Two-dimensional tin-based perovskite field effect transistor based on small molecule doping and preparation method and application thereof

Abstract

The invention discloses a two-dimensional tin-based perovskite field effect transistor based on small molecule doping and a preparation method and application thereof, and belongs to the technical field of photoelectric materials and semiconductor devices. The method disclosed by the invention comprises the following steps: coating the surface of a substrate with a 4-fluorophenethyl tin iodide perovskite precursor solution, and then carrying out annealing treatment to obtain a 4-fluorophenethyl tin iodide perovskite thin film; evaporating a small molecule doped layer on the surface of the 4-fluorophenethyl tin iodide perovskite thin film by adopting a vacuum evaporation coating method, so that the small molecule doped layer and the 4-fluorophenethyl tin iodide perovskite thin film form a heterojunction structure; and depositing a metal source electrode and a metal drain electrode on the surface of the heterojunction structure to obtain the two-dimensional tin-based perovskite field effect transistor based on small molecule doping. The method provided by the invention solves the problem of insufficient charge transport capability caused by the insulativity of large-volume organic cations in the existing two-dimensional tin-based perovskite.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and semiconductor devices, specifically relating to a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, its fabrication method, and its application. Background Technology

[0002] Perovskite materials are a novel type of ionic crystal semiconductor. Due to their advantages such as continuously tunable band gaps, high carrier mobility, and low-cost solution preparation processes, they have attracted widespread attention in recent years in fields such as solar cells, light-emitting diodes, and thin-film transistors. Tin-based perovskites, due to their lower effective mass, exhibit even higher carrier mobility. Among them, two-dimensional tin-based perovskites, by introducing mechanical spacer cations to form a layered structure, significantly improve material stability, thus showing important application prospects in flexible electronics and integrated circuits.

[0003] However, in two-dimensional tin-based perovskite thin-film field-effect transistors, the insulating properties of the bulky organic spacer cations hinder efficient carrier transport, resulting in low overall mobility. Simultaneously, the layered structure weakens the antibonding coupling between the Sn 5s and I 5p orbitals, leading to a relatively high tin vacancy formation energy. This limits the concentration of free holes available for transport within the system itself, thus amplifying the impact of defect states on transport performance. In tin-based perovskites, tin vacancies, as the primary source of negatively charged shallow-level defect centers, trap positively charged free holes. Trapped carriers require additional energy excitation (such as photoexcitation or thermal activation) to be released from the trap and re-engage in transport. Although the "trapping" and "detrapping" processes occur only on a microsecond timescale, this phenomenon delays drift transport and reduces the overall carrier mobility. Summary of the Invention

[0004] The purpose of this invention is to provide a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, its preparation method and application, to address the problem of insufficient charge transport capacity caused by the insulation of large-volume organic cations in existing two-dimensional tin-based perovskites.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, comprising the following steps: A 4-fluorophenylethyl tin iodide perovskite precursor solution was coated onto the substrate surface, followed by annealing to obtain a 4-fluorophenylethyl tin iodide perovskite film. A small molecule doped layer was deposited on the surface of a 4-fluorophenylethyl tin iodide perovskite film by vacuum evaporation, so that the small molecule doped layer and the 4-fluorophenylethyl tin iodide perovskite film form a heterojunction structure. Metal source and drain electrodes are deposited on the surface of the heterojunction structure to obtain a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping.

[0006] Furthermore, before adding the 4-fluorophenylethyl tin iodide perovskite precursor solution, the substrate was sequentially cleaned in anhydrous ethanol, a silicon-based cleaning agent, deionized water, and isopropanol, and the cleaned substrate was dried and then subjected to ozone-ultraviolet UV treatment.

[0007] Furthermore, the 4-fluorophenylethyl tin iodide perovskite precursor liquid coating is obtained by dissolving 4-fluorophenylethyl amine iodide, stannous iodide, and tin compensator tin powder in an organic solvent and stirring. The molar ratio of the tin compensator tin powder to stannous iodide is 0.01-0.05:1; The concentration of the 4-fluorophenylethyl tin iodide perovskite precursor solution is 0.18-0.22 M; The organic solvent is a mixture of N,N-dimethylformamide and dimethyl sulfoxide, wherein the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide is (3.5~4.5):1.

[0008] Furthermore, the 4-fluorophenylethyl tin iodide perovskite precursor solution was prepared at room temperature under a nitrogen atmosphere; The substrate is an n-type heavily doped silicon wafer with a SiO2 dielectric layer deposited on its surface.

[0009] Furthermore, the method for coating the 4-fluorophenylethyl tin iodide perovskite precursor solution onto the substrate surface is spin coating; the process parameters of the spin coating method are: rotation speed 4000~6000 rpm, acceleration 4000~6000 rpm, spin coating time 45~60 s, and 100-300 μL of anti-solvent added dropwise at 12-18 s; The annealing process is performed at a temperature of 100-120 °C for 10-12 min.

[0010] Furthermore, the thickness of the 4-fluorophenylethyl tin iodide perovskite film is 40~80 nm; the thickness of the small molecule doped layer is 2~8 nm; and the thickness of the metal source and drain is 30~35 nm.

[0011] Furthermore, the specific process of depositing a small molecule doped layer on the surface of the 4-fluorophenylethyl tin iodide perovskite thin film using vacuum evaporation deposition is as follows: At 1.0×10 -5 -5.0×10 -4 Under Pa conditions, small molecule dopants are vapor-deposited onto the surface of a 4-fluorophenylethyl tin iodide perovskite thin film to form the small molecule doped layer. The small molecule dopants are NDP-9 and HAT-CN; the evaporation rate is 0.1~0.15 Å / s.

[0012] Furthermore, the metal source and drain are Cr electrodes; the specific process of depositing the metal source and drain is as follows: under a vacuum degree of less than 10... -5 At Pa, the evaporation current is 102-112 A, the evaporation rate is 0.3 Å / s, and Cr is deposited using a mask as the metal source and drain of the transistor.

[0013] The present invention also discloses a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping prepared by the above preparation method.

[0014] The present invention also discloses the application of the above-mentioned two-dimensional tin-based perovskite field-effect transistor based on small molecule doping in low-power integrated circuits, optoelectronic devices or smart sensors.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for fabricating two-dimensional tin-based perovskite field-effect transistors based on small molecule doping. This method employs vacuum evaporation to achieve precise molecular doping on the perovskite surface, thus avoiding solvent damage. Furthermore, the acceptor-dominated ground-state charge transfer during the doping process allows electrons to spontaneously transfer to the dopant, enabling precise control over the Fermi level, band structure, carrier concentration, and carrier migration of the two-dimensional tin-based perovskite semiconductor. Controllable p-type doping using organic small molecules significantly increases the concentration of free carriers (holes) in the two-dimensional tin-based perovskite film. Under a trap-decapture transport mechanism dominated by shallow-level traps, newly added holes preferentially fill negatively charged shallow traps, achieving effective passivation. When the traps approach saturation, the remaining holes directly participate in continuous intraband transport, thereby significantly improving the average hole mobility of the system. This method solves the problem of insufficient charge transport capacity in existing two-dimensional tin-based perovskites due to the insulating properties of large-volume organic cations.

[0016] Furthermore, the method of the present invention is based on a mild organic small molecule doping process with high compatibility with device structures, and can be used to construct various types of perovskite electronic and optoelectronic devices, including but not limited to field-effect transistors, solar cells, light-emitting diodes and photodetectors, which facilitates large-scale and batch applications.

[0017] Furthermore, this invention employs vacuum thermal evaporation to perform molecular doping, which allows for precise setting of the doping thickness and coverage by controlling the evaporation rate and time, and enables localized electrodoping at the interface. This avoids interference with crystallization kinetics and residual solvent side reactions in solution methods, resulting in high consistency and repeatability, and facilitating large-area and batch preparation. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to the present invention; Figure 2 The structural formulas of the doped molecules NDP-9 and HAT-CN are shown. Figure 3 The transfer and output characteristics of the two-dimensional tin-based perovskite field-effect transistor device prepared for Comparative Example 1 are shown in a nitrogen glove box atmosphere. Where: a - transfer characteristic curve; b - output characteristic curve; Figure 4 The transfer and output characteristic curves of the two-dimensional tin-based perovskite field-effect transistor device prepared in Example 1 are shown in a nitrogen glove box atmosphere. Wherein: a- Transfer characteristic curves of HAT-CN with different doping thicknesses; b- Output characteristic curves when the HAT-CN doping layer thickness is 2 nm; c- Output characteristic curves when the HAT-CN doping layer thickness is 4 nm; d- Output characteristic curves when the HAT-CN doping layer thickness is 6 nm; e- Output characteristic curves when the HAT-CN doping layer thickness is 8 nm. Figure 5 The transfer and output characteristic curves of the two-dimensional tin-based perovskite field-effect transistor device prepared in Example 2 are shown in a nitrogen glove box atmosphere. Among them: a-Transfer characteristic curves of NDP-9 with different doping thicknesses; b-Output characteristic curves when the NDP-9 doping layer thickness is 2 nm; c-Output characteristic curves when the NDP-9 doping layer thickness is 4 nm; d-Output characteristic curves when the NDP-9 doping layer thickness is 6 nm; e-Output characteristic curves when the NDP-9 doping layer thickness is 8 nm.

[0019] Figure 6 The transfer and output characteristics of the two-dimensional tin-based perovskite field-effect transistor prepared for Comparative Example 2 are shown in a nitrogen glove box atmosphere. Among them: a- Transfer characteristic curves of MoO3 with different thicknesses; b- Output characteristic curves when the MoO3 doping layer thickness is 2 nm; c- Output characteristic curves when the MoO3 doping layer thickness is 4 nm; d- Output characteristic curves when the MoO3 doping layer thickness is 6 nm; e- Output characteristic curves when the MoO3 doping layer thickness is 8 nm. Detailed Implementation To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0022] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0023] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0024] This invention provides a method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, specifically including the following steps: Step 1: Select an n-type heavily doped silicon wafer with a SiO2 dielectric layer deposited on its surface as a substrate. Clean it in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol in sequence, and then dry it. Before use, treat it with ultraviolet ozone in a UV-O3 device for 30 minutes to remove organic residues and improve surface energy. Then place it in a nitrogen glove box for later use. 4-Fluorophenylethylamine iodide (4-FPEAI), stannous iodide (SnI2), and tin compensator tin powder (Sn) were dissolved in an organic solvent and stirred to obtain a 4-fluorophenylethyl tin iodide perovskite precursor solution. Step 2: The 4-fluorophenylethyl tin iodide perovskite precursor solution was spin-coated onto the substrate, followed by annealing to obtain a 4-fluorophenylethyl tin iodide perovskite film. Step 3: Using vacuum evaporation deposition technology, deposit small molecule dopants on the surface of a 4-fluorophenylethyl tin iodide perovskite film: 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)-malononitrile [2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)-malononitrile [2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)-malononitrile, 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile, HAT-CN] or MoO3. The structures of NDP-9 and HAT-CN are as follows: Figure 2 As shown; and then construct a heterojunction; Step 4: Use vacuum evaporation coating technology to coat the film at a vacuum level of less than 10. -5 At Pa, the evaporation current is 102~112 A and the evaporation rate is 0.3 Å / s. Cr is deposited using a mask as the metal source and drain of the transistor, thus completing the fabrication of a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping.

[0025] Preferably, in step 1, the organic solvent used in the preparation of the 4-fluorophenylethyl tin iodide perovskite precursor solution is a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), with a volume ratio of (3.5~4.5):1.

[0026] Preferably, in step 1, the concentration of the 4-fluorophenylethyl tin iodide perovskite precursor solution is 0.18~0.22 M.

[0027] Preferably, in step 1, the preparation of the 4-fluorophenylethyl tin iodide perovskite precursor solution is carried out under nitrogen glove, at room temperature, stirred at 300-500 rpm for 1.5-2 h, and then filtered using a 0.22 μm organic filter head for later use.

[0028] Preferably, in step 1, an n-type heavily doped silicon wafer with a SiO2 dielectric layer is selected as the substrate. It is cleaned in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol in sequence, then dried. Before use, it is treated with ultraviolet ozone in a UV-O3 device for 30 minutes to remove organic residues and improve surface energy. Then it is placed in a nitrogen glove box for later use.

[0029] Preferably, in step 2, the prepared precursor solution is spin-coated onto the pretreated silicon wafer surface. The spin-coating process parameters are: rotation speed 4000-6000 rpm, time 45-60 s, and 100-300 μL of antisolvent is added dropwise at 12-18 s after the start of spin-coating. Subsequently, the wafer is annealed on a hot stage at 100-120 ℃ for 10-12 min to prepare a 4-fluorophenylethyl tin iodide perovskite thin film.

[0030] Preferably, in step 3, a vacuum evaporation process is used to deposit the vapor at a depth of 1.0 × 10⁻⁶ m². -5 ~5.0×10 -4 Under Pa conditions, small molecule doped layers of different thicknesses were deposited on the surface of 4-fluorophenylethyl tin iodide perovskite thin films using a mask, with evaporation rates ranging from 0.1 to 0.15 Å / s.

[0031] Preferably, the thickness of the 4-fluorophenylethyl tin iodide perovskite film is 40~80 nm, the thickness of the heterojunction is 2~8 nm, and the thickness of the chromium used as the source and drain electrodes is 30~35 nm.

[0032] Device performance testing was conducted under dark conditions, using a Keysight B 2912 digital source meter to test its transfer characteristic curves and output characteristic curves.

[0033] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0034] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0035] Example 1 A method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping includes the following steps: Step 1: Select an n-type heavily doped silicon wafer with a SiO2 dielectric layer as the substrate. Clean it in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol in sequence and then dry it. Before use, place it in a UV-O3 device for ultraviolet ozone treatment for 30 min to remove organic residues and improve surface energy. Then place it in a nitrogen glove box for later use. Step 2: 106.8 mg of 4-fluorophenylethyl iodide, 74.6 mg of stannous iodide, and 10 mg of tin powder were added to 800 μL of N,N-dimethylformamide and 200 μL of dimethyl sulfoxide solvent, and stirred at room temperature for 2 hours until completely dissolved to obtain a 4-fluorophenylethyl tin iodide perovskite precursor solution. 50 μL of the prepared 4-fluorophenylethyl tin iodide perovskite precursor solution was dropped onto the substrate, and a 4-fluorophenylethyl tin iodide perovskite film was prepared by spin coating. The process of coating the perovskite precursor solution was as follows: rotation speed 6000 rpm, acceleration 6000 rpm, spin coating time 60 s, 100 μL of antisolvent was added at 15 s, and then annealed at 100 °C for 10 min in a nitrogen glove box to obtain the 4-fluorophenylethyl tin iodide perovskite film. Step 3: Vacuum evaporation deposition technology is used on the surface of the 4-fluorophenylethyl tin iodide perovskite thin film at a vacuum degree of less than 10. -5 At Pa, the evaporation temperature was 186 ℃, the evaporation rate was 0.1 Å / s, and 6 nm HAT-CN was deposited as a small molecule doping layer to construct a heterojunction. Step 4: Employ vacuum evaporation coating technology at a vacuum level of less than 10... -5 At a deposition rate of 112 A and 0.3 Å / s, a 35 nm layer of Cr was deposited using a mask as the source and drain of the transistor. This completed the fabrication of a 4-fluorophenylethyl tin iodide field-effect transistor device (based on a small-molecule-doped two-dimensional tin-based perovskite field-effect transistor). The specific structure is shown below. Figure 1 As shown.

[0036] Device performance testing. Under dark conditions, the transfer and output characteristic curves of the above transistors were tested using a Keysight B 2912 digital source meter. The results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the source and drain currents of the transistor gradually increase with the increase of the doped layer thickness from 2 nm to 8 nm. Compared with the undoped 4-fluorophenylethyl tin iodide transistor, the source and drain currents are increased by about two orders of magnitude after HAT-CN doping, demonstrating the strong electron extraction capability of HAT-CN. Through effective charge transfer, it significantly increases the hole concentration in the 4-fluorophenylethyl tin iodide film. The results show that HAT-CN doping increases the field-effect hole mobility of the 4-fluorophenylethyl tin iodide transistor to 0.314 cm⁻¹. 2 V-1 s -1 This further optimized the device performance.

[0037] Example 2 A method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping includes the following steps: Step 1: Select an n-type heavily doped silicon wafer with a SiO2 dielectric layer as the substrate. Clean it in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol in sequence, and then dry it. Before use, treat it with ultraviolet ozone in a UV-O3 device for 30 minutes to remove organic residues and improve surface energy. Then place it in a nitrogen glove box for later use. Step 2: 106.8 mg of 4-fluorophenylethyl iodide, 74.6 mg of stannous iodide, and 10 mg of tin powder were added to 800 μL of N,N-dimethylformamide and 200 μL of dimethyl sulfoxide solvent, and stirred at room temperature for 2 hours until completely dissolved to obtain a 4-fluorophenylethyl tin iodide perovskite precursor solution. 50 μL of the prepared 4-fluorophenylethyl tin iodide perovskite precursor solution was dropped onto the substrate, and a 4-fluorophenylethyl tin iodide perovskite film was prepared by spin coating. The process of the 4-fluorophenylethyl tin iodide perovskite precursor solution was as follows: rotation speed 6000 rpm, acceleration 6000 rpm, spin coating time 60 s, 100 μL of antisolvent was added dropwise at 15 s, and then annealed at 100 °C for 10 min in a nitrogen glove box to obtain a 4-fluorophenylethyl tin iodide perovskite film. Step 3: Vacuum evaporation deposition technology is used on the surface of the 4-fluorophenylethyl tin iodide perovskite thin film at a vacuum degree of less than 10. -5 At Pa, the evaporation temperature was 122 ℃, the evaporation rate was 0.1 Å / s, and 6 nm of NDP-9 was deposited as a small molecule doping layer to construct a heterojunction. Step 4: Employ vacuum evaporation coating technology at a vacuum level of less than 10... -5 At Pa, with a deposition current of 112 A and a deposition rate of 0.3 Å / s, 35 nm of Cr was deposited using a mask as the metal source and drain of the transistor, thus completing the fabrication of a 4-fluorophenylethyl tin iodide field-effect transistor device.

[0038] Device performance testing: Under dark conditions, the transfer characteristic curves and output characteristic curves of the above transistors were tested using a Keysight B 2912 digital source meter. The results are as follows: Figure 5 As shown. From Figure 5It can be seen that after NDP-9 doping, the source and drain currents are increased by two orders of magnitude compared to the undoped 4-fluorophenylethyl tin iodide transistor, indicating that NDP-9 significantly increases the hole concentration in the perovskite film through effective charge transfer, thus optimizing carrier transport. Simultaneously, NDP-9 can provide higher mobility at lower doping concentrations, increasing the field-effect hole mobility of the 4-fluorophenylethyl tin iodide transistor to 0.351 cm⁻¹. 2 V -1 s -1 Furthermore, the smooth transfer and output characteristic curves further demonstrate that the NDP-9 effectively reduces trapping effects and improves device stability.

[0039] Comparative Example 1 The fabrication method based on undoped two-dimensional tin-based perovskite field-effect transistors includes the following specific steps: Step 1: Select an n-type heavily doped silicon wafer with a SiO2 dielectric layer as the substrate, place it in a UV-O3 device for ultraviolet ozone treatment for 30 min to remove organic residues and improve surface energy, and then place it in a nitrogen glove box for later use. Step 2: 106.8 mg of 4-fluorophenylethylamine iodide, 74.6 mg of stannous iodide, and 10 mg of tin powder were added to 800 μL of N,N-dimethylformamide and 200 μL of dimethyl sulfoxide solvent, and stirred at room temperature for 2 hours until completely dissolved to obtain a two-dimensional tin-based perovskite precursor solution. 50 μL of the prepared precursor solution was dropped onto the substrate, and a perovskite film was prepared by spin coating. The process of coating the perovskite precursor solution was as follows: rotation speed 6000 rpm, acceleration 6000 rpm, spin coating time 60 s, 100 μL of antisolvent was added dropwise at 15 s, and then annealed at 100 °C for 10 min in a nitrogen glove box to obtain a two-dimensional tin-based perovskite film. Step 3: Using vacuum evaporation coating technology, at a vacuum level of less than 10... -5 At Pa, with a deposition current of 112 A and a deposition rate of 0.3 Å / s, 35 nm of Cr was deposited on the surface of a two-dimensional tin-based perovskite thin film using a mask as the source and drain of the transistor, thus completing an undoped two-dimensional tin-based perovskite field-effect transistor.

[0040] Device performance testing: Under dark conditions, the transfer characteristic curves and output characteristic curves of the above transistors were tested using a Keysight B 2912 digital source meter. The results are as follows: Figure 3 As shown, from Figure 3 It can be seen that the undoped 4-fluorophenylethyl tin iodide transistor has low source and drain currents and a field-effect hole mobility of only 0.002 cm⁻¹. 2 V -1 s -1Furthermore, due to the large number of defect states in the thin film, the transfer characteristic curve and output characteristic curve are not smooth.

[0041] Comparative Example 2 A method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on MoO3 doping includes the following steps: Step 1: Select an n-type heavily doped silicon wafer with a SiO2 dielectric layer as the substrate. Clean it in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol in sequence, and then dry it. Before use, treat it with ultraviolet ozone in a UV-O3 device for 30 minutes to remove organic residues and improve surface energy. Then place it in a nitrogen glove box for later use. Step 2: 106.8 mg of 4-fluorophenylethyl iodide, 74.6 mg of stannous iodide, and 10 mg of tin powder were added to 800 μL of N,N-dimethylformamide and 200 μL of dimethyl sulfoxide solvent, and stirred at room temperature for 2 hours until completely dissolved to obtain a 4-fluorophenylethyl tin iodide perovskite precursor solution. 50 μL of the prepared 4-fluorophenylethyl tin iodide perovskite precursor solution was dropped onto the substrate, and a 4-fluorophenylethyl tin iodide perovskite film was prepared by spin coating. The process of coating the 4-fluorophenylethyl tin iodide perovskite precursor solution was as follows: rotation speed 6000 rpm, acceleration 6000 rpm, spin coating time 60 s, 100 μL of antisolvent was added at 15 s, and then annealed at 100 °C for 10 min in a nitrogen glove box to obtain a 4-fluorophenylethyl tin iodide perovskite film. Step 3: Vacuum evaporation deposition technology is used on the surface of the 4-fluorophenylethyl tin iodide perovskite thin film at a vacuum degree of less than 10. -5 At Pa, the evaporation current was 55 A, the evaporation rate was 0.1 Å / s, and 6 nm of MoO3 was deposited as a charge transfer doping layer to construct a heterojunction. Step 4: Employ vacuum evaporation coating technology at a vacuum level of less than 10... -5 At Pa, with a deposition current of 112 A and a deposition rate of 0.3 Å / s, 35 nm of Cr was deposited using a mask as the metal source and drain of the transistor, thus completing the fabrication of a 4-fluorophenylethyl tin iodide field-effect transistor device.

[0042] Device performance testing: Under dark conditions, the transfer characteristic curves and output characteristic curves of the above transistors were tested using a Keysight B 2912 digital source meter. The results are as follows: Figure 6 As shown. From Figure 6It can be seen that the source and drain currents of the transistor increase with increasing doped layer thickness. This is because electrons are transferred from the 4-fluorophenylethyl tin iodide thin film to the MoO3 doped layer after doping, leading to an increase in the hole concentration in the perovskite thin film. Simultaneously, extremely thin MoO3 doped layers (e.g., 2 nm) can also significantly improve the source and drain currents of the transistor, while thicker MoO3 doped layers (e.g., 8 nm) accumulate more holes, resulting in an increased transistor turn-on voltage. This is because a higher hole concentration requires a larger gate voltage to drive the transistor to the turn-on state. The field-effect hole mobility of the MoO3-doped 4-fluorophenylethyl tin iodide transistor increases to 0.021 cm⁻¹. 2 V -1 s -1 This indicates that doping significantly improves the carrier migration capability of transistors, thereby improving their electrical performance.

[0043] Reliable control of carrier concentration and conductivity in semiconductors is a core technology in modern electronics. Molecular doping is an effective means of improving the electrical performance of semiconductors. Molecular dopants with high electron affinity can induce charge transfer between the dopant and the host semiconductor, significantly improving carrier mobility and conductivity, thereby optimizing device performance. As a universal semiconductor control method, molecular doping offers advantages such as flexible energy level matching, high structural diversity, and mild doping conditions, and has been widely used in organic semiconductors and nanomaterials. However, perovskite precursor solutions are highly sensitive to composition, and molecular doping may interfere with crystallization kinetics, introducing uncontrollable defects. Therefore, this invention employs vacuum evaporation technology to achieve precise molecular doping on the perovskite surface, thus avoiding solvent damage and providing a reliable approach to revealing the doping mechanism and improving device performance.

[0044] In this invention, organic molecule doping engineering primarily suppresses the hole trapping effect of shallow-level traps by improving energy level matching and carrier distribution. The free holes added by doping first fill the negatively charged trap states, achieving effective passivation of defects; subsequently, the remaining holes directly participate in in-band transport, significantly alleviating the mobility limitation imposed by the "capture-decapture" kinetics. Therefore, the two-dimensional tin-based perovskite field-effect transistors fabricated based on organic molecule doping exhibit higher mobility and a larger current on / off ratio compared to undoped devices.

[0045] In summary, this invention primarily addresses the problems of low free carrier concentration, high defect state density, and insufficient mobility in two-dimensional tin-based perovskite thin films by providing a control method based on organic molecular doping engineering. This method can achieve precise control over the band structure and carrier transport characteristics while ensuring the integrity and morphological stability of the film, thereby improving the overall performance of two-dimensional tin-based perovskite field-effect transistors. This is of great significance for promoting the application of tin-based perovskites in optoelectronic devices and semiconductor integration.

[0046] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, characterized in that, Includes the following steps: A 4-fluorophenylethyl tin iodide perovskite precursor solution was coated onto the substrate surface, followed by annealing to obtain a 4-fluorophenylethyl tin iodide perovskite film. A small molecule doped layer was deposited on the surface of a 4-fluorophenylethyl tin iodide perovskite film by vacuum evaporation, so that the small molecule doped layer and the 4-fluorophenylethyl tin iodide perovskite film form a heterojunction structure. Metal source and drain electrodes are deposited on the surface of the heterojunction structure to obtain a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping.

2. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, Before adding the 4-fluorophenylethyl tin iodide perovskite precursor solution, the substrate was sequentially cleaned in anhydrous ethanol, silicon-based cleaning agent, deionized water and isopropanol, and then dried and subjected to ozone-ultraviolet UV treatment.

3. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, The 4-fluorophenylethyl tin iodide perovskite precursor liquid coating is obtained by dissolving 4-fluorophenylethyl amine iodide, stannous iodide, and tin powder as a tin compensator in an organic solvent and stirring. The molar ratio of the tin compensator tin powder to stannous iodide is 0.01-0.05:1; The concentration of the 4-fluorophenylethyl tin iodide perovskite precursor solution is 0.18-0.22 M; The organic solvent is a mixture of N,N-dimethylformamide and dimethyl sulfoxide, wherein the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide is (3.5~4.5):

1.

4. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, The 4-fluorophenylethyl tin iodide perovskite precursor solution was prepared at room temperature under a nitrogen atmosphere. The substrate is an n-type heavily doped silicon wafer with a SiO2 dielectric layer deposited on its surface.

5. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, The method for coating the 4-fluorophenylethyl tin iodide perovskite precursor solution onto the substrate surface is spin coating; the process parameters of the spin coating method are: rotation speed 4000~6000 rpm, acceleration 4000~6000 rpm, spin coating time 45~60 s, and 100-300 μL of anti-solvent added dropwise at 12-18 s; The annealing process is performed at a temperature of 100-120 °C for 10-12 min.

6. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, The thickness of the 4-fluorophenylethyl tin iodide perovskite film is 40~80 nm; the thickness of the small molecule doped layer is 2~8 nm; and the thickness of the metal source and drain is 30~35 nm.

7. The method for fabricating a two-dimensional tin-based field-effect transistor based on small molecule doping according to claim 1, characterized in that, The specific process for depositing a small molecule doped layer on the surface of a 4-fluorophenylethyl tin iodide perovskite thin film using vacuum evaporation is as follows: At 1.0×10 -5 -5.0×10 -4 Under Pa conditions, small molecule dopants are vapor-deposited onto the surface of a 4-fluorophenylethyl tin iodide perovskite thin film to form the small molecule doped layer. The small molecule dopants are NDP-9 and HAT-CN; the evaporation rate is 0.1~0.15 Å / s.

8. The method for fabricating a two-dimensional tin-based perovskite field-effect transistor based on small molecule doping according to claim 1, characterized in that, The metal source and drain are Cr electrodes; the specific process of depositing the metal source and drain is as follows: under a vacuum degree of less than 10... -5 At Pa, the evaporation current is 102-112 A, the evaporation rate is 0.3 Å / s, and Cr is deposited using a mask as the metal source and drain of the transistor.

9. A two-dimensional tin-based perovskite field-effect transistor based on small molecule doping, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of the two-dimensional tin-based perovskite field-effect transistor based on small molecule doping as described in claim 9 in low-power integrated circuits, optoelectronic devices, or smart sensors.

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