Packaging method based on tin-based perovskite thin film transistor

Abstract

The invention provides a packaging method based on a tin-based perovskite thin film transistor, and aims to solve the problem of poor environmental stability of perovskite thin film crystals in application. According to the method, the FAPEASnI film is prepared through spin coating and annealing treatment, the surface of the FAPEASnI film is spin-coated with polymethyl methacrylate (PMMA) to form the organic packaging layer, and the aluminum oxide (Al2O3) inorganic packaging layer grows on the PMMA layer through the ALD technology. The environment stability of the tin-based perovskite thin film transistor is remarkably improved, the service life of the tin-based perovskite thin film transistor is remarkably prolonged, moisture and oxygen erosion is effectively blocked, and good electrical performance is kept. The method is simple and convenient in material and process and low in production cost, has industrial application potential, and promotes the development of the tin-based perovskite material in the photoelectric field.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor device packaging, and relates to a packaging method based on tin-based perovskite thin film transistors. Background Art

[0002] As a key electronic device, thin film transistors (TFTs) are widely used in modern display technology, logic circuits, sensors and other fields, especially in liquid crystal displays (LCDs), organic light-emitting diodes (OLEDs) and flexible display devices. Traditional TFTs mostly use silicon (Si) or indium gallium zinc oxide (IGZO) as active layer materials. Although these materials have good electrical properties and mature processes, silicon-based materials have limitations such as high manufacturing costs and difficulty in applying to flexible electronic devices. As an N-type material, IGZO lacks high-performance P-type materials in the driving circuit, which limits its application in efficient logic circuits. Tin-based halide perovskites have gradually become an ideal P-type active layer material due to their advantages such as high carrier mobility, small effective mass and solution processability, and have attracted widespread attention. However, tin-based perovskite materials have poor chemical stability in the air and are easily corroded by moisture and oxygen, resulting in the degradation of their crystal structure and a sharp decline in electrical properties, which seriously affects their application in thin film transistors. Therefore, developing a packaging technology that combines the advantages of both organic and inorganic layers is of great significance to the stability improvement and practical application of tin-based perovskite thin-film transistors. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a packaging method for a tin-based perovskite thin film transistor.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a packaging method based on a tin-based perovskite thin film transistor, the steps of which are as follows:

[0006] Preparation of FAPEASnI solution: FAI, PEAI and SnI2 were dissolved in DMF solution, and then DMSO solution was added to obtain FAPEASnI solution, and the FAPEASnI solution was spin-coated on a substrate that had been treated with oxygen plasma, and anti-solvent chlorobenzene was dropped in the middle of the substrate 10 to 15 seconds after the start of spin coating, and then placed on a 100° C. heating table for annealing for 10 minutes to prepare the FAPEASnI film;

[0007] Preparation of PMMA organic encapsulation layer: dissolving PMMA in chlorobenzene, stirring to fully dissolve, and then spin coating on the surface of FAPEASnI film to prepare the organic encapsulation layer;

[0008] Preparation of Al2O3 inorganic encapsulation layer: The tin-based perovskite thin film transistor coated with organic polymer PMMA is placed on the liner of the reaction chamber of the ALD equipment, the reaction chamber is evacuated to 0.01-0.05 Torr, the reaction chamber is heated to 60°C, and the precursor TMA is introduced into the reaction chamber with nitrogen gas with a pulse time of 0.01-0.05s to make TMA adsorb on the top surface of the sample, and then the oxidant H2O gas is introduced into the reaction chamber with a pulse time of 0.01-0.04s to make H2O react with TMA on the surface of the sample to form an Al2O3 inorganic encapsulation layer;

[0009] Preferably, the molar concentration of FAI is 0.4M, the molar concentration of PEAI is 0.8M, the molar concentration of SnI2 is 0.4M, and the SnI2 solution contains 10% mol SnF2;

[0010] Preferably, the volume ratio of FAI:PEAI:SnI2 is 6:1:7;

[0011] Preferably, the volume ratio of DMF to DMSO in the preparation of FAPEASnI solution is 4:1;

[0012] Preferably, the PMMA concentration is 20 mg / ml, and the PMMA organic encapsulation layer is 10 nm;

[0013] Preferably, the thickness of the Al2O3 inorganic encapsulation layer is 12 nm.

[0014] The beneficial effects of the present invention are:

[0015] (1) Solve the long-term environmental stability of tin-based perovskite thin-film transistors in practical applications, extend the service life of the device, and reduce performance degradation caused by environmental factors.

[0016] (2) The materials and processes used in this technology are relatively simple, which reduces the overall production cost and allows the encapsulation process to be completed at room temperature, so that the encapsulated device can still maintain good electrical properties. By combining the organic polymer PMMA with the aluminum oxide (Al2O3) layer, the device achieves excellent air stability and can effectively block the corrosion of moisture and oxygen. At the same time, the double encapsulation structure significantly improves the electrical performance of the thin film transistor, including high mobility, low leakage current and high switching ratio.

[0017] (3) As perovskite materials have excellent optoelectronic properties and adjustable band structures, this packaging technology has promoted their development in the optoelectronic field. The flexible properties of PMMA and the high uniformity of the atomic layer deposition (ALD) process make this method suitable for the preparation of large-area uniform devices, and has the potential for industrial application. By combining with CMOS technology, more efficient integrated circuits, sensors, displays and other applications can be realized in the future, promoting the development of a new generation of electronic devices.

[0018] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 Schematic diagram of the preparation process of the encapsulated tin-based perovskite thin film transistor of the present invention, (a) FAPEASnI thin film transistor, (b) FAPEASnI thin film transistor encapsulated by organic polymer PMMA, (c) FAPEASnI thin film transistor encapsulated by organic polymer PMMA and inorganic layer Al2O3;

[0021] Figure 2 The transfer characteristic curve and output characteristic curve of the tin-based perovskite thin film transistor provided by the present invention, FAPEASnI thin film transistor (a) transfer characteristic curve (b) output characteristic curve;

[0022] Figure 3 Comparison of transfer characteristic curves of tin-based perovskite thin-film transistors before and after traditional alumina encapsulation;

[0023] Figure 4 This is a comparison of the transfer characteristic curves of the tin-based perovskite thin-film transistor before and after the organic polymer and aluminum oxide stack encapsulation in this case. DETAILED DESCRIPTION

[0024] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0025] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0026] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0027] Example 1

[0028] Traditional alumina packaging preparation method:

[0029] (I) 2D PEA + The binary A-site cation engineering of 3D FASnI3 is introduced to prepare thin film transistors. The specific steps are as follows:

[0030] (1) Item cleaning: The items to be cleaned include SiO2 substrates, 4 ml brown glass bottles, and magnetic stirrers. The items are soaked in acetone, anhydrous ethanol, deionized water, and isopropanol in turn. Ultrasonic cleaning is performed in each solvent for 5 minutes. The cleaned items are blown dry with a nitrogen gun.

[0031] (2) Preparation of precursor solution: Clean the glove box for 10-20 minutes before use and maintain a stable environment (O2: 1-10ppm, H2O: 1-10ppm). Dissolve FAI (0.3-0.4M), PEAI (0.7-0.8M), and SnI2 (0.4-0.5M, containing 10%-20% mol SnF2) in DMF solution, and then mix them in a volume ratio of 6:1:7 to prepare a mixed solution with a ratio of DMF to DMSO of 4:1 to obtain FAPEASnI solution. Place on a stirring table and stir at 60°C for 2-3 hours. After stirring, cool at room temperature for about 10-20 minutes for use. All steps are performed in a glove box filled with nitrogen.

[0032] (3) Spin coating: The FAPEASnI solution was spin coated on the substrate that had been treated with oxygen plasma, and the anti-solvent chlorobenzene was dripped in the middle of the substrate 10 to 15 seconds after the start of spin coating. The sample was then placed on a heating table at 100°C for annealing for 10 minutes to complete the preparation of the FAPEASnI film. The entire film formation process was carried out in a glove box.

[0033] (4) Electrode deposition: Place the sample on the mask, paying attention to the front and back, and place the metal Au required for the evaporation electrode. Close the hatch and start vacuuming. Wait for the vacuum degree of the evaporation equipment to drop to 5x10 -4 Pa, evaporation can begin, 40nm Au is evaporated, and electrode deposition preparation is completed.

[0034] (5) Electrical performance test: The electrical performance was measured by a semiconductor parameter analyzer. The gate voltage (Vg) of the transfer characteristic curve was scanned from 40 V to -40 V (forward scan), and the gate voltage was scanned from -40 V to 40 V (reverse scan). The source-drain voltage of the output characteristic curve was scanned from 0 V to -40 V. The gate voltage (Vg) was scanned from 40 V to -40 V in units of 10 V. The channel length and width of the thin film transistor were 100 μm and 500 μm, respectively.

[0035] (II) Preparation method of traditional aluminum oxide (Al2O3) encapsulation film

[0036] The prepared perovskite film is placed in the ALD chamber. Trimethylaluminum (TMA) TMA with good volatility and non-self-decomposition is used as the aluminum source, water vapor is used as the oxygen source, nitrogen is used as the inert gas carrier gas, the reaction temperature is 60°C, and the cycle period is 200 cycles-250 cycles, that is, ALD is used to grow about 20-25nm. The specific method of growing aluminum oxide is the same as Example 1, that is:

[0037] (1) The prepared FAPEASnI perovskite thin film transistor sample was placed on the liner of the reaction chamber of the ALD equipment, the reaction chamber was evacuated to 0.01-0.05 Torr, and the temperature of the reaction chamber was raised to 60°C.

[0038] (2) After the temperature and pressure are stabilized, the precursor TMA is introduced into the reaction chamber along with nitrogen gas with a pulse time of 0.01 to 0.05 s, so that TMA is adsorbed on the top surface of the sample.

[0039] (3) Nitrogen gas is then introduced into the reaction chamber for 10 to 30 seconds to purge excess TMA that is not adsorbed on the sample surface.

[0040] (4) Then, an oxidant H2O gas is introduced into the reaction chamber with a pulse time of 0.01 to 0.04 s to allow H2O to react with TMA on the sample surface to form Al2O3.

[0041] (5) Nitrogen gas is introduced into the reaction chamber again for 10 to 30 seconds to purge excess H2O and reaction byproducts that have not reacted with TMA.

[0042] (6) Since the thickness of each cycle is the same, the film thickness can be precisely controlled by controlling the number of cycles. The above steps were repeated according to the set number of cycles, and 200-250 cycles of Al2O3 thin films were grown on the sample at 60°C. The thickness of the Al2O3 film was 20-25 nm, and the preparation of the ALD-Al2O3 thin layer was achieved.

[0043] Although the Al2O3 layer has an extremely high ability to block water vapor penetration, the perovskite film will be corroded by the water vapor it comes into contact with during its preparation process, causing the packaging performance of the device to gradually decrease. Therefore, it is necessary to further find ways to improve the packaging performance.

[0044] Example 2

[0045] The encapsulation method of organic and aluminum oxide laminates of the present invention:

[0046] (I) 2D PEA + The binary A-site cation engineering of 3D FASnI3 is introduced to prepare thin film transistors. The specific steps are as follows:

[0047] (1) Item cleaning: The items to be cleaned include SiO2 substrates, 4 ml brown glass bottles, and magnetic stirrers. The items are soaked in acetone, anhydrous ethanol, deionized water, and isopropanol in turn. Ultrasonic cleaning is performed in each solvent for 5 minutes. The cleaned items are blown dry with a nitrogen gun.

[0048] (2) Preparation of precursor solution: Clean the glove box for 10-20 minutes before use and maintain a stable environment (O2: 1-10ppm, H2O: 1-10ppm). Dissolve FAI (0.3-0.4M), PEAI (0.7-0.8M), and SnI2 (0.4-0.5M, containing 10%-20% mol SnF2) in DMF solution, and then mix them in a volume ratio of 6:1:7 to prepare a mixed solution with a ratio of DMF to DMSO of 4:1 to obtain FAPEASnI solution. Place on a stirring table and stir at 60°C for 2-3 hours. After stirring, cool at room temperature for about 10-20 minutes for use. All steps are performed in a glove box filled with nitrogen.

[0049] (3) Spin coating: The FAPEASnI solution was spin coated on the substrate that had been treated with oxygen plasma, and the anti-solvent chlorobenzene was dripped in the middle of the substrate 10 to 15 seconds after the start of spin coating. The sample was then placed on a heating table at 100°C for annealing for 10 minutes to complete the preparation of the FAPEASnI film. The entire film formation process was carried out in a glove box.

[0050] (4) Electrode deposition: Place the sample on the mask, paying attention to the front and back, and place the metal Au required for the evaporation electrode. Close the hatch and start vacuuming. Wait for the vacuum degree of the evaporation equipment to drop to 5x10 -4 Pa, evaporation can begin, 40nm Au is evaporated, and electrode deposition preparation is completed.

[0051] (5) Electrical performance test: The electrical performance was measured by a semiconductor parameter analyzer. The gate voltage (Vg) of the transfer characteristic curve was scanned from 40 V to -40 V (forward scan), and the gate voltage was scanned from -40 V to 40 V (reverse scan). The source-drain voltage of the output characteristic curve was scanned from 0 V to -40 V. The gate voltage (Vg) was scanned from 40 V to -40 V in units of 10 V. The channel length and width of the thin film transistor were 100 μm and 500 μm, respectively.

[0052] (II) Preparation method of organic polymer PMMA encapsulation film

[0053] (1) Solution preparation: Dissolve PMMA in chlorobenzene at a concentration of 20-40 mg / ml and stir for 2 hours to ensure that it is fully dissolved.

[0054] (2) Spin coating: Use 50-100 μl of the PMMA solution to spin coat it on the surface of the FAPEASnI film to form an organic encapsulation layer of about 10-30 nm.

[0055] (III) Preparation method of aluminum oxide (Al2O3) encapsulation film prepared by low temperature deposition process in this embodiment

[0056] (1) A sample on which organic polymer PMMA has been spin-coated is placed on a liner of a reaction chamber of an ALD device, the reaction chamber is evacuated to 0.01-0.05 Torr, and the temperature of the reaction chamber is raised to 60°C.

[0057] (2) After the temperature and pressure are stabilized, the precursor TMA is introduced into the reaction chamber along with nitrogen gas with a pulse time of 0.01 to 0.05 s, so that TMA is adsorbed on the top surface of the sample.

[0058] (3) Nitrogen gas is then introduced into the reaction chamber for 10 to 30 seconds to purge excess TMA that is not adsorbed on the sample surface.

[0059] (4) Then, an oxidant H2O gas is introduced into the reaction chamber with a pulse time of 0.01 to 0.04 s to allow H2O to react with TMA on the sample surface to form Al2O3.

[0060] (5) Nitrogen gas is introduced into the reaction chamber again for 10 to 30 seconds to purge excess H2O and reaction byproducts that have not reacted with TMA.

[0061] (6) Since the thickness of each cycle is the same, the film thickness can be precisely controlled by controlling the number of cycles. The above steps were repeated according to the set number of cycles, and 120 cycles of Al2O3 thin films were grown on the sample at 60°C. The thickness of the Al2O3 film was 12 nm, and the preparation of the ALD-Al2O3 thin layer was achieved.

[0062] (7) At this point, the packaging and preparation process of the tin-based perovskite thin-film transistor is completed. Next, the electrical properties of the sample are tested after being placed in the air for a period of time.

[0063] Example 3

[0064] Performance comparison analysis

[0065] The present invention spin-coats a layer of hydrophobic polymer (PMMA) on the surface of the prepared perovskite thin film transistor, and then places the sample in an ALD device to grow Al2O3. The PMMA layer and Al2O3 grow into a stacked structure, which improves the environmental stability of the perovskite thin film transistor. The difference between the present invention and the traditional packaging method is that there is an additional layer of PMMA film. The performance comparison of the prepared perovskite thin film transistor is as follows:

[0066] (1) Traditional aluminum oxide packaging method: aluminum oxide is directly grown on the surface of the perovskite film. The perovskite film is exposed to water vapor erosion in the ALD process, resulting in a significant decrease in the packaging performance of the device. Figure 3 As shown in the figure, the mobility of the packaged thin film transistor is reduced from 8cm 2 V-1 s -1 Down to 0.08cm 2 V -1 s -1 , as shown in Table 1, and the current switching ratio decreased by four times. In subsequent experiments, the packaged samples were placed in the air for less than a day, and the device performance showed conductor characteristics and lost the characteristics of the transistor.

[0067] Table 1: Package parameter comparison

[0068]

[0069] (2) The organic and aluminum oxide stacking packaging method of the present invention: a layer of PMMA is spin-coated on the surface of the perovskite film and Al2O3 is grown. The device performance of the perovskite thin film transistor is improved compared with that of the traditional method and is relatively stable in the air. Figure 4 As shown in the figure, the packaged thin film transistor is placed in the air (temperature ~22°C, humidity ~50%), and the mobility of the device increases from 6.5 cm 2 V -1 s -1 Down to 0.45cm 2 V -1 s -1 , as shown in Table 2, while the current switching ratio remains essentially unchanged. Due to the intrinsic properties of Sn-based perovskites, Sn 2+ Sn is easily oxidized to produce Sn vacancies, leading to p-type self-doping and increasing the hole concentration, which increases the conductivity of the perovskite film and makes it appear "metallic", ultimately causing the photoelectric performance of the device to deteriorate or even disappear. This packaging method allows the tin-based perovskite thin-film transistor to still have the characteristics of a thin-film transistor after being placed in the air for 10 days, improving the environmental stability of the device and further promoting the application of Sn-based perovskite materials in the optoelectronic field.

[0070] Table 2: Comparison of oxidation parameters

[0071]

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A packaging method based on a tin-based perovskite thin film transistor, characterized in that: The steps are as follows: Preparation of FAPEASnI film: FAI, PEAI and SnI2 were dissolved in DMF solution, and then DMSO solution was added to obtain FAPEASnI solution, and the FAPEASnI solution was spin-coated on a substrate that had been treated with oxygen plasma, and anti-solvent chlorobenzene was dropped in the middle of the substrate 10 to 15 seconds after the start of spin coating, and then placed on a 100° C. heating table for annealing for 10 minutes to prepare the FAPEASnI film; Preparation of a double encapsulation layer composed of an organic layer and an inorganic layer: Preparation of the organic layer: dissolve polymethyl methacrylate (PMMA) in chlorobenzene, stir to fully dissolve, and then spin-coat it on the surface of the FAPEASnI film to prepare the organic encapsulation layer; other polymers soluble in chlorobenzene (polyvinyl alcohol PVA, polyvinyl pyrrolidone PVP, etc.) can also be selected. Preparation of inorganic layer: The tin-based perovskite thin film transistor coated with organic polymer PMMA is placed on the liner of the reaction chamber of the ALD equipment, the reaction chamber is evacuated to 0.01-0.05 Torr, the reaction chamber is heated to 60°C, and the precursor TMA is introduced into the reaction chamber with nitrogen gas with a pulse time of 0.01-0.05s to make TMA adsorb on the top surface of the sample, and then the oxidant H2O gas is introduced into the reaction chamber with a pulse time of 0.01-0.04s to make H2O react with TMA on the surface of the sample to form an Al2O3 inorganic encapsulation layer.

2. The packaging method according to claim 1, characterized in that: The molar concentration of FAI is 0.3-0.4M, the molar concentration of PEAI is 0.7-0.8M, the molar concentration of SnI2 is 0.4-0.5M, and the SnI2 solution contains 10%-20% mol SnF2.

3. The packaging method according to claim 1, characterized in that: The volume ratio of FAI:PEAI:SnI2 is 6:1:7 to 8:1:

7.

4. The packaging method according to claim 1, characterized in that: The volume ratio of DMF to DMSO in the preparation of FAPEASnI solution is 3:1 to 4:

1.

5. The packaging method according to claim 1, characterized in that: The polymer concentration is 20 mg / ml to 40 mg / ml, the spin coating speed is 2000 rpm to 4000 rpm, and the thickness is 20 to 30 nm.

6. The packaging method according to claim 1, characterized in that: The thickness of the Al2O3 inorganic encapsulation layer is 10-20 nm.

Images