Eu-based rare earth electroluminescent white light device and preparation method thereof

Abstract

The present invention belongs to the field of optoelectronic devices and discloses an Eu-based rare earth electroluminescent white light device and a preparation method thereof. The Eu-based rare earth electroluminescent white light device comprises, from top to bottom, a top electrode, an electron transport layer, a light-emitting layer, a hole transport layer, and a bottom electrode. The light-emitting layer is a system based on ligand-regulated nanocrystal luminescence, specifically deposited by a three-source co-evaporation method using mCP material, CsI material, and EuI2 material as independent evaporation sources. Furthermore, the molar ratio of CsI, EuI2, and mCP corresponding to the light-emitting layer is CsI:EuI2:mCP=0.020-0.080:0.025:0.5-2. The present invention utilizes a ternary co-doped CsEuI3@mCP system material composed of mCP, CsI, and EuI2 as a single-matrix light-emitting layer and utilizes ligand-regulated nanocrystal luminescence. Compared to existing single-matrix white light technologies, the device has the advantages of high brightness, high efficiency, and high spectral quality.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic devices, and more specifically, relates to an Eu-based rare earth electroluminescent white light device and a preparation method thereof, which is particularly suitable for white light electroluminescence or photoluminescence in the wavelength range of 400nm-1000nm. Background Art

[0002] With the increasing global demand for energy-efficient, environmentally friendly, and long-life lighting, traditional white light LED and fluorescent lamp technologies are gradually showing limitations in terms of color variability, energy efficiency, and lifespan. To meet the demand for high-performance, low-power lighting, the development of new, efficient, and environmentally friendly white light emitting technologies has become a key research direction. Among them, single-matrix white light technology has attracted considerable attention due to its unique advantages. Compared with traditional multi-matrix light-emitting systems, single-matrix white light technology achieves high luminous efficacy, long life, low power consumption, and tunable color temperature, while avoiding the color variability and light decay issues common to traditional LEDs and fluorescent lamps. This technology achieves white light emission through a single matrix material, which not only simplifies the device structure but also significantly improves the stability and purity of the light output, offering new possibilities for the development of next-generation lighting technologies.

[0003] Taking the previous research of rare earth-based white light electroluminescence by our research group as an example, Chinese patent application CN202410306005.0 reported a Mn 2+ Doped CsEuI3 thin films and their preparation methods. This all-inorganic host-guest system incorporates Mn ion guest luminescence centers within the inorganic CsEuI3 system. While this system can achieve white light emission, improving device brightness remains difficult. This is primarily due to barriers to charge injection from the Eu-4f localized orbital, and carrier injection into the device still requires further optimization.

[0004] Furthermore, our research group also reported a Ce-based rare earth electroluminescent device and its preparation method (see Chinese patent application CN202410357835.6 for details). It mainly uses the energy transfer of the CsI, CeI3, and TAPC combination, but the energy transfer efficiency is low. Therefore, although the device can improve the brightness, the brightness improvement is limited. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the purpose of the present invention is to provide a Eu-based rare earth electro-luminescent white light device and a preparation method thereof. By improving the composition of the light-emitting layer and adopting a coupling mechanism of "crystal field-ligand field" dual-field regulation, a ternary co-doped CsEuI3@mCP (ligand-coated nanocrystal) system material composed of mCP, CsI, and EuI2 is used as a single matrix light-emitting layer. The light emission of the nanocrystal is regulated by the ligand, which has the advantages of high brightness, high efficiency, and high spectral quality compared with the existing single matrix white light technology. Moreover, the device has a simple structure, a simple process, low equipment investment, and can be compatible with the existing OLED production process, and has application value in display.

[0006] To achieve the above object, according to one aspect of the present invention, a Eu-based rare earth electro-luminescent white light device is provided, which sequentially includes a top electrode, an electron transport layer, a light-emitting layer, a hole transport layer, and a bottom electrode from top to bottom;

[0007] Among them, the light-emitting layer is a system based on ligand-regulated nanocrystal luminescence. Specifically, mCP material, CsI material, and EuI2 material are used as evaporation sources independently, and are deposited by a three-source co-evaporation thermal evaporation method; moreover, the molar ratio of CsI, EuI2, and mCP corresponding to the light-emitting layer is CsI:EuI2:mCP = 0.020~0.080:0.025:0.5~2.

[0008] As a further preference of the present invention, a transition layer is further provided between the light-emitting layer and the hole transport layer, and the transition layer is an mCP layer.

[0009] As a further preference of the present invention, the molar ratio of CsI, EuI2, and mCP corresponding to the light-emitting layer is 0.025:0.025:z,

[0010] When 0.5≤z<1, the light-emitting layer can emit cold white light;

[0011] When z = 1, the light-emitting layer can emit white light with a color coordinate of (0.33, 0.34);

[0012] When 1<z≤2, the light-emitting layer can emit warm white light.

[0013] As a further preference of the present invention, the electron transport layer uses an organic electron transport material.

[0014] As a further preference of the present invention, the electron transport layer uses TPBi.

[0015] As a further preference of the present invention, the hole transport layer uses an organic hole transport layer material.

[0016] As a further preferred embodiment of the present invention, the hole transport layer is a stack of TAPC and HATCN.

[0017] 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;

[0018] The bottom electrode is an ITO electrode.

[0019] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned Eu-based rare earth electroluminescent white light device, characterized in that the preparation process of the light-emitting layer is as follows: based on a thermal evaporation process of three-source co-evaporation, three independent raw materials of mCP, CsI and EuI2 are used as three evaporation sources, and these three raw materials are respectively placed in three independent evaporation boats, and then the thermal evaporation chamber is evacuated, and the three evaporation boats are heated to jointly deposit the light-emitting layer.

[0020] According to another aspect of the present invention, the present invention provides the use of the Eu-based rare earth electroluminescent white light device in a display screen.

[0021] Through the above technical solutions conceived by the present invention, compared with the existing technology, the present invention adopts a strategy of ligand-regulated nanocrystal luminescence, and constructs a rare earth electroluminescent white light device by using a ternary co-doped CsEuI3@mCP (ligand-wrapped nanocrystal; wherein the nanocrystal is specifically CsEuI3 nanocrystal, and the organic ligand is specifically mCP) system material composed of three components: mCP, CsI and EuI2 (which can be obtained by, for example, ternary co-evaporation deposition of CsI, EuI2 and mCP) as the light-emitting layer, thereby expanding the types of light-emitting material systems of single-matrix white light LEDs; and the device has adjustable spectral voltage (as illustrated in the embodiments below, the operating voltage can be adjusted from 6V to 9V), with a wide spectral broadening (400~1000nm); the device has a simple structure, a simple process, low equipment investment, is compatible with existing OLED production processes, and has certain development potential in display.

[0022] The present invention can broaden the color gamut of existing displays and address the technical issues of poor OLED stability, susceptibility to aging, and the resulting color distortion of white light. The core technology of the present invention is dual-field modulation: the inner core crystal field and the outer shell ligand field independently regulate the splitting of the Eu-5d orbital, generating a dual-emission mechanism. This synergistic effect achieves white light across the entire visible spectrum, with near-ideal chromaticity coordinates and a high color rendering index. Furthermore, resonant energy transfer between mCP and CsEuI3 solves the problem of charge injection and overcomes the problem of Eu-4f orbital localization. Application to WLEDs has demonstrated high efficiency and brightness.

[0023] This invention utilizes a ternary co-doped CsEuI3@mCP (ligand-coated nanocrystal) system composed of three components: mCP, CsI, and EuI2, effectively expanding the material variety of existing single-matrix white light emitting systems. The authors discovered that when the molar ratio of CsI, EuI2, and mCP is controlled to be 0.02-0.08:0.025:0.5-2, the film emits a brighter, broad-spectrum white fluorescence from 400nm to 1000nm. The spectrum can also be adjusted from cool white to warm white by adjusting the molar ratio of the three components. The composite white light is produced by the synergistic effect of coordination luminescence and crystal luminescence. This invention addresses the limitations of efficient charge injection and spectral tunability in traditional single-matrix white light-emitting devices through a dual-field modulation strategy. In the luminescent layer of the device, the core crystal field and shell ligand field of the CsEuI3 nanocrystals independently induce controlled splitting of the Eu-5d orbital, resulting in a dual emission mechanism. This synergistic effect produces white light across the entire visible spectrum from 400 nm to 1000 nm, achieving near-ideal chromaticity coordinates (0.33, 0.34) and a high color rendering index (CRI) of 85.7. Most importantly, charge injection is effectively facilitated through resonant energy transfer between the mCP and CsEuI3, overcoming the charge injection barrier associated with localized Eu-4f orbitals. When the CsEuI3@mCP luminescent layer is used as a single emitter in a white light-emitting diode (WLED), as demonstrated in the examples below, the invention provides a stable white light-emitting diode with a peak external quantum efficiency of 7.7% and a maximum luminance of 7326 cd·m⁻². It can be seen that the present invention adopts a strategy of ligand-regulated nanocrystal luminescence, which effectively increases charge injection and obtains white light emission with good chromaticity and tunable spectrum.

[0024] Several challenges hinder the further development of single-component electroluminescent WLEDs based on rare earth elements. For example, existing single-component materials based on rare earth elements lack universal design strategies and efficient spectral compensation mechanisms for white light across the entire visible spectrum. Furthermore, multi-effect crystallographic sites reduce the inter-ion distance between luminescent ions, leading to concentrated quenching. Furthermore, charge injection is poor due to the screening effect of outer-shell 5s / 5p electrons on the inner-shell LN-4f orbitals. Achieving efficient emission from single-matrix rare earth electroluminescence requires addressing this injection issue. This invention pioneered the "crystal field-ligand field" synergistically regulated lanthanide core-shell nanocrystals (CsEuI3@mCP NCs). Through the dual-field coupling mechanism of the inner core crystal field-induced Eu-5d orbital splitting and the outer ligand field fine-tuning, it achieved the first 400-1000 nm full visible spectrum white light emission in a single-component material, breaking through the bottleneck of insufficient spectral coverage of traditional single-component materials and achieving chromaticity coordinates close to ideal white light (0.33, 0.34) and high color rendering index (CRI 85.7). On this basis, efficient charge injection was achieved through the resonance energy transfer (RET) mechanism between the mCP ligand and the CsEuI3 core, bypassing the Eu-4f localized orbital charge injection barrier, so that the device quantum efficiency was improved to 7.7% and the maximum brightness reached 7326 cd·m⁻², overcoming the core problem of low carrier mobility in lanthanide materials; at the same time, the single-component active layer design simplifies the device structure (no charge blocking layer or multi-material blending is required), avoids the problem of multi-component phase separation, and achieves highly stable white light emission.

[0025] The light-emitting layer in the present invention can be deposited by a three-source co-evaporation thermal evaporation method using mCP material, CsI material and EuI2 material as independent evaporation sources. The spectrum can be regulated by the ratio and voltage of the three components of the light-emitting layer. For example, the present invention controls the molar ratio of the components of the light-emitting layer material to CsI:EuI2:mCP=0.02~0.08:0.025:0.5~2. By adjusting the ratio, the shape of the spectrum can be regulated within the white light range.

[0026] Taking the lighting sector as an example, this invention can provide efficient, environmentally friendly light sources, meeting market demands for long life, low energy consumption, and environmental performance. In the display sector, its high color purity and adjustable color temperature significantly enhance display quality. In the automotive and medical fields, its stability and reliability meet the needs of applications in specialized environments, demonstrating broad market prospects and technological development potential. Therefore, this invention is not only scientifically feasible but also offers significant potential for industrialization and commercialization.

[0027] Specifically, the present invention can achieve the following beneficial effects:

[0028] 1. The present invention provides a rare earth electroluminescent white light device, the luminescent layer of which comprises a rare earth nanocrystal plus organic ligand system (which can be prepared by ternary co-evaporation of mCP, CsI, and EuI2). This inorganic and organic material exhibits excellent stability, is resistant to aging, and has a long lifespan. Furthermore, it possesses high mobility, making it suitable for use as the luminescent layer of an electroluminescent material. The device exhibits dual emission peaks at wavelengths of 470nm and 600nm, making it particularly suitable for white light electroluminescence in the 400nm-1000nm wavelength range. The present invention utilizes a three-source co-evaporation thermal evaporation method to prepare the luminescent layer material. In particular, the luminescent system of rare earth nanocrystal plus organic ligand can be used to prepare thin-film electroluminescent devices.

[0029] 2. The rare earth electroluminescent white light device provided by the present invention has a higher carrier mobility than the all-inorganic white light material system, which can achieve higher injection and greater brightness. Figure 8 As shown, compared with the use of Mn 2+ The all-inorganic host-guest system constructed by doping CsEuI3 thin film and the device using dual-field coupling modulation in the present invention can easily achieve higher brightness improvement.

[0030] 3. The present invention also preferably utilizes appropriate hole transport layers and electron transport layers to obtain efficient electroluminescent devices. The rare earth electroluminescent white light device provided by the present invention preferably uses HATCN and TAPC as the hole transport layer, mCP as the transition layer between the hole transport layer and the light-emitting layer, and TPBi as the electron transport layer, which can effectively adjust the injection balance and improve efficiency.

[0031] 4. The light-emitting layer in the present invention can be obtained by ternary co-evaporation deposition of mCP, CsI, and EuI2, without the need for complex chemical synthesis, and the raw materials are non-toxic and environmentally friendly.

[0032] 5. The light-emitting layer film and all parts of the device in the present invention can be processed at room temperature by thermal evaporation (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, and lightweight displays.

[0033] 6. The light-emitting layer of the rare earth electroluminescent white light device provided by the present invention can be prepared by thermal evaporation. By combining with the existing OLED industry chain, a light-emitting layer with high fluorescence yield can be effectively and controllably prepared.

[0034] In summary, the present invention realizes a single-matrix white light perovskite emitting device with excellent comprehensive performance. By designing a new type of rare earth electro white light thin film device, the emission spectrum of the film can be changed by regulating the composition ratio of the light-emitting layer and the voltage of the device. As illustrated in the embodiments below, stable, high-brightness, and high-efficiency electro white light can be achieved. At the same time, the thermal evaporation processing of the white light film 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 manufactured on various substrates to achieve large-area, flexible, and lightweight displays. At the same time, the device has a simple structure and is 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 advantages over existing technical solutions, provides a reliable new way to achieve single-matrix electro white light, and provides a new white light option for current full-color displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The structure diagram of the rare earth electroluminescent white light device in Examples 1 to 4 of the present invention is shown. The “ / ” in the figure represents a stacked structure. For example, Al / LiF represents a stacked structure of an Al film and a LiF film.

[0036] Figure 2 Schematic diagram of the three-source co-evaporation of CsI, EuI2, and mCP provided in an embodiment of the present invention.

[0037] Figure 3 The rare earth white light photoluminescence spectrum and electroluminescence spectrum of the devices obtained in Example 1, Example 2 and Example 3 of the present invention are shown; wherein, Figure 3 (a) corresponds to the photoluminescence spectrum, Figure 3 (b) corresponds to the electroluminescence spectrum. The ratio of CsI, EuI2, and mCP shown in the legend is the molar ratio of CsI, EuI2, and mCP in the luminescent layer (which is equivalent to the ratio of the evaporation rates of the three evaporation sources during the co-evaporation process; the same applies below).

[0038] Figure 4 This is a performance comparison chart of the devices obtained in Example 2 and Example 3 of the present invention; wherein, Figure 4 (a) corresponds to the current density-efficiency diagram; Figure 4 (b) corresponds to the voltage-current density-brightness diagram.

[0039] Figure 5 This is a performance comparison chart of the devices obtained in Example 1 of the present invention and Comparative Example 1; wherein, Figure 5 (a) corresponds to the current density-efficiency diagram; Figure 5 (b) corresponds to the voltage-current density-brightness diagram.

[0040] Figure 6The following is a CIE coordinate diagram of the electroluminescence spectra of the devices obtained in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention.

[0041] Figure 7 This is a spectrum diagram of the electroluminescence of the device prepared in Example 1 of the present invention at different voltages. The inset in the figure is a physical diagram of the device prepared in Example 1 in the lighting state when the operating voltage is 6V.

[0042] Figure 8 This is a columnar data comparison chart of the maximum brightness of the device obtained in Example 1 of the present invention and the maximum brightness of the inorganic host device.

[0043] Figure 9 PL spectra comparison diagram of the light-emitting layer thin films of the devices prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention. The illustrations in the figures are fluorescent photographs of the light-emitting layer thin films of the devices corresponding to the corresponding legends.

[0044] Figure 10 TEM comparison diagram of the light-emitting layer thin film of the device obtained in Example 1, Example 2, and Example 3 of the present invention; wherein, Figure 10 (a) and (d) correspond to TEM images of the light-emitting layer at different magnifications in Example 3 (the molar ratio of CsI:EuI2:mCP is 0.025:0.025:2.0). Figure 10 (b) and (e) correspond to TEM images of the light-emitting layer at different magnifications in Example 1 (the molar ratio of CsI:EuI2:mCP is 0.025:0.025:1.0). Figure 10 (c) and (f) correspond to TEM images of the light-emitting layer of Example 2 (the molar ratio of CsI:EuI2:mCP is 0.025:0.025:0.5) at different magnifications.

[0045] Figure 11 The following are color coordinate diagrams of the luminescence of the devices prepared in Example 1, Example 2, and Example 3.

[0046] Figure 12 The figure is a comparison of the fluorescence lifetimes of the films prepared in Example 1 and Comparative Example 3.

[0047] Figure 13 2 is a stability comparison chart of the devices prepared in Example 1 and Comparative Example 1.

[0048] Figure 14 The figure is a comparison chart of device performance obtained in Example 1 and Example 5; wherein, Figure 14 (a) corresponds to the voltage-current density diagram; Figure 14 (b) in the figure corresponds to the voltage-luminance diagram. DETAILED DESCRIPTION

[0049] 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.

[0050] The rare earth electroluminescent white light device in the following embodiments, such as Figure 1 As shown, it includes: a top electrode, an electron transport layer, a light-emitting layer, a transition layer (optional, not required), a hole transport layer, and a bottom electrode; wherein,

[0051] 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;

[0052] The material of the light-emitting layer is a system of rare earth nanocrystals and organic ligands formed by co-evaporation of CsI, EuI2 and mCP;

[0053] The transition layer is an mCP layer, which is a preferred configuration and can further improve the performance of the device;

[0054] 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, TAPC, and HATCN 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;

[0055] 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.

[0056] The evaporation 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 previously reported many reports), and the target material is obtained by deposition and crystal growth reaction on the substrate. The principle diagram of three-source co-evaporation is shown in the figure below. Figure 2 shown.

[0057] The following detailed description of the present invention uses a Fangsheng FS-300 instrument as an example for three-source co-evaporation. (During three-source co-evaporation, the substrate temperature is room temperature; of course, the substrate temperature can also be actively controlled, as long as mCP, CsI, and EuI2 can be successfully co-evaporated.) The mCP material (Chinese name: 1,3-di-9-carbazolylbenzene; CAS number: 550378-78-4) used in the following examples was purchased from Biolight.

[0058] In addition, the device performance tests mentioned later are all performed after the device is packaged and isolated from water and oxygen.

[0059] Example 1:

[0060] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0061] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0062] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0063] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0064] d) Using a co-evaporation method, deposit CsI at a rate of 0.0025 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.10 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer is 0.025:0.025:1). Then, deposit TPBi at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0065] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0066] The performance test results of the obtained device (denoted as CsEuI3@mCP) are as follows:

[0067] Figure 3 The photoluminescence and electroluminescence spectra of the device are shown.

[0068] Figure 5 The device efficiency, brightness, and current density curves are shown. The device has a current density of 6.8 mA / cm 2The efficiency reaches 7.7% when the voltage is 10V, and the brightness reaches the maximum at 7326 cd / m 2 , the device performance is excellent.

[0069] like Figure 6 As shown, the color coordinates of the device (0.33, 0.34) are close to standard white light, and the color rendering index CRI is 85.7 and the color temperature CT is 5260K.

[0070] like Figure 7 The EL spectra of the device at different voltages are shown. While the spectral shapes vary slightly at different voltages, the peaks are at 470nm and 600nm, indicating white light emission. The inset in the upper right corner of the figure shows a photo of the device illuminated at a 6V operating voltage, showing bright white light.

[0071] like Figure 9 As shown, the light-emitting layer film of the device emits white fluorescence and has a wide spectrum of 400nm-1000nm, which has higher color rendering and wider adaptability.

[0072] Figure 10 (b) and (e) show the TEM images of the light-emitting layer of the device and the calculated average nanocrystal size. It can be seen that in the light-emitting layer of the device prepared in Example 1, the size of the CsEuI3 nanocrystals is about 18.6 nm and is wrapped by mCP.

[0073] like Figure 11 As shown, it also shows that the color coordinates of the device (0.33, 0.34) are close to standard white light.

[0074] like Figure 12 As shown, the fluorescence lifetime of the 380nm peak (mCP after adding CsEuI3) of the light-emitting layer of the device is about 2.75 ns.

[0075] like Figure 13 As shown, the stability of the device is shown, 100 cd·m −2 Next, T 50 About 840 minutes.

[0076] like Figure 14 As shown, the performance of the device is also shown.

[0077] The light-emitting layer of the device obtained in Example 1 is based on both inorganic and organic materials. In order to further illustrate the performance effect, the inventors also experimented with a device in which the light-emitting layer obtained based on Chinese patent application CN 202410306005.0 is formed of all inorganic materials. The layer structure and thickness of each layer of the inorganic main device are as follows: ITO / ZnO (30nm) / Al2O3 (5nm) / CsI+EuI2+MnI2 (200nm) / mCP (5nm) / TAPC (25nm) / HATCN (5nm) / Al (80nm), and its light-emitting layer is Mn 2+ Doped CsEuI3 film (deposited by three-source co-evaporation thermal evaporation method using CsI, EuI2 and MnI2 as independent evaporation sources, where the molar ratio of CsI:EuI2:MnI2 is 1:1:0.01). Figure 8 As shown, the Mn 2+ The maximum brightness of the CsEuI3-doped thin-film device is only 289 cd·m⁻².

[0078] At the same time, the electroluminescence (EL) performance of the single-component white LED corresponding to Example 1 and other light-emitting layer materials reported in the prior art is compared. The results are shown in Table 1. It can be seen that the device of the present invention has a brightness of 7326 cd·m⁻² and an efficiency of 7.7% based on the color coordinates close to the standard white light. The device has a brightness of 100 cd·m⁻² and an efficiency of 7.7%. −2 Lower T 50 The overall performance is the best:

[0079] .

[0080] Note: For details of [1] to

[12] in the table, please see:

[0081] [1] Journal document "Samarium-Doped Metal Halide Perovskite NanocrystalsforSingle-Component Electroluminescent White Light-Emitting Diodes", https: / / doi.org / 10.1021 / acsenergylett.0c00931

[0082] [2] Journal literature "Efficient single-component white lightemitting diodesenabled by lanthanide ions doped lead halide perovskites via controlling Förster energy transfer and specific defect clearance", https: / / doi.org / 10.1038 / s41377-022-01027-9

[0083] [3] Journal literature "Highly Bright and Stable Lead-FreeDouble PerovskiteWhite Light-Emitting Diodes", https: / / doi.org / 10.1002 / adma.202308487

[0084] [4] Journal literature "Efficient and stable emission ofwarm-white light fromlead-free halide double perovskites", https: / / doi.org / 10.1038 / s41586-018-0691-0

[0085] [5] Journal literature "Lead-free Double PerovskiteCs2AgIn0.9Bi0.1Cl6 QuantumDots for White Light-Emitting Diodes", https: / / doi.org / 10.1002 / advs.202102895

[0086] [6] Journal literature "Stable Yellow Light-Emitting DevicesBased on TernaryCopper Halides with Broadband Emissive Self-Trapped Excitons", https: / / pubmed.ncbi.nlm.nih.gov / 32167288 /

[0087] [7] Journal literature "Efficient and bright warm-white electroluminescence from lead-free metal halides", https: / / doi.org / 10.1038 / s41467-021-21638-x

[0088] [8] Journal literature "Come to light: Detailed analysis of thermally treated Phenyl modified Carbon Nitride Polymorphs for bright phosphors in lighting applications", https: / / hal.science / hal-02565038v1

[0089] [9] Journal literature "High-performance single-component white light-emitting diodes based on donor-acceptor integrated carbon nitride", https: / / www.researchgate.net / publication / 386035699

[0090]

[10] Journal literature "Multiphotoluminescence from a Triphenylamine Derivative and Its Application in White Organic Light-Emitting Diodes Based on a Single Emissive Layer", https: / / pubmed.ncbi.nlm.nih.gov / 30993785 /

[0091]

[11] Journal literature "Insight into the Mechanism and Outcoupling Enhancement of the Excimer Associated White Light Generation", https: / / www.researchgate.net / publication / 294276852

[0092]

[12] Journal document “Versatile Molecular Structure Strategy Toward HighlyEfficient Single-Component White Organic Light–Emitting Diodes”, https: / / advanced.onlinelibrary.wiley.com / doi / 10.1002 / adom.202401721.

[0093] Example 2:

[0094] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0095] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0096] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0097] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0098] d) Using a co-evaporation method, CsI was evaporated at a rate of 0.0025 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.050 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer was 0.025:0.025:0.5). TPBi was then evaporated at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0099] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0100] The performance test results of the obtained device are as follows:

[0101] Figure 3 The photoluminescence and electroluminescence spectra of the device are shown.

[0102] Figure 4 The performance of the device is shown, including voltage-current density-luminance plots and current density-efficiency plots.

[0103] Figure 10 (c) and (f) show the TEM images of the light-emitting layer of the device and the calculated average nanocrystal size. It can be seen that in the light-emitting layer of the device prepared in Example 2, the size of the CsEuI3 nanocrystals is about 27.4 nm and is wrapped by mCP.

[0104] Figure 11 The CIE diagram of the device's light emission shows a color coordinate of (0.25, 0.26), which is cool white light.

[0105] Example 3:

[0106] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0107] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm.

[0108] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0109] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0110] d) Using a co-evaporation method, CsI was evaporated at a rate of 0.0025 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.20 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer was 0.025:0.025:2). TPBi was then evaporated at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0111] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0112] The performance test results of the obtained device are as follows:

[0113] Figure 3 The photoluminescence spectrum and electroluminescence spectrum of the device are shown; Figure 3 ,It is not difficult to see that with the increase of mCP ratio, the peak position of the red light peak becomes larger relative to the blue light peak.

[0114] Figure 4 The performance of the device is shown, including voltage-current density-luminance plots and current density-efficiency plots.

[0115] Figure 10 Figures (a) and (d) show the TEM images of the light-emitting layer of the device and the calculated average nanocrystal size. It can be seen that in the light-emitting layer of the device prepared in Example 3, the size of the CsEuI3 nanocrystals is about 7.9 nm and is wrapped by mCP. Figure 10 ,It is not difficult to see that with the increase of the proportion of mCP, the size of CsEuI3 nanocrystals in the light-emitting layer becomes smaller.

[0116] Figure 11 The CIE diagram of the device's light emission shows color coordinates of (0.45, 0.36), which is warm white light.

[0117] Example 4:

[0118] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0119] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0120] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0121] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0122] d) Using a co-evaporation method, CsI was evaporated at a rate of 0.0080 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.050 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer was 0.08:0.025:0.5). TPBi was then evaporated at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0123] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0124] Example 5:

[0125] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0126] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0127] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0128] c) Using a co-evaporation method, CsI was evaporated at a rate of 0.0025 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.100 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer was 0.025:0.025:1). TPBi was then evaporated at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0129] d) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0130] The obtained device has no mCP transition layer, and its performance test results are as follows:

[0131] like Figure 14 The following figure shows the performance of the device. Comparing devices with and without an mCP transition layer, the device with the mCP transition layer exhibits a more normal rise in current density and a significantly lower threshold voltage. This demonstrates that the inclusion of the transition layer significantly reduces threshold voltage and improves performance.

[0132] Example 6:

[0133] This embodiment takes an electroluminescent white light device whose luminescent layer material is a luminescent system material (mCP, CsI, EuI2 ternary co-evaporation) of rare earth nanocrystals plus organic ligands as an example, and its specific preparation method includes the following steps:

[0134] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm.

[0135] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 3nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0136] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0137] d) Using a co-evaporation method, deposit CsI at a rate of 0.0020 nm / s, EuI2 at a rate of 0.0025 nm / s, and mCP at a rate of 0.050 nm / s, for a total thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer is 0.02:0.025:0.5). Then, deposit TPBi at a rate of 0.01-0.02 nm / s to a thickness of 25 nm.

[0138] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0139] Comparative Example 1:

[0140] This comparative example takes an electroluminescent device whose luminescent layer material is a CsEuI3 nanocrystal luminescent system material as an example, and its specific preparation method includes the following steps:

[0141] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0142] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 4nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0143] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0144] d) Using a co-evaporation method, deposit EuI2 at a rate of 0.02nm / s and CsI at a rate of 0.04nm / s, for a total thickness of 30nm (the molar ratio of EuI2 to CsI in the resulting light-emitting layer is 1:2). Then, deposit TPBi at a rate of 0.01-0.02nm / s to a thickness of 25nm;

[0145] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0146] The performance test results of the obtained device (denoted as CsEuI3) are as follows:

[0147] Figure 5 The device efficiency, brightness, and current density curves are shown. The device can work well, but the device performance is far inferior to that of the device in Example 1.

[0148] like Figure 6 As shown, the color coordinates (0.14, 0.11) of the device obtained in Comparative Example 1 are blue light.

[0149] like Figure 9 As shown, the light-emitting layer film of the device obtained in Comparative Example 1 emits blue fluorescence.

[0150] like Figure 13 As shown, the stability of the device is shown, 100 cd·m−2 Under the same conditions, T50 is about 58 min.

[0151] Comparative Example 2:

[0152] This comparative example takes an electroluminescent device in which the luminescent layer material is a mCP-EuI2 binary luminescent system material as an example, and its specific preparation method includes the following steps:

[0153] a) Ultrasonic cleaning of the ITO substrate using detergent, deionized water, acetone, and anhydrous ethanol, in sequence, for half an hour each time. The ITO substrate had two etched strips and a luminous area of ​​approximately 2 mm*2 mm;

[0154] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Pa below, the substrate is at room temperature throughout the entire process; first, HATCN is evaporated at a rate of 0.005-0.006nm / s to a film thickness of 4nm; then TAPC is evaporated at a rate of 0.035-0.040nm / s to a film thickness of 20nm;

[0155] c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm;

[0156] d) Using a co-evaporation method, deposit EuI2 at a rate of 0.002nm / s and mCP at a rate of 0.200nm / s, for a total thickness of 25nm (the molar ratio of EuI2 to mCP in the resulting light-emitting layer is 0.02:2). Then, deposit TPBi at a rate of 0.01-0.02nm / s to a thickness of 25nm;

[0157] e) Change the wafer and evaporate the electrode part; evaporate 2nm LiF film at a rate of 0.005nm / s, and then evaporate at a rate 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.

[0158] The performance test results of the obtained device (denoted as EuI2@mCP) are as follows:

[0159] like Figure 6 As shown, the color coordinates of the device (0.50, 0.42) are orange light.

[0160] like Figure 9 As shown, the light-emitting layer film of the device emits orange fluorescence.

[0161] Comparative Example 3:

[0162] The method for preparing pure mCP film in this comparative example is as follows:

[0163] a) Ultrasonic cleaning of the ITO substrate was performed using detergent, deionized water, acetone, and anhydrous ethanol, respectively, for half an hour each time.

[0164] b) Place the cleaned ITO substrate into the evaporation glove box and pump the vacuum degree to 4*10 -5 Below Pa, the substrate is at room temperature throughout the process; mCP is evaporated at a rate of 0.05~0.06nm / s, and the film thickness is 25nm.

[0165] The obtained film: Figure 12 As shown in Figure 3, the 380nm peak (pure mCP) fluorescence lifetime of the film is about 5.33ns. Figure 12 The data show that the ligand energy transfer efficiency is about 48%.

[0166] 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. An Eu-based rare earth electroluminescent white light 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 a system based on ligand-regulated nanocrystal luminescence, specifically, mCP material, CsI material and EuI2 material are independently used as evaporation sources, and are deposited by three-source co-evaporation thermal evaporation method; and the molar ratio of CsI, EuI2 and mCP corresponding to the light-emitting layer is CsI:EuI2:mCP=0.020~0.080:0.025:0.5~2.

2. The Eu-based rare earth electroluminescent white light device according to claim 1, wherein: A transition layer is further provided between the light-emitting layer and the hole transport layer, and the transition layer is an mCP layer.

3. The Eu-based rare earth electroluminescent white light device according to claim 1, wherein: The molar ratio of CsI, EuI2 and mCP corresponding to the light-emitting layer is 0.025:0.025:z. When 0.5≤z<1, the light-emitting layer can emit cool white light; When z=1, the light-emitting layer can emit white light with color coordinates of (0.33, 0.34); When 1<z≤2, the light-emitting layer can emit warm white light.

4. The Eu-based rare earth electroluminescent white light device according to claim 1, wherein: The electron transport layer is made of organic electron transport material.

5. The Eu-based rare earth electroluminescent white light device according to claim 4, characterized in that: The electron transport layer is made of TPBi.

6. The Eu-based rare earth electroluminescent white light device according to claim 1, wherein: The hole transport layer is made of organic hole transport layer material.

7. The Eu-based rare earth electroluminescent white light device according to claim 6, characterized in that: The hole transport layer is a stack of TAPC and HATCN.

8. The Eu-based rare earth electroluminescent white light 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.

9. The method for preparing the Eu-based rare earth electroluminescent white light device according to any one of claims 1 to 8, characterized in that: The preparation process of the light-emitting layer is as follows: based on the thermal evaporation process of three-source co-evaporation, three independent raw materials, mCP, CsI and EuI2, are used as three evaporation sources. These three raw materials are placed in three independent evaporation boats respectively, and then the thermal evaporation chamber is vacuumed and the three evaporation boats are heated to jointly deposit the light-emitting layer.

10. Use of the Eu-based rare earth electroluminescent white light device according to any one of claims 1 to 8 in a display screen.

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