Pure blue-light perovskite light-emitting diode modified by polymer network and preparation method of pure blue-light perovskite light-emitting diode

Abstract

The invention provides a polymer network modified pure blue-light perovskite light emitting diode and a preparation method thereof, and the polymer network modified pure blue-light perovskite light emitting diode constructs a PVPh network modified 3D lead-based halide perovskite structure by introducing a PVPh additive into a perovskite light emitting layer. According to the invention, PVPh and perovskite form a coordination effect, a perovskite crystallization process is delayed, and a rigid 3D lead-based halide perovskite material is bridged with a hole transport layer made of a flexible polymer material, so that deep energy level defects caused by chloride ion vacancies in the 3D lead-based halide perovskite material are passivated, the morphology of the perovskite film is optimized, the interface lattice strain is reduced, and the performance of the perovskite film is improved. Therefore, the migration of halogen ions is inhibited, the balanced injection of current carriers is realized, the non-radiative recombination loss is reduced, the pure blue light perovskite light-emitting diode with high external quantum efficiency, high color purity and high stability is finally obtained, and the performance bottleneck problem of the existing pure blue light perovskite light-emitting diode is solved.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and in particular to a polymer network-modified pure blue perovskite light-emitting diode and its fabrication method. Background Technology

[0002] Light-emitting diodes (PeLEDs) based on metal halide perovskite materials possess excellent optical properties such as high photoluminescence quantum yield (PLQY) and high color purity, showing great potential for development in next-generation displays and lighting. In 2014, researchers first reported organic-inorganic hybrid perovskite light-emitting diodes (PeLEDs) prepared by a room-temperature solution method, at which time the external quantum efficiency (EQE) of green and near-infrared devices was only 0.1% and 0.76%, respectively. After a decade of development, the EQE of green, red, and near-infrared PeLEDs has now reached approximately 30%. Due to the insulating and unstable nature of organic ligands in quantum dots and quasi-two-dimensional perovskites, advanced PeLEDs that simultaneously achieve high efficiency, high luminous performance, and high operational stability are currently mainly based on three-dimensional (3D) perovskite systems. However, the performance of 3D blue PeLEDs still lags significantly behind, which has become a major challenge that cannot be ignored in the commercialization of perovskite full-color displays.

[0003] The performance bottleneck of blue PeLEDs typically stems from the inherent characteristics of perovskite materials. Besides the wide bandgap of blue perovskites leading to a high carrier injection barrier and difficulty in achieving balanced hole-electron injection, the core limiting factor for the poor performance of 3D blue PeLEDs is the deep-level defects induced by chloride ion vacancies. These defects become non-radiative recombination centers, significantly reducing the device's luminous efficiency. From an electronic structure perspective, the conduction band bottom (CBM) and valence band top (VBM) of lead halide perovskites are composed of hybrid antibonding orbitals of Pb's 6p orbitals and halogen X's p orbitals (X corresponds to Cl, Br, and I, with valence electron layers of 3p, 4p, and 5p, respectively), and Pb's 6s orbitals and halogen X's p orbitals. This electronic structure characteristic is the fundamental root cause of the aforementioned difficulties in carrier injection and defect-related problems.

[0004] Studies generally believe that bromide ions (Br) - ) and iodide ions (I - Defects created by vacancies are usually located inside or near the energy band, and are considered shallow level defects; while chloride ions (Cl...) - ) Vacancy-induced energy level defects and Br - I -Unlike other defects, chloride ions are typically located in the middle of the band gap and belong to deep-level defects. Meanwhile, chloride ions have low solubility in polar solvents such as dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), leading to excessively rapid crystallization during film formation and deterioration of the perovskite film morphology. At the device level, residual compressive stress inevitably remains at the interface between the rigid 3D perovskite formed after annealing and the polymer hole transport layer. This interfacial lattice strain, coupled with the relatively small radius of chloride ions, results in an unstable lattice structure at the interface, accelerating defect formation. These defects, acting as non-radiative recombination centers for charge carriers, are the main reason for the low efficiency of 3D blue PeLEDs. Furthermore, chloride ions in blue perovskites are considered to have a low ion migration barrier, which adversely affects the spectral and operational stability of PeLEDs. Summary of the Invention

[0005] The purpose of this invention is to provide a polymer network-modified pure blue perovskite light-emitting diode and its preparation method, which solves the technical problems of existing polymer network-modified pure blue perovskite light-emitting diodes, such as unbalanced carrier injection due to wide bandgap, deep-level defects caused by chloride ion vacancies (increased non-radiative recombination centers), poor 3D perovskite phase stability (easy to cause crystal phase distortion), low external quantum efficiency (EQE) and insufficient color purity (halogen phase separation).

[0006] To address the aforementioned technical problems, this invention first provides a polymer network-modified pure blue perovskite light-emitting diode, comprising a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal electrode stacked from bottom to top; wherein, the perovskite light-emitting layer is a 3D lead-based halide perovskite structure modified with a PVPh network.

[0007] Preferably, the perovskite luminescent layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

[0008] Preferably, the conductive substrate is ITO conductive glass, and the hole injection layer is a lower NiO layer. x The material is a double-layer stacked structure formed by the material and the upper 2PACz material. The hole transport layer is a double-layer stacked structure formed by the lower PVK material and the upper PVP material. The electron transport layer is TPBi material. The electrode modification layer is made of LiF or MoO3. The metal electrode is made of one of Al, Ag, Au and Zn.

[0009] Preferably, the polymer network-modified pure blue perovskite light-emitting diode has a maximum external quantum efficiency of 9.82%, a maximum brightness of 1544 cd / m², and an emission peak wavelength of 467 nm in the voltage range of 3V to 6V.

[0010] Preferably, the thickness of the conductive substrate is 50–200 nm, the thickness of the hole injection layer is 10–100 nm, the thickness of the hole transport layer is 10–100 nm, the thickness of the perovskite light-emitting layer is 50–200 nm, the thickness of the electron transport layer is 10–100 nm, the thickness of the electrode modification layer is 0.1–10 nm, and the thickness of the metal electrode is 50–150 nm.

[0011] Accordingly, the present invention also provides a method for preparing a pure blue perovskite light-emitting diode modified with a polymer network as described in any of the above claims, the method comprising the following steps: S10, a hole injection layer is prepared on a conductive substrate; S20, Prepare a hole transport layer on the hole injection layer; S30, a perovskite luminescent layer is prepared on the hole transport layer. The perovskite luminescent layer is a 3D lead-based halide perovskite structure modified with a PVPh network. S40, an electron transport layer is prepared on the perovskite light-emitting layer; S50, an electrode modification layer is prepared on the electron transport layer; S60, a metal electrode is prepared on the electrode modification layer.

[0012] Preferably, in step S30, the perovskite luminescent layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

[0013] Preferably, the method for preparing the perovskite light-emitting layer includes the following steps: S301, CsBr, FABr, RbCl, PbBr2 and PbCl2 are mixed and then added to an organic solvent and shaken to obtain a perovskite precursor solution; S302, PVPh was added to the perovskite precursor solution, stirred on a hot plate at 60°C for 2 hours, and filtered to obtain a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

[0014] Preferably, in step S301, the molar ratio of CsBr, FABr, RbCl, PbBr2 to PbCl2 is 1.2:0.2:0.1:0.26:0.74, and the organic solvent is TTDDA and DMSO.

[0015] Preferably, in step S302, the mass ratio of PVPh to PbBr2 is 2% to 3%.

[0016] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides a polymer network-modified pure blue perovskite light-emitting diode and its fabrication method. This polymer network-modified pure blue perovskite light-emitting diode introduces a PVPh additive into the perovskite light-emitting layer to construct a PVPh-modified 3D lead-based halide perovskite structure. This allows PVPh to coordinate with the perovskite, delaying the perovskite crystallization process. Furthermore, it bridges the rigid 3D lead-based halide perovskite material with a flexible polymer hole transport layer, thereby passivating deep-level defects caused by chloride ion vacancies in the 3D lead-based halide perovskite material, optimizing the perovskite film morphology, reducing interface lattice strain, and thus suppressing halide ion migration, achieving balanced carrier injection, and reducing non-radiative recombination losses. Ultimately, this results in a pure blue perovskite light-emitting diode with high external quantum efficiency, high color purity, and high stability, solving the performance bottleneck problem of existing pure blue perovskite light-emitting diodes. Attached Figure Description

[0017] Figure 1a This is a schematic diagram of the chemical structure of poly(4-vinylphenol) (PVPh); Figure 1b The graph shows the relationship between the logarithmic transformation absorption coefficient and photon energy for the control perovskite film and the PVPh-modified perovskite film. Figure 1c The PLQY spectrum of the control perovskite film is shown below. Figure 1d The PLQY spectrum of the PVPh-modified perovskite film; Figure 1e X-ray diffraction (XRD) patterns of the control perovskite film and the PVPh-modified perovskite film; Figure 1f Normalized electroluminescence (EL) spectra of the PeLED devices provided in Example 1 and Comparative Example 1; Figure 1g Electroluminescence (EL) spectra of the PeLED device under different bias voltages provided for Comparative Example 1; Figure 1h The electroluminescence (EL) spectra of the PeLED device provided in Example 1 under different bias voltages; Figure 2a XPS spectra of Pb 4f orbitals of perovskite films and PVPh-modified perovskite films were compared. Figure 2b XPS spectra of Br 3d orbitals of perovskite films and PVPh-modified perovskite films were compared. Figure 2c The Cl 2p orbital XPS spectra of the perovskite film and the PVPh-modified perovskite film are shown for comparison. Figure 2dFourier transform infrared (FTIR) spectra of pure PVPh and PVPh-modified perovskite films; Figure 2e The UV-Vis absorption spectra of the perovskite film and the PVPh-modified perovskite film are shown for comparison. Figure 2f The photoluminescence (PL) spectra of the perovskite film and the PVPh-modified perovskite film are shown for comparison. Figure 2g The time-resolved photoluminescence (TRPL) spectra of the perovskite film and the PVPh-modified perovskite film are shown for comparison. Figure 2h Current-voltage (JV) curves for a hole-only device without PVPh. Figure 2i Current-voltage (JV) curves for hole-only devices with added PVPh; Figure 3a A scanning electron microscope (SEM) image of a control perovskite thin film; Figure 3b Scanning electron microscope (SEM) image of PVPh-modified perovskite film; Figure 3c An atomic force microscope (AFM) image of a control perovskite thin film; Figure 3d Atomic force microscopy (AFM) images of PVPh-modified perovskite films; Figure 3e 3D atomic force microscopy (3D AFM) image of a control perovskite thin film; Figure 3f 3D atomic force microscopy (3D AFM) image of PVPh-modified perovskite film; Figure 4a For reference, the grazing incidence X-ray diffraction (GIXRD) pattern of the perovskite thin film; Figure 4b Grazing incidence X-ray diffraction (GIXRD) pattern of PVPh-modified perovskite thin film; Figure 4c This is a schematic diagram showing the compressive stress of perovskite crystals after PVPh modification of the perovskite film as a control. Figure 5a This is a schematic diagram of the PeLED device provided in Example 1; Figure 5b Current density-voltage curves of the PeLED devices provided for Example 1 and Comparative Example 1; Figure 5c Brightness-voltage curves of the PeLED devices provided in Example 1 and Comparative Example 1; Figure 5d External quantum efficiency-current density (EQE-J) curves of the PeLED devices provided for Example 1 and Comparative Example 1; Figure 5e A summary chart of reported 3D pure blue light (~467nm) PeLEDs performance; Figure 5f A graph showing the maximum EQE statistics for 50 PeLED devices provided in Example 1 and 50 PeLED devices provided in Comparative Example 1; Figure 6a Forward and reverse current density-voltage (JV) scan curves of the PeLED device provided for Comparative Example 1; Figure 6b Forward and reverse current density-voltage (JV) scan curves of the PeLED device provided in Example 1; Figure 6c The time evolution of the electroluminescence (EL) spectrum of the PeLED device provided for Comparative Example 1; Figure 6d The time evolution diagram of the electroluminescence (EL) spectrum of the PeLED device provided in Example 1; Figure 7 A schematic diagram of the transient discharge current of the PeLED device provided in Example 1 and Comparative Example 1. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Currently, state-of-the-art perovskite light-emitting diodes (PeLEDs) have achieved efficiency and luminous performance comparable to organic light-emitting diodes (OLEDs), making them potential candidates for next-generation display and lighting technologies. However, the performance of blue PeLEDs is still far from commercialization standards, mainly due to inherent problems with chloride-based perovskite materials, such as high defect density, poor film quality, and halide ion migration.

[0020] The purpose of this invention is to overcome the aforementioned technical shortcomings and propose a polymer network coating strategy based on poly(4-vinylphenol) (PVPh) to address the challenges. PVPh can bind to perovskite, effectively passivating perovskite defects, optimizing film morphology, alleviating interfacial lattice strain, and suppressing halide ion migration. Results show that the optimized three-dimensional (3D) pure blue PeLEDs achieve a record-breaking external quantum efficiency (EQE) of 9.82% and a density of 1544 cd / m². 2 The highest brightness was achieved, with the emission peak stabilizing at 467nm.

[0021] This invention first provides a polymer network modified pure blue perovskite light-emitting diode, comprising a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal electrode stacked from bottom to top; wherein, the perovskite light-emitting layer is a 3D lead-based halide perovskite structure modified by a PVPh network.

[0022] In this embodiment of the invention, the conductive substrate serves as the anode substrate of the device, undertaking three major functions: mechanical support, conductive transmission, and visible light transmission; it is an ITO conductive glass, mainly prepared by depositing ITO (indium tin oxide) material onto glass through magnetron sputtering.

[0023] In this embodiment of the invention, the hole injection layer is a lower NiO layer. x The material forms a bilayer stacked structure with the upper 2PACz ([2-(9H-carbazole-9-yl)ethyl]phosphonic acid) material: wherein, NiO x Direct contact with ITO allows its work function to match that of ITO, reducing the hole injection barrier. Meanwhile, NiO... x As an inorganic metal oxide, it exhibits high stability and can suppress carrier recombination at the interface; 2PACz is a self-assembled monolayer that combines with NiO through phosphonic acid groups. x Formation of strong coordination bonds, passivation of NiO x The interface defects can be mitigated, and its work function can be further adjusted to match the hole transport layer (PVK) to achieve efficient hole transmission.

[0024] In this embodiment of the invention, the hole transport layer is a double-layer stacked structure formed by a lower PVK (poly-9-vinylcarbazole) material and an upper PVP (polyvinylpyridine) material. PVK serves as the primary hole transport material; its carbazole group's π-conjugated system exhibits excellent hole mobility, enabling rapid hole transport. Simultaneously, its energy level matches the valence band top (VBM) of the perovskite emitting layer, ensuring smooth hole injection into the perovskite emitting layer. PVP serves as an auxiliary modification layer; it does not possess hole transport capabilities itself, but it can passivate interface defects between PVK and the perovskite emitting layer. Furthermore, its carbonyl group can form hydrogen bonds with halide ions on the perovskite surface, inhibiting halide ion migration (specifically targeting Cl in blue light perovskites). - (The problem of easy migration).

[0025] In this embodiment of the invention, the electron transport layer is a TPBi (perovskite / 2,2',2''-(1,3,5-phenyltriyl)tris(1-phenyl-1-H-benzimidazole)) material, which is responsible for transporting electrons from the metal electrode to the perovskite light-emitting layer, while simultaneously achieving hole blocking.

[0026] In this embodiment of the invention, the electrode modification layer is made of LiF or MoO3, and the metal electrode is made of one of Al, Ag, Au and Zn. The electrode modification layer serves as a buffer layer between the metal electrode and the electron transport layer, optimizing the interface contact and improving the electron injection efficiency. The metal electrode serves as the cathode of the device, responsible for collecting electrons and providing the electrical path of the device.

[0027] In this embodiment of the invention, the perovskite light-emitting layer is constructed using a PVPh network (its chemical structure is as follows). Figure 1a The 3D lead-based halide perovskite structure modified as shown is preferably a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

[0028] In this embodiment of the invention, the polymer network-modified pure blue perovskite light-emitting diode has a maximum external quantum efficiency of 9.82%, a maximum brightness of 1544 cd / m², and an emission peak wavelength of 467 nm in the voltage range of 3V to 6V.

[0029] In this embodiment of the invention, the thickness of the conductive substrate is 50–200 nm, the thickness of the hole injection layer is 10–100 nm, the thickness of the hole transport layer is 10–100 nm, the thickness of the perovskite light-emitting layer is 50–200 nm, the thickness of the electron transport layer is 10–100 nm, the thickness of the electrode modification layer is 0.1–10 nm, and the thickness of the metal electrode is 50–150 nm.

[0030] Specifically, the thickness of the conductive substrate balances mechanical support, high blue light transmittance, and efficient hole collection capability; the thicknesses of the hole injection layer and hole transport layer are adapted to its bilayer material structure, reducing the hole injection barrier while avoiding transmission losses caused by excessive thickness, thus alleviating the carrier injection difficulties caused by the wide bandgap of pure blue perovskite; the thickness of the perovskite emitting layer is adapted to the crystallization kinetics and defect passivation requirements of the PVPh network-modified 3D lead-based halide perovskite structure, effectively suppressing chloride ion vacancy defects and halide ion migration; the thickness of the electron transport layer ensures electron transport efficiency and hole blocking effect; the ultra-thin electrode modification layer optimizes the interface contact between the metal electrode and the electron transport layer without increasing transmission resistance; the thickness of the metal electrode balances high conductivity and blue light reflection efficiency, improving light extraction effect.

[0031] Accordingly, the present invention also provides a method for preparing a pure blue perovskite light-emitting diode modified with a polymer network as described in any of the above claims, the method comprising the following steps: S10, a hole injection layer is prepared on a conductive substrate; S20, Prepare a hole transport layer on the hole injection layer; S30, a perovskite luminescent layer is prepared on the hole transport layer. The perovskite luminescent layer is a 3D lead-based halide perovskite structure modified with a PVPh network. S40, an electron transport layer is prepared on the perovskite light-emitting layer; S50, an electrode modification layer is prepared on the electron transport layer; S60, a metal electrode is prepared on the electrode modification layer.

[0032] In step S30, the perovskite luminescent layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film, which is prepared on the hole transport layer by spin coating.

[0033] Preferably, the method for preparing the perovskite light-emitting layer includes the following steps: S301, CsBr, FABr, RbCl, PbBr2 and PbCl2 are mixed and then added to an organic solvent and shaken to obtain a perovskite precursor solution; S302, PVPh was added to the perovskite precursor solution, stirred on a hot plate at 60°C for 2 hours, and filtered to obtain a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

[0034] Specifically, in step S301, the molar ratio of CsBr, FABr, RbCl, PbBr2 to PbCl2 to TTDDA is 1.2:0.2:0.1:0.26:0.74, and the organic solvent is TTDDA and DMSO; in step S302, the mass ratio of PVPh to PbBr2 is 2% to 3%, preferably 2.5%.

[0035] Specifically, a spin-coating method combined with precise process parameter control is used to prepare the perovskite luminescent layer. This not only utilizes the solvent properties of TTDDA to promote the uniform dissolution and dispersion of the precursor raw materials, but also precisely controls the composition of the (Cs / FA / Rb)Pb(Br / Cl)3 perovskite by adjusting the raw material ratio to achieve precise adjustment of the pure blue light bandgap. At the same time, the addition ratio of PVPh and the processing conditions ensure that it can fully combine with the perovskite, effectively passivating chloride ion vacancy defects, delaying crystallization to optimize film morphology, and inhibiting halide ion migration. The application of the spin-coating method ensures the uniformity and thickness controllability of the perovskite film, meeting the overall thickness design requirements of the adapter device.

[0036] In this embodiment of the invention, X-ray photoelectron spectroscopy (XPS) is used to study the interaction between PVPh and perovskite. For example... Figures 2a to 2c As shown: Compared with the control perovskite film ((Cs / FA / Rb)Pb(Br / Cl)3 perovskite film, Control sample), the PVPh-modified sample (PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film, With PVPh sample) shows that the Pb 4f characteristic peak, Br 3d characteristic peak, and Cl 2p characteristic peak are all shifted towards lower binding energies. These results indicate that this binding energy change originates from electron transfer between the hydroxyl groups and halide ions on PVPh. The interaction between the hydroxyl groups and halide ions further modulates the Pb binding energy. 2+ With Br - / Cl - The electrostatic interaction between them.

[0037] Please see Figure 2d , Figure 2d Fourier transform infrared (FTIR) spectra of pure PVPh and PVPh-modified perovskite films; by Figure 2d It can be seen that the stretching vibration peak of the hydroxyl group (-OH) in the pure PVPh sample is located at 3245 cm⁻¹. - At position ¹; however, after bonding with perovskite, the characteristic stretching vibration peak of -OH in the mixed sample (PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film) shifts to a lower wavenumber, appearing at 3163 cm⁻¹. - ¹ This shift originates from the coordination of halide ions in the perovskite with the hydroxyl groups on PVPh, resulting in a decrease in the stretching vibration frequency of the hydroxyl groups.

[0038] Please see Figure 2e , Figure 2e The UV-Vis absorption spectra of the perovskite film and the PVPh-modified perovskite film are shown for comparison; among them, the... Figure 2e It can be seen that the two samples have similar absorption curves, and both show obvious absorption peaks in the blue light region. Notably, the absorption intensity of the PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film is higher than that of the (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film. Furthermore, based on the natural logarithmic transformation diagram of absorption coefficient versus photon energy (e.g., ...), ... Figure 1b As shown), the Urbach energy (Eu) of the two perovskite thin films mentioned above is calculated using the following formula: ; in, E Photon energy, α The absorption coefficient is... α 0 and E C The constant is denoted by . The Eu values ​​of the control perovskite film and the PVPh-modified perovskite film can be obtained by taking the inverse of the slope of the linear portion of the curve, which are 86.2 meV and 65.6 meV, respectively. The above results indicate that the introduction of PVPh reduces the Urbach energy of the perovskite film, suggesting a reduction in the density of trapped states and optimization of lattice distortion.

[0039] Please see Figure 2f , Figure 2f To compare the photoluminescence (PL) spectra of the perovskite film and the PVPh-modified perovskite film; by Figure 2f It can be seen that the emission peak position of both is 467 nm; the incorporation of PVPh significantly enhances the photoluminescence quantum yield (PL) intensity of the perovskite film. Furthermore, photoluminescence quantum yield (PLQY) testing shows that the PLQY of the PVPh-modified sample increased from 26.6% to 43.9% (e.g., ...). Figure 1c and Figure 1d As shown in the figure, this improvement confirms that PVPh can effectively passivate nonradiative recombination centers associated with perovskite defects. Meanwhile, the time-resolved photoluminescence (TRPL) spectra of the perovskite film and the PVPh-modified perovskite film are compared as shown in the figure. Figure 2g As shown: the average PL lifetime (the time required for the PL intensity to decay to the initial value 1 / e) of the control perovskite film is 3.52 ns, while it is extended to 12.52 ns after adding PVPh.

[0040] To further evaluate the defect passivation effect of PVPh on perovskite, space charge confinement current (SCLC) tests were performed on pure hole devices prepared from control perovskite films and PVPh-modified perovskite films, respectively. Figure 2h and Figure 2i As shown: Trap-fill limit voltage (V) of a hole-only device without added PVPh TFL The trap fill limit voltage (V) of a pure hole device with added PVPh is 0.69V. TFL The value is 0.42V; the lower trap fill limit voltage indicates that the trap state density of the pure hole device with added PVPh is lower.

[0041] Specifically, the hole-only device without PVPh adopts a bottom-up stacked structure, comprising a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electrode modification layer, and a metal electrode. The specific configurations of each layer are as follows: the conductive substrate is ITO conductive glass; the hole injection layer is a double-layer stacked structure, with the lower layer being NiOx and the upper layer being 2PACz; the hole transport layer is a double-layer stacked structure, with the lower layer being PVK and the upper layer being PVP; the perovskite light-emitting layer is a (Cs / FA / Rb)Pb(Br / Cl)3 perovskite thin film; the electrode modification layer is made of MoO3; and the metal electrode is made of Ag.

[0042] Specifically, the structure of the pure hole device with added PVPh is basically the same as that of the pure hole device without added PVPh. The only difference between the two is that the perovskite light-emitting layer is a (Cs / FA / Rb)Pb(Br / Cl)3 perovskite thin film modified with PVPh.

[0043] Please see Figures 3a to 3f , Figure 3a A scanning electron microscope (SEM) image of a control perovskite thin film; Figure 3b Scanning electron microscope (SEM) image of PVPh-modified perovskite film; Figure 3c An atomic force microscope (AFM) image of a control perovskite thin film; Figure 3d Atomic force microscopy (AFM) images of PVPh-modified perovskite films; Figure 3e 3D atomic force microscopy (3D AFM) image of a control perovskite thin film; Figure 3f These are 3D atomic force microscopy (3D AFM) images of PVPh-modified perovskite films; the PVPh-modified perovskite films exhibit higher coverage, better density, and better uniformity (e.g., Figure 3b As shown), the control perovskite film without PVPh exhibits numerous large-area pinholes (e.g. Figure 3a (Marked by the red circle in the middle), resulting in poor film coverage and continuity. Figure 3c and Figure 3dThe AFM test results showed that the root mean square roughness (rms) of the control perovskite film and the PVPh-modified perovskite film were 8.94 nm and 5.99 nm, respectively, indicating that PVPh modification can improve the film morphology. Figure 3e and Figure 3f The 3D AFM images further confirmed this conclusion: compared with the control perovskite film, the perovskite grains of the PVPh-modified perovskite film were more dense and uniform.

[0044] X-ray diffraction (XRD) patterns (such as...) Figure 1e As shown in the figure, the incorporation of PVPh did not significantly alter the 3D crystal structure of perovskite, but the diffraction peaks corresponding to the (100) and (200) crystal planes were significantly enhanced, indicating an increase in the crystallinity of the perovskite. Typically, perovskite films are prepared by spin-coating a precursor solution onto a lower hole transport layer and then annealing. When cooled to room temperature, the mismatch in thermal expansion coefficients between the lower substrate and the perovskite can generate residual stress at the perovskite interface. To investigate the effect of the polymer additive PVPh on the residual strain of perovskite, the inventors selected the grazing incidence X-ray diffraction (GIXRD) pattern of the (200) crystal plane at 31.1° for analysis, as shown in the figure. Figures 4a to 4b As shown: For the control group sample ( Figure 4a When the incident angle (ω) increases from 0.3° to 1.2°, the diffraction peaks gradually shift to higher angles, indicating that compressive stress causes lattice strain at the bottom of the control perovskite film; conversely, Figure 4b In the results, when ω increases from 0.3° to 1.2°, the diffraction peak shift is negligible, indicating that the PVPh-modified perovskite has almost no lattice strain. This result shows that incorporating the flexible polymer PVPh into rigid 3D perovskites can effectively alleviate the interfacial lattice compressive stress between the organic hole transport layer and the perovskite, thereby reducing lattice distortion, which is consistent with previous calculations of the Urbach energy. Figure 4c This is a schematic diagram of the compressive stress of perovskite crystals after PVPh modification of the perovskite film as a reference: the polymer PVPh forms a network layer on the surface and interface of the perovskite, promoting the formation of a more ordered and regular perovskite lattice.

[0045] The technical solution of this application will now be described in further detail with reference to specific embodiments.

[0046] Example 1 (With PVPh sample): Example 1 provides a pure blue perovskite light-emitting diode modified with poly(4-vinylphenol) (e.g. Figure 5a As shown, the structure includes, from bottom to top, a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal electrode; wherein, the conductive substrate is ITO conductive glass, and the hole injection layer is the lower NiO layer.x The material is a double-layer stacked structure formed by the material and the upper 2PACz material. The hole transport layer is a double-layer stacked structure formed by the lower PVK material and the upper PVP material. The perovskite light-emitting layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film. The electron transport layer is TPBi material. The electrode modification layer is LiF material. The metal electrode is Al material. Example 1 also provides a method for preparing a pure blue perovskite light-emitting diode modified with poly(4-vinylphenol). The specific preparation method of the perovskite light-emitting layer of the above-mentioned pure blue perovskite light-emitting diode includes: Step (1): CsBr, FABr, RbCl, PbBr2, PbCl2, and TTDDA (4,7,10-trioxa-1,13-tetanediamine) were dissolved in DMSO (dimethyl sulfoxide) in a molar ratio of 1.2:0.2:0.1:0.26:0.74:0.1, so that Pb... 2+ A perovskite precursor solution was prepared at a concentration of 0.1 M.

[0047] Step (2): PVPh was added to the perovskite precursor solution at a mass ratio of 2.5 wt% relative to PbBr2. The solution was then stirred on a hot plate at 60°C for 2 hours. After filtration with a 0.45 μm hydrophilic filter, PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film was obtained.

[0048] Comparative Example 1 (Control Sample): Comparative Example 1 provides a pure blue perovskite light-emitting diode fabricated by a conventional method, comprising, from bottom to top, a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal electrode; wherein, the conductive substrate is ITO conductive glass, and the hole injection layer is a lower NiO layer. x The material is a double-layer stacked structure formed by the material and the upper 2PACz material. The hole transport layer is a double-layer stacked structure formed by the lower PVK material and the upper PVP material. The perovskite light-emitting layer is a (Cs / FA / Rb)Pb(Br / Cl)3 perovskite thin film. The electron transport layer is a TPBi material. The electrode modification layer is made of LiF. The metal electrode is made of Al.

[0049] Please see Figures 5b to 5e , Figure 5b Current density-voltage curves of the PeLED devices provided for Example 1 and Comparative Example 1; Figure 5c Brightness-voltage curves of the PeLED devices provided in Example 1 and Comparative Example 1; Figure 5dExternal quantum efficiency-current density (EQE-J) curves of the PeLED devices provided for Example 1 and Comparative Example 1; Figure 5e This is a summary chart of reported performance of 3D pure blue light (~467nm) PeLEDs; among them, by Figures 5b to 5e It can be seen that the PeLED device provided in Example 1 has lower leakage current and higher brightness than the PeLED device provided in Comparative Example 1: the maximum brightness of the PeLED device provided in Comparative Example 1 is 1224 cd / m². 2 The maximum brightness of the PeLED device provided in Example 1 is increased to 1544 cd / m². 2 .

[0050] Furthermore, the peak EQE of the PeLED device provided in Comparative Example 1 is 6.23%, while the highest EQE of the PeLED device provided in Example 1 reaches 9.82%, and the electroluminescence (EL) peak is located at 467nm (e.g., Figure 5d and Figure 1f (As shown). It is noteworthy that the EL full width at half maximum (FWHM) of the PeLED devices provided in Comparative Example 1 and Example 1 are 18 nm and 16 nm, respectively, a trend consistent with the Urbach energy variation of both. It is worth emphasizing that this is currently the highest efficiency reported for 3D pure blue light (emission peak ~467 nm) PeLEDs (e.g., as shown). Figure 5e (As shown).

[0051] Please see Figure 5f , Figure 5f Figure 5 shows the maximum EQE statistics of 50 PeLED devices provided in Example 1 and 50 PeLED devices provided in Comparative Example 1. As can be seen from Figure 5, the average EQE of the PeLED devices provided in Comparative Example 1 is 5.01%, while the average EQE of the PeLED devices provided in Example 1 is 8.29%.

[0052] Please see Figure 1g and Figure 1h , Figure 1g Electroluminescence (EL) spectra of the PeLED device under different bias voltages provided for Comparative Example 1; Figure 1h The electroluminescence (EL) spectra of the PeLED device provided in Example 1 under different bias voltages; by Figure 1g and Figure 1h It can be seen that within the voltage range of 3V to 6V, the electroluminescence spectra of the PeLED devices provided in Comparative Example 1 and Example 1 show no significant shift, and the EL peak remains stable at 467nm.

[0053] Please see Figure 6a and Figure 6b , Figures 6a to 6b To investigate the current hysteresis behavior of PeLEDs using forward and reverse JV scans. Figure 6a In the comparison, the JV curves of the PeLED device provided in Example 1 showed significant differences in three scans; conversely, the PeLED device provided in Example 1 not only had a smaller hysteresis loop, but also a high degree of overlap in the hysteresis curves of the three scans. Figure 6b As shown in the figure, the introduction of the PVPh network can effectively suppress ion migration in PeLEDs under voltage bias.

[0054] Typically, mixed halide perovskites are prone to phase separation due to halide ion migration when a voltage is applied, leading to changes in the EL spectrum. To evaluate the halide ion migration, the inventors tested the spectral stability of different PeLEDs devices under constant voltage. Figure 6c and Figure 6d As shown, the spectrum of the PeLED device provided in Comparative Example 1 gradually broadens and shifts towards the red region over time; while the PeLED device provided in Example 1 exhibits better spectral stability over the same time period.

[0055] To further verify the inhibitory effect of the PVPh network on ion migration, the relative concentration of mobile ions in the perovskite was estimated based on the transient discharge current, such as... Figure 7 As shown: By dividing the integral transient current by the sample volume and elementary charge, the relative concentration of mobile ions in the PeLED device provided in Comparative Example 1 was calculated to be 1.09 × 10¹. 7 cm - ³, while in the PeLED device provided in Example 1, this concentration was reduced to 7.04 × 10³. 16 cm - ³. This result is consistent with Figures 6a to 6d The experimental results are consistent with those observed in the study, confirming that PVPh can effectively inhibit the migration of halide ions.

[0056] In summary, unlike existing technologies, this application introduces the polymer additive poly(4-vinylphenol) (PVPh) into the perovskite system, enabling it to form a network covering structure on the 3D perovskite surface. Through a series of chemical characterizations, morphological analyses, and density functional theory (DFT) calculations, it is confirmed that PVPh can passivate deep-level defects in blue perovskites through coordination with the perovskite. The steric hindrance effect of its polymer network effectively suppresses halide ion migration and alleviates phase separation, while also delaying perovskite crystallization to optimize film morphology and bridging the rigid 3D perovskite with the flexible polymer hole transport layer to reduce interfacial lattice strain. Ultimately, the PVPh-doped pure blue PeLEDs achieved an optimal EQE of 9.82% and a peak brightness of 1544 cd / m², with the emission peak stable at 467 nm. This study demonstrates that the polymer additive PVPh can improve the performance of 3D pure blue PeLEDs, providing a simple and effective strategy for developing high-performance 3D blue PeLEDs and promoting their application in next-generation displays and lighting.

[0057] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0058] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A polymer network-modified pure blue perovskite light-emitting diode, characterized in that, It includes a conductive substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer, and a metal electrode stacked from bottom to top; wherein, the perovskite light-emitting layer is a 3D lead-based halide perovskite structure modified with a PVPh network.

2. The polymer network-modified pure blue perovskite light-emitting diode according to claim 1, characterized in that, The perovskite luminescent layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

3. The polymer network-modified pure blue perovskite light-emitting diode according to claim 2, characterized in that, The conductive substrate is ITO conductive glass, and the hole injection layer is a lower NiO layer. x The material is a double-layer stacked structure formed by the material and the upper 2PACz material. The hole transport layer is a double-layer stacked structure formed by the lower PVK material and the upper PVP material. The electron transport layer is TPBi material. The electrode modification layer is made of LiF or MoO3. The metal electrode is made of one of Al, Ag, Au and Zn.

4. The polymer network-modified pure blue perovskite light-emitting diode according to claim 3, characterized in that, The polymer network-modified pure blue perovskite light-emitting diode has a maximum external quantum efficiency of 9.82%, a maximum brightness of 1544 cd / m², and an emission peak wavelength of 467 nm in the voltage range of 3V to 6V.

5. The polymer network-modified pure blue perovskite light-emitting diode according to claim 1, characterized in that, The conductive substrate has a thickness of 50–200 nm, the hole injection layer has a thickness of 10–100 nm, the hole transport layer has a thickness of 10–100 nm, the perovskite light-emitting layer has a thickness of 50–200 nm, the electron transport layer has a thickness of 10–100 nm, the electrode modification layer has a thickness of 0.1–10 nm, and the metal electrode has a thickness of 50–150 nm.

6. A method for preparing a pure blue perovskite light-emitting diode modified with a polymer network as described in any one of claims 1 to 5, characterized in that, The method includes the following steps: S10, the hole injection layer is prepared on the conductive substrate; S20, the hole transport layer is prepared on the hole injection layer; S30, the perovskite light-emitting layer is prepared on the hole transport layer, wherein the perovskite light-emitting layer is a 3D lead-based halide perovskite structure modified with PVPh. S40, an electron transport layer is prepared on the perovskite light-emitting layer; S50, the electrode modification layer is prepared on the electron transport layer; S60, the metal electrode is prepared on the electrode modification layer.

7. The method for preparing a pure blue perovskite light-emitting diode modified with a polymer network according to claim 6, characterized in that, In step S30, the perovskite luminescent layer is a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

8. The method for preparing a pure blue perovskite light-emitting diode modified with a polymer network according to claim 7, characterized in that, The method for preparing the perovskite luminescent layer includes the following steps: S301, CsBr, FABr, RbCl, PbBr2 and PbCl2 are mixed and then added to an organic solvent and shaken to obtain a perovskite precursor solution; S302, PVPh is added to the perovskite precursor solution, stirred on a hot plate at 60°C for 2 hours, and filtered to obtain a PVPh-modified (Cs / FA / Rb)Pb(Br / Cl)3 perovskite film.

9. The method for preparing a pure blue perovskite light-emitting diode modified with a polymer network according to claim 8, characterized in that, In step S301, the molar ratio of CsBr, FABr, RbCl, PbBr2 and PbCl2 to TTDDA is 1.2:0.2:0.1:0.26:0.74, and the organic solvent is TTDDA and DMSO.

10. The method for preparing a pure blue perovskite light-emitting diode modified with a polymer network according to claim 8, characterized in that, In step S302, the mass ratio of PVPh to PbBr2 is 2% to 3%.

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