Device beneficial to improving light extraction efficiency of laminated perovskite light-emitting device

Abstract

The invention discloses a device beneficial to improving the light extraction efficiency of a laminated perovskite light-emitting device. In the device, a perovskite thin film of at least one light-emitting unit is composed of discrete-structure perovskite crystal grains with a light scattering effect. Light emitted by a light-emitting unit of the device has a scattering effect after passing through the discrete perovskite thin film, so that wide-angle emission of light is increased, absorption of photons by perovskite crystal grains in each layer is enhanced, the photon circulation effect is further improved, and the light-emitting efficiency of the LED device is improved. Through the discrete perovskite thin film structure design, the probability that photons are absorbed by perovskite crystal grains and then emitted can be increased through light scattering, and therefore the performance of the laminated LED is improved.

Description

Technical Field

[0001] This invention belongs to the field of display technology and relates to a device and its preparation method that are beneficial to improving the light extraction efficiency of multilayer perovskite light-emitting devices. Background Technology

[0002] Light-emitting diodes (PeLEDs) based on metal halide perovskite materials have shown great application potential in next-generation lighting and display fields due to their high color purity, high fluorescence quantum yield, and low manufacturing cost. Multilayer perovskite light-emitting devices integrate two or more light-emitting units vertically through a charge-connecting layer, achieving higher brightness at lower currents. This is considered a crucial technological path to overcome the performance bottlenecks of single-junction devices and realize industrial applications.

[0003] Currently, research on stacked PeLEDs largely focuses on achieving energy level matching between the charge-connecting layer and each functional layer to ensure effective injection and recombination of charge carriers in each emitting unit. However, those skilled in the art are increasingly recognizing that while pursuing optimized electrical performance, internal optical management, particularly the "photon cycling" effect, plays a crucial role in improving the luminous efficiency of stacked structures. Photon cycling refers to the process by which photons generated in the emitting layer are reabsorbed and re-emitted during transmission. An efficient photon cycling process can significantly increase the probability of the final emitted photons escaping from the device, and is key to breaking through the theoretical limits of traditional light extraction efficiency.

[0004] In a stacked LED device, photons generated by one light-emitting unit may not only be reabsorbed by the light-emitting layer of that unit, but may also penetrate to adjacent light-emitting units and be reused. Therefore, effective internal optics management can activate the synergistic effect between multiple light-emitting units, achieving a luminous efficiency improvement of "1+1>2". However, existing stacked device structures typically use continuous, dense perovskite thin films, whose emitted photons are easily confined to waveguide modes or ultimately absorbed and dissipated by electrodes and functional layers, which is not conducive to achieving high light output efficiency in stacked LED devices. Summary of the Invention

[0005] To address the aforementioned problems, a device is proposed that improves the light extraction efficiency of multilayer perovskite light-emitting devices. By introducing a light-emitting layer with internal scattering effect, the limitation of photons being confined to waveguide modes in traditional multilayer devices is overcome, thereby greatly enhancing photon circulation and improving the device's light extraction efficiency. Another objective of this invention is to provide a method for fabricating the aforementioned device. This method has strong process compatibility and can achieve a highly efficient light-emitting device without complex precision optical design.

[0006] To achieve the above objectives, the present invention provides the following solution: A device that enhances the photon cycling effect of a multilayer perovskite light-emitting device is characterized in that: the device has at least two perovskite light-emitting units, wherein the perovskite thin film of at least one light-emitting unit is composed of discrete perovskite grains with light scattering properties.

[0007] The light emitted by all light-emitting units undergoes a scattering effect after passing through the discrete perovskite film, thereby increasing the wide-angle emission of light, enhancing the absorption of photons by each layer of perovskite grains, and thus improving the photon recycling effect and increasing the light extraction efficiency of the LED device. Furthermore, the morphology of this discrete perovskite film directly affects the morphology of the upper charge transport layer and electrodes, causing them to spontaneously form a wrinkled structure with varying heights and depths. This wrinkled structure also scatters light within and between the perovskite film layers, increasing the probability of photons being absorbed and re-emitted by the perovskite grains, further improving the light extraction efficiency of the LED.

[0008] Preferably, the perovskite grain size is between 10 nm and 3 mm.

[0009] Preferably, the thickness of the perovskite grains is between 5 nm and 500 nm.

[0010] Preferably, the distribution period of the perovskite grains ranges from 50 nm to 5 mm.

[0011] Preferably, the distribution period of the perovskite grains ranges from 200 nm to 2 mm.

[0012] Preferably, the average duty cycle of the perovskite grains ranges from 0.2 to 0.9.

[0013] Preferably, the emission spectrum of at least one perovskite light-emitting unit in the stacked device overlaps with the absorption spectrum of the perovskite thin film of one or more light-emitting units.

[0014] Preferably, the surface morphology of the perovskite thin film is obtained by one or more methods, such as introducing additives, controlling the surface energy of the substrate, or using a patterned substrate, during the preparation process.

[0015] Preferably, the selected additive is an alkylammonium salt and / or an organic molecule with a functional group, wherein the alkylammonium salt includes CH3NH3X, NH2CHNH2X; the functional group of the organic molecule includes one or more of -X, -NH2, -OH, -COOH, -CN, -NC, -SH, -PH2, -SCN, -CHO, -SO3H, and -CH(O)CH, and X is a halogen.

[0016] Preferably, the substrate surface energy can be controlled by polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), self-assembled monolayers (4PACz, F-4PACz, Br-4PACz, I-4PACz, Poly-4PACz), etc.

[0017] Preferably, the perovskite thin film material is A2B. N-1 M N X 3N+1 Or BMX3, where A is a long-chain organic cation with 1 to 50 C atoms, B is a monovalent cation, M is a divalent metal cation, X is any one or more of the halogen elements Cl, Br, I, and N is an integer from 1, 2, ..., ¥, representing the number of layers of the inorganic framework of the perovskite thin film material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention is beneficial to improving the light extraction efficiency of stacked perovskite light-emitting devices. By utilizing the strong scattering effect of discrete grains, loss photons that were originally trapped in the waveguide mode are "captured" and "re-introduced" into the light-emitting layer for reabsorption. This process greatly enhances the photon circulation process within and between layers, transforming ineffective optical losses into effective photon resources, thereby improving the light extraction efficiency of the device.

[0019] (2) This invention breaks the "simple superposition" limit of the performance of stacked devices, achieving a "synergistic multiplication" effect with strong process compatibility. The efficiency limit of existing stacked devices is usually the algebraic sum of the efficiencies of each light-emitting unit. This invention enhances the interlayer photon exchange and reuse through discrete structures, enabling photons generated by one unit to be effectively utilized and re-emitted by other units. This synergistic effect makes the final external quantum efficiency of the device exceed the sum of the efficiencies of each unit, achieving an efficiency multiplication of "1+1>2". In addition, this strategy does not require the introduction of complex external optical structures or harsh fabrication processes, has good compatibility with existing semiconductor device fabrication processes, is easy to integrate, and provides convenience for large-area production and commercial applications. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the perovskite light-emitting device based on the interlayer photon cycling effect of the present invention. Figure 2 The above are simulation diagrams of the electric field intensity (|E|²) and absorption of the stacked perovskite light-emitting device with a significantly discrete morphology in the second perovskite layer of this invention. Figure 3 The UV absorption-wavelength-photoluminescence diagrams of the first and second perovskite layer films in Embodiment 1 of the present invention are shown. Figure 4The images shown are scanning electron microscope (SEM) surface morphology images of the first and second perovskite layer films prepared in Example 1 of this invention. The scale bar is 1 mm. Figure 5 This is a grain period distribution diagram of the first and second perovskite layer films prepared in Example 1 of the present invention. Figure 6 This is a graph showing the variation of the periodic-light-emission coupling efficiency of the second perovskite layer thin film grains prepared in Example 1 of the present invention. Figure 7 The voltage-current density diagram of the device prepared in Example 1 of this invention. Figure 8 The voltage-radiance diagram of the device prepared in Example 1 of this invention. Figure 9 The current density-external quantum efficiency diagram of the device fabricated in Example 1 of this invention. Figure 10 This is a wavelength-normalized electroluminescence intensity diagram of the device prepared in Example 1 of the present invention. Figure 11 This is a scanning electron microscope image of the surface morphology of the second perovskite layer film prepared in Example 2 of the present invention. The scale bar is 1 mm. Figure 12 The voltage-current density diagram of the device prepared in Example 2 of this invention. Figure 13 The voltage-radiance diagram of the device prepared in Example 2 of this invention. Figure 14 The current density-external quantum efficiency diagram of the device fabricated in Example 2 of this invention. Figure 15 This is a wavelength-normalized electroluminescence intensity diagram of the device prepared in Example 2 of the present invention. Figure 16 This is a scanning electron microscope image of the surface morphology of the second perovskite layer film prepared in Example 3 of the present invention. The scale bar is 1 mm. Figure 17 The voltage-current density diagram of the device prepared in Example 3 of this invention. Figure 18 The voltage-radiance diagram of the device prepared in Example 3 of this invention. Figure 19 The current density-external quantum efficiency diagram of the device fabricated in Example 3 of this invention. Figure 20 This is a wavelength-normalized electroluminescence intensity diagram of the device prepared in Example 3 of the present invention. Figure 21 This is a scanning electron microscope image of the surface morphology of the second perovskite layer film prepared in Example 4 of the present invention. The scale bar is 1 mm. Figure 22 The voltage-current density diagram of the device prepared in Example 4 of this invention. Figure 23 The voltage-radiance diagram of the device prepared in Example 4 of this invention. Figure 24 The current density-external quantum efficiency diagram of the device fabricated in Example 4 of this invention. Figure 25 This is a wavelength-normalized electroluminescence intensity diagram of the device prepared in Example 4 of the present invention. Figure 26 The voltage-current density diagram of the device prepared in Comparative Example 1 of this invention. Figure 27 The voltage-radiance diagram of the device prepared in Comparative Example 1 of this invention. Figure 28 The diagram shows the current density versus external quantum efficiency of the device fabricated in Comparative Example 1 of this invention. Figure 29 This is a wavelength-normalized electroluminescence intensity diagram of the device prepared in Comparative Example 1 of this invention. Detailed Implementation

[0021] Preferred embodiments of the invention will now be described in more detail. It should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein.

[0022] Figure 1 The working principle of a stacked perovskite light-emitting device based on the enhanced photon cycling effect of discrete morphology is described. The device consists of a glass substrate, ITO, electrodes, a charge transport layer, and two perovskite thin films. The key feature is that both perovskite layers exhibit a discrete island-like grain structure with obvious voids.

[0023] The core advantage of this structure lies in the fact that the discrete grain morphology provides a large number of internal scattering interfaces, which greatly promotes photon exchange and synergistic reuse between the upper and lower light-emitting units. Specifically, when the bottom perovskite layer emits photons, some photons propagate upwards. If they reach the wrinkled metal electrode formed by the discrete grain structure, they will change the direction of propagation and be scattered back to the bottom perovskite layer in a smaller direction. Some of these "returned" photons are reabsorbed by the bottom perovskite material due to its high extinction coefficient, exciting it to emit new photons again. Conversely, photons emitted by the top discrete layer itself will also be scattered during propagation by the boundaries of the grains in this layer or by the wrinkled electrode, which increases the probability of them being reabsorbed by this layer. In addition, some photons propagating downwards and some photons scattered to the bottom perovskite layer by the top electrode can be absorbed by the bottom perovskite layer, thereby triggering the light emission process of the bottom light-emitting layer.

[0024] This interlayer photon reabsorption and re-emission process, mediated by scattering grains, constitutes a highly efficient photon recycling network, tightly coupling two originally optically independent light-emitting units into a synergistic organic whole. It transforms dissipated mode light into reusable photon resources, ultimately significantly improving the overall light extraction efficiency of the device by increasing photon recycling.

[0025] Figure 2 The electric field intensity (|E|²) and absorption simulation diagrams of a stacked perovskite LED with a significantly discrete morphology of the second perovskite layer are described, revealing the physical mechanism by which the photon cycling effect is enhanced in a stacked perovskite LED with discrete grains on top. Four sub-figures characterize the photoelectric behavior in TE and TM polarization modes, respectively.

[0026] Simulation results clearly show that the light field energy undergoes a significant change as it passes through the top discrete perovskite layer. The irregularly distributed grains in this layer create a strong refractive index contrast with the surrounding medium, acting as efficient internal scattering centers. This causes light waves that might otherwise be confined to a specific mode to be strongly scattered. The electric field intensity distribution map shows that the light field is no longer concentrated at a single point or interface, but exhibits a highly dispersed and homogeneous distribution, forming extensive field strength enhancement regions within and around multiple discrete grains. This redistribution of the light field caused by scattering directly translates into more efficient photon capture and utilization. Absorption maps confirm that the overall absorption efficiency of the perovskite layer for light field energy is significantly improved. The dispersion of light field energy greatly extends the effective propagation path of photons within the emitting layer, thereby significantly increasing the probability of their reabsorption by the perovskite material. This lays the foundation for the subsequent "reabsorption-re-emission" photon cycle process.

[0027] In summary, the simulation confirms from a physical perspective that the discrete grain structure at the top efficiently couples and disperses light energy to other areas of the device through effective internal scattering, promoting interlayer photon circulation and thus improving the device's light extraction efficiency. Example 1: A stacked perovskite light-emitting device based on highly discrete grains that are beneficial for improving photon cycling effect

[0028] The preparation method is as follows: 1) A ZnO layer of about 20 nm was prepared on a cleaned ITO substrate by spin coating as the first bottom transport layer, and then modified with a polyethoxyethyleneimine (PEIE) layer of about 2 nm thickness.

[0029] 2) A first perovskite layer approximately 30 nm thick was deposited on the prepared first bottom charge transport layer using a one-step spin-coating method. The perovskite layer was prepared as follows: a precursor solution was prepared by mixing NH₂C₄H₈COOH (5AVA), Zn(Ac)₂, NH₂CH=NH₂I (FAI), and PbI₂ in a molar ratio of 0.35:0.4:2.5:1. The precursor solution was spin-coated onto the first bottom charge transport layer, and the mixture was annealed at 105 °C for 15 minutes to obtain the perovskite film of the first luminescent layer. 5AVA and Zn(Ac)₂ were used as additives. The chemical interaction between the amino and carboxyl groups in 5AVA and the carboxyl groups in Zn(Ac)₂ with lead ions controlled the nucleation and crystal growth process of FAPbI₃, thereby controlling the surface morphology of the perovskite.

[0030] 3) A TFB layer with a thickness of about 60 nm was deposited by spin coating, and a TCTA layer with a thickness of about 30 nm was evaporated as the first top charge transport layer.

[0031] 4) MoO is deposited sequentially by thermal evaporation. x HATCN serves as the first and second charge generation layers, with thicknesses of 2.5 nm and 10 nm, respectively.

[0032] 5) Using atomic layer deposition, a SnO2 layer with a thickness of about 15 nm was grown on HATCN. A ZnO layer with a thickness of about 20 nm was prepared by spin coating as a second bottom charge transport layer, and then modified with a polyethoxyethyleneimine (PEIE) layer with a thickness of about 2 nm.

[0033] 6) A second perovskite layer approximately 40 nm thick was deposited on the prepared second bottom charge transport layer using a one-step spin-coating method. The perovskite layer was prepared as follows: a precursor solution was prepared by mixing C5H7IN2 (PyNI), NH2C4H8COOH (5AVA), NH2CH=NH2I (FAI), and PbI2 in a molar ratio of 0.25:0.25:2.4:1. The precursor solution was spin-coated onto the second bottom charge transport layer, and the mixture was annealed at 105 °C for 15 minutes to obtain the second perovskite film. 5AVA and PyNI are additives used to control the perovskite crystal quality and film surface morphology.

[0034] 7) TFB was deposited by spin coating as the second top charge transport layer with a thickness of about 60 nm.

[0035] 8) MoO is deposited sequentially by thermal evaporation. x Au and Au, with thicknesses of 4.5 nm and 100 nm respectively, were used as the second electrode.

[0036] Figure 3 The image shows the UV absorption-wavelength-photoluminescence diagrams of the first and second perovskite thin films. The photoluminescence wavelength of both films is 803 nm, and the UV absorption edge and photoluminescence peak position almost coincide, indicating that the Stokes shift of the two perovskite thin films is very small.

[0037] Figure 4 The images show the surface morphology of the first and second perovskite layers under a scanning electron microscope. It can be seen that the first luminescent layer perovskite film has a grain size of approximately 100–200 nm and a thickness of approximately 35 nm, with an average duty cycle of 0.9, indicating a relatively more continuous structure. The second luminescent layer perovskite film has a grain size of approximately 200–400 nm and a thickness of 40 nm, with an average duty cycle of 0.5, indicating a lower coverage and higher grain dispersion, which is beneficial for light scattering.

[0038] Figure 5 The image shows the grain period distribution of the first and second perovskite layers. It can be seen that the second luminescent layer perovskite film is more discrete, with its distribution period concentrated in the 600 nm-800 nm range.

[0039] Figure 6 The influence of photon cycling on light emission was considered for different periods of the second perovskite layer thin film grains. It can be seen that larger periods and more discrete grains have a positive effect on light emission, and photon cycling has a more significant effect on the light emission gain in larger periods. This indicates that enhanced scattering helps to improve the photon cycling of the multilayer perovskite LED device, thereby improving the light emission efficiency of the device.

[0040] Figure 7 The figure shows the voltage-current density of the fabricated device. As shown, although the current decreases due to the increased series resistance of the stacked device, the charge generation layer can effectively connect the two light-emitting units, realizing the series connection of the device.

[0041] Figure 8 The figure shows the voltage-radiance diagram of the fabricated device. As shown, the turn-on voltage of the multilayer device is 3.6V, and the maximum radiance is 147W Sr. -1 m -2 It has a higher radiance than single-junction devices.

[0042] Figure 9 The figure shows the current density versus external quantum efficiency of the fabricated device. As shown, the maximum external quantum efficiency of the stacked device is 49.3%, which is much higher than the sum of the external quantum efficiencies of the two single-layer light-emitting units.

[0043] Figure 10 The figure shows the wavelength-normalized electroluminescence intensity of the fabricated device. As shown, the emission peak of the monolayer emitting unit is 803 nm, while the emission peak of the stacked device is red-shifted to 806 nm. Example 2: Stacked perovskite light-emitting device based on high-dispersion grains that are beneficial for improving photon cycling effect

[0044] The device employs the same device structure and first perovskite layer as in Example 1. The second perovskite layer is modified as follows: a precursor solution is prepared by mixing C5H7IN2 (PyNI), NH2C4H8COOH (5AVA), NH2CH=NH2I (FAI), and PbI2 in a molar ratio of 0.25:0.25:2.2:1. The precursor solution is then spin-coated onto the second bottom charge transport layer, and the mixture is annealed at 105 °C for 15 minutes to obtain the second perovskite layer film. The types and functions of the additives are the same as in Example 1.

[0045] Figure 11 The image shows the surface morphology of the second perovskite layer film under a scanning electron microscope. It can be seen that the grain size of the second perovskite layer film is about 150~300 nm, the thickness is about 40 nm, the period range is between 400 nm and 700 nm, and the average duty cycle is 0.65, indicating a high degree of dispersion.

[0046] Figure 12 The figure shows the voltage-current density curve of the fabricated device. As shown, the current-voltage characteristic curve of the multilayer device is obvious, consistent with the characteristics of a classic light-emitting diode.

[0047] Figure 13 The figure shows the voltage-radiance diagram of the fabricated device. As shown, the turn-on voltage of the multilayer device is 3.2 V, and the maximum radiance is 304 W / sr. -1 m -2 .

[0048] Figure 14 The figure shows the current density-external quantum efficiency of the fabricated device. As shown, the maximum external quantum efficiency of the stacked device is 43.6%, which is higher than the sum of the external quantum efficiencies of the two single-layer light-emitting units, but the efficiency improvement is lower than that of the stacked perovskite light-emitting device with high discrete grains in Example 1.

[0049] Figure 15 The figure shows the wavelength-normalized electroluminescence intensity of the fabricated device. As shown, the emission peak of the monolayer emitting unit is 803 nm, while the emission peak of the stacked device is red-shifted to 805 nm. Example 3: Stacked perovskite light-emitting device based on medium-dispersion grains that are beneficial for improving photon cycling effect

[0050] The device adopts the same device structure and first perovskite layer as in Example 1. The second perovskite layer is adjusted as follows: C5H7IN2 (PyNI), NH2C4H8COOH (5AVA), NH2CH=NH2I (FAI) and PbI2 are prepared into a precursor solution in a molar ratio of 0.25:0.25:2.0:1. The precursor solution is spin-coated onto the second bottom charge transport layer and annealed at 105 °C for 15 minutes to obtain the perovskite film of the second perovskite layer.

[0051] Figure 16 The image shows the surface morphology of the second perovskite layer film under a scanning electron microscope. It can be seen that the grain size of the second luminescent layer perovskite film is about 150~250 nm, the thickness is about 40 nm, the period range is between 350 nm and 550 nm, and the average duty cycle is 0.75, which means that the dispersion is moderate.

[0052] Figure 17 The figure shows the voltage-current density diagram of the fabricated device. As shown, the charge generation layer can still effectively connect the two light-emitting units, realizing the series connection of the device.

[0053] Figure 18 The figure shows the voltage-radiance diagram of the fabricated device. As shown, the turn-on voltage of the multilayer device is 4.0 V, and the maximum radiance is 259 W / sr. -1 m -2 .

[0054] Figure 19 The figure shows the current density-external quantum efficiency of the fabricated device. As shown, the maximum external quantum efficiency of the stacked device is 41.5%, which is higher than the sum of the external quantum efficiencies of the two single-layer light-emitting units, but the efficiency improvement is lower than that of the stacked perovskite light-emitting device with higher grain dispersion in Example 2.

[0055] Figure 20 The figure shows the wavelength-electroluminescence intensity diagrams of the fabricated devices under different bias voltages. As shown in the figure, the emission peak of the single-layer emitting unit is 803 nm, while the emission peak of the stacked device is red-shifted to 805 nm. Example 4: Stacked perovskite light-emitting device based on lower discrete grain size, which is beneficial for improving photon cycling effect

[0056] The device employs the same device structure and first perovskite layer as in Example 1. The second perovskite layer is modified as follows: a precursor solution is prepared by mixing C5H7IN2 (PyNI), NH2C4H8COOH (5AVA), NH2CH=NH2I (FAI), and PbI2 in a molar ratio of 0.25:0.25:1.8:1. The precursor solution is then spin-coated onto the second bottom charge transport layer, and the mixture is annealed at 105 °C for 15 minutes to obtain the second perovskite layer film. The types and functions of the additives are the same as in Example 1.

[0057] Figure 21 The image shows the surface morphology of the second perovskite layer film under a scanning electron microscope. It can be seen that the grain size of the second luminescent layer perovskite film is about 150~300 nm, the thickness is about 40 nm, the period range is between 250 nm and 450 nm, and the average duty cycle is 0.85, which means that the dispersion is low.

[0058] Figure 22 The figure shows the voltage-current density diagram of the fabricated device. As shown, the two light-emitting units can still be connected in series even with the charge generation layer connected.

[0059] Figure 23 The figure shows the voltage-radiance diagram of the fabricated device. As shown, the turn-on voltage of the multilayer device is 4.0 V, and the maximum radiance is 308 W Sr. -1 m -2 .

[0060] Figure 24 The figure shows the current density-external quantum efficiency of the fabricated device. As shown, the maximum external quantum efficiency of the stacked device is 39.6%, which is higher than the sum of the external quantum efficiencies of the two single-layer light-emitting units, but the efficiency improvement is lower than that of the stacked perovskite light-emitting device with medium-dispersion grains.

[0061] Figure 25 The figure shows the wavelength-electroluminescence intensity diagrams of the fabricated device under different bias voltages. As shown in the figure, the emission peaks of the monolayer and stacked emitting units are almost identical, both at 803 nm. Comparative Example 1: Stacked perovskite light-emitting device based on extremely low dispersion, which is detrimental to improving photon cycling effect

[0062] The device employs the same device structure and first perovskite layer as in Example 1, and the second perovskite layer film is identical to the first perovskite layer. Specifically, a precursor solution is prepared by mixing NH2C4H8COOH (5AVA), Zn(Ac)2, NH2CH=NH2I (FAI), and PbI2 in a molar ratio of 0.35:0.4:2.5:1. This precursor solution is then spin-coated onto the second bottom charge transport layer, and annealed at 105 °C for 15 minutes to obtain the perovskite film of the second luminescent layer. The types and functions of the additives are the same as in Example 1.

[0063] Figure 26 The figure shows the voltage-current density plot of the fabricated device. As shown, consistent with previous results, the stacked device operates well under power-on conditions.

[0064] Figure 27 The figure shows the voltage-radiance diagram of the fabricated device. As shown, the turn-on voltage of the multilayer device is 3.6 V, and the maximum radiance is 215 W / s. -1 m -2 .

[0065] Figure 28 The diagram shows the current density versus external quantum efficiency of the fabricated device. In this structure, both thin films are relatively dense and flat with low dispersion. The photon cycling effect in the device does not effectively improve the light extraction efficiency of the stacked device. Therefore, the maximum external quantum efficiency of the stacked device is 32.1%, which is much lower than the sum of the external quantum efficiencies of the two single-layer light-emitting units.

[0066] Figure 29 The figure shows the wavelength-electroluminescence intensity diagrams of the fabricated device under different bias voltages. As shown in the figure, the emission peaks of the monolayer and stacked emitting units are almost identical, both at 803 nm.

[0067] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A device for improving light extraction efficiency of a stacked perovskite light-emitting device, characterized in that: The device has at least two perovskite light-emitting units, wherein the perovskite thin film of at least one light-emitting unit is composed of discrete perovskite grains with light scattering properties.

2. The perovskite light-emitting device of claim 1, wherein: The perovskite grain size is between 10 nm and 3 mm.

3. The perovskite light-emitting device of claim 1, wherein: The thickness of the perovskite grains is between 5 nm and 500 nm.

4. The perovskite light-emitting device of claim 1, wherein: The distribution period of the perovskite grains ranges from 50 nm to 5 mm.

5. The perovskite light-emitting device of claim 1, wherein: The distribution period of the perovskite grains ranges from 200 nm to 2 mm. 6.The perovskite light-emitting device of claim 1, wherein: The average duty cycle of the perovskite grains ranges from 0.2 to 0.

9.

7. The perovskite light-emitting device of claim 1, wherein: The perovskite thin film material is A2B. N- 1M N X 3N+1 Or BMX3, where A is a long-chain organic cation with 1 to 50 C atoms, B is a monovalent cation, M is a divalent metal cation, X is any one or more of the halogen elements Cl, Br, I, and N is an integer from 1, 2, ..., ¥, representing the number of layers of the inorganic framework of the perovskite thin film material.

8. The perovskite light-emitting device according to claim 1, characterized in that: The emission spectrum of at least one perovskite luminescent unit overlaps with the absorption spectrum of one or more perovskite thin films containing luminescent units.

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