Perovskite light-emitting device based on 4pacz interfacial layer by thermal evaporation and preparation method thereof

Abstract

The application belongs to the technical field of perovskite electroluminescent devices, and discloses a perovskite electroluminescent device based on a thermal evaporation 4PACz interface layer and a preparation method thereof. The device comprises, from bottom to top, a substrate, a bottom electrode, a 4PACz interface layer, a perovskite light-emitting layer, an electron transport layer and a top electrode. The 4PACz interface layer is located between the bottom electrode and the perovskite light-emitting layer and is formed by vacuum thermal evaporation deposition. The 4PACz interface layer is formed by vacuum thermal evaporation deposition between the bottom electrode and the perovskite light-emitting layer, so that the problems of difficult co-consideration of interface coverage and carrier transport on the bottom electrode side, insufficient compatibility of the solution method interface layer and the vacuum process and difficult continuous vacuum integration between different functional layers are solved.

Description

Technical Field

[0001] This invention belongs to the technical field of perovskite electroluminescent devices, and more specifically, relates to a perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer and its preparation method. Background Technology

[0002] Perovskite light-emitting diodes (PeLEDs) possess advantages such as high luminous efficiency, narrow emission half-width, and tunable emission color, making them promising candidates for applications in displays and lighting. In particular, green perovskite systems, due to their high luminous purity and device brightness, have become an important research focus for high-performance perovskite light-emitting devices.

[0003] For all-vacuum perovskite electroluminescent devices, the buried interface on the bottom electrode side has a significant impact on device performance. On the one hand, this interface affects hole injection, interface energy level matching, and local surface potential distribution; on the other hand, it serves as the basis for the subsequent growth of the evaporated perovskite light-emitting layer, influencing perovskite nucleation, crystallization, and interface defect formation. In existing technologies, organic hole transport materials such as TCTA (Chinese name: 4,4',4''-tris(carbazole-9-yl)triphenylamine; CAS number: 139092-78-7) are commonly used as hole transport layers, but there is still room for further optimization in terms of interface contact, injection balance, and buried interface control.

[0004] In recent years, carbazole-phosphonic acid interface materials such as 4PACz (Chinese name: (4-(9H-carbazole-9-yl)butyl)phosphonic acid; CAS number: 20999-36-4) have attracted attention due to their low interfacial loss and ability to form a stable interaction with oxide bottom electrodes. However, most existing 4PACz interface layers are constructed using solution methods, which have insufficient compatibility with all-vacuum thermal evaporation processes. Furthermore, solution-based 4PACz interface layers may be affected by solvent evaporation, wettability, and interface coverage uniformity during actual fabrication, thus hindering the continuous integration of subsequent evaporation-based light-emitting layers and improving device performance. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to provide a perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer and its fabrication method. The 4PACz interface layer is formed between the bottom electrode and the perovskite light-emitting layer by vacuum thermal evaporation deposition, which solves the problems of difficulty in balancing interface coverage and carrier transport on the bottom electrode side, insufficient compatibility between solution-based interface layers and vacuum processes, and difficulty in continuous vacuum integration between different functional layers.

[0006] To achieve the above objectives, according to one aspect of the present invention, a perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer is provided. The device comprises, from bottom to top, a substrate, a bottom electrode, a 4PACz interface layer, a perovskite luminescent layer, an electron transport layer, and a top electrode. The 4PACz interface layer is located between the bottom electrode and the perovskite luminescent layer and is formed by vacuum thermal evaporation deposition.

[0007] As a further preferred embodiment of the present invention, the thickness of the 4PACz interface layer is 2 nm to 10 nm.

[0008] As a further preferred embodiment of the present invention, the 4PACz interface layer is prepared under a vacuum degree not exceeding 5 × 10⁻⁶. -4 It was deposited under vacuum conditions and the evaporation rate was 0.10–0.15 Å / s.

[0009] As a further preferred embodiment of the present invention, the vacuum thermal evaporation deposition process of the 4PACz interface layer adopts a stepped heating method, including several set heating temperatures arranged from small to large, the absolute value of the temperature difference between two adjacent set heating temperatures does not exceed 20 °C, and each set heating temperature is held for at least 5 min after reaching each set heating temperature.

[0010] As a further preferred embodiment of the present invention, the substrate temperature is 25 °C during the vacuum thermal evaporation deposition process of the 4PACz interface layer.

[0011] As a further preferred embodiment of the present invention, the bottom electrode is an ITO transparent conductive electrode. The electron transport layer is made of organic electron transport material. The top electrode is a LiF-modified Al electrode.

[0012] As a further preferred embodiment of the present invention, the organic electron transport material is TPBi.

[0013] According to another aspect of the present invention, the present invention provides a method for fabricating the above-mentioned perovskite electroluminescent device, comprising the following steps: (1) The substrate with the bottom electrode is cleaned, dried and surface activated; (2) Under vacuum conditions, 4PACz is evaporated and deposited on the surface of the bottom electrode obtained in step (1) to form a 4PACz interface layer; (3) Under vacuum conditions, a perovskite luminescent layer is formed on the surface of the 4PACz interface layer by multi-source co-evaporation; (4) Under vacuum conditions, an electron transport layer is evaporated and deposited on the surface of the perovskite luminescent layer; (5) Under vacuum conditions, a top electrode is deposited by evaporation on the surface of the electron transport layer to obtain a perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer. In particular, steps (2) to (5) do not involve solution treatment.

[0014] As a further preferred embodiment of the present invention, steps (2) to (5) are performed continuously in the same preparation system; the preparation system includes a first vacuum deposition chamber and a second vacuum deposition chamber, which are connected by a vacuum transfer module; Step (3) is completed in the first vacuum deposition chamber; Steps (2), (4) and (5) are completed in the second vacuum deposition chamber, and steps (4) and (5) are completed consecutively in the second vacuum deposition chamber; Steps (2) through (5) are not exposed to air.

[0015] As a further preferred embodiment of the present invention, the vacuum transfer module is a vacuum connection cavity.

[0016] As a further preferred embodiment of the present invention, the perovskite light-emitting layer is FA. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer, correspondingly, step (3) specifically involves: under vacuum conditions, FABr, CsBr, PbBr2 and ligands containing phosphorus oxygen groups are used as discrete evaporation sources and deposited through multi-source co-evaporation at a nominal deposition rate ratio of 3:7:10:(0.5~5).

[0017] As a further preferred embodiment of the present invention, the thickness of the perovskite light-emitting layer is 20 nm; The ligand of the phosphoroyl group is TPPO; The ratio of nominal deposition rates was calibrated using a quartz crystal film thickness monitor.

[0018] As a further preferred embodiment of the present invention, in step (1), the cleaning includes ultrasonic cleaning of the substrate sequentially with deionized water, acetone and ethanol; the surface activation treatment is ultraviolet ozone treatment. In step (2), the 4PACz evaporation deposition is performed under a vacuum degree not exceeding 5 × 10⁻⁶. -4 The deposition was carried out under conditions of Pa, with an evaporation rate of 0.10~0.15 Å / s and a substrate temperature of 25~40 ℃ during the deposition process; In step (4), the electron transport layer is TPBi with a thickness of 20~60 nm; In step (5), the top electrode includes a LiF layer and an Al layer, wherein the thickness of the LiF layer is 0.5~2 nm and the thickness of the Al layer is 60~120 nm.

[0019] As a further preferred embodiment of the present invention, the thickness of the electron transport layer is 40 nm; the thickness of the LiF layer is 1 nm; and the thickness of the Al layer is 80 nm.

[0020] Compared with the prior art, the present invention constructs a 4PACz interface layer in situ on the surface of the bottom electrode through a vacuum thermal evaporation process, thereby improving the performance of the perovskite luminescent layer (e.g., FA). 0.3 Cs 0.7 By synergistically optimizing the PbBr3 perovskite luminescent layer, a high-brightness, low-roll-off electroluminescent device can be obtained. As illustrated in the embodiments below, this invention constructs a 4PACz interface layer in situ on the bottom electrode surface without introducing solution processing, and further co-evaporates it with FA formed from multiple sources. 0.3 Cs 0.7 PbBr3 perovskite light-emitting layers can be continuously deposited in vacuum, especially by using a full vacuum fabrication process, thus taking into account interface contact, device efficiency, efficiency roll-off, and integrated design.

[0021] This invention addresses the problem of insufficient rate stability during the vacuum evaporation of 4PACz by synergistically controlling the heating process, evaporation rate, interface layer thickness, and continuous vacuum integration method of the 4PACz evaporation source. In this way, a 4PACz interface layer is formed between the bottom electrode and the perovskite light-emitting layer through vacuum thermal evaporation deposition, which can effectively solve the problems of difficulty in balancing interface coverage and carrier transport on the bottom electrode side, insufficient compatibility between solution-based interface layers and vacuum processes, and difficulty in continuous vacuum integration between different functional layers.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses vacuum thermal evaporation to construct a 4PACz interface layer in situ on the surface of the bottom electrode, avoiding the influence of solvent introduction, wettability and solution treatment on interface formation in the traditional solution-based 4PACz preparation process. This is beneficial to improving the coverage uniformity of the 4PACz interface layer and enhancing its compatibility with subsequent vacuum deposition processes.

[0023] Vacuum thermal evaporation technology is a key technology for achieving integrated light-emitting devices and display chips. However, converting 4PACz from the traditional solution-based interface modification method to vacuum thermal evaporation is not a simple process replacement. Solution-based film formation of 4PACz mainly relies on the adsorption, anchoring, and self-assembly of molecules on the oxide electrode surface, while vacuum thermal evaporation involves material heating, vaporization, transport, condensation, and interface alignment, resulting in significantly different film formation mechanisms and process conditions. Compared to conventional vaporizable organic hole-transporting materials, 4PACz lacks a directly applicable stable evaporation process window; the heating method and evaporation rate of the evaporation source directly affect the uniformity and repeatability of the resulting interface layer. Furthermore, the thickness of the 4PACz interface layer must simultaneously consider the coverage of the bottom electrode surface, leakage suppression, hole transport, and the subsequent nucleation and growth of the perovskite layer. An excessively thin interface layer may lead to insufficient local coverage of the bottom electrode, while an excessively thick interface layer may increase carrier transport resistance. Therefore, the interface conditions applicable to traditional solution-based SAM cannot be directly used to determine the 4PACz thermal evaporation conditions in all-vacuum perovskite electroluminescent devices. Meanwhile, all-vacuum devices also require the continuous integration of the 4PACz interface layer, perovskite light-emitting layer, electron transport layer, and top electrode under different material evaporation conditions, while minimizing the exposure of the interface to air during interlayer transfer. Therefore, how to balance stable 4PACz evaporation, interface layer thickness control, subsequent perovskite film formation, and continuous vacuum integration of multifunctional layers are key technical challenges that need to be addressed to realize this type of all-vacuum perovskite electroluminescent device.

[0024] 2. This invention addresses the vacuum evaporation characteristics of 4PACz material by employing a controlled heating and low-speed stable deposition method to form the 4PACz interface layer. This helps reduce rate fluctuations during evaporation and improves the stability and controllability of the 4PACz deposition process. Simultaneously, by adjusting the thickness of the 4PACz interface layer, a better balance is achieved between bottom electrode surface coverage, leakage current suppression, and hole transport.

[0025] 3. The 4PACz interface layer in this invention is located between the bottom electrode and the perovskite light-emitting layer. It can not only adjust the carrier injection interface on the bottom electrode side, but also serve as the growth interface for the subsequent vacuum co-evaporation of the perovskite light-emitting layer. Compared with solution-based 4PACz interface layers and traditional TCTA hole transport layers, thermally evaporated 4PACz interface layers can improve the surface morphology and light emission uniformity of perovskite films, and are beneficial to reducing device leakage current.

[0026] 4. This invention integrates the vacuum deposition process of the 4PACz interface layer, the perovskite light-emitting layer, the electron transport layer and the top electrode continuously. From the beginning of the deposition of the 4PACz interface layer to the end of the deposition of the top electrode, no solution treatment is required, and the functional layers are not exposed to air. This reduces the influence of moisture, oxygen and external pollution on the interlayer interface, and improves the continuity of the device fabrication process, the cleanliness of the interface and the degree of process integration.

[0027] 5. This invention achieves higher device brightness and external quantum efficiency by synergistically controlling the 4PACz interface layer deposition process, interface layer thickness, and subsequent perovskite light-emitting layer vacuum deposition process. This reduces leakage current while improving carrier injection and recombination balance, thereby enhancing efficiency retention under high-brightness operating conditions. Example results show that, compared with solution-based 4PACz interface layer devices and devices using TCTA hole transport layers, the device of this invention exhibits superior overall performance in terms of peak brightness, external quantum efficiency, and efficiency retention under high-brightness conditions. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the perovskite electroluminescent device according to an embodiment of the present invention. The " / " in the diagram indicates a stacked structure; for example, LiF / Al represents a stacked structure of a LiF thin film and an Al film.

[0029] Figure 2 This is a schematic diagram of the all-vacuum thermal evaporation perovskite device fabrication system used in the embodiments of the present invention. The arrangement of the functional cavities is only for illustrating the system configuration and does not limit the actual deposition sequence. Figure 2 HTL in the text corresponds to the deposited 4PACz material.

[0030] Figure 3 The images show the surface morphology of the 4PACz interface layer prepared by different processes in Example 1 and Comparative Example 1; wherein, Figure 3 In this context, 'a' corresponds to Example 1. Figure 3 The ratio of b to the corresponding ratio is 1.

[0031] Figure 4 The images show the fluorescence of the perovskite luminescent layer in Example 1 and Comparative Example 1; wherein, Figure 4 In this context, 'a' corresponds to Example 1. Figure 4 The ratio of b to the corresponding ratio is 1.

[0032] Figure 5 The images show the surface morphology and fluorescence of perovskite samples at different interfaces in Example 1 and Comparative Example 2; among them, Figure 5 a and c in the text correspond to Example 1. Figure 5 The ratio of b and d in the equation is 2.

[0033] Figure 6This is a comparison chart of the voltage-current density, voltage-luminance, voltage-external quantum efficiency, and luminance-external quantum efficiency curves of the devices in Embodiments 1, 2, and 3 of this invention; wherein, Figure 6 In the figure, 'a' corresponds to the voltage-current density curve. Figure 6 In the figure, b corresponds to the voltage-brightness curve. Figure 6 In the figure, 'c' corresponds to the voltage-external quantum efficiency curve. Figure 6 In the figure, d corresponds to the efficiency roll-off; and the legend “4PACz-6 nm” corresponds to the device of Example 1, the legend “4PACz-2 nm” corresponds to the device of Example 2, and the legend “4PACz-10 nm” corresponds to the device of Example 3.

[0034] Figure 7 This is a comparison chart of the voltage-current density, voltage-luminosity, and voltage-external quantum efficiency curves of the devices in Embodiments 1 and 4 of the present invention; wherein, Figure 7 In the figure, 'a' corresponds to the voltage-current density curve. Figure 7 In the figure, b corresponds to the voltage-brightness curve. Figure 7 In the figure, 'c' corresponds to the voltage-external quantum efficiency curve; and the legend "6 nm (0.10 Å / s)" corresponds to the device in Example 1, and the legend "6 nm (0.15 Å / s)" corresponds to the device in Example 4.

[0035] Figure 8 This is a comparison chart of the voltage-current density, voltage-luminance, voltage-external quantum efficiency, and luminance-external quantum efficiency curves of the devices in Embodiment 1 and Comparative Example 1 of the present invention; wherein, Figure 8 In the figure, 'a' corresponds to the voltage-current density curve. Figure 8 In the figure, b corresponds to the voltage-brightness curve. Figure 8 In the figure, 'c' corresponds to the voltage-external quantum efficiency curve. Figure 8 In the figure, d corresponds to the efficiency roll-off; and the legend “4PACz (vacuum method)” corresponds to the device in Example 1, and the legend “4PACz (solution method)” corresponds to the device in Example 1.

[0036] Figure 9 This is a comparison chart of the voltage-current density, voltage-luminance, voltage-external quantum efficiency, and luminance-external quantum efficiency curves of the devices in Embodiment 1 and Comparative Example 2 of the present invention; wherein, Figure 9 In the figure, 'a' corresponds to the voltage-current density curve. Figure 9 In the figure, b corresponds to the voltage-brightness curve. Figure 9 In the figure, 'c' corresponds to the voltage-external quantum efficiency curve. Figure 9 In the figure, d corresponds to the efficiency roll-off; and the legend “4PACz” corresponds to the device in Example 1, and the legend “TCTA” corresponds to the device in Example 2. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] FA in the following examples 0.3 Cs 0.7 PbBr3 perovskite electroluminescent devices, such as Figure 1 As shown, it includes: a top electrode, an electron transport layer, a light-emitting layer, a hole transport layer, and a bottom electrode; wherein, The top electrode material can be a LiF-modified Al electrode; the top electrode can also be other electrode materials commonly used in the art. The material of the luminescent layer is formed by co-evaporation of FABr, CsBr, PbBr2 and TPPO ligands. 0.3 Cs 0.7 PbBr3 luminescent system; Both the electron transport layer and the hole transport layer are used to localize electrons or holes in the light-emitting layer and to regulate the injection balance of electrons and holes. The bottom electrode is an ITO electrode, which can be an ITO substrate obtained by etching; the bottom electrode can also be other transparent conductive substrates commonly used in the art.

[0039] The deposition method of the luminescent layer described below adopts a multi-source co-evaporation approach, using FABr, CsBr, PbBr2 and TPPO ligands as discrete evaporation sources, respectively, to obtain the target material through in-situ synthesis reaction on the substrate.

[0040] The thermal evaporation deposition of the perovskite luminescent layer is carried out in the Shenyang Qihui Organic Evaporation Vacuum System. In this invention, the substrate temperature is 0 degrees Celsius during multi-source co-evaporation of the perovskite luminescent layer; depending on the actual situation, the substrate temperature can also be controlled within the range of -10℃ to 50℃ (thereby controlling the crystallization rate and grain size of the perovskite luminescent layer), as long as FABr, CsBr, PbBr2 and ligands can be successfully co-evaporated.

[0041] Furthermore, the 4PACz material used in the following examples was purchased from Biolight.

[0042] The thermal evaporation deposition of the 4PACz interface layer was carried out in the Shenyang Qihui Organic Evaporation Vacuum System. Specifically, the 4PACz material was placed in an organic evaporation source, and the vacuum level was no higher than 5 × 10⁻⁶. -4Heating and evaporation were performed under Pa conditions. The 4PACz evaporation source temperature was first increased in a stepped manner, with each increase being 20 °C. After reaching the set temperature, the temperature was held for 5 minutes until it reached 80 °C, which was close to the evaporation temperature of the 4PACz material. Subsequently, the evaporation source temperature was slowly increased to allow the evaporation rate of 4PACz to gradually increase and stabilize. Once the evaporation rate stabilized at 0.10–0.15 Å / s, preferably 0.10 Å / s, the baffle was opened to allow 4PACz to deposit on the bottom electrode surface, forming a 4PACz interface layer. During deposition, the substrate temperature was 25 °C, but could be adjusted within the range of 25–40 °C depending on the actual situation. The evaporation rate (or deposition rate) of the thermal evaporation deposition process in the following examples and comparative examples was calibrated using a quartz crystal film thickness monitor.

[0043] Steps 2 to 5 in the various embodiments described below are all performed in the Shenyang Qihui Organic Evaporation Vacuum System, such as... Figure 2 As shown, the system includes a first vacuum deposition chamber and a second vacuum deposition chamber. The first vacuum deposition chamber is a dedicated vacuum chamber for perovskite deposits, and the second vacuum deposition chamber is an organic / inorganic vacuum evaporation chamber. Both vacuum deposition chambers are conventional thermal evaporation equipment. Notably, the first and second vacuum deposition chambers are connected via a vacuum transfer module (e.g., a vacuum connection chamber). Step 3 is completed in the first vacuum deposition chamber; steps 2, 4, and 5 are completed in the second vacuum deposition chamber, and steps 4 and 5 are completed consecutively within the second vacuum deposition chamber; steps 2 to 5 are not exposed to air.

[0044] The following are specific examples: Example 1 In this embodiment, a thermally evaporated 4PACz interface layer is used as the hole transport layer and FA is used as the light-emitting layer material. 0.3 Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0045] 2. Deposition of the 4PACz interface layer: The pretreated substrate was transferred into a vacuum evaporation system, with a vacuum level not exceeding 5 × 10⁻⁶. -4 4PACz was deposited by evaporation under Pa conditions. The evaporation rate was 0.10 Å / s, the substrate temperature was 25 °C, and the deposition thickness was 6 nm, forming a 4PACz interface layer on the ITO surface.

[0046] 3. FA 0.3 Cs0.7 Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively, at a substrate temperature of 0 °C. FABr was formed on the surface of the 4PACz interface layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0047] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0048] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0049] From step 2 to step 5, the samples were not treated with solutions and were not exposed to air.

[0050] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 6 When the 4PACz interface layer thickness is 6 nm, the resulting device has a turn-on voltage of 2.38 V and a peak luminance of 227,865 cd / m². 2 The peak external quantum efficiency is 16.85%; the highest luminance is 227,865 cd / m². 2 At this point, the external quantum efficiency is 11.95%, maintaining 70.92% of the peak external quantum efficiency. The device exhibits a superior overall balance between current density, brightness, external quantum efficiency, and efficiency roll-off. Furthermore, due to... Figure 6 It can be seen that within the voltage range of [0V, 2V], when the device is not yet turned on, the leakage current density of the device is 10. -4 ~10 -3 mA cm -2 The magnitude is small, and the leakage current is low.

[0051] Example 2 In this embodiment, a thermally evaporated 4PACz interface layer is used as the hole transport layer and FA is used as the light-emitting layer material. 0.3Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0052] 2. Deposition of the 4PACz interface layer: The pretreated substrate was transferred into a vacuum evaporation system, with a vacuum level not exceeding 5 × 10⁻⁶. -4 4PACz was deposited by evaporation under Pa conditions. The evaporation rate was 0.10 Å / s, the substrate temperature was 25 °C, and the deposition thickness was 2 nm, forming a 4PACz interface layer on the ITO surface.

[0053] 3. FA 0.3 Cs 0.7 Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively, at a substrate temperature of 0 °C. FABr was formed on the surface of the 4PACz interface layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0054] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0055] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0056] From step 2 to step 5, the samples were not treated with solutions and were not exposed to air.

[0057] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 6When the thickness of the 4PACz interface layer is 2 nm, the device current density and brightness are high, but the efficiency is slightly lower than that of Example 1.

[0058] Example 3 In this embodiment, a thermally evaporated 4PACz interface layer is used as the hole transport layer and FA is used as the light-emitting layer material. 0.3 Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0059] 2. Deposition of the 4PACz interface layer: The pretreated substrate was transferred into a vacuum evaporation system, with a vacuum level not exceeding 5 × 10⁻⁶. -4 4PACz was deposited by evaporation under Pa conditions. The evaporation rate was 0.10 Å / s, the substrate temperature was 25 °C, and the deposition thickness was 10 nm, forming a 4PACz interface layer on the ITO surface.

[0060] 3. FA 0.3 Cs 0.7 Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively, at a substrate temperature of 0 °C. FABr was formed on the surface of the 4PACz interface layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0061] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0062] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0063] From step 2 to step 5, the samples were not treated with solutions and were not exposed to air.

[0064] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 6 When the 4PACz interface layer thickness is 10 nm, the maximum brightness and highest efficiency of the device are slightly lower than those of Example 1, but it has a very low leakage current (similar to the device obtained in Example 1, at voltages of [0V, 2V], when the device is not yet turned on, the leakage current density is 10). -4 ~10 -3 mA cm -2 (Small magnitude, low leakage current) and better efficiency roll-off.

[0065] Example 4 In this embodiment, a thermally evaporated 4PACz interface layer is used as the hole transport layer and FA is used as the light-emitting layer material. 0.3 Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0066] 2. Deposition of the 4PACz interface layer: The pretreated substrate was transferred into a vacuum evaporation system, with a vacuum level not exceeding 5 × 10⁻⁶. -4 4PACz was deposited by evaporation under Pa conditions. The evaporation rate was 0.15 Å / s, the substrate temperature was 25 °C, and the deposition thickness was 6 nm, forming a 4PACz interface layer on the ITO surface.

[0067] 3. FA 0.3 Cs 0.7 Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively, at a substrate temperature of 0 °C. FABr was formed on the surface of the 4PACz interface layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0068] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0069] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0070] From step 2 to step 5, the samples were not treated with solutions and were not exposed to air.

[0071] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 7 It is easy to see that, compared with Example 1, which uses an evaporation rate of 0.10 Å / s for thermal evaporation deposition of 4PACz, this example uses an evaporation rate of 0.15 Å / s for thermal evaporation deposition of 4PACz. When the deposition thickness of 4PACz is 6 nm, there is no significant difference in the current density, brightness and efficiency of the device.

[0072] Comparative Example 1 In this comparative example, a 4PACz interface layer was prepared using a solution method, with FA as the hole transport layer and the light-emitting layer material being FA. 0.3 Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0073] 2. Preparation of the solution-based 4PACz interface layer: 4PACz was dissolved in methanol to prepare a 4PACz solution with a concentration of 0.3 mg / mL. The pretreated ITO glass substrate was immersed in the 4PACz solution for 10 min, then removed, dried, and annealed at 100 °C for 10 min to form a solution-based 4PACz interface layer on the ITO surface. The thickness of the 4PACz interface layer was 2 nm.

[0074] 3. FA 0.3 Cs 0.7Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively, at a substrate temperature of 0 °C. FABr was formed on the surface of the 4PACz interface layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0075] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0076] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0077] From step 3 to step 5, the samples were not treated with solutions and were not exposed to air.

[0078] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 8 Compared to Example 1, the device in Comparative Example 1 has a turn-on voltage of 2.43 V and a peak luminance of 93,097 cd / m². 2 The peak external quantum efficiency is 5.20%; and, at a voltage of [0V, 2V], before the device is turned on, the leakage current density is 10. -3 ~10 -2 mA cm -2 The leakage current of Example 1 is significantly reduced compared to Comparative Example 1. The peak luminance of the device in Example 1 is increased by 144.76%, and the peak external quantum efficiency is increased by 224.04%.

[0079] Additionally, it should be noted that Comparative Example 1 is the example with the highest external quantum efficiency among devices obtained by preparing 4PACz interface layers using the solution method (by adjusting the concentration of the 4PACz solution in step 2 to 0.1 mg / mL and 0.5 mg / mL, and the soaking time to 10 min, we obtained 4PACz interface layers with thicknesses of 1 nm and 4 nm after annealing in step 2, respectively. The peak external quantum efficiencies of the corresponding devices were 2.59% and 4.41%, respectively, both lower than those of the device in Comparative Example 1).

[0080] Comparative Example 2 This comparative example uses thermally evaporated TCTA as the hole transport layer (TCTA, purchased from Biolight) and FA as the light-emitting layer material. 0.3 Cs 0.7 Taking the electroluminescent device based on the PbBr3 luminescent material system as an example, its specific preparation method includes the following steps: 1. Substrate pretreatment: The patterned ITO glass substrate was ultrasonically cleaned sequentially in deionized water, acetone and ethanol for 15 min each step; after cleaning, it was dried and then surface activated with ultraviolet ozone for 15 min.

[0081] 2. Deposition of TCTA hole transport layer: The pretreated substrate is transferred into a vacuum evaporation system, with a vacuum level not exceeding 5 × 10⁻⁶. -4 TCTA was deposited by evaporation under Pa conditions. The evaporation rate was 0.10 Å / s, the substrate temperature was 25 °C, and the deposition thickness was 40 nm, forming a TCTA hole transport layer on the ITO surface.

[0082] 3. FA 0.3 Cs 0.7 Preparation of the PbBr3 luminescent layer: Using the sample obtained in step 2 as a substrate, FABr, CsBr, PbBr2 and TPPO ligands were evaporated separately under vacuum conditions using a multi-source co-evaporation process, with a vacuum level not exceeding 1×10⁻⁶. -4 The evaporation rates of Pa, FABr, CsBr, PbBr2, and TPPO ligands were 0.03 Å / s, 0.07 Å / s, 0.10 Å / s, and 0.05 Å / s, respectively. The substrate temperature was 0 °C. FA ligands were formed on the surface of the TCTA hole transport layer. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer has a thickness of 20 nm.

[0083] 4. Fabrication of the electron transport layer: A TPBi electron transport layer with a thickness of 40 nm is further deposited by evaporation on the surface of the luminescent layer. During the evaporation deposition process, the vacuum level does not exceed 5 × 10⁻⁶. -4 Pa, evaporation rate of 0.50 Å / s, substrate temperature of 25 ℃.

[0084] 5. Fabrication of the top electrode: After changing the mask template, a LiF layer is first deposited by evaporation, followed by an Al layer to form a LiF / Al top electrode. The LiF thickness is 1 nm, and the Al thickness is 80 nm.

[0085] From step 2 to step 5, the samples were not treated with solutions and were not exposed to air.

[0086] The performance test results of the obtained device are as follows: The device is capable of achieving normal electroluminescence. According to... Figure 9 Compared to Example 1, the device in Comparative Example 2 has a turn-on voltage of 2.54 V and a peak luminance of 69,890 cd / m². 2 The peak external quantum efficiency was 15.08%. Compared with Comparative Example 2, the peak luminance of the device in Example 1 was increased by 226%, and the peak external quantum efficiency was increased by 11.7%. In addition, the efficiency retention rate of Comparative Example 2 under the highest luminance condition was 50.46%, which was lower than the 70.92% of the device in Example 1.

[0087] Additionally, it should be noted that Comparative Example 2 is the example with the highest external quantum efficiency among devices obtained by evaporating and depositing TCTA as a hole transport layer (we also obtained perovskite electroluminescent devices with TCTA thicknesses of 20 nm and 80 nm by adjusting only the deposition time in step 2, respectively. The peak external quantum efficiencies of the corresponding devices were 10.36% and 8.59%, respectively, both of which were lower than the device with a TCTA thickness of 40 nm obtained in Comparative Example 2).

[0088] The above embodiments are merely examples. For instance, in addition to using TPPO as a discrete evaporation source to participate in FA... 0.3 Cs 0.7 In addition to multi-source co-evaporation deposition of PbBr3 perovskite, other ligands containing phosphorus oxygen groups can also be used.

[0089] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer, characterized in that, The device comprises, from bottom to top, a substrate, a bottom electrode, a 4PACz interface layer, a perovskite light-emitting layer, an electron transport layer, and a top electrode; wherein, the 4PACz interface layer is located between the bottom electrode and the perovskite light-emitting layer, and is formed by vacuum thermal evaporation deposition.

2. The perovskite electroluminescent device as described in claim 1, characterized in that, The thickness of the 4PACz interface layer is 2 nm to 10 nm.

3. The perovskite electroluminescent device as described in claim 1, characterized in that, The 4PACz interface layer is applied at a vacuum level not exceeding 5 × 10⁻⁶. -4 It was deposited under vacuum conditions and the evaporation rate was 0.10–0.15 Å / s.

4. The perovskite electroluminescent device as described in claim 1, characterized in that, The vacuum thermal evaporation deposition process of the 4PACz interface layer adopts a stepped heating method, which includes several set heating temperatures arranged from small to large. The absolute value of the temperature difference between two adjacent set heating temperatures does not exceed 20 °C, and each set heating temperature is held for at least 5 minutes after reaching each set heating temperature.

5. The perovskite electroluminescent device as described in claim 1, characterized in that, During the vacuum thermal evaporation deposition process of the 4PACz interface layer, the substrate temperature is 25 °C.

6. The perovskite electroluminescent device as described in claim 1, characterized in that, The bottom electrode is an ITO transparent conductive electrode. The electron transport layer is made of organic electron transport material. The top electrode is a LiF-modified Al electrode.

7. The perovskite electroluminescent device as described in claim 6, characterized in that, The organic electron transport material is TPBi.

8. The method for fabricating the perovskite electroluminescent device according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The substrate with the bottom electrode is cleaned, dried and surface activated; (2) Under vacuum conditions, 4PACz is evaporated and deposited on the surface of the bottom electrode obtained in step (1) to form a 4PACz interface layer; (3) Under vacuum conditions, a perovskite luminescent layer is formed on the surface of the 4PACz interface layer by multi-source co-evaporation; (4) Under vacuum conditions, an electron transport layer is evaporated and deposited on the surface of the perovskite luminescent layer; (5) Under vacuum conditions, a top electrode is deposited by evaporation on the surface of the electron transport layer to obtain a perovskite electroluminescent device based on a thermally evaporated 4PACz interface layer. In particular, steps (2) to (5) do not involve solution treatment.

9. The preparation method according to claim 8, characterized in that, Steps (2) to (5) are completed consecutively in the same preparation system; the preparation system includes a first vacuum deposition chamber and a second vacuum deposition chamber, which are connected by a vacuum transfer module; Step (3) is completed in the first vacuum deposition chamber; Steps (2), (4) and (5) are completed in the second vacuum deposition chamber, and steps (4) and (5) are completed consecutively in the second vacuum deposition chamber; Steps (2) through (5) are not exposed to air.

10. The preparation method according to claim 9, characterized in that, The vacuum transfer module is a vacuum connection cavity.

11. The preparation method according to claim 8, characterized in that, The perovskite light-emitting layer is FA. 0.3 Cs 0.7 The PbBr3 perovskite luminescent layer, correspondingly, step (3) specifically involves: under vacuum conditions, FABr, CsBr, PbBr2 and ligands containing phosphorus oxygen groups are used as discrete evaporation sources and deposited through multi-source co-evaporation at a nominal deposition rate ratio of 3:7:10:(0.5~5).

12. The preparation method according to claim 11, characterized in that, The thickness of the perovskite luminescent layer is 20 nm; The ligand of the phosphoroyl group is TPPO; The ratio of nominal deposition rates was calibrated using a quartz crystal film thickness monitor.

13. The preparation method according to claim 8, characterized in that, In step (1), the cleaning includes ultrasonic cleaning of the substrate sequentially with deionized water, acetone and ethanol; the surface activation treatment is ultraviolet ozone treatment. In step (2), the 4PACz evaporation deposition is performed under a vacuum degree not exceeding 5 × 10⁻⁶. -4 The deposition was carried out under conditions of Pa, with an evaporation rate of 0.10~0.15 Å / s and a substrate temperature of 25~40 ℃ during the deposition process; In step (4), the electron transport layer is TPBi with a thickness of 20~60 nm; In step (5), the top electrode includes a LiF layer and an Al layer, wherein the thickness of the LiF layer is 0.5~2 nm and the thickness of the Al layer is 60~120 nm.

14. The preparation method according to claim 13, characterized in that, The electron transport layer has a thickness of 40 nm; the LiF layer has a thickness of 1 nm; and the Al layer has a thickness of 80 nm.

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