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

Abstract

The invention belongs to the field of photoelectric devices, and discloses an Eu-based rare earth white light electroluminescent device and a preparation method thereof.The Eu-based rare earth white light electroluminescent device sequentially comprises a top electrode, an electron transport layer, a light emitting layer, a hole transport layer and a bottom electrode from top to bottom; wherein the light-emitting layer is a system for regulating and controlling luminescence of nanocrystals based on ligands, specifically, an mCP material, a CsI material and an EuI2 material are independently used as evaporation sources, and the light-emitting layer is obtained through deposition by a three-source co-evaporation heat evaporation method; in addition, the molar ratio of CsI, EuI2 and mCP corresponding to the light-emitting layer is as follows: CsI: EuI2: mCP = (0.020-0.080): (0.025): (0.5-2). According to the invention, the ternary co-doped CsEuI3 (at) mCP system material composed of three components of mCP, CsI and EuI2 is used as the single-matrix light-emitting layer, and the luminescence of the nanocrystal is regulated and controlled by using the ligand, so that compared with the existing single-matrix white light technology, the single-matrix white light-emitting 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. More specifically, it relates to a Eu-based rare-earth electroluminescent white light device and a preparation method thereof, which are particularly suitable for white electroluminescence or photoluminescence in the wavelength range of 400 nm - 1000 nm. Background Art

[0002] With the continuous improvement of the global demand for energy efficiency, environmental protection, and long-life lighting, traditional white light LED and fluorescent lamp technologies have gradually shown limitations in terms of color difference, energy efficiency, and lifespan. To meet the lighting requirements of high performance and low power consumption, the development of new high-efficiency and environmentally friendly white light emitting technologies has become an important research direction. Among them, single matrix white light technology has attracted much attention due to its unique advantages. Compared with traditional multi-matrix light emitting systems, single matrix white light technology can achieve high luminous efficiency, long lifespan, low power consumption, and adjustable color temperature, while avoiding common color difference and light decay problems in traditional LEDs and fluorescent lamps. This technology realizes white light emission through a single matrix material, which not only simplifies the device structure but also significantly improves the stability and purity of light output, providing new possibilities for the development of the next generation of lighting technologies.

[0003] Taking the previous research on rare-earth-based white electroluminescent in this research group as an example, Chinese Patent Application CN202410306005.0 reported a Mn 2+ doped CsEuI3 thin film and its preparation method. This all-inorganic host-guest system adds a Mn ion guest luminescent center to the inorganic CsEuI3 system. Although white light emission can be achieved, it is still difficult to improve the brightness of the device. This is mainly because there is a barrier in the charge injection of the Eu-4f local orbit, and the carrier injection of the device still needs to be further optimized.

[0004] Furthermore, this research group also reported a Ce-based rare-earth electroluminescent yellow light device and its preparation method (see Chinese Patent Application CN202410357835.6 for details). It mainly utilizes the energy transfer of the CsI, CeI3, TAPC combination, but the energy transfer efficiency is relatively low. Therefore, although the brightness of this device can be improved, the improvement is limited. Summary of the Invention

[0005] In view of the above deficiencies or improvement requirements of the prior art, the object of the present invention is to provide a Eu-based rare-earth electroluminescent 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 luminescence 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 electroluminescent 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; 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.

[0007] 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.

[0008] 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, When 0.5≤z<1, the light-emitting layer can emit cold white light; When z = 1, the light-emitting layer can emit white light with a chromaticity coordinate of (0.33, 0.34); When 1<z≤2, the light-emitting layer can emit warm white light.

[0009] As a further preference of the present invention, the electron transport layer uses an organic electron transport material.

[0010] As a further preference of the present invention, the electron transport layer uses TPBi.

[0011] As a further preference of the present invention, the hole transport layer uses an organic hole transport layer material.

[0012] As a further preference of the present invention, the hole transport layer is a stack of TAPC and HATCN.

[0013] As a further preference of the present invention, the top electrode is an Al electrode modified with LiF, and the work function of the top electrode is 3.2 eV; 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 Eu-based rare earth electroluminescent white light device, which is characterized in that the preparation process of the light-emitting layer is as follows: Based on the thermal evaporation process of triple-source co-evaporation, using three raw materials of mCP, CsI, and EuI2 that are independent of each other as three evaporation sources, putting these three raw materials into three independent evaporation boats respectively, then evacuating the thermal evaporation chamber, and heating the three evaporation boats, the light-emitting layer can be co-deposited.

[0015] According to yet another aspect of the present invention, the present invention provides the application of the above-mentioned Eu-based rare earth electroluminescent white light device in a display screen.

[0016] Through the above technical solution conceived by the present invention, compared with the prior art, the present invention adopts the strategy of ligand-regulated nanocrystal luminescence, and constructs a rare earth electroluminescent white light device by using a ternary co-doped CsEuI3@mCP (ligand-coated nanocrystals; where the nanocrystals are specifically CsEuI3 nanocrystals and the organic ligand is specifically mCP) system material composed of three components of 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, expanding the types of luminescent material systems for single-matrix white LEDs; and the spectrum voltage of this device is adjustable (as shown in the following examples, the operating voltage can be adjusted between 6V and 9V), with a relatively wide spectral broadening (400~1000nm); the device structure is simple, the process is simple, the equipment investment is low, and it can be compatible with the existing OLED production process, showing certain development potential in the display aspect.

[0017] The present invention can broaden the color gamut of the existing display, and solve the technical problems of poor stability of OLEDs and easy aging, which easily lead to white light color distortion. The technical core of the present invention is dual-field modulation: the inner core crystal field and the outer shell ligand field respectively regulate the splitting of Eu-5d orbitals, generating a dual-emission mechanism. Such a synergistic effect realizes white light with a full visible spectrum, the chromaticity coordinates are close to ideal, and the color rendering index is high. In addition, the problem of charge injection is solved through the resonance energy transfer between mCP and CsEuI3, overcoming the problem of Eu-4f orbital localization. Applied to WLEDs, it demonstrates high efficiency and brightness.

[0018] The present invention uses a ternary co-doped CsEuI3@mCP (ligand-coated nanocrystal) system material composed of three components, namely mCP, CsI, and EuI2, which effectively expands the types of materials in the existing single matrix white light emission system. The present invention discovers that when the molar ratio of the three components CsI, EuI2, and mCP is controlled to be 0.02~0.08:0.025:0.5~2, the thin film emits a brighter broadband white fluorescence in the range of 400 nm to 1000 nm, and the spectrum can also be adjusted from cold white light to warm white light by adjusting the molar ratio of these three components. Moreover, the composite white light is generated by the synergistic effect of coordination luminescence and crystal luminescence. The present invention solves the limitations of efficient charge injection and spectral tunability existing in traditional single matrix white light through a dual-field modulation strategy. In the light-emitting layer of the device of the present invention, the crystal field of the CsEuI3 nanocrystal core and the ligand field of the outer shell can respectively induce the controlled splitting of the Eu-5d orbitals, thus generating a dual emission mechanism. This synergistic effect produces white light with a full visible spectrum from 400 nm to 1000 nm, achieving a chromaticity coordinate close to the ideal value (0.33, 0.34) and a high color rendering index (CRI) of 85.7. Most importantly, through the resonance energy transfer between mCP and CsEuI3, charge injection is effectively promoted, overcoming the charge injection barrier related to the local Eu-4f orbitals. When the CsEuI3@mCP light-emitting layer is used as a single emitter of a white light-emitting diode (WLED), as demonstrated in the following examples, the present invention provides a stable white light-emitting diode with a peak external quantum efficiency of 7.7% and a maximum brightness of 7326 cd·m⁻². It can be seen that the present invention adopts a strategy of ligand-regulated nanocrystal luminescence, effectively increasing charge injection and obtaining white light emission with good chromaticity and adjustable spectrum.

[0019] There are some challenges in single-component electro-luminescent WLEDs based on rare earth elements, which hinder their further development. For example, existing single-component materials based on rare earth elements lack a general design strategy for white light across the entire visible spectrum and an efficient spectral compensation mechanism. Additionally, there is concentration quenching caused by the reduction of the interionic distance of luminescent ions due to multi-effect crystal sites. Another example is that due to the shielding effect of the outer 5s / 5p electrons on the inner LN-4f orbitals, the charge injection effect is poor. To achieve efficient luminescence in rare earth single-matrix electroluminescence, the injection problem must be solved. The present invention innovatively creates lanthanide core-shell nanocrystals (CsEuI3@mCP NCs) with "crystal field-ligand field" cooperative regulation. Through the dual-field coupling mechanism of the inner-core crystal field-induced splitting of Eu-5d orbitals and the fine regulation of the outer-ligand field, white light emission across the entire visible spectrum from 400 to 1000 nm is achieved for the first time in a single-component material, breaking through the bottleneck of insufficient spectral coverage in traditional single-component materials, and reaching chromaticity coordinates close to ideal white light (0.33, 0.34) and a high color rendering index (CRI 85.7). On this basis, efficient charge injection is achieved through the resonance energy transfer (RET) mechanism between the mCP ligand and the CsEuI3 inner core, bypassing the charge injection barrier of the Eu-4f local orbit, increasing the device quantum efficiency to 7.7% and the maximum brightness to 7326 cd·m⁻², and 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 (eliminating the need for charge blocking layers or multi-material blending), avoids multi-component phase separation problems, and realizes high-stability white light emission.

[0020] In particular, the light-emitting layer in the present invention can be deposited by three-source co-evaporation thermal evaporation method with mCP material, CsI material, and EuI2 material independently as evaporation sources. The spectrum can be regulated by the ratio of the three components of the light-emitting layer and the voltage. For example, in the present invention, the molar ratio of each component of the light-emitting layer material is controlled as CsI:EuI2:mCP = 0.02~0.08:0.025:0.5~2, and by adjusting the ratio, the shape of the spectrum can be regulated within the white light range.

[0021] Taking the lighting field as an example, the present invention can provide efficient and environmentally friendly light sources, meeting the market's demand for long life, low energy consumption, and environmental performance. In the display field, its high color purity and adjustable color temperature characteristics can significantly improve the display effect. In the automotive and medical fields, its stability and reliability can meet the application requirements in special environments, with broad market prospects and great potential for technological development. Therefore, the present invention not only has scientific feasibility but also shows great development space in industrialization and commercialization.

[0022] Specifically, the present invention can achieve the following beneficial effects: 1. The present invention provides a rare-earth electro-luminescent white light device, the material of the light-emitting layer of which is a system material of rare-earth nanocrystals plus organic ligands (which can be co-evaporated by mCP, CsI, and EuI2); this material is an inorganic and organic material with good stability, not easily aged, and long lifespan. At the same time, this material has a high mobility and is suitable for being used as the light-emitting layer of electro-luminescent materials. The emission double-peak wavelengths of the corresponding device are 470 nm and 600 nm, and it is particularly suitable for white electro-luminescence in the wavelength range of 400 nm - 1000 nm. The present invention can prepare the light-emitting layer material by using a three-source co-evaporation thermal evaporation method, and in particular, can use a light-emitting system material of rare-earth nanocrystals plus organic ligands to prepare a thin-film electro-luminescent device.

[0023] 2. The rare-earth electro-luminescent white light device provided by the present invention has a higher carrier mobility for the material of the light-emitting layer compared with the all-inorganic white light material system, and can achieve higher injection and greater brightness. As shown later Figure 8 as, compared with the all-inorganic host-guest system constructed by using Mn 2+ doped CsEuI3 thin film, the device using dual-field coupling modulation in the present invention can easily obtain a higher brightness improvement.

[0024] 3. The present invention also preferably uses a suitable hole transport layer and electron transport layer to obtain an efficient electro-luminescent device. For the rare-earth electro-luminescent white light device provided by the present invention, it is preferred to use 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 the efficiency.

[0025] 4. The light-emitting layer in the present invention can be particularly obtained by co-evaporating mCP, CsI, and EuI2, without going through complex chemical synthesis, and the raw materials are non-toxic and environmentally friendly.

[0026] 5. The light-emitting layer thin film and each part of the device in the present invention can be processed at room temperature by the thermal evaporation method (as shown in the examples later), with simple process, low reaction temperature, compatible with various substrates, and having significant advantages in large-area, flexible, and lightweight displays.

[0027] 6. For the rare-earth electro-luminescent white light device provided by the present invention, the light-emitting layer can be prepared by thermal evaporation coating. By combining with the existing OLED industrial chain, a light-emitting layer with a high fluorescence yield can be effectively and controllably prepared.

[0028] In summary, the present invention realizes a single-matrix white perovskite light-emitting device with excellent comprehensive performance. By designing a novel rare-earth electro-luminescent white thin-film device, the emission spectrum of the thin film can be changed by adjusting the component ratio of the light-emitting layer and the voltage of the device. As shown in the following examples, stable electro-luminescence with high brightness and high efficiency can be achieved. At the same time, the white thin film is processed by thermal evaporation, which is simple and convenient. Its room-temperature process not only has low requirements for equipment and less equipment investment, but also enables it to be directly fabricated on various substrates to achieve large-area, flexible, and lightweight displays. At the same time, the device structure is simple and can be compatible with existing integrated circuits, making pixelated display possible. The brand-new technical solution provided by the present invention combines the advantages of materials and processes, has advantages over the existing technical solutions, provides a reliable new approach for the realization of single-matrix electro-luminescent white light, and provides a new white light option for current full-color displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the structure diagram of the rare-earth electro-luminescent white light device in Examples 1-4 of the present invention. The " / " in the figure represents a stacked structure. For example, Al / LiF represents a stacked structure of an Al film and a LiF thin film.

[0030] Figure 2 It is the schematic diagram of the co-evaporation of three sources of CsI, EuI2, and mCP provided in the examples of the present invention.

[0031] Figure 3 It is the rare-earth white light photoluminescence spectrum and electroluminescence spectrum diagram of the devices prepared in Examples 1, 2, and 3 of the present invention; among them, Figure 3 the (a) in it corresponds to the photoluminescence spectrum, Figure 3 the (b) in it corresponds to the electroluminescence spectrum. The ratio of CsI, EuI2, and mCP shown in the legend in the figure is the molar ratio of CsI, EuI2, and mCP in the light-emitting layer (equal to the evaporation rate ratio of the three evaporation sources during the co-evaporation process; the same below).

[0032] Figure 4 It is the performance comparison diagram of the devices prepared in Examples 2 and 3 of the present invention; among them, Figure 4 the (a) in it corresponds to the current density-efficiency diagram; Figure 4 the (b) in it corresponds to the voltage-current density-brightness diagram.

[0033] Figure 5 It is the performance comparison diagram of the devices prepared in Example 1 and Comparative Example 1 of the present invention; among them, Figure 5 the (a) in it corresponds to the current density-efficiency diagram; Figure 5 the (b) in it corresponds to the voltage-current density-brightness diagram.

[0034] Figure 6This is the CIE coordinate diagram of the electroluminescence spectra of the devices prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention.

[0035] Figure 7 This is the 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 lighting state of the device prepared in Example 1 when the operating voltage is 6V.

[0036] Figure 8 This is a bar chart data comparison diagram of the maximum brightness of the device prepared in Example 1 of the present invention and the maximum brightness of the inorganic host device.

[0037] Figure 9 This is a comparison diagram of the PL spectra 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 inset in the figure is a fluorescence photograph of the light-emitting layer thin film of the device corresponding to the respective legend.

[0038] Figure 10 This is a TEM comparison diagram of the light-emitting layer thin films of the devices prepared in Example 1, Example 2, and Example 3 of the present invention; among them, Figure 10 in (a) and (d) correspond to TEM diagrams of the light-emitting layer of Example 3 (the molar ratio of CsI:EuI2:mCP is 0.025:0.025:2.0) at different magnifications, Figure 10 in (b) and (e) correspond to TEM diagrams of the light-emitting layer of Example 1 (the molar ratio of CsI:EuI2:mCP is 0.025:0.025:1.0) at different magnifications, Figure 10 in (c) and (f) correspond to TEM diagrams 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.

[0039] Figure 11 This is the chromaticity coordinate diagram of the light emission of the devices prepared in Example 1, Example 2, and Example 3.

[0040] Figure 12 This is a comparison diagram of the fluorescence lifetimes of the thin films prepared in Example 1 and Comparative Example 3.

[0041] Figure 13 This is a comparison diagram of the stabilities of the devices prepared in Example 1 and Comparative Example 1.

[0042] Figure 14 This is a comparison diagram of the device performances of the devices prepared in Example 1 and Example 5; among them, Figure 14 in (a) corresponds to the voltage-current density diagram; Figure 14 in (b) corresponds to the voltage-brightness diagram. Detailed implementation manners

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] The rare earth electroluminescent white light device in the subsequent embodiments, such as Figure 1 shown, includes: a top electrode, an electron transport layer, a light-emitting layer, a transition layer (optional, not essential), a hole transport layer, and a bottom electrode; wherein, The material of the top electrode can be an Al electrode modified with LiF, and the work function is 3.2 eV; of course, other electrode materials known in the prior art can also be used; The material of the light-emitting layer is a system of rare earth nanocrystals plus organic ligands formed by co-evaporating CsI, EuI2, and mCP; The transition layer is an mCP layer, which is a preferred setting and can further improve the performance of the device; 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 the materials of TPBi, TAPC, and HATCN, 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; 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.

[0045] The evaporation method of the subsequent light-emitting layer draws on the prior art and adopts a three-source co-evaporation method (regarding three-source co-evaporation, there have been many reports in the previous research group of the inventor), and the target material is obtained through a crystal growth reaction on the substrate. The schematic diagram of three-source co-evaporation is as Figure 2 shown.

[0046] Below, taking the instrument FangSheng FS-300 for three-source co-evaporation as an example (when performing three-source co-evaporation, the temperature of the substrate is room temperature; of course, according to the actual situation, the substrate temperature can also be actively regulated as long as mCP, CsI, and EuI2 can successfully complete the ternary co-evaporation), the present invention will be introduced in detail. In addition, the mCP material used in the subsequent embodiments (Chinese name: 1,3-di-9-carbazolylbenzene; CAS number: 550378-78-4) is purchased from BaolaiTe.

[0047] In addition, for the device performance tests involved later, the devices are all encapsulated to isolate water and oxygen.

[0048] Example 1: This example takes an electroluminescent white light device with a luminescent layer material being a luminescent system material of rare earth nanocrystals plus an organic ligand (co-evaporation of mCP, CsI, and EuI2) as an example. Its specific preparation method includes the following steps: a) Ultrasonically clean the ITO substrate with dishwashing liquid, deionized water, acetone, and absolute ethanol in sequence, each time for half an hour; among them, the ITO uses a substrate etched with two lines, and its luminescent area is about 2 mm * 2 mm; b) Put the cleaned ITO substrate into an evaporation glove box, and pump the vacuum to below 4 * 10 -5 Pa, and the substrate is at room temperature throughout the process; first, evaporate HATCN at a rate of 0.005 - 0.006 nm / s, with a film thickness of 3 nm; then evaporate TAPC at a rate of 0.035 - 0.040 nm / s, with a film thickness of 20 nm; c) Then evaporate the mCP interlayer at a rate of 0.006 - 0.008 nm / s, with a film thickness of 5 nm; d) Adopt the co-evaporation method, evaporate CsI at a speed of 0.0025 nm / s, evaporate EuI2 at a speed of 0.0025 nm / s, and evaporate mCP at a rate of 0.10 nm / s, with a total evaporation thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the obtained luminescent layer thin film is 0.025:0.025:1). Then evaporate a 25 nm thick TPBi at a speed of 0.01 - 0.02 nm / s; e) Change the substrate and evaporate the electrode part; evaporate a 2 nm thick LiF thin film at a speed of 0.005 nm / s, and then evaporate an 80 nm thick Al film at a speed of 0.1 nm / s under the condition of below 5 * 10 -4 Pa, thus completing the device.

[0049] The obtained device (denoted as CsEuI3@mCP), its performance test results are as follows: Figure 3 The photoluminescence spectrum and electroluminescence spectrum of this device are shown.

[0050] Figure 5 The efficiency, brightness, and current density curves of this device are shown. The efficiency of the device reaches 7.7% when the current density is 6.8 mA / cm 2 and the brightness reaches the maximum of 7326 cd / m 2 at a voltage of 10 V, and the device performance is excellent.

[0051] As Figure 6 shown, the color coordinates of this 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 5260 K.

[0052] As Figure 7 shown in the EL spectra of the device at different voltages, it can be seen that the spectral shapes at different voltages are slightly different, but the emission peak positions are at 470 nm and 600 nm, still emitting white light. The inset in the upper right corner of the figure is a photo of the illuminated white light device. At this time, the working voltage is 6 V, and it can be seen that the device emits bright white light.

[0053] As Figure 9 shown, the light-emitting layer thin film of this device emits white fluorescence and also has a broad spectrum of 400 nm - 1000 nm, which has higher color rendering and wider adaptability.

[0054] Figure 10 Figures (b) and (e) in

[0055] As Figure 11 shown, it also shows that the color coordinates of this device (0.33, 0.34) are close to standard white light.

[0056] As Figure 12 shown, it shows the fluorescence lifetime of the 380 nm peak of the light-emitting layer of this device (mCP after adding CsEuI3), which is about 2.75 ns.

[0057] As Figure 13 shown, it shows the stability of this device. At 100 cd·m −2 under, T 50 is about 840 min.

[0058] As Figure 14 shown, it also shows the performance of this device.

[0059] The light-emitting layer of the device obtained in Example 1 is based on both inorganic and organic materials. To further illustrate the performance effect, the inventor also experimented with a device formed by a light-emitting layer of all-inorganic materials obtained based on Chinese Patent Application CN 202410306005.0. The layer structure and thickness of each layer of this inorganic main device are as follows: ITO / ZnO(30 nm) / Al2O3(5 nm) / CsI+EuI2+MnI2(200 nm) / mCP(5 nm) / TAPC(25 nm) / HATCN(5 nm) / Al(80 nm), and its light-emitting layer is Mn 2+The CsEuI3-doped thin film (is deposited by co-evaporation of three sources with CsI, EuI2, and MnI2 as independent evaporation sources respectively through the three-source co-evaporation thermal evaporation method, where the molar ratio of CsI:EuI2:MnI2 is 1:1:0.01). As Figure 8 shown, the maximum brightness of this Mn 2+ -doped CsEuI3 thin film device is only 289 cd·m⁻².

[0060] Meanwhile, the electroluminescence (EL) performance of the device in Example 1 was compared with that of other single-matrix white light devices (single-component white LEDs) corresponding to the reported luminescent layer materials in the prior art. The results are shown in Table 1. It is not difficult to see from this that on the basis of the color coordinates of the device in the present invention being close to standard white light, the brightness can reach 7326 cd·m⁻², the efficiency can reach 7.7%, and the T −2 of the device at 100 cd·m 50 is 840 min, and the comprehensive performance is the best: .

[0061] Note: For the specific details of [1]~

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

[12] Journal literature "Versatile Molecular Structure Strategy Toward Highly Efficient Single-Component White Organic Light–Emitting Diodes", https: / / advanced.onlinelibrary.wiley.com / doi / 10.1002 / adom.202401721。

[0062] Example 2: This example takes an electroluminescent white light device with a light-emitting layer material being a light-emitting system material of rare earth nanocrystals plus an organic ligand (co-evaporation of mCP, CsI, and EuI2) as an example, and its specific preparation method includes the following steps: a) Ultrasonically clean the ITO substrate with dishwashing liquid, deionized water, acetone, and absolute ethanol in sequence, each for half an hour; among them, the ITO uses a substrate etched with two lines, and its light-emitting area is about 2 mm * 2 mm; 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; c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm; 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. 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.

[0063] The performance test results of the obtained device are as follows: Figure 3 The photoluminescence and electroluminescence spectra of the device are shown.

[0064] Figure 4 The performance of the device is shown, including voltage-current density-luminance plots and current density-efficiency plots.

[0065] 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.

[0066] 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.

[0067] Example 3: 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: a) Ultrasonically clean the ITO substrate successively with dishwashing liquid, deionized water, acetone, and absolute ethanol for half an hour each time. Among them, the ITO uses the substrate etched with two lines, and its light-emitting area is about 2 mm * 2 mm; b) Put the cleaned ITO substrate into the evaporation glove box, and pump the vacuum to below 4 * 10 -5 Pa. The substrate is at room temperature throughout the process. First, evaporate HATCN at a rate of 0.005 - 0.006 nm / s, with a film thickness of 3 nm; then evaporate TAPC at a rate of 0.035 - 0.040 nm / s, with a film thickness of 20 nm; c) Then evaporate the mCP interlayer at a rate of 0.006 - 0.008 nm / s, with a film thickness of 5 nm; d) Adopt the co-evaporation method to evaporate CsI at a speed of 0.0025 nm / s, evaporate EuI2 at a speed of 0.0025 nm / s, and evaporate mCP at a rate of 0.20 nm / s, with a total evaporation thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the obtained light-emitting layer thin film is 0.025:0.025:2). Then evaporate 25 nm thick TPBi at a speed of 0.01 - 0.02 nm / s; e) Change the substrate and evaporate the electrode part; evaporate a 2 nm thick LiF thin film at a speed of 0.005 nm / s, and then evaporate an 80 nm thick Al film at a speed of 0.1 nm / s under the condition of below 5 * 10 -4 Pa, thus completing the device.

[0068] For the obtained device, the performance test results are as follows: Figure 3 The photoluminescence spectrum and electroluminescence spectrum of the device are shown; comprehensively Figure 3 , it is not difficult to see that as the proportion of mCP increases, the peak position of the red light peak is relatively larger than that of the blue light peak.

[0069] Figure 4 The performance of the device is shown, including the voltage-current density-luminance graph and the current density-efficiency graph.

[0070] Figure 10 In (a) and (d) of , the TEM image of the light-emitting layer of the device and the calculated average nanocrystal size are shown. It can be seen from this that in the light-emitting layer of the device prepared in Example 3, the size of CsEuI3 nanocrystals is about 7.9 nm and is wrapped by mCP. Comprehensively Figure 10 , it is not difficult to see that as the proportion of mCP increases, the size of CsEuI3 nanocrystals in the light-emitting layer becomes smaller.

[0071] Figure 11 The CIE graph of the device's light emission is shown, and the indicated color coordinates are (0.45, 0.36), which is warm white light.

[0072] Example 4: This example takes an electroluminescent white light device with a light-emitting layer material being a luminescent system material of rare earth nanocrystals plus an organic ligand (co-evaporation of mCP, CsI, and EuI2) as an example. Its specific preparation method includes the following steps: a) Ultrasonically clean the ITO substrate successively with dishwashing liquid, deionized water, acetone, and absolute ethanol for half an hour each time. Among them, the ITO uses a substrate etched with two lines, and its light-emitting area is about 2 mm * 2 mm; b) Place the cleaned ITO substrate into an evaporation glove box, and evacuate the vacuum to below 4 * 10 -5 Pa. The substrate is at room temperature throughout the process. First, evaporate HATCN at a rate of 0.005 - 0.006 nm / s with a film thickness of 3 nm. Then, evaporate TAPC at a rate of 0.035 - 0.040 nm / s with a film thickness of 20 nm; c) Then, evaporate the mCP interlayer at a rate of 0.006 - 0.008 nm / s with a film thickness of 5 nm; d) Adopt the co-evaporation method to evaporate CsI at a speed of 0.0080 nm / s, EuI2 at a speed of 0.0025 nm / s, and mCP at a rate of 0.050 nm / s, with a total evaporation thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the obtained light-emitting layer thin film is 0.08:0.025:0.5). Then, evaporate a 25-nm-thick TPBi at a speed of 0.01 - 0.02 nm / s; e) Replace the substrate and evaporate the electrode part. Evaporate a 2-nm-thick LiF thin film at a speed of 0.005 nm / s, and then evaporate an 80-nm-thick Al film at a speed of 0.1 nm / s under the condition of below 5 * 10 -4 Pa, thus completing the device.

[0073] Example 5: This example takes an electroluminescent white light device with a light-emitting layer material being a luminescent system material of rare earth nanocrystals plus an organic ligand (co-evaporation of mCP, CsI, and EuI2) as an example. Its specific preparation method includes the following steps: a) Ultrasonically clean the ITO substrate successively with dishwashing liquid, deionized water, acetone, and absolute ethanol for half an hour each time. Among them, the ITO uses a substrate etched with two lines, and its light-emitting area is about 2 mm * 2 mm; b) Place the cleaned ITO substrate into an evaporation glove box, and evacuate the vacuum to below 4 * 10 -5Below Pa, the substrate is at room temperature throughout; first, HATCN is evaporated at a rate of 0.005 - 0.006 nm / s with a film thickness of 3 nm; then, TAPC is evaporated at a rate of 0.035 - 0.040 nm / s with a film thickness of 20 nm; c) By means of co-evaporation, CsI is evaporated at a speed of 0.0025 nm / s, EuI2 is evaporated at a speed of 0.0025 nm / s, and mCP is evaporated at a rate of 0.100 nm / s, with a total evaporation thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the obtained light-emitting layer thin film is 0.025:0.025:1). Then, TPBi with a thickness of 25 nm is evaporated at a speed of 0.01 - 0.02 nm / s; d) Replace the wafer and evaporate the electrode part; LiF thin film with a thickness of 2 nm is evaporated at a speed of 0.005 nm / s, and then Al film with a thickness of 80 nm is evaporated under the condition of below 5 * 10 -4 Pa, thus completing the device.

[0074] For the obtained device without the mCP interlayer, the performance test results are as follows: As Figure 14 shown, the performance diagram of the device is presented. It can be seen that when comparing the devices with and without the mCP interlayer, the current density curve of the device with the added mCP interlayer rises more normally, and the turn-on voltage is significantly lower. Evidently, the setting of the interlayer is more conducive to reducing the turn-on voltage and improving the performance of the device.

[0075] Example 6: This example takes an electroluminescent white light device with a light-emitting layer material being a luminescent system material of rare earth nanocrystals plus an organic ligand (ternary co-evaporation of mCP, CsI, and EuI2) as an example, and its specific preparation method includes the following steps: a) The substrate ITO is ultrasonically cleaned successively with dishwashing liquid, deionized water, acetone, and absolute ethanol for half an hour each time; among them, the ITO uses a substrate with two etched lines, and its light-emitting area is approximately 2 mm * 2 mm; b) Put the cleaned ITO substrate into the evaporation glove box, and pump the vacuum to 4 * 10 -5 Below Pa, the substrate is at room temperature throughout; first, HATCN is evaporated at a rate of 0.005 - 0.006 nm / s with a film thickness of 3 nm; then, TAPC is evaporated at a rate of 0.035 - 0.040 nm / s with a film thickness of 20 nm; c) Then, the mCP interlayer is evaporated at a rate of 0.006 - 0.008 nm / s with a film thickness of 5 nm; d) By using the co-evaporation method, CsI is evaporated at a rate of 0.0020 nm / s, EuI2 is evaporated at a rate of 0.0025 nm / s, and mCP is evaporated at a rate of 0.050 nm / s, with a total evaporation thickness of 25 nm (the molar ratio of CsI, EuI2, and mCP in the resulting light-emitting layer thin film is 0.02:0.025:0.5). Then, TPBi with a thickness of 25 nm is evaporated at a rate of 0.01 - 0.02 nm / s; e) Replace the substrate and evaporate the electrode part; evaporate a 2-nm-thick LiF thin film at a rate of 0.005 nm / s, and then evaporate an 80-nm-thick Al film at a rate of 0.1 nm / s under the condition of 5*10 -4 Pa or less to complete the device.

[0076] Comparative Example 1: This comparative example takes an electroluminescent device with a CsEuI3 nanocrystal luminescent system material as the light-emitting layer material, and its specific preparation method includes the following steps: a) Ultrasonically clean the ITO substrate with dishwashing liquid, deionized water, acetone, and absolute ethanol in sequence, each for half an hour; among them, the ITO uses a substrate etched with two lines, and its light-emitting area is about 2 mm * 2 mm; b) Put the cleaned ITO substrate into an evaporation glove box, evacuate the vacuum to 4*10 -5 Pa or less, and the substrate is at room temperature throughout the process; first, evaporate HATCN at a rate of 0.005 - 0.006 nm / s with a film thickness of 4 nm; then evaporate TAPC at a rate of 0.035 - 0.040 nm / s with a film thickness of 20 nm; c) Then, evaporate an mCP interlayer at a rate of 0.006 - 0.008 nm / s with a film thickness of 5 nm; d) By using the co-evaporation method, evaporate EuI2 at a rate of 0.02 nm / s and CsI at a rate of 0.04 nm / s, with a total evaporation thickness of 30 nm (the molar ratio of EuI2 and CsI in the resulting light-emitting layer thin film is 1:2). Then, evaporate TPBi with a thickness of 25 nm at a rate of 0.01 - 0.02 nm / s; e) Replace the substrate and evaporate the electrode part; evaporate a 2-nm-thick LiF thin film at a rate of 0.005 nm / s, and then evaporate an 80-nm-thick Al film at a rate of 0.1 nm / s under the condition of 5*10 -4 Pa or less to complete the device.

[0077] For the obtained device (denoted as CsEuI3), the performance test results are as follows: Figure 5The 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.

[0078] like Figure 6 As shown, the color coordinates (0.14, 0.11) of the device obtained in Comparative Example 1 are blue light.

[0079] like Figure 9 As shown, the light-emitting layer film of the device obtained in Comparative Example 1 emits blue fluorescence.

[0080] 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.

[0081] Comparative Example 2: 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: 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; 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; c) Then, an mCP transition layer was deposited at a rate of 0.006-0.008 nm / s to a thickness of 5 nm; 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; 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.

[0082] The performance test results of the obtained device (denoted as EuI2@mCP) are as follows: like Figure 6 As shown, the color coordinates of the device (0.50, 0.42) are orange light.

[0083] like Figure 9 As shown, the light-emitting layer film of the device emits orange fluorescence.

[0084] Comparative Example 3: The method for preparing pure mCP film in this comparative example is as follows: a) Ultrasonic cleaning of the ITO substrate was performed using detergent, deionized water, acetone, and anhydrous ethanol, respectively, for half an hour each time. 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.

[0085] 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%.

[0086] 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 Eu-based rare-earth white electroluminescent device, characterized in that, From top to bottom, it successively includes a top electrode, an electron transport layer, a light-emitting layer, a hole transport layer, and a 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 used independently as evaporation sources, 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.

2. The Eu-based rare-earth white light-emitting device according to claim 1, characterized in that, 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 white light-emitting device according to claim 1, characterized in that, 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 cold white light; When z = 1, the light-emitting layer can emit white light with a color coordinate of (0.33, 0.34); When 1 < z ≤ 2, the light-emitting layer can emit warm white light.

4. The Eu-based rare earth electro-luminescent white light device according to claim 1, wherein The electron transport layer uses an organic electron transport material.

5. The Eu-based rare-earth electro-luminescent white light device according to claim 4, wherein The electron transport layer uses TPBi.

6. The Eu-based rare earth electroluminescent white light device according to claim 1, wherein The hole transport layer uses an organic hole transport layer material.

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

8. The Eu-based rare earth white light-emitting device according to claim 1, wherein The top electrode is an Al electrode modified with LiF, and the work function of this top electrode is 3.2 eV; The bottom electrode is an ITO electrode.

9. The preparation method of the Eu-based rare earth white electroluminescent device according to any one of claims 1-8, 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, mCP, CsI, and EuI2, these three raw materials that are independent of each other, are used as three evaporation sources. 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, and then the light-emitting layer can be deposited together.

10. The application of the Eu-based rare earth electro-luminescent white light device according to any one of claims 1-8 in a display screen.

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