White light nanosheet light-emitting diode

Abstract

The invention discloses a white light nanosheet light emitting diode. The light emitting diode includes: a substrate; a first electrode; a first carrier injection layer; a first carrier transport layer; a light-emitting layer; a second carrier transport layer; a second carrier injection layer; and a second electrode. Wherein the light-emitting layer comprises a nanosheet CQW and a blue light nanocrystalline material; the nanometer sheet CQW is CdSe / CdZnS, and the nanometer sheet CQW is CdSe / CdZnS; at least one of the first carrier transport layer and the second carrier transport layer is an organic material layer; the blue light nanocrystalline material generates blue light with the wavelength smaller than 500 nm; the forbidden bandwidth of the organic material is larger than 2.48 eV, and the organic material can generate blue light with the wavelength smaller than 500 nm; and the nanosheet CQW and the organic material generate exciplex luminescence. The light-emitting diode has the advantages of high luminous efficiency and good color rendering property.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diodes, and particularly to a white nanosheet light-emitting diode and its fabrication method. Background Technology

[0002] With increasing global demands for energy efficiency and environmental sustainability, lighting and display technologies are undergoing a revolutionary shift towards light-emitting diode (LED) technology. Against this backdrop, white LEDs (WLEDs) based on nanocrystals, as a cutting-edge technology in the display and solid-state lighting fields, utilize the unique optoelectronic properties of nanocrystals, such as QDs (Quantum Dots) and CQWs (Colloidal Quantum Wells), to achieve efficient and stable white light emission. Nanocrystal white LEDs have attracted widespread attention due to their superior color performance, low-cost manufacturing potential, and solution processability. With continuous technological advancements and optimization, nanocrystal white LEDs will play an increasingly important role in future optoelectronic applications and lighting systems markets.

[0003] The two-dimensional quantum confinement effect of colloidal quantum wells (CQWs) on semiconductor nanosheets enables them to exhibit high exciton binding energies along their thickness, thereby improving exciton stability and significantly suppressing Auger recombination. This property makes CQWs an ideal material for light emission. Furthermore, by controlling the thickness of CQWs, precise emission from blue to deep red light can be achieved. This tunability lays the technological foundation for the application of CQWs in LED displays and solid-state lighting.

[0004] However, the fabrication of white LEDs using CQW materials still faces some challenges, such as low blue light efficiency. These issues can lead to a decrease in overall luminous efficiency, especially in cases of suboptimal energy transfer efficiency or nonradiative recombination. Furthermore, in some applications, white LEDs are required to more accurately reproduce the colors of objects in lighting applications. For example, in scenarios with extremely high color rendering requirements, such as museum lighting and medical lighting, providing illumination that more closely resembles natural light would help protect exhibits and improve the accuracy of medical diagnoses. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a white nanosheet light-emitting diode to solve the problems of low luminous efficiency and poor color rendering of traditional white nanosheet LEDs.

[0006] The objective of this invention is achieved through the following technical solution: This invention provides a white nanosheet light-emitting diode, comprising: Substrate; A first electrode is disposed on the substrate; A first carrier injection layer is disposed on the first electrode; The first carrier transport layer is disposed on the first carrier injection layer; A light-emitting layer is disposed on the first carrier transport layer; A second carrier transport layer is disposed on the light-emitting layer; A second carrier injection layer is disposed on the second carrier transport layer; and The second electrode is disposed on the second carrier injection layer; The light-emitting layer comprises nanosheet CQW and blue light-emitting nanocrystalline material; the nanosheet CQW is CdSe / CdZnS; at least one of the first carrier transport layer and the second carrier transport layer is an organic material layer; the blue light-emitting nanocrystalline material generates blue light with a wavelength less than 500 nm; the organic material has a band gap greater than 2.48 eV and generates blue light with a wavelength less than 500 nm; the nanosheet CQW and the organic material form an excitopolymer complex to emit light, producing light in the 501-700 nm range.

[0007] In some embodiments of the present invention, the blue light nanocrystalline material includes one of quantum dots or nanowires.

[0008] In some embodiments of the present invention, the quantum dot is ZnSe / ZnS or CdSe / ZnS.

[0009] In some embodiments of the present invention, the organic material is PF8Cz or TFB.

[0010] In some embodiments of the present invention, the specific structure of the white light nanosheet light-emitting diode is ITO / PEDOT:PSS / TFB / QD+CQW / ZnMgO / Al, wherein ZnMgO serves as both the electron injection layer and the electron transport layer.

[0011] In some embodiments of the present invention, the thickness of the ZnMgO is 30~50 nm.

[0012] In some embodiments of the present invention, the specific structure of the white light nanosheet light-emitting diode is ITO / MoO3 / TFB / QD+CQW / ZnO / Ag, wherein ZnO serves as both the electron injection layer and the electron transport layer.

[0013] The present invention also provides a method for preparing the white nanosheet light-emitting diode, comprising the following steps: Provide a substrate; A first electrode is fabricated on the substrate; A first carrier injection layer is fabricated on the first electrode; A first carrier transport layer is fabricated on the first carrier injection layer; A light-emitting layer is fabricated on the first carrier transport layer; A second carrier transport layer is fabricated on the light-emitting layer; A second carrier injection layer is fabricated on the second carrier transport layer; A second electrode is fabricated on the second carrier injection layer.

[0014] In some embodiments of the present invention, the light-emitting layer is prepared as follows: The quantum dot luminescent material is dissolved in an octane solution to obtain an octane solution of the quantum dot luminescent material; The nanosheet luminescent material is added to an octane solution containing the quantum dot luminescent material to obtain a luminescent layer solution; The light-emitting layer solution is coated on the surface of the first carrier transport layer to form the light-emitting layer.

[0015] In some embodiments of the present invention, the mass ratio of the quantum dot luminescent material to the nanosheet luminescent material in the luminescent layer solution is 1:1 to 40:1.

[0016] Compared with the prior art, the white nanosheet light-emitting diode and its fabrication method of the present invention have the following advantages and beneficial effects: 1. In one embodiment, at least one of the carrier transport layers on both sides of the luminescent layer is made of an organic material with a bandgap greater than 2.48 eV, capable of generating blue light with a wavelength less than 500 nm, thus ensuring blue light emission. This organic material can generate interfacial luminescence with the nanosheet luminescent material, and the resulting excitocomplex adds an additional emission peak, thereby improving the color rendering index. The light emitted by the nanosheet luminescent material has a wavelength greater than 500 nm, thus complementing the other two emission peaks to obtain high color rendering index white light. The quantum dot luminescent material in the luminescent layer can generate blue light with a wavelength less than 500 nm, thus compensating for the lack of blue light. Simultaneously, the quantum dot luminescent material can also generate interfacial luminescence with the organic carrier transport material, obtaining an additional excitocomplex emission peak, further improving the color rendering index.

[0017] 2. In one embodiment, the material used to fabricate the light-emitting layer further includes an organic light-emitting material. Because the light-emitting layer contains an organic light-emitting material with a band gap greater than 2.48 eV, it can generate blue light with a wavelength less than 500 nm, thus ensuring the emission of blue light and compensating for the deficiency of blue light. The organic light-emitting material can also generate interfacial luminescence with organic carrier transport materials, resulting in additional exciton complex emission peaks and further improving the color rendering index. The organic light-emitting material is preferably a delayed fluorescence material, which can effectively capture triplet and singlet excitons, significantly increasing device efficiency and lifetime, and can transfer high-energy excitons to the nanosheet light-emitting material, assisting in the color of the nanosheet light-emitting material and further improving the color rendering index. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a white nanosheet light-emitting diode provided in one embodiment of the present invention; Figure 2 Electroluminescence spectra of nanosheet light-emitting diodes with different hole transport layers; Figure 3 Electroluminescence spectra of quantum dot light-emitting diodes with different hole transport layers; Figure 4 The electroluminescence spectra of white nanosheet light-emitting diodes with different nanosheet doping amounts in this invention are shown. Figure 5 for Figure 4 The CIE 1931 coordinates of device W3 in the color space; Figure 6 for Figure 4 Current density-voltage-brightness curve of device W3; Figure 7 for Figure 4 The current density-EQE curve and current density-PE curve of device W3; Figure 8 Electroluminescence spectrum of a white nanosheet light-emitting diode provided in another embodiment of the present invention. Detailed Embodiments The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited thereto.

[0019] Please see Figure 1 One embodiment of the present invention provides a white light-emitting nanosheet diode 100. The white light-emitting nanosheet diode 100 includes: Substrate 110; A first electrode 120 is disposed on the substrate 110; A first carrier injection layer 130 is disposed on the first electrode 120; The first carrier transport layer 140 is disposed on the first carrier injection layer 130; A light-emitting layer 150 is disposed on the first carrier transport layer 140; A second carrier transport layer 160 is disposed on the light-emitting layer 150; The second carrier injection layer 170 is disposed on the second carrier transport layer 160; and The second electrode 180 is disposed on the second carrier injection layer 170.

[0020] The light-emitting layer 150 comprises CQW nanosheets and blue light-emitting nanocrystalline material; the CQW nanosheets are CdSe / CdZnS; at least one of the first and second carrier transport layers is an organic material layer; the blue light-emitting nanocrystalline material generates blue light with a wavelength less than 500 nm; the organic material has a band gap greater than 2.48 eV and generates blue light with a wavelength less than 500 nm; the CQW nanosheets and the organic material form an exciton complex to emit light, producing light in the 501-700 nm range. The blue light-emitting nanocrystalline material can be either quantum dots or nanowires.

[0021] In this embodiment, the first electrode 120 is the anode, fabricated from ITO. The first carrier injection layer 130 is the hole injection layer, fabricated from PEDOT:PSS, with a thickness of 40 nm. The first carrier transport layer 140 is the hole transport layer, fabricated from TFB hole transport material, with a thickness of 30 nm. The light-emitting layer 150 includes blue quantum dot (QD) material and crystalline quantum wave (CQW) material. The blue quantum dot material is ZnSe / ZnS, and the CQW material is CdSe / CdZnS. The second carrier transport layer 160 is the electron transport layer, fabricated from ZnMgO, with a thickness of 40 nm. The second carrier injection layer 170 is the electron injection layer. In this embodiment, the electron injection layer is also composed of ZnMgO. That is, in this device, both the electron injection layer and the electron transport layer are composed of ZnMgO, totaling 40 nm. The second electrode 180 is a cathode, made of metallic Al, with a thickness of 100 nm.

[0022] In this embodiment, at least one of the carrier transport layers on both sides of the luminescent layer 150 is made of an organic material with a band gap greater than 2.48 eV, capable of generating blue light with a wavelength less than 500 nm, thus ensuring blue light emission. This organic material can produce interfacial luminescence with the nanosheet luminescent material, and the resulting excitocomplex adds an additional emission peak, thereby improving the color rendering index. The light emitted by the nanosheet luminescent material has a wavelength greater than 500 nm, thus complementing the other two emission peaks to obtain high color rendering index white light. The quantum dot luminescent material in the luminescent layer 150 can generate blue light with a wavelength less than 500 nm, compensating for the deficiency of blue light. Simultaneously, the quantum dot luminescent material can also produce interfacial luminescence with the organic carrier transport material, obtaining an additional excitocomplex emission peak, further improving the color rendering index.

[0023] In fact, white LEDs can be realized through various strategies, including the use of nanocrystalline conversion layers, the mixing of multicolor nanocrystals, the integration of nanocrystals with organic materials, and the stacking of multiple nanocrystalline layers. In the fields of lighting and display technology, researchers have been dedicated to improving the performance of nanosheet LEDs. In recent years, CQWs (cell-quantum-waxed lights) have been considered promising two-dimensional materials for fabricating high-performance LEDs due to their tunable bandgap and high quantum yield. However, the lack of efficient blue CQWs has hindered the development of CQW-based WLEDs to some extent. This technological bottleneck has prompted researchers to turn their attention to the synergistic integration of other blue materials with complementary color CQWs, providing new ideas for breakthroughs in white LED performance. These blue materials include quantum dots (QDs), nanowires, and organic materials.

[0024] In this embodiment, the integration of QD quantum dot materials and CQW nanosheet materials significantly improves the photoelectric conversion efficiency of the device by optimizing exciton utilization efficiency. Furthermore, the tunable size and bandgap of the QD quantum dot materials and CQW nanosheet materials allow for adjustable emission spectra, enabling a broad emission range from blue to red light, which is crucial for achieving white light. These materials also provide high color purity during emission, which is significant for enhancing the color rendering and color gamut coverage of white LEDs. By utilizing the combination of QD quantum dot materials and CQW nanosheet materials, many problems can be alleviated, resulting in more efficient, stable, and environmentally friendly white light emission. The innovation of this combined approach lies in its potential to optimize the performance of white LEDs while minimizing manufacturing costs. The introduction of the QD quantum dot-based CQW nanosheet structure allows for further fine-tuning and optimization of luminescence characteristics, promoting the realization of white light emission.

[0025] This application, through in-depth research on the complex integration of QD quantum dots and CQW nanosheets, aims to obtain a white nanosheet light-emitting diode (LED) with high efficiency, high brightness, and superior white light emission and color rendering properties. In the above embodiments, a groundbreaking design concept was introduced that cleverly utilizes the synergistic emission effect of blue QD, complementary color CQW, and interface emission, ultimately successfully realizing an energy-saving white nanosheet LED with a high color rendering index. Building upon this, an even higher color rendering index was achieved through interface emission between CQW nanosheets and TFB hole transport materials. This approach demonstrates the superior efficiency and color rendering performance of white LEDs manufactured under all-solution process conditions, thus providing a new pathway for the advancement of white LED technology.

[0026] In one embodiment, the material used to fabricate the light-emitting layer 150 further includes nanowire light-emitting materials. The nanowire light-emitting materials are used to emit light with wavelengths less than 500 nm. An excitopolymer complex is formed between the nanowire light-emitting materials and the organic material to emit light with wavelengths greater than 500 nm.

[0027] In one embodiment, the material used to fabricate the light-emitting layer 150 further includes an organic light-emitting material. The organic light-emitting material has a band gap greater than 2.48 eV and is used to emit light with a wavelength less than 500 nm. An excimer complex is formed between the organic light-emitting material and the organic material to emit light with a wavelength greater than 500 nm.

[0028] In the above embodiments, the material used to fabricate the light-emitting layer 150 also includes an organic light-emitting material. Since the light-emitting layer 150 contains an organic light-emitting material with a band gap greater than 2.48 eV, it can generate blue light with a wavelength less than 500 nm, thus ensuring blue light emission and compensating for the deficiency of blue light. The organic light-emitting material can also generate interfacial luminescence with organic carrier transport materials, resulting in additional exciton complex emission peaks and further improving the color rendering index. The organic light-emitting material is preferably a delayed fluorescence material, which can effectively capture triplet and singlet excitons, significantly increasing device efficiency and lifetime, and can transfer high-energy excitons to the nanosheet light-emitting material, assisting in the color of the nanosheet light-emitting material and further improving the color rendering index.

[0029] In one embodiment, the organic material includes PF8Cz hole transport material or TFB hole transport material. In this embodiment, the PF8Cz hole transport material is poly(9,9-n-dioctyl-2,7-fluorene-alt-9-isooctyl-3,6-carbazole). The TFB hole transport material is poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)].

[0030] In this embodiment, the first carrier injection layer is a hole injection layer made of PEDOT:PSS; the first carrier transport layer is a hole transport layer made of TFB hole transport material; the second carrier injection layer is an electron injection layer; the second carrier transport layer is an electron transport layer; and both the electron injection layer and the electron transport layer are made of ZnMgO material. The nanosheet luminescent material includes CdSe / CdZnS luminescent material, and the quantum dot luminescent material includes ZnSe / ZnS luminescent material.

[0031] In this embodiment, to investigate the influence of hole transport layer material on the photoelectric performance of CQW-LED devices, the applicant fabricated two CQW-LED devices with different structures. One structure uses PVK as the hole transport layer, with an overall structure of ITO / PEDOT:PSS / PVK / CQW / ZnMgO / Al. The other structure uses TFB as the hole transport layer, with an overall structure of ITO / PEDOT:PSS / TFB / CQW / ZnMgO / Al. The photoelectric performance of the two CQW-LED devices with different structures is as follows: Figure 2 As shown. In Figure 2 In the results, both devices exhibited a characteristic electroluminescence peak at 651 nm. The device using TFB as the hole transport layer also showed a significant side peak to the left of the main peak. This phenomenon may be due to the higher energy level matching between ZnMgO and TFB, and the higher electron mobility of ZnMgO. Simultaneously, the relatively thin emissive layer structure may cause some electrons to leak into the hole transport layer when injected from ZnMgO into the emissive layer, leading to recombination with holes at the TFB and CQW interface for luminescence. Furthermore, the interfacial luminescence phenomenon between CQW and TFB also provides a potential technical path for realizing WLEDs. Considering the high turn-on voltage and low hole mobility of PVK materials, we believe that TFB materials may have greater application potential in the co-fabrication of hybrid white light devices with luminescent materials. Therefore, excitocomplex luminescence was generated between the organic carrier transport layer TFB and the nanosheet emissive layer.

[0032] In another embodiment, the applicant also investigated the effect of the hole transport layer on the performance of quantum dot LEDs.

[0033] The performance of blue quantum dot LEDs is largely limited by hole injection and transport efficiency. This is primarily because blue QDs typically have deep valence band levels, resulting in a significant injection barrier between the hole transport layer and the emissive layer. This energy level mismatch severely hinders normal hole injection and transport, ultimately leading to a situation where the number of electrons in the emissive layer exceeds the number of holes. This, in turn, causes a series of problems such as increased nonradiative recombination and reduced device efficiency. By using organic hole transport materials to form directional hole channels, hole transport can be made more controllable. In blue quantum dot LED devices, if the hole transport layer has low mobility and a large injection barrier exists between it and the emissive layer, the hole injection efficiency will be significantly lower than the electron injection efficiency. Therefore, optimizing the material selection and structural design of the hole transport layer is crucial for achieving electron-hole balance, reducing the injection barrier, and minimizing energy loss during hole injection. When designing the hole transport layer, energy level matching between it and the QD emissive layer must be considered to reduce charge accumulation at the interface, thereby reducing short-circuit current loss. PVK, a hole transport layer material, possesses a deep HOMO level, exhibiting a high degree of matching with the valence band level of blue QLEDs. This allows for a reduction in the hole injection barrier to below 0.2 eV, thereby improving hole injection efficiency. However, PVK's relatively low hole mobility limits the device's current density to some extent. In contrast, TFB exhibits a higher hole mobility, contributing to a more balanced electron and hole distribution, thus reducing the device's turn-on voltage to below 3 V and extending its lifespan. However, TFB's relatively shallow HOMO level creates a significant energy level mismatch with blue QLEDs, affecting its hole injection efficiency. Based on the above analysis, we selected PVK and TFB as hole transport layer materials for blue QLEDs for in-depth investigation. Simultaneously, ZnMgO was used as the electron transport layer, and PEDOT:PSS as the hole injection layer. PEDOT:PSS is widely used in optoelectronic devices due to its excellent conductivity and film-forming properties. Its good light transmittance and excellent mechanical flexibility also make it particularly suitable for the fabrication of flexible optoelectronic devices. Furthermore, the work function of PEDOT:PSS matches well with the HOMO energy levels of most organic semiconductor materials, which is beneficial for achieving efficient hole injection.

[0034] Specifically, blue QLEDs with structures of ITO / PEDOT:PSS / PVK / QD / ZnMgO / Al and ITO / PEDOT:PSS / TFB / QD / ZnMgO / Al were fabricated using PVK and TFB as hole transport layer materials, respectively. Figure 3This study demonstrates the electroluminescence characteristics and performance differences of blue quantum dot LEDs using different hole transport layer materials. The HOMO level of the TFB (Thin Focal Bundle) is 5.4 eV, which differs significantly from the valence band level of the blue ZnSe / ZnS QD. This implies a large energy barrier for hole transport from the TFB to the QD. However, this energy level mismatch does not necessarily negatively impact device performance; rather, it may optimize the performance of the blue quantum dot LED by modulating the carrier injection balance. Figure 3 The figure shows the electroluminescence spectra of the two devices. The inset is a photograph of the blue QLED fabricated by PVK when lit, emitting deep blue light. As can be seen from the figure, the emission peak of the PVK device is relatively pure, while the TFB device shows a side peak to the right of the main peak, located at 552 nm. Analysis suggests that this side peak is due to the interfacial luminescence effect between the TFB and the QD. Because the HOMO level of TFB is relatively shallow, holes easily accumulate at the interface between TFB and the emitting layer, and then recombine with a small number of leaked electrons, producing interfacial luminescence. This phenomenon suggests that by introducing an additional red light source into the TFB device, white light emission may be achieved, providing a potential approach for the development of novel white LED devices. Therefore, excitogenes luminescence is generated between the organic carrier transport layer TFB and the quantum dot emitting layer.

[0035] To illustrate the effect of the white light nanosheet light-emitting diode 100 in this solution, the following specific implementation method will be used for explanation.

[0036] Example 1: Research on white light devices based on QD quantum dots and CQW nanosheets mainly focuses on utilizing the unique optical properties of these two materials to achieve efficient and stable white light emission. To achieve precise spectral control of mixed white light emission, this application employs a direction-oriented method based on a wavelength selection formula, as follows: λ2 = (λ1 + λ3) / 2 Where λ1 represents the wavelength position of the main emission peak of the device, λ2 represents the wavelength of the side peaks, and λ3 corresponds to the emission wavelength of the additional material required to obtain a balanced white light spectrum. Through in-depth analysis of the spectral characteristics of existing blue quantum dot LEDs, combined with the calculation results of this formula, we infer that a relevant emission wavelength compensation material needs to be introduced to improve the existing spectral distribution. The introduction of this material can not only effectively fill the emission gap in the red light region but also produce a synergistic effect with QD quantum dots, thereby achieving ideal white light emission. CQW nanosheets possess tunable and adaptive optical properties, as well as high quantum efficiency and excellent thermal stability, showing great potential in this research objective and considered a very suitable candidate material. Their unique band structure and physical properties enable them to form efficient optical coupling with QD quantum dot materials, providing new possibilities for obtaining high-quality white light emission.

[0037] Based on this, this application fabricated a series of white LED devices with an ITO / PEDOT:PSS / TFB / QD+CQW / ZnMgO / Al structure. In this embodiment, the QD quantum dot material is ZnSe / ZnS, and the nanosheet (CQW) material is CdSe / CdZnS. In these devices, different volumes of CQW nanosheet material were added to devices W1, W2, W3, W4, and W5, namely 50 μL, 100 μL, 200 μL, 400 μL, and 800 μL, respectively.

[0038] Specifically, the fabrication process of a white nanosheet light-emitting diode is as follows: In the device fabrication process, the ITO substrate was first cleaned, and then a PEDOT:PSS layer was deposited on the surface of the ITO substrate as a hole injection layer using spin coating at 3000 rpm for 40 seconds. Afterward, it was annealed in air at 150°C for 30 minutes to optimize the electrical properties and surface smoothness of the PEDOT:PSS film. After annealing, the substrate was allowed to cool naturally to room temperature before being transferred to a nitrogen glove box to avoid adverse effects from oxygen and moisture in the air on the subsequent fabrication of the organic functional layers.

[0039] Inside the glove box, the hole transport layer was prepared by dissolving TFB in chlorobenzene to prepare solutions with different concentration gradients to meet the requirements for device performance optimization. The solution was spin-coated at 2000 rpm for 40 seconds and then annealed at 150°C for 30 minutes to remove residual solvent from the film and enhance the crystallinity and electrical properties of the hole transport layer film.

[0040] Next, the luminescent layer was prepared. QD was dissolved in n-octane solution at a concentration of 10 mg / ml. Different volumes of 10 mg / ml nanosheets were then added: 50 μL, 100 μL, 200 μL, 400 μL, and 800 μL. The mixture was spin-coated at 2000 rpm for 45 seconds to uniformly cover the hole transport layer surface, forming the luminescent layer. The uniformity and quality of the QD layer directly affect the luminous efficiency and stability of the device.

[0041] Subsequently, an electron transport layer was prepared by dissolving ZnMgO in ethanol to prepare solutions of different concentrations. These solutions were then spin-coated at 2000 rpm for 45 seconds, followed by annealing at 80°C for 30 minutes to form a thin electron transport layer. Finally, a metallic Al electrode was fabricated on top of the electron transport layer using a vapor deposition method, serving as the cathode of the device. The vapor deposition rate was controlled at 0.08–0.10 nm / s, and the thickness was 100 nm.

[0042] Table 1 shows a detailed comparison of the performance parameters of white LED devices with different CQW nanosheet doping amounts. The electroluminescence spectra of the prepared WLEDs at an applied voltage of 4.0V are shown below. Figure 4 As shown, with the gradual increase in the amount of CQW nanosheet material added, the emission spectrum of the device gradually approaches the white light spectrum. Figure 5 As shown, the CIE 1931 coordinates of device W3 in this color space are (0.33, 0.34), and the color rendering indices of devices W1-W5 are 81, 84, 85 (85.33), 85 (84.53), and 84, respectively. When the volume of CQW nanosheet material added is 200 μL, device W3 exhibits the highest color rendering index, reaching 85.33, and its CIE color coordinates are very close to the ideal white light coordinates (0.33, 0.33), indicating a significant advantage in colorimetric performance. Figure 6 As shown, the current density-voltage-luminance characteristic curve of device W3 indicates that the maximum luminance of the device reaches 1290 cd / m², while its turn-on voltage is only 2.2 V. This low turn-on voltage has a significant advantage in the WLED field, meaning that the device can achieve effective light emission with low energy consumption. Figure 7 As shown, the maximum EQE of device W3 is 0.085%, and the PE is 0.148 lm / W. This result fully demonstrates the great potential of the hybrid system of blue QD quantum dot material and CQW nanosheet material used in this application in realizing high-performance WLEDs.

[0043] Table 1. Summary of white LED device performance with different CQW nanosheet doping amounts

[0044] Example 2: Another embodiment of the present invention provides a white nanosheet light-emitting diode. In this embodiment, the device structure is ITO / MoO3 / TFB / QD+CQW / ZnO / Ag, and the preparation method is basically the same, but here the QD is the common CdSe / ZnS quantum dot.

[0045] like Figure 8As shown, the electroluminescence spectrum of this device exhibits distinct emission peaks at multiple wavelengths, indicating its rich luminescence characteristics and ability to effectively cover the visible light range, thus achieving high-quality white light emission. TFB, as a highly efficient polymeric hole transport material, can effectively promote hole injection and exciton formation through optimized energy level matching with CQW. The radiative recombination process of excitons releases photons, whose energies are typically close to or slightly less than the bandgap energy of QD. This energy difference may lead to additional emission peaks in the spectrum, enriching the device's emission spectrum. In CQW-LEDs, the HOMO energy level of TFB needs to be precisely matched with the valence band of CQW to achieve efficient hole injection. However, if a large energy level barrier exists at the interface, holes may accumulate at the TFB / CQW interface, forming a localized high-concentration hole region. Simultaneously, the energy level difference between the conduction band of CQW and the electron transport layer ZnMgO may cause partial electron leakage to the TFB layer. This electron leakage or hole accumulation provides the necessary conditions for interfacial recombination. This similar mechanism is even more pronounced in blue QLEDs. Furthermore, the two-dimensional confinement characteristic of CQW allows the exciton wavefunction to expand in the plane but is confined in the vertical direction. When localized states exist at the TFB / QW interface, excitons may transfer energy to the excited states of molecules in the TFB via Förster resonance energy transfer (FRET), leading to intrinsic luminescence of the TFB. Therefore, the interfacial luminescence between TFB and CQW in CQW-LED originates from charge accumulation and exciton recombination caused by energy level mismatch. Its mechanism is similar to that of TFB / QD interfacial luminescence in blue QLED, but the specific dynamic path differs due to the difference in material dimensionality. The color coordinates of this hybrid white light device are (0.31, 0.35), which is very close to the ideal white light region (0.33, 0.33). This result indicates that the device can emit light close to natural white light. Its color rendering index (CRI) reaches 91, a significant improvement over the previous WLED's 85. This means the device can more realistically reproduce the colors of objects in lighting applications, especially in scenarios with extremely high CRI requirements, such as museum lighting and medical lighting. It can provide lighting effects closer to natural light, helping to protect exhibits and improve the accuracy of medical diagnoses. The hybrid white light device achieves a maximum luminance of 643 cd / m², slightly lower than the previous white light device. Meanwhile, the device's maximum EQE is 0.04%, and its maximum PE is 0.058 lm / W. Furthermore, the hybrid white light device has a turn-on voltage of only 2.2 V. This low turn-on voltage characteristic indicates that it can achieve effective light emission under low voltage drive. This feature not only helps reduce energy consumption but also extends the device's lifespan, making it more competitive in practical applications.Low-voltage drive capability means that the device can operate at lower voltages, thereby reducing power loss and lowering the thermal effects and electrical stress at high voltages, which helps improve the stability and reliability of the device. A detailed comparison of the performance parameters of CQW and TFB hybrid white light devices is shown in Table 2.

[0046] Table 2 Summary of the performance of CQW and TFB white light emitting diode devices

[0047] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the embodiments described above. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A white nanosheet light-emitting diode, characterized in that, include: Substrate; A first electrode is disposed on the substrate; A first carrier injection layer is disposed on the first electrode; The first carrier transport layer is disposed on the first carrier injection layer; A light-emitting layer is disposed on the first carrier transport layer; A second carrier transport layer is disposed on the light-emitting layer; The second carrier injection layer is disposed on the second carrier transport layer; as well as The second electrode is disposed on the second carrier injection layer; The light-emitting layer comprises nanosheet CQW and blue light-emitting nanocrystalline material; the nanosheet CQW is CdSe / CdZnS; at least one of the first carrier transport layer and the second carrier transport layer is an organic material layer; the blue light-emitting nanocrystalline material generates blue light with a wavelength less than 500 nm; the organic material has a band gap greater than 2.48 eV and generates blue light with a wavelength less than 500 nm; the nanosheet CQW and the organic material form an excitopolymer complex to emit light, producing light in the 501-700 nm range.

2. The white nanosheet light-emitting diode according to claim 1, characterized in that, The blue light nanocrystalline material includes either quantum dots or nanowires.

3. The white nanosheet light-emitting diode according to claim 2, characterized in that, The quantum dots are ZnSe / ZnS or CdSe / ZnS.

4. The white nanosheet light-emitting diode according to claim 3, characterized in that, The organic material is PF8Cz or TFB.

5. The white nanosheet light-emitting diode according to claim 1, characterized in that, Its specific structure is ITO / PEDOT:PSS / TFB / QD+CQW / ZnMgO / Al, where ZnMgO serves as both the electron injection layer and the electron transport layer.

6. The white nanosheet light-emitting diode according to claim 5, characterized in that, The thickness of the ZnMgO is 30~50nm.

7. The white nanosheet light-emitting diode according to claim 1, characterized in that, Its specific structure is ITO / MoO3 / TFB / QD+CQW / ZnO / Ag, where ZnO serves as both the electron injection layer and the electron transport layer.

8. The method for preparing a white nanosheet light-emitting diode according to any one of claims 1 to 7, characterized in that, Includes the following steps: Provide a substrate; A first electrode is fabricated on the substrate; A first carrier injection layer is fabricated on the first electrode; A first carrier transport layer is fabricated on the first carrier injection layer; A light-emitting layer is fabricated on the first carrier transport layer; A second carrier transport layer is fabricated on the light-emitting layer; A second carrier injection layer is fabricated on the second carrier transport layer; A second electrode is fabricated on the second carrier injection layer.

9. The method for preparing a white nanosheet light-emitting diode according to claim 8, characterized in that, The light-emitting layer is prepared as follows: The quantum dot luminescent material is dissolved in an octane solution to obtain an octane solution of the quantum dot luminescent material; The nanosheet luminescent material is added to an octane solution containing the quantum dot luminescent material to obtain a luminescent layer solution; The light-emitting layer solution is coated on the surface of the first carrier transport layer to form the light-emitting layer.

10. The method for preparing a white nanosheet light-emitting diode according to claim 9, characterized in that, In the luminescent layer solution, the mass ratio of the quantum dot luminescent material to the nanosheet luminescent material is 1:1 to 40:1.

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