm / s, with a total thickness of 40 nm. TAPC was then evaporated at a rate of 0.035-0.040 nm / s, with a film thickness of 5 nm. CsBr was evaporated at a rate of 0.11 nm / s, PbBr2 was evaporated at a rate of 0.10 nm / s, and MBABr was evaporated at a rate of 0.10 nm / s, with a total thickness of 20 nm. TPBi was then evaporated at a rate of 0.02-0.03 nm / s to a thickness of 10 nm, and Bphen was evaporated at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0100] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0101] In this comparative example, although CsBr, PbBr2 and MBABr materials were co-evaporated to form the light-emitting layer, the deposition rate was too fast during the co-evaporation to form a ligand-coated quantum dot structure, and the resulting device emitted green light.

[0102] Comparative Example 3

[0103] In this comparative example, the light-emitting layer material is CsPbBr3 light-emitting system material, and MBABr is not used, but the weakly coordinated ligand TPPO is used. The three-source co-evaporation electroluminescent device is prepared. The specific preparation method includes the following steps:

[0104] a) ultrasonically cleaning a patterned ITO glass substrate in acetone, ethanol, and deionized water for 20 minutes each, and then drying in a nitrogen environment; wherein the ITO substrate has two etched lines and a light-emitting area of ​​approximately 2 mm*2 mm;

[0105] b) Transfer the dried ITO glass substrate to the organic evaporation chamber and place it in a vacuum chamber below 1×10 -4 Under the conditions of Pa, TCTA was first co-evaporated at a rate of 0.100-0.110 nm / s, and MoO3 was evaporated at a rate of 0.010-0.011 nm / s, with a total thickness of 40 nm. TAPC was then evaporated at a rate of 0.035-0.040 nm / s, with a film thickness of 5 nm. CsBr was evaporated at a rate of 0.011 nm / s, PbBr2 was evaporated at a rate of 0.010 nm / s, and TPPO was evaporated at a rate of 0.010 nm / s, with a total thickness of 20 nm. TPBi was then evaporated at a rate of 0.02-0.03 nm / s to a thickness of 10 nm, and Bphen was evaporated at a rate of 0.040-0.050 nm / s to a thickness of 30 nm.

[0106] c) Change the mask and evaporate the electrode part; evaporate 1nm LiF film at a speed of 0.001nm / s, and then evaporate at a speed of 0.1nm / s at 5*10 -4 The device is completed by evaporating an 80nm thick Al film under the condition of less than Pa.

[0107] In this comparative example, since the weakly coordinating ligand TPPO was used instead of MBABr, the obtained device emitted green light.

[0108] The above embodiments are merely examples. For example, when a CsPbBr3 quantum dot light-emitting layer is formed by three-source co-evaporation, the deposition rate of PbBr2 can also use other deposition rates not exceeding 0.020 nm / s (e.g., 0.020-0.001 nm / s); the deposition rates of the CsBr material and the MBABr material are 110% and (20%-100%) of the deposition rate of PbBr2, respectively, so that the molar ratio of CsBr:PbBr2:MBABr corresponding to the formed light-emitting layer is 1.10:1:0.2-1. For another example, the device efficiency can be further improved by subsequently optimizing the device structure (e.g., the thickness of each layer structure).

[0109] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A perovskite blue light electroluminescent device, characterized in that: From top to bottom, it includes top electrode, electron transport layer, light-emitting layer, hole transport layer and bottom electrode; Among them, the light-emitting layer is based on the CsPbBr3 quantum dot light-emitting system, specifically, CsBr material, PbBr2 material and MBABr material are independently used as evaporation sources, and are deposited through a three-source co-vapor phase deposition process, wherein the deposition rate of PbBr2 material does not exceed 0.020nm / s; and the molar ratio of CsBr:PbBr2:MBABr corresponding to the light-emitting layer is 1.10:1:0.2~1.

2. The perovskite blue light electroluminescent device according to claim 1, characterized in that: The electron transport layer is made of organic electron transport material.

3. The perovskite blue light electroluminescent device according to claim 2, characterized in that: The electron transport layer preferably comprises a stack of TPBi and Bphen.

4. The perovskite blue light electroluminescent device according to claim 1, wherein: The hole transport layer is made of organic and inorganic doped hole transport layer materials.

5. The perovskite blue light electroluminescent device according to claim 4, characterized in that: The hole transport layer is preferably a stack of TAPC and TCTA doped with MoO3.

6. The perovskite blue light electroluminescent device according to claim 1, wherein: The top electrode is a LiF-modified Al electrode, and the work function of the top electrode is 3.2 eV; The bottom electrode is an ITO electrode.

7. The method for preparing a perovskite blue light electroluminescent device according to any one of claims 1 to 6, characterized in that: The preparation process of the light-emitting layer is as follows: based on the three-source co-evaporation vapor deposition process, three independent raw materials, CsBr, PbBr2 and MBABr, are used as three evaporation sources. These three raw materials are placed in three independent evaporation boats respectively, and then the vapor deposition chamber is evacuated. The three evaporation boats are heated to jointly deposit the light-emitting layer; among them, the deposition rate of the PbBr2 material does not exceed 0.020nm / s.

8. The preparation method according to claim 7, wherein: The vacuuming is to make the vacuum degree ≤1×10 -4 Pa; The deposition rate of PbBr2 material is 0.020~0.001nm / s.

9. The method for preparing a perovskite blue light electroluminescent device according to any one of claims 1 to 6, characterized in that: The preparation method is based on a full vacuum deposition process and includes the following steps: (1) Prepare a clean and dry ITO glass substrate and place it in a vapor deposition chamber under a vacuum of ≤1×10 -4 Under the condition of Pa, TCTA and MoO3 were simultaneously evaporated by dual-source co-evaporation method, and TAPC was evaporated separately to form a hole transport layer on the ITO glass substrate; (2) Using the substrate obtained in step (1) as the base, a three-source co-evaporation vapor deposition process is performed, using three independent raw materials, CsBr, PbBr2 and MBABr, as three evaporation sources. These three raw materials are placed in three independent evaporation boats, and then the vapor deposition chamber is evacuated to a vacuum degree of ≤1×10 -4 Pa, and heating the three evaporation boats to co-deposit a light-emitting layer formed on the hole transport layer; wherein the deposition rate of the PbBr2 material does not exceed 0.020 nm / s; (3) The substrate obtained in step (2) was placed in a vapor deposition chamber under a vacuum of ≤1×10 -4 Pa, first evaporating TPBi and then evaporating Bphen to form an electron transport layer on the light-emitting layer; (4) The substrate obtained in step (3) was placed in a vapor deposition chamber under a vacuum of ≤1×10 -4 Under the condition of Pa, a LiF thin film is first evaporated, and then an Al film is evaporated, thereby forming a top electrode on the electron transport layer.

10. Use of the perovskite blue light electroluminescent device according to any one of claims 1 to 6 in a display screen.

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