A 585 nm perovskite light-emitting diode structure with interface synergistic passivation effect and a preparation method thereof

Abstract

A 585 nm perovskite light-emitting diode structure with interface synergistic passivation effect and preparation method, by introducing organic cationic ligand PEA + and inorganic LiF interface passivation layer, a quasi-two-dimensional PEA-CsPb(Br x I 1‑x )3 perovskite light-emitting layer material and device with low defect state density is constructed, a multiple quantum well structure is formed to enhance the dielectric confinement effect and exciton binding energy of perovskite material, realize efficient radiation recombination, passivate the defect state density between the carrier transport layer and the active layer, reduce the interface recombination, improve the light-emitting quantum yield, and thus realize the improvement of the key parameters and energy conversion efficiency of perovskite light-emitting material and LED device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of luminescent materials and devices, especially perovskite luminescent materials and light-emitting diode devices. BACKGROUND

[0002] Yellow light-emitting diodes (LEDs) have an emission wavelength of 570-600 nm, which have important applications in high-quality lighting, light fidelity (LiFi), indicator lights, optogenetics, etc. Commercial yellow LEDs are mainly prepared by metal organic chemical vapor deposition (MOCVD) of highly crystalline indium gallium nitride (InGaN). The preparation of high-quality InGaN requires a high growth temperature (>750℃), and the cost of rare metal elements (such as In and Ga) is high, so it is limited in industrial production. Compared with other materials, perovskite has obvious advantages in cost and preparation conditions. Although the highest EQE (External Quantum Efficiency) of perovskite LEDs in the green, red and near-infrared regions has exceeded 20%, which is comparable to organic LEDs. However, there are relatively few studies on yellow perovskite LEDs, and the external quantum efficiency (EQE) of the yellow perovskite LEDs prepared by the current researches is generally low, which has attracted widespread attention from researchers. See the literature: Neumann A, Wierer JJ, Davis W, et al, Opt Express , 2011, 19(A982); Janjua B, Oubei HM, Retamal JRD, et al, Opt Express , 2015, 23(18746); Xu W, Hu Q, Bai S, et al, Nature Photonics , 2019, 13(418) Kim Y H, Kim S, Kakekhani A, et al, Nature Photonics , 2021, 15(2).

[0003] In the organic-inorganic hybrid perovskite structure, by adding organic polymer long-chain cations, the three-dimensional perovskite structure can be separated into two-dimensional or quasi-two-dimensional Ruddlesden-Popper layered structure perovskite. The chemical formula of this structure is usually L2A n-1 B n X 3n₋1 or L2(ABX3) n₋1BX4, where L represents an organic long-chain cation with an amine group, such as phenylethylammonium (PEA), n-butylammonium (n-BA), and the like. The organic long-chain L cannot fill the space between the octahedral structures due to its large volume, so it is connected to the octahedral structure through hydrogen bonding in the amine group. The organic long-chain L is regularly arranged through van der Waals forces. The n in the chemical formula represents the number of layers of the perovskite structure. When n = 1, the octahedral structure is sandwiched between two layers of organic groups, forming a three-layer quasi-two-dimensional perovskite. When n approaches infinity, the perovskite structure gradually tends to be three-dimensional. The formation of this organic-inorganic hybrid structure makes it possible to prepare quasi-two-dimensional perovskites and provides a new way to control their optoelectronic properties. See: Wu C, Wu T, Yang Y, et al, ACS Nano , 2019, 13(1645); Tian Y, Zhou C, Worku M, et al, Advanced Materials , 2018, 30(1707093); Li Z, Chen Z, Yang Y, et al, Nature Communications , 2019, 10(1).

[0004] Compared with 3D perovskites, the growth of 2D perovskites in a specific direction is limited by the organic long-chain ligand. By adjusting the n value and the organic long-chain ligand, the photophysical properties of 2D perovskites can be effectively controlled. Due to the difference in dielectric constant between the organic long-chain ligand and the octahedral structure, the layered structure forms a natural multiple quantum well structure, in which the octahedral structure acts as a "well" and the organic long-chain ligand forms a "barrier". As the n value increases, the quantum confinement effect decreases and the band gap of the perovskite film decreases. When carriers are injected into the perovskite film, energy is transferred from areas with larger band gaps to areas with smaller band gaps, causing radiative recombination to occur in areas with smaller band gaps, increasing the probability of exciton radiative recombination. The quantum well can be adjusted by the n value to enhance the dielectric confinement effect and exciton binding energy of the perovskite material. The increase in exciton binding energy effectively confines electrons and holes in a smaller band gap space, enabling efficient radiative recombination and improving the luminescence quantum yield. In addition, the organic long-chain ligand is hydrophobic, which can improve the water and oxygen stability of the quasi-two-dimensional perovskite material in air, further improving the luminescence lifetime and stability of the luminescent device. Therefore, the 2D layered perovskite structure has a larger exciton binding energy, higher luminescence lifetime and stability than the 3D perovskite, which can improve the luminance, efficiency and stability. See: Quan L N, Zhao Y, Garcia deArquer F P, et al, Nano Letters, 2017, 17(3701); Booker E P, Thomas T H, Quarti C, et al, Journal of the American Chemical Society , 2017, 139(18632); Cortecchia D, Yin J, Bruno A, et al, Journal of Materials Chemistry C , 2017, 5(2771).

[0005] In addition, it is still not enough to optimize the device only from the perspective of the quality of the perovskite film. The interface transmission problem between functional layers also has an important impact on the photoelectric performance of the device. PEDOT:PSS is a commonly used hole transport material for LED devices. Its conductivity, solution processing, and high light transmittance are widely used in photovoltaic devices. However, for perovskite LEDs, when PEDOT:PSS is in direct contact with the perovskite layer, the excitons in the perovskite film will undergo severe quenching. Directly preparing a perovskite film on PEDOT:PSS is prone to have many pore defects and other film quality problems, causing serious leakage current in the device. To solve these problems, functional layer materials can be doped in PEDOT:PSS or additional buffer layers can be introduced to improve quenching and pore defect states. However, most hole transport materials are organic, and have poor tolerance to solvents such as DMF and DMSO used to prepare perovskites, so their application in perovskite LEDs is limited. See Yu J C, Kim D W, Kim D B, et al., Nanoscale , 2017, 9(2088); Yuan F, Fu F, Zhu C, et al., Organic electronics , 2022, 10(106); Tan P, Wang H F, Lu. et al., Nature communications , 2022, 13(358); Daboczi M, Luke J, Kim JS, et al., ACS Energy Letters , 2022, 7(560).

[0006] As can be seen, if effective methods are used to introduce long-chain organic ligands to construct a quasi-two-dimensional 585 nm yellow light LED light-emitting layer material, and inorganic passivation layers are introduced between the hole transport layer and the light-emitting layer and between the electron transport layer and the light-emitting layer, the defects in the light-emitting layer and the interface can be effectively passivated. On the one hand, it can reduce the non-radiative recombination probability and increase the probability of exciton radiative recombination, thereby improving the light-emitting intensity. On the other hand, it can improve the stability of the device, which will positively promote the performance improvement of the perovskite LED device.

[0007] Based on this, the application provides a 585 nm perovskite light-emitting diode structure with a light-emitting layer and interface synergistic passivation effect and a preparation method. x I 1-x )3, a perovskite light-emitting layer material with a band gap of 2.12 eV and a photoluminescence wavelength of 585 nm is realized, then an organic cation ligand PEA + is introduced, a quasi-two-dimensional PEA-CsPb(Br x I 1-x )3 perovskite light-emitting layer material is prepared by using a pure solution method, the photoluminescence intensity and the fluorescence lifetime of the perovskite thin film are improved, and a LiF interface passivation layer is introduced simultaneously in the middle of a hole transport layer PEDOT:PSS and the light-emitting layer PEA-CsPb(Br x I 1-x )3 and the middle of an electron transport layer TPBi and the light-emitting layer PEA-CsPb(Br x I 1-x )3, and a LED device structure of ITO / PEDOT:PSS / LiF / PVK / LiF / TPBi / Al is constructed, so that a high-efficiency and stable yellow light perovskite LED device with a photoluminescence wavelength of 585 nm is realized. SUMMARY

[0008] The application aims to introduce an organic cation ligand PEA + and an inorganic LiF interface passivation layer, construct a quasi-two-dimensional PEA-CsPb(Br x I 1-x )3 perovskite light-emitting layer material and device with low defect state density, form a multiple quantum well structure, enhance the dielectric confinement effect and exciton binding energy of the perovskite material, realize high-efficiency radiative recombination, passivate the defect state density between the carrier transport layer and the active layer, reduce the interface recombination, improve the light-emitting quantum yield, and thus improve the key parameters and energy conversion efficiency of the perovskite light-emitting material and the LED device.

[0009] The technical scheme of the application is as follows:

[0010] A 585 nm perovskite light-emitting diode structure with a light-emitting layer and interface synergistic passivation effect and a preparation method, comprising the following three parts: the first part is to prepare a perovskite LED device capable of emitting yellow light, first, the material of the light-emitting layer thin film is adjusted by halogen, the CsPbBr3 solution and the CsPbI3 solution are adjusted according to different proportions to adjust the band gap and the light-emitting wavelength range of the light-emitting layer; the second part is to introduce a PEA organic ligand into the light-emitting layer material to construct a quasi-two-dimensional PEA-CsPb(Br x I 1-x)3 material, in order to keep the emission wavelength unchanged, the PEABr x I 3-x The proportion of halogen atoms in the third part is the same as that in the original light-emitting layer; the third part is a LiF interface layer between the hole transport layer PEDOT:PSS and the PEA-CsPb(Br x I 1-x )3 light-emitting layer and the electron transport layer TPBi and the PEA-CsPb(Br x I 1-x )3 light-emitting layer. The characteristics are that the quasi-two-dimensional PEA-CsPb(Br x I 1-x )3 perovskite light-emitting layer material can form a multiple quantum well structure to enhance the dielectric confinement effect and exciton binding energy of the perovskite material, realize efficient radiative recombination; the passivated defects between the hole transport layer and the light-emitting layer reduce the quenching of excitons, improve the transport efficiency of carriers, and reduce the leakage current and the turn-on voltage of the device; the method has a significant improvement effect on the interface defect problem on the electron transport path of the perovskite LED device, thereby realizing the synchronous improvement of the device efficiency and stability.

[0011] The device structure of the 585 nm perovskite light-emitting diode is ITO / PEDOT:PSS / LiF / PVK / LiF / TPBi / Al, wherein the perovskite light-emitting layer is PEA-CsPb(Br x I 1-x )3 has a quasi-two-dimensional structure, and has a LiF interface modification layer between the electron transport layer and the hole transport layer.

[0012] The perovskite light-emitting layer is prepared by a solution method, the perovskite precursor solution is a mixed solution of CsPbBr3 and CsPbI3, the solution uses one of dimethyl sulfoxide, dimethyl formamide, and isopropyl alcohol or a mixed solvent, to prepare a perovskite light-emitting layer material CsPb(Br x I 1-x )3, wherein x is 0.4-0.8, and the thickness is 20 nm-80 nm.

[0013] The quasi-two-dimensional structure is realized by introducing an organic ligand PEA into the precursor solution, by introducing an organic ligand PEABr x I 1-x with the same Br:I ratio, to construct a PEA-CsPb(Br x I 1-x )3 with a quasi-two-dimensional structure, wherein the organic ligand PEABr x I 1-xThe volume ratio of the volume to the total solution volume is 0.1-0.5.

[0014] The LiF interface modification layer is prepared by at least one of magnetron sputtering, atomic layer deposition, thermal evaporation, electron beam evaporation, and molecular beam epitaxy technology, and has a thickness of 1-5 nm.

[0015] The ITO transparent conductive layer is prepared by at least one of magnetron sputtering, thermal evaporation, and electron beam evaporation, and has a thickness of 70-150 nm.

[0016] The hole transport layer PEDOT:PSS is prepared by a solution method, and has a thickness of 20-60 nm.

[0017] The electron transport layer TPBi is prepared by a vacuum evaporation method, and has a thickness of 20-60 nm.

[0018] The metal Al electrode is prepared by magnetron sputtering or thermal evaporation technology, and has a thickness of 80-200 nm. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of a 585 nm perovskite light-emitting diode structure with a light-emitting layer and interface synergistic passivation effect.

[0020] Figure 2 It is a comparison result diagram of photoluminescence intensity of a 585 nm perovskite light-emitting material with a light-emitting layer passivation effect.

[0021] Figure 3 It is a comparison result diagram of photoluminescence intensity of a 585 nm perovskite light-emitting material with an interface layer passivation effect.

[0022] Figure 4 It is a comparison result diagram of electroluminescence brightness of a 585 nm perovskite light-emitting diode with a light-emitting layer and interface synergistic passivation effect.

[0023] Figure 5 It is a comparison result diagram of external quantum efficiency of a 585 nm perovskite light-emitting diode with a light-emitting layer and interface synergistic passivation effect. DETAILED DESCRIPTION

[0024] Example 1:

[0025] A 585 nm perovskite light-emitting diode structure with a light-emitting layer and interface synergistic passivation effect and a preparation method, the method being as follows:

[0026] 1) Depositing a PEDOT:PSS hole transport layer on the ITO charge transport layer, spin-coating the filtered PEDOT:PSS aqueous solution on the ITO transparent conductive glass substrate at a rotation speed of 3500 rpm, the spin-coating time is 30 seconds, then placing the spin-coated sample on a heating table at 130°C for annealing treatment for 10 minutes, obtaining a PEDOT:PSS hole transport layer with a thickness of 50 nm.

[0027] 2) Depositing a 2 nm LiF interface passivation layer on the PEDOT:PSS hole transport layer by using a thermal evaporation process.

[0028] 3) Mixing the CsPbBr3 solution and the CsPbI3 solution according to a volume ratio of 0.6:0.4, selecting dimethyl sulfoxide as the solvent, obtaining a CsPb(Br 0.6 I 0.4 )3 perovskite light-emitting layer material reaction precursor solution.

[0029] 4) Mixing the PEABr 0.6 I 0.4 solution and the CsPb(Br 0.6 I 0.4 )3 solution according to a volume ratio of 0.2:1, obtaining a quasi-two-dimensional PEA-CsPb(B r0.6 I 0.4 )3 perovskite light-emitting layer material reaction precursor solution, and preparing a light-emitting layer material with a thickness of 40 nm on glass by using a spin-coating process, the photoluminescence spectrum is shown in Figure 2 , and compared with the light-emitting layer without passivation material, the photoluminescence intensity is increased by 4.7 times.

[0030] 5) Depositing a 1 nm LiF interface passivation layer on the PEA-CsPb(B r0.6 I 0.4 )3 perovskite light-emitting layer by using a thermal evaporation process, the photoluminescence spectrum of the light-emitting layer with double interface passivation layers is shown in Figure 3 , and compared with the light-emitting layer without passivation material, the photoluminescence intensity is increased by 5.8 times.

[0031] 6) Depositing a TPBi electron transport layer with a thickness of 40 nm by using a thermal evaporation process.

[0032] 7) Depositing an aluminum electrode with a thickness of 150 nm by using a thermal evaporation process.

[0033] The schematic diagram of a 585 nm perovskite light-emitting diode structure with a light-emitting layer and interface synergistic passivation effect is shown in Figure 1 , the brightness comparison results of the obtained LED device are shown in Figure 4 , and the external quantum efficiency comparison results of the obtained LED device are shown inFigure 5 shown.

[0034] Application results show that a 585 nm perovskite light-emitting diode structure and preparation method with synergistic passivation effects of the light-emitting layer and interface can enhance the dielectric confinement effect and exciton binding energy of the perovskite material, achieve efficient radiative recombination, passivate the defect state density between the carrier transport layer and the active layer, reduce interface recombination, and improve the luminescence quantum yield. The device's turn-on voltage is reduced from 4.6 V to 2.8 V, and the brightness is increased from 22.8 cd / m 2 Increased to 367.8 cd / m 2 The corresponding external quantum efficiency increased from 0.1% to 1.83%, which has obvious application effects.

[0035] Example 2:

[0036] A 585 nm perovskite light-emitting diode structure and preparation method with a synergistic passivation effect of a light-emitting layer and an interface is disclosed, wherein:

[0037] 1) A PEDOT:PSS hole transport layer was deposited on top of the ITO charge transport layer. The filtered PEDOT:PSS aqueous solution was spin-coated onto the ITO transparent conductive glass substrate at 3500 rpm for 30 seconds. The spin-coated sample was then annealed on a heating plate at 130°C for 10 minutes to obtain a 50 nm thick PEDOT:PSS hole transport layer.

[0038] 2) A 1 nm thick LiF interfacial passivation layer was deposited on top of the PEDOT:PSS hole transport layer using a thermal evaporation process.

[0039] 3) CsPbBr3 solution and CsPbI3 solution were mixed in a volume ratio of 0.6:04, and dimethyl sulfoxide was selected as the solvent to obtain CsPb(Br 0.6 I 0.4 )3 Perovskite light-emitting layer material reaction precursor liquid.

[0040] 4) PEABr 0.6 I 0.4 solution and CsPb(Br 0.6 I 0.4 )3 solutions were mixed at a volume ratio of 0.4:1 to obtain quasi-two-dimensional PEA-CsPb(B r0.6 I 0.4 )3 The perovskite light-emitting layer material reacts with the precursor liquid, and the light-emitting layer material with a thickness of 40 nm is prepared on the glass by spin coating process.

[0041] 5) Using thermal evaporation process to r0.6 I0.4 )3 A 2 nm LiF interfacial passivation layer is deposited on top of the perovskite light-emitting layer.

[0042] 6) A TPBi electron transport layer is deposited by a thermal evaporation process, with a thickness of 30 nm.

[0043] 7) An aluminum electrode is deposited by a thermal evaporation process, with a thickness of 100 nm.

[0044] The application results show that the 585 nm perovskite light-emitting diode structure and preparation method with the light-emitting layer and the interfacial synergistic passivation effect can enhance the dielectric confinement effect and the exciton binding energy of the perovskite material, realize efficient radiative recombination, passivate the defect state density between the carrier transport layer and the active layer, reduce the interfacial recombination, and improve the light-emitting quantum yield. The opening voltage of the device is reduced from 4.6 V to 3.2 V, the brightness is increased from 22.8 cd / m 2 to 238.7 cd / m 2 , the corresponding external quantum efficiency is increased from 0.1% to 1.68%, and the device has obvious application effect.

[0045] The above describes only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

[0046] The English abbreviations in the present application are explained as follows:

[0047] PEA (phenethylamine)

[0048] PEDOT: PSS (Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate))

[0049] TPBi (1,3,5-Tris(1-phenyl-1H-benzimidazol-2-yl)benzene)

Claims

1. A method for preparing a 585nm perovskite light-emitting diode structure with a synergistic passivation effect of a light-emitting layer and an interface, comprising the following three parts: the first part is to prepare a perovskite LED device that can emit yellow light, firstly, halogen adjustment is performed on the material of the light-emitting layer film, and CsPbBr3 solution and CsPbI3 solution are adjusted according to different proportions to adjust the band gap and emission wavelength range of the light-emitting layer; the second part is to introduce PEA organic ligands into the light-emitting layer material to construct a quasi-two-dimensional PEA-CsPb (Br x I 1-x )3 materials, in order to keep the emission wavelength unchanged, it is necessary to keep PEABr x I 1-x The ratio of halogen atoms in the hole transport layer is the same as that in the original light-emitting layer; the third part is the hole transport layer PEDOT:PSS and PEA-CsPb(Br x I 1-x )3 between the light-emitting layer and the electron transport layer TPBi and the light-emitting layer PEA- CsPb(Br x I 1-x ) 3 simultaneously introduces a LiF interface layer to passivate interface defects and form a complete LED device; characterized by: Quasi-two-dimensional PEA-CsPb(Br) with low defect state density x I 1-x )3 Perovskite light-emitting layer materials can form a multiple quantum well structure to enhance the dielectric confinement effect and exciton binding energy of the perovskite material, achieve efficient radiative recombination, passivate the defects between the hole transport layer and the light-emitting layer, reduce the quenching of excitons, improve the carrier transport efficiency, and reduce the leakage current and turn-on voltage of the device; the method has a significant improvement effect on the interface defect problem on the electron transmission path of the perovskite LED device, thereby achieving a simultaneous improvement in device efficiency and stability.

2. According to the preparation method of claim 1, the device structure of the 585nm perovskite light-emitting diode is ITO / PEDOT:PSS / LiF / PVK / LiF / TPBi / Al, wherein the perovskite light-emitting layer is PEA-CsPb(Br x I 1-x )3 has a quasi-two-dimensional structure and has a LiF interface modification layer between the electron transport layer and the hole transport layer.

3. The preparation method according to claim 2, wherein the perovskite light-emitting layer is prepared by a solution method, the perovskite precursor solution is a mixture of CsPbBr3 and CsPbI3, and the solution adopts one of dimethyl sulfoxide, dimethylformamide, isopropanol or a mixed solvent to prepare the perovskite light-emitting layer material CsPb (Br x I 1-x )3, where x is 0.4-0.8 and the thickness is 20nm-80nm.

4. The preparation method according to claim 2, wherein the quasi-two-dimensional structure is achieved by introducing an organic ligand PEA into the precursor solution, and by introducing an organic ligand PEABr having the same Br:I ratio x I 1-x , constructing PEA-CsPb(Br) with quasi-two-dimensional structure x I 1-x )3, wherein the organic ligand PEABr x I 1-x The volume ratio to the total solution volume is 0.1-0.

5.

5. The preparation method according to claim 2, wherein the LiF interface layer is prepared by at least one of magnetron sputtering, atomic layer deposition, thermal evaporation, electron beam evaporation, and molecular beam epitaxy, and has a thickness of 1-5 nm.

6. The preparation method according to claim 2, wherein the ITO is prepared by at least one of magnetron sputtering, thermal evaporation, and electron beam evaporation, and has a thickness of 70-150 nm.

7. The preparation method according to claim 2, wherein the hole transport layer PEDOT:PSS is prepared by a solution method and has a thickness of 20-60 nm.

8. The preparation method according to claim 2, wherein the electron transport layer TPBi is prepared by vacuum evaporation and has a thickness of 20-60 nm.

9. The preparation method according to claim 2, wherein the Al electrode is prepared by magnetron sputtering or thermal evaporation technology and has a thickness of 80-200 nm.

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