Deep red light perovskite light emitting diode device based on interface modification and preparation method thereof

Abstract

The invention discloses a deep red light perovskite light-emitting diode device based on interface modification and a preparation method, and relates to the technical field of light-emitting display, a perovskite light-emitting diode adopts an inversion structure, and comprises a glass substrate, a bottom electrode, an electron injection layer, an electron transport layer, a perovskite light-emitting layer, an interface modification layer, a hole transport layer and a top electrode from bottom to top in sequence; and the electron transmission layer is a zinc oxide film formed by spin-coating zinc hydroxide on the electron injection layer and then annealing and converting. The electron injection layer is spin-coated and annealed, and Zn (OH) 2 is converted into a thin film, so that a harmful interface deprotonation reaction between the electron transport layer and the perovskite layer is blocked, and the operation stability of the perovskite light-emitting diode is remarkably improved; and the interface modification layer is introduced, so that the potential barrier between the hole transport layer and the perovskite light-emitting layer is reduced, and a perovskite thin film with low defect density and good morphology can be formed.

Description

Technical Field

[0001] This invention belongs to the field of light-emitting display technology, specifically relating to a deep red perovskite light-emitting diode device based on interface modification and its fabrication method. Background Technology

[0002] With the rapid development of science and technology, display technology, as a crucial cornerstone of the information industry, is widely applied across various fields. Display technology, 5G, artificial intelligence, big data, and other next-generation information technologies are constantly evolving and converging, jointly presenting new development trends such as ultra-high definition, deep integration, intelligent interaction, and green environmental protection. Currently, light-emitting diodes (LEDs) are gradually gaining market dominance due to their low energy consumption, small size, and rich color reproduction. Among them, perovskite LEDs (PeLEDs) have attracted significant attention due to their high color purity, continuously tunable colors, solution-based fabrication, and low material costs. Deep red perovskite LEDs also demonstrate unique advantages in multiple application scenarios. They can bring significant technological breakthroughs in the field of medical imaging, as deep red light (approximately 655-703 nm) can effectively penetrate biological tissues, improving image quality and enhancing early disease diagnosis capabilities. Furthermore, deep red LEDs also demonstrate excellent color reproduction and energy efficiency in high-efficiency lighting and display devices, and are considered an important component of future display technology.

[0003] However, the performance of deep red perovskite light-emitting diodes (LEDs) is severely affected by deprotonation reactions and interface defects. Deprotonation reactions between the narrow-bandgap CsPbI3 thin film and the electron transport layer impair the long-term stability of perovskite LEDs. Furthermore, grain boundaries or interfaces of the thin film typically contain more defects. Defect states can trap transported charges, reducing carrier transport velocity, and may also lead to non-radiative recombination processes, which adversely affect the performance and efficiency of perovskite LEDs. While some existing technologies have shown some improvement, they still cannot effectively solve the problems of interface reactions and defects under specific conditions. This not only affects the efficiency and reliability of the device but also significantly increases manufacturing costs and operational complexity due to the high dependence on materials and manufacturing processes.

[0004] Therefore, improving the stability of deep red perovskite light-emitting diodes while balancing high efficiency and high brightness remains a challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a deep-red perovskite light-emitting diode (LED) device and its fabrication method based on interface modification, aiming to solve the problems of reduced carrier transport velocity, device stability, and energy conversion efficiency caused by deprotonation reactions and interface defects in perovskite LEDs. By controlling the deprotonation reaction at the interface between the perovskite emitting layer and the electron transport layer, and introducing an interface modification layer, the operational stability of the perovskite LED is improved, and the potential barrier between the hole transport layer and the perovskite emitting layer is reduced. This facilitates the formation of a perovskite thin film with low defect density and good morphology, thereby obtaining a deep-red perovskite LED with high stability and high brightness.

[0006] The technical solution of this invention is as follows: The deep red perovskite light-emitting diode (LED) device based on interface modification comprises, from bottom to top, an ITO glass substrate, a bottom electrode, an electron injection layer, an electron transport layer, a perovskite emitting layer, an interface modification layer, a hole transport layer, a hole injection layer, and a top electrode. The electron transport layer is formed by spin-coating Zn(OH)₂ onto the electron injection layer and then annealing it to convert it into a ZnO thin film. The interface modification layer material is one of aminoguanidine hydrochloride (AGH), choline iodide (CHI), or triphenylthiotrifluoromethanesulfonate (TPS). By spin-coating Zn(OH)₂ onto the electron injection layer and then annealing it to convert it into a ZnO thin film, the harmful interfacial deprotonation reaction between the electron transport layer and the perovskite layer is blocked, significantly improving the operational stability of the perovskite LED. Furthermore, the introduction of the interface modification layer reduces the potential barrier between the hole transport layer and the perovskite emitting layer, which is beneficial for forming a perovskite thin film with low defect density and good morphology.

[0007] Preferably, the substrate is glass, SiO2 / Si sheet, quartz sheet or polymer film.

[0008] Preferably, the bottom electrode is an ITO substrate with a sheet resistance of 30 Ω / m².

[0009] Preferably, the electron injection layer material is tin oxide (SnO2), and the electron injection layer solution is a SnO2 solution with a mass fraction of 3wt% after dilution with deionized water, and the thickness of the electron injection layer ranges from 50 to 150 nm.

[0010] Preferably, the electron transport layer is made of zinc hydroxide (Zn(OH)2), and the thickness of the electron transport layer is in the range of 10-50 nm.

[0011] Preferably, the perovskite luminescent layer is prepared from a mixed solution of guanidine iodide (GAI), cesium iodide (CsI), lead iodide (PbI2), and dimethyl sulfoxide (DMSO). The molar ratio of GAI, CsI, and PbI2 in the perovskite precursor solution is 0.8:1.2:1 to 1.0:1.6:1, the concentration of the perovskite precursor solution is 0.2 mmol / L, and the thickness of the perovskite luminescent layer ranges from 30 to 200 nm.

[0012] Preferably, the material of the interface modification layer is one of aminoguanidine hydrochloride (AGH), choline iodide (CHI), and triphenylthiotrifluoromethanesulfonate (TPS), and the post-treatment solution is one of AGH solution with a concentration of 2 mg / mL, CHI solution with a concentration of 2 mg / mL, and TPS solution with a concentration of 2 mg / mL. The thickness of the interface modification layer ranges from 500 nm to 1 µm.

[0013] Preferably, the hole transport layer is made of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), the hole transport layer solution is a TFB solution with a concentration of 15 mg / mL, and the thickness of the hole transport layer is in the range of 20-60 nm.

[0014] Preferably, the hole injection layer is made of MoO3 and has a thickness of 10 nm.

[0015] Preferably, the top electrode is made of gold (Au) or silver (Ag) and has a thickness of 100 nm.

[0016] This invention also discloses a method for fabricating a deep red perovskite light-emitting diode device based on interface modification, the process of which includes the following steps: Step 1: Clean and dry the ITO glass substrate with detergent, acetone, deionized water and isopropanol using ultrasonic cleaning. Then, treat the surface of the ultra-thin glass substrate with a UV ozone cleaner for 10-30 minutes. Step 2: Spin-coat the electron injection layer solution onto the substrate surface, and then perform thermal annealing. Step 3: Spin-coat the electron transport layer solution onto the electron injection layer, and then perform thermal annealing. Step 4: Spin-coat the perovskite precursor solution onto the electron transport layer, and then perform thermal annealing. Step 5: Spin-coat the post-treatment solution onto the perovskite luminescent layer; Step 6: Spin-coat the hole transport layer solution onto the interface modification layer; Step 7: In a vacuum of 1×10 -6MoO3 was deposited by vapor deposition under Torr conditions; Step 8: In a vacuum of 1×10 -6 Under Torr conditions, metal anodes are vapor-deposited; As a preferred technical solution, in step 2, the annealing temperature of the electron injection layer is 150°C and the time is 10 minutes.

[0017] As a preferred technical solution, in step 3, the electron transport layer annealing temperature is 60°C and the time is 10 minutes.

[0018] As a preferred technical solution, in step 4, the annealing temperature of the perovskite luminescent layer is 150°C and the annealing time is 8 minutes.

[0019] The advantages of this invention are: 1. To address the harmful deprotonation reaction between the perovskite luminescent layer and the electron transport layer, this study employs a strategy of introducing Zn(OH)₂ as the electron transport layer. During crystallization, alkaline Zn(OH)₂ initiates the interfacial deprotonation reaction, thereby forming a high-quality CsPbI₃ thin film. Simultaneously, after annealing, Zn(OH)₂ transforms into an alkaline ZnO thin film. This transformation helps to block the harmful interfacial deprotonation reaction between the perovskite luminescent layer and the electron transport layer, thus improving the performance and stability of the device.

[0020] 2. To address the issue of thin-film interface defects, this study introduced an interface modification layer between the perovskite light-emitting layer and the hole transport layer to enhance interface stability. In this process, we selected aminoguanidine hydrochloride (AGH) as the interface modification material. Through this modification, the performance of the perovskite LED device was significantly improved. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the proportional relationships of the various components in the accompanying drawings do not represent the actual proportional relationships in the material selection and design, but are merely schematic diagrams of the structure or position, wherein: Figure 1 This is a schematic diagram of the deep red perovskite light-emitting diode device based on interface modification according to the present invention; Figure 2 (a) is a SEM image of the perovskite thin film of the perovskite light-emitting diode device before interface treatment. Figure 2 (b) is a SEM image of the perovskite thin film of the perovskite light-emitting diode device after AGH modification, with the scale bar in the figure being 1µm.

[0022] Explanation of the labels in the attached drawings: 1-ITO glass substrate, 2-bottom electrode, 3-electron injection layer, 4-electron transport layer, 5-perovskite light-emitting layer, 6-interface modification layer, 7-hole transport layer, 8-hole injection layer, 9-top electrode. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments and accompanying drawings. 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 skilled in the art without creative effort are within the protection scope of the present invention.

[0024] Example 1 (Control Group): 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) on the surface of an ITO substrate, and the resulting film was subjected to thermal annealing treatment (150 °C, 10 min). 3. Spin-coat the perovskite precursor solution onto the electron-injected layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 4. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 5. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 6. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0025] Example 2: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Spin-coat AGH solution onto the perovskite luminescent layer (5000 rpm, 30 s), and then perform thermal annealing treatment on the resulting film (150 ℃, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0026] Example 3: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Spin-coat CHI solution onto the perovskite luminescent layer (5000 rpm, 30 s), and then perform thermal annealing treatment on the resulting film (150 ℃, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0027] Example 4: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Dilute TPS with CB (1:1) and spin-coat the TPS solution onto the perovskite luminescent layer (5000 rpm, 30 s). The resulting film is then subjected to thermal annealing (150 °C, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0028] Example 5: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Dilute TPS with CB (1:2), spin-coat the TPS solution onto the perovskite luminescent layer (5000 rpm, 30 s), and then perform thermal annealing on the resulting film (150 °C, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0029] Example 6: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Dilute TPS with CB (1:3) and spin-coat the TPS solution onto the perovskite luminescent layer (5000 rpm, 30 s). The resulting film is then subjected to thermal annealing (150 °C, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, metal anodes Au (25 nm) and Ag (75 nm) were vapor-deposited.

[0030] Example 7: 1. The ITO glass substrate was ultrasonically cleaned and dried using detergent, acetone, deionized water and isopropanol respectively. The ultra-thin glass substrate was then surface-treated with an ultraviolet ozone cleaner for 10-30 minutes. 2. An electron injection layer was prepared by spin-coating SnO2 solution (5000 rpm, 40 s) onto the surface of an ITO substrate, and the resulting film was subjected to thermal annealing (150 °C, 10 min). 3. An electron transport layer was prepared by spin-coating Zn(OH)2 solution onto the electron injection layer (4000 rpm, 40 s), and the resulting film was subjected to thermal annealing treatment (60℃, 10 min). 4. Spin-coat the perovskite precursor solution onto the electron transport layer (4000 rpm, 2 min), and then perform thermal annealing on the resulting film (150 °C, 8 min). 5. Dilute TPS with CB (1:4) and spin-coat the TPS solution onto the perovskite luminescent layer (5000 rpm, 30 s). The resulting film is then subjected to thermal annealing (150 °C, 8 min). 6. Spin-coat TFB solution onto the perovskite luminescent layer (4000 rpm, 30 s). 7. At a vacuum degree of 1×10 -6 MoO3 (10 nm) was deposited under Torr conditions. 8. At a vacuum degree of 1×10 -6 Under Torr conditions, vapor-deposited metal anodes Au (25 nm) and Ag (75 nm) were deposited. The test structures of the control group in Example 1 and the high-temperature resistant diffusion films in Examples 2-8 are shown in Table 1.

[0031] Table 1:

[0032] It can be seen that the deep red perovskite light-emitting diodes (LEDs) prepared through interface modification (i.e., Examples 2-7) exhibit significantly enhanced external quantum efficiency and irradiance compared to the untreated deep red perovskite LED (i.e., Example 1), with a slightly reduced turn-on voltage, resulting in a significant improvement in device performance. Furthermore, comparisons show that adding Zn(OH)₂ and AGH respectively optimizes the device interface modification, leading to the best performance. This is because the interface modification layer reduces the potential barrier between the hole transport layer and the perovskite light-emitting layer, resulting in a better match between the energy levels of electrons and holes; modifying the thin film surface reduces interface defects and irregularities (such as…). Figure 2 As shown in the figure, this enhances the injection efficiency of electrons and holes, thereby improving the photoelectric conversion efficiency.

[0033] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A deep red perovskite light-emitting diode device based on interface modification, characterized in that, From bottom to top, it includes a substrate, a bottom electrode, an electron injection layer, an electron transport layer, a perovskite light-emitting layer, an interface modification layer (6), a hole transport layer, a hole injection layer, and a top electrode.

2. The deep red perovskite light-emitting diode device based on interface modification according to claim 1, characterized in that, The substrate is glass, silicon dioxide / silicon wafer, quartz wafer or polymer film, the top electrode is made of gold (Au) or silver (Ag) and has a thickness of 100 nm, the bottom electrode is an ITO substrate with a sheet resistance of 30 Ω / m², and the electron injection layer is made of tin oxide (SnO2) with a thickness ranging from 50 to 150 nm.

3. The deep red perovskite light-emitting diode device based on interface modification according to claim 1, characterized in that, The electron transport layer is made of zinc hydroxide (Zn(OH)2), and its thickness ranges from 10 to 50 nm.

4. The deep red perovskite light-emitting diode device based on interface modification according to claim 1, characterized in that, The perovskite luminescent layer is prepared from a mixed solution of guanidine iodide (GAI), cesium iodide (CsI), lead iodide (PbI2), and dimethyl sulfoxide (DMSO). The molar ratio of GAI, CsI, and PbI2 in the perovskite precursor solution is 0.8:1.2:1 to 1.0:1.6:

1. The concentration of the perovskite precursor solution is 0.2 mmol / L. The thickness of the perovskite luminescent layer ranges from 30 to 200 nm.

5. The deep red perovskite light-emitting diode device based on interface modification according to claim 1, characterized in that, The interface modification layer is made of one of aminoguanidine hydrochloride (AGH), choline iodide (CHI), or triphenylsulfonyl trifluoromethane sulfonate (TPS), and the thickness of the interface modification layer ranges from 500 nm to 1 µm. The hole transport layer is made of poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)] (TFB), and the thickness of the hole transport layer ranges from 20 to 60 nm.

6. The deep red perovskite light-emitting diode device based on interface modification according to claim 1, characterized in that, The hole injection layer is made of transition metal oxides (MoO3, WO3). x NiO x It is one of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS), and the thickness of the hole injection layer ranges from 5 to 10 nm.

7. A method for fabricating a deep red perovskite light-emitting diode device based on interface modification, used to fabricate the deep red perovskite light-emitting diode device based on interface modification as described in any one of claims 1-6, characterized in that, The preparation process includes the following steps: Step 1: Clean and dry the ITO glass substrate with detergent, acetone, deionized water and isopropanol using ultrasonic cleaning. Then, treat the surface of the ultrathin glass substrate with a UV ozone cleaner for 10-30 minutes. Step 2: Spin-coat the electron injection layer solution onto the substrate surface, and then perform thermal annealing. Step 3: Spin-coat the electron transport layer solution onto the electron injection layer, and then perform thermal annealing. Step 4: Spin-coat the perovskite precursor solution onto the electron transport layer, and then perform thermal annealing. Step 5: Spin-coat the post-treatment solution onto the perovskite luminescent layer; Step 6: Spin-coat the hole transport layer onto the interface decoration layer; Step 7: MoO3 is deposited by vapor deposition under a vacuum of 1×10-6 Torr; Step 8: Deposit the metal anode under a vacuum of 1×10-6 Torr.

8. The deep red perovskite light-emitting diode device based on interface modification and its fabrication method according to claim 7, characterized in that, In step 2, the electron injection layer annealing temperature is 150°C and the time is 10 minutes.

9. A deep red perovskite light-emitting diode device based on interface modification and its fabrication method according to claim 7, characterized in that, In step 3, the electron transport layer is annealed at 60°C for 10 minutes.

10. A deep red perovskite light-emitting diode device based on interface modification and its fabrication method according to claim 7, characterized in that, In step 4, the annealing temperature of the perovskite luminescent layer is 150°C and the annealing time is 8 minutes.

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