Bismuth-based perovskite photosynaptic transistor and preparation method thereof

Abstract

The invention discloses a bismuth-based perovskite photosynapse transistor and a preparation method thereof, and the bismuth-based perovskite photosynapse transistor is of a layered structure, and sequentially comprises a silicon dioxide / silicon substrate layer, a bismuth-based perovskite light absorption layer doped with stannous iodide, a semiconductor channel layer, and a source / drain electrode layer from bottom to top. The source / drain electrode layer comprises a source electrode and a drain electrode which are respectively arranged on two sides of the upper surface of the semiconductor channel layer; in the preparation process, bivalent tin ions of stannous iodide with relatively strong Lewis acidity compete with trivalent bismuth ions of cesium iodide in a precursor, so that rapid reaction of cesium iodide and bismuth iodide is prevented, the crystallization speed of the bismuth-based perovskite film is slowed down, and unstable tin-iodine bonds can be broken through annealing treatment after combination, so that the performance of the bismuth-based perovskite film is improved. Therefore, the crystallization quality of the bismuth-based perovskite film is regulated and controlled; part of bivalent tin ions in the bismuth-based perovskite light absorption layer are easily oxidized by a DMSO solvent in annealing treatment to form tetravalent tin ions to generate tin vacancies, and the tin vacancies of the bismuth-based perovskite light absorption layer are used for increasing the number of photogenerated charges captured by the bismuth-based perovskite photosynapse transistor. According to the invention, the film forming quality and the carrier lifetime of the bismuth-based perovskite can be improved, so that the conductivity variation range of the device is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of artificial vision, and particularly to a bismuth-based perovskite opto-synaptic transistor and a preparation method thereof. Background Art

[0002] Currently, the main architecture of artificial vision systems is composed of vision sensors and von Neumann computers. The physical separation of sensors, processing units, and memory makes artificial vision systems face bottleneck problems such as signal delay and high energy consumption. Neuromorphic computing, based on the efficient information processing mode of the human brain, is expected to break through the bottleneck of existing artificial vision systems. Artificial synaptic devices are the core components for constructing brain-inspired neuromorphic computing, and their performance determines the energy efficiency of the entire neuromorphic computing. Novel opto-synaptic transistors can directly use optical signals to adjust the synaptic weights of devices, realizing the integration of sensors, processors, and memories simultaneously, and have become a research hotspot in the field of neuromorphic devices in recent years.

[0003] To improve the accuracy of neuromorphic recognition, large conductance changes, i.e., synaptic weight changes, and small nonlinearity are very important for artificial synaptic devices. Currently, opto-synaptic transistors mainly use a combination of a light absorption layer and a high-mobility semiconductor to form a type-II heterojunction to simulate the behavior of biological synapses. After the light absorption layer senses the optical signal and generates excitons, the excitons are then separated at the heterojunction interface and transported into the semiconductor to adjust the channel conductance. Larger conductance changes can be achieved by increasing the amplitude and width of the optical pulse signal. However, the conductance change of opto-synaptic devices is limited by light absorption saturation and will eventually tend to flatten, deteriorating the linearity of the weight change and leading to a reduction in recognition accuracy. Therefore, to simultaneously achieve large conductance changes and small nonlinearity in opto-synaptic transistors, it is necessary to improve the optoelectronic conversion efficiency of the devices.

[0004] Opto-synaptic devices sense optical signals mainly by combining light absorption materials. Metal halide perovskites, as light absorption materials, have broad prospects in the application of opto-synaptic devices due to their unique optoelectronic properties. Compared with lead-based perovskite materials, bismuth-based perovskite (CsBi 3 I 10 ) has been applied in opto-synaptic transistors in recent years to sense optical signals due to its low toxicity, narrow bandgap width (~1.7 eV), and good stability (to water, heat, and light). The photocurrent-to-dark current ratio of opto-synaptic devices reflects the regulation range of optical signals on conductance. However, it has been reported that the ratio of the maximum conductance to the minimum conductance of the CsBi 3 I 10 composite opto-synaptic transistor is less than 10 after applying 30 optical pulse stimulations. The uncontrollable crystallization process and short carrier lifetime of CsBi 3 I 10 result in low optoelectronic conversion efficiency of its opto-synaptic devices. The uncontrollable crystallization process makes CsBi 3 I10 The film formation morphology is poor and the number of film layer defects increases, resulting in low transport efficiency of photo-generated charges at the heterojunction interface. In addition, CsBi 3 I 10 The short carrier lifetime is also not conducive to the separation of excitons in the device. These factors make CsBi 3 I 10 The low optoelectronic efficiency of the CsBiI optosynaptic transistor results in a small range of device conductance changes. SUMMARY OF THE INVENTION

[0005] In view of the above-mentioned partial defects of the prior art, the technical problem to be solved by the present invention is to provide a bismuth-based perovskite optosynaptic transistor and a preparation method thereof, aiming to improve the optoelectronic efficiency of the bismuth-based perovskite optosynaptic transistor, and further expand the range of device conductance changes.

[0006] To achieve the above object, in the first aspect of the present invention, a preparation of a bismuth-based perovskite optosynaptic transistor is disclosed. The bismuth-based perovskite optosynaptic transistor is a layered structure, which sequentially includes from bottom to top: a silicon dioxide / silicon-based bottom layer, a bismuth-based perovskite light absorption layer that is doped with stannous iodide and then annealed to form tin vacancies, a semiconductor channel layer, and a source / drain electrode layer; the source / drain electrode layer includes a source electrode and a drain electrode respectively disposed on both sides of the upper surface of the semiconductor channel layer; wherein, in the stage of doping the bismuth-based perovskite light absorption layer with stannous iodide, the solubility of cesium iodide and bismuth iodide in the precursor and the film crystallization quality are improved by adding the stannous iodide; in the annealing treatment stage of the bismuth-based perovskite light absorption layer, part of the divalent tin ions in the bismuth-based perovskite light absorption layer are oxidized to tetravalent tin ions by DMSO solvent during annealing to generate tin vacancies, and the tin vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photo-generated charge captures of the bismuth-based perovskite optosynaptic transistor.

[0007] In the second aspect of the present invention, a preparation method of a bismuth-based perovskite optosynaptic transistor is disclosed, which is applied to the above-mentioned bismuth-based perovskite optosynaptic transistor, and the method includes:

[0008] Step S1: Dissolve cesium iodide and bismuth iodide in a mixed solvent of DMF and DMSO according to a first ratio, and add a corresponding preset amount of stannous iodide to obtain a first mixed solution; wherein, the DMF is N,N-dimethylformamide, the DMSO is dimethyl sulfoxide, and the stannous iodide is used to improve the solubility of cesium iodide and bismuth iodide in the precursor;

[0009] Step S2: Spin-coat the first mixed solution onto a silicon dioxide / silicon substrate to form a bismuth-based perovskite film doped with tin(II) iodide. Here, tin(II) iodide is used to regulate the crystallization rate of the bismuth-based perovskite film and improve the crystallization quality of the bismuth-based perovskite film. Anneal the bismuth-based perovskite film to break unstable tin-iodine bonds, and cause some divalent tin ions to be oxidized to tetravalent tin ions by DMSO solvent during annealing to generate tin vacancies. The tin vacancies in the bismuth-based perovskite photoabsorber layer are used to increase the number of photo-generated charges captured by the bismuth-based perovskite photonic synapse transistor.

[0010] Step S3: Prepare a semiconductor channel layer on the bismuth-based perovskite photoabsorber layer.

[0011] Step S4: Prepare source and drain electrodes on both sides of the upper surface of the semiconductor channel layer to form a source / drain electrode layer.

[0012] Optionally, the concentration of the first mixed solution in the first mixed solution is 0.15 M, and the ratio of bismuth to tin is adjusted between 0 and 0.4 according to the chemical formula Cs(Bi 1-x Sn x ) 3 I 10 .

[0013] Optionally, step S2 includes:

[0014] Step S201: Clean the silicon dioxide / silicon substrate with acetone, isopropyl alcohol, and deionized water respectively. Treat the silicon dioxide / silicon substrate with oxygen plasma to improve the surface hydrophilicity of the silicon dioxide / silicon substrate.

[0015] Step S202: Place the silicon dioxide / silicon substrate in a nitrogen atmosphere and set the spin-coating speed to 3000 rpm. Drop the first mixed solution on the silicon dioxide / silicon substrate and spin-coat to form a film.

[0016] Step S203: Anneal the spin-coated silicon dioxide / silicon substrate in a nitrogen atmosphere at an annealing temperature of 100 - 150 °C for a first annealing treatment with an annealing duration of 20 - 40 min to break the tin-iodine bonds, regulate the crystallization rate of the bismuth-based perovskite film, and at the same time cause some divalent tin ions to be oxidized to tetravalent tin ions by DMSO solvent during annealing to generate tin vacancies.

[0017] Optionally, preparing a semiconductor channel layer on the bismuth-based perovskite photoabsorber layer includes:

[0018] Mix TIPS-pentacene and polystyrene with a concentration of 10 mg / mL in a volume ratio of 3:1 in chlorobenzene to obtain a second mixed solution; take the second mixed solution and drop-coat it on the bismuth-based perovskite light absorption layer to form the semiconductor channel layer, and then anneal it at 100 °C for 30 min in a nitrogen environment to obtain a bismuth-based perovskite / semiconductor composite film.

[0019] Optionally, in step S4, a source electrode and a drain electrode are prepared on both sides of the upper surface of the semiconductor channel layer to form a source / drain electrode layer, including:

[0020] Thermally evaporate a 50-nm-thick gold electrode on the semiconductor channel layer using a metal mask as the source electrode and the drain electrode to form a source / drain electrode layer.

[0021] Optionally, the silicon dioxide / silicon substrate is n-type and has a thickness of 100 nm.

[0022] Optionally, the channel length of the semiconductor channel layer is 80 μm and the width is 200 μm.

[0023] Advantages of the present invention: 1. The present invention improves the solubility of cesium iodide and bismuth iodide in the precursor by adding stannous iodide. The divalent tin ions of stannous iodide with relatively strong Lewis acidity compete with the trivalent bismuth ions of cesium iodide in the precursor, preventing the rapid reaction of cesium iodide and bismuth iodide, slowing down the crystallization rate of the bismuth-based perovskite film. Combining with post-annealing treatment can break the unstable tin-iodine bonds, realizing the controllability of the crystallization process of the bismuth-based perovskite, improving the film formation uniformity and the quality of its heterojunction interface, which is beneficial to improving the photo-generated charge transport efficiency to enhance the modulation ability of the optical signal on the device and increasing the conductance change range, and realizing the improvement of the image recognition accuracy of the bismuth-based perovskite photonic synaptic transistor. 2. Some divalent tin ions in the bismuth-based perovskite light absorption layer of the present invention are oxidized to tetravalent tin ions by DMSO solvent during annealing treatment to form tin vacancies. The tin vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photo-generated charges captured by the bismuth-based perovskite photonic synaptic transistor. The present invention utilizes the tin vacancies to capture the photo-generated electrons in the bismuth-based perovskite to cause a stronger optical gating effect, and the carrier lifetime is increased to 50 ns, accelerating the exciton separation of the bismuth-based perovskite photonic synaptic transistor to improve the device's photoelectric conversion efficiency and expand the device's conductance change range.

[0024] In summary, the present invention effectively expands the conductance change range of the device by controlling the crystallization of the bismuth-based perovskite to improve the film formation uniformity and using tin vacancies to capture photo-generated charges to increase the carrier lifetime. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a bismuth-based perovskite photonic synaptic transistor provided by a specific embodiment of the present invention;

[0026] Figure 2 It is a schematic flow chart of a method for preparing a bismuth-based perovskite optosynaptic transistor provided by a specific embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the principle of slowing down the crystallization efficiency, a schematic diagram of the device structure, and a schematic energy level diagram for enhancing the capture of photo-generated charges provided by a specific embodiment of the present invention;

[0028] Figure 4 It is a comparative diagram of the film formation experiments of bismuth-based perovskite with and without the addition of stannous iodide provided by a specific embodiment of the present invention;

[0029] Figure 5 It is a comparative diagram of the optical properties of the bismuth-based perovskite film layer with the addition of stannous iodide under different annealing conditions provided by a specific embodiment of the present invention. Detailed implementation manners

[0030] The present invention discloses a bismuth-based perovskite optosynaptic transistor and a preparation method thereof. Those skilled in the art can draw on the content of this article and appropriately improve the technical details to implement. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make changes or appropriate modifications and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0031] After research by the applicant, it is found that: Currently, there are still challenges in regulating the crystallization kinetics of CsBi 3 I 10 and the exciton separation efficiency of its optosynaptic transistor. Due to the low solubility of the precursor, CsBi 3 I 10 has too fast a crystallization rate during the solution deposition process. This leads to random crystal orientation, poor film uniformity, and an increase in the number of defects. Therefore, the key factor in improving the solution film formation quality is to slow down the crystallization rate of CsBi 3 I 10 One effective method to slow down the crystallization rate is to utilize the Lewis acid-base reaction, that is, to form a complex between the precursor and an additive with Lewis acid or basicity to increase solubility. In recent years, research teams at home and abroad have reported a variety of Lewis base solvents (such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone, and π-conjugated organic ligands, etc.) for forming complexes with metal halide perovskites to regulate their crystallization kinetics. Currently, research teams at home and abroad mainly use DMF solvent to mix a certain proportion of DMSO to form a highly soluble complex with Bi3+, so that CsBi 3 I10 The crystallization rate of the film during spin-coating film formation. The rapid reaction between Cs and Bi results in CsBi 3 I 10 having a faster crystallization rate than any other organic-inorganic or hybrid lead-based bismuth-based perovskite film. Also, DMSO, as a weakly coordinating solvent, is difficult to effectively retard the crystallization of CsBi 3 I 10 In the experiment, it was found that the CsBi 3 I 10 precursor prepared using a mixed solvent of DMSO and DMF gradually forms a precipitate after being left for some time, which is related to the limited solubility of CsI and BiI 3 in DMF. However, adding too much hydrophobic DMSO will reduce the adhesion of the precursor to the substrate. Therefore, new ways need to be explored to regulate the crystallization process of CsBi 3 I 10 .

[0032] Therefore, the embodiments of the present invention provide a bismuth-based perovskite opto-synaptic transistor. As Figure 1 shown, the bismuth-based perovskite opto-synaptic transistor is a hierarchical structure, which successively includes from bottom to top: a silicon dioxide / silicon-based bottom layer 101, a bismuth-based perovskite light absorption layer 102 that is first doped with stannous iodide and then annealed to form tin vacancies, a semiconductor channel layer 103, and a source / drain electrode layer 104; the source / drain electrode layer 104 includes a source electrode and a drain electrode respectively disposed on both sides of the upper surface of the semiconductor channel layer 103; wherein, in the stage of doping the bismuth-based perovskite light absorption layer with stannous iodide, the solubility of cesium iodide and bismuth iodide in the precursor and the film crystallization quality are improved by adding the stannous iodide; in the annealing treatment stage of the bismuth-based perovskite light absorption layer, some divalent tin ions in the bismuth-based perovskite light absorption layer are oxidized by a DMSO solvent during annealing to form tetravalent tin ions to generate tin vacancies, and the tin vacancies of the bismuth-based perovskite light absorption layer are used to increase the number of photo-generated charge captures of the bismuth-based perovskite opto-synaptic transistor.

[0033] It should be noted that the chemical formula of the bismuth-based perovskite is CsBi 3 I 10 , and the chemical formula of stannous iodide is SnI 2 . The silicon dioxide / silicon (SiO 2 / Si)-based bottom layer is composed of a silicon substrate and a silicon dioxide layer grown on its surface.

[0034] In this specific embodiment, the concentration of the first mixed solution in the bismuth-based perovskite light absorption layer 102 is 0.15M, and the ratio of bismuth to tin is Cs(Bi 1-x Sn x ) 3 I 10For chemical formula calculation, x is adjusted between 0 and 0.4. The divalent tin ions in stannous iodide are used to form divalent tin ion complexes during the preparation of the bismuth-based perovskite light absorption layer 102 to slow down the crystallization efficiency of the bismuth-based perovskite.

[0035] In this specific embodiment, the vacancy density of tin vacancies in the bismuth-based perovskite light absorption layer 102 is 10 16 -10 18 cm -3 .

[0036] It should be noted that the density of tin vacancies determines its ability to capture photo-generated charges. The greater the density, the more photo-generated charges are captured.

[0037] In this specific embodiment, the semiconductor channel layer 103 is prepared from TIPS-pentacene, and the source electrode and the drain electrode are prepared from one or more conductive materials including silver, gold, and aluminum.

[0038] It should be noted that TIPS-pentacene is a high-performance organic semiconductor material and is widely used in the field of organic electronic devices.

[0039] In this specific embodiment, the photocurrent / dark current ratio of the bismuth-based perovskite photonic synapse transistor is greater than or equal to 10 4 , and the maximum / minimum conductance ratio is 30 after applying 30 optical pulse stimulations.

[0040] It should be noted that the photocurrent / dark current ratio is a key indicator for evaluating the bismuth-based perovskite photonic synapse transistor and directly reflects the signal-to-noise ratio and sensitivity of the bismuth-based perovskite photonic synapse transistor. The conductance change range (maximum / minimum conductance ratio) of the photonic synapse transistor is one of its core performance indicators and directly determines its applicability in fields such as neuromorphic computing.

[0041] In this specific embodiment, the channel length of the semiconductor channel layer 103 is 80 μm and the width is 200 μm.

[0042] The embodiment of the present invention also provides a method for preparing a bismuth-based perovskite photonic synapse transistor, which is applied to the bismuth-based perovskite photonic synapse transistor provided above, as Figure 2 shown. This method includes

[0043] Step S1: Dissolve cesium iodide and bismuth iodide in a mixed solvent of DMF and DMSO according to a first ratio, and add a corresponding preset amount of stannous iodide to obtain a first mixed solution; wherein, the DMF is N,N-dimethylformamide, the DMSO is dimethyl sulfoxide, and the stannous iodide is used to increase the solubility of cesium iodide and bismuth iodide in the precursor;

[0044] Among them, DMF is N,N-dimethylformamide, DMSO is dimethyl sulfoxide, and the divalent tin ions in stannous iodide compete with the cesium ions in cesium iodide to slow down the combination of cesium iodide and bismuth iodide, and slow down the crystallization rate of the bismuth-based film.

[0045] In this specific embodiment, the concentration of the first mixed solution is 0.15 M, and the ratio of bismuth to tin is adjusted between 0 and 0.4 according to the chemical formula Cs(Bi 1-x Sn x ) 3 I 10 chemical formula calculation.

[0046] Step S2: Spin-coat the first mixed solution on the silicon dioxide / silicon substrate to form a bismuth-based perovskite film, and anneal the bismuth-based perovskite film to obtain a bismuth-based perovskite light-absorbing layer.

[0047] Among them, the bismuth-based perovskite light-absorbing layer is doped with stannous iodide.

[0048] Step S2: Spin-coat the first mixed solution on the silicon dioxide / silicon substrate to form a bismuth-based perovskite film doped with stannous iodide. Among them, the stannous iodide is used to regulate the crystallization rate of the bismuth-based perovskite film and improve the crystallization quality of the bismuth-based perovskite film; anneal the bismuth-based perovskite film to break the unstable tin-iodine bonds so that some divalent tin ions are oxidized to form tetravalent tin ions during the annealing process by the DMSO solvent to generate tin vacancies; among them, the tin vacancies in the bismuth-based perovskite light-absorbing layer are used to increase the number of photo-generated charges captured by the bismuth-based perovskite photo-synaptic transistor.

[0049] It should be noted that the pre-treatment of the substrate can ensure the film-forming quality on the substrate, and the spin-coating can make the formed film more uniform. In addition, the DMSO solvent can be replaced by other oxidants. The present invention does not limit the type of oxidant, and the equivalent oxidant replacement materials for the DMSO solvent also fall within the protection scope of the present invention.

[0050] In this specific embodiment, step S2 includes:

[0051] Step S201: Clean the silicon dioxide / silicon substrate with acetone, isopropyl alcohol and deionized water respectively; perform oxygen plasma treatment on the silicon dioxide / silicon substrate to improve the surface hydrophilicity of the silicon dioxide / silicon substrate;

[0052] Step S202: Place the silicon dioxide / silicon substrate in a nitrogen atmosphere, set the spin-coating speed to 3000 rpm; drop the bismuth-based perovskite precursor solution on the silicon dioxide / silicon substrate and spin-coat to form a film;

[0053] Step S203: Perform a first annealing treatment on the spin-coated silica / silicon substrate in a nitrogen atmosphere at an annealing temperature of 100 - 150 °C for an annealing duration of 20 - 40 min, so as to break the tin-iodine bonds, regulate the crystallization rate of the bismuth-based perovskite film, and at the same time oxidize part of the divalent tin ions to tetravalent tin ions during the annealing treatment in the DMSO solvent to generate tin vacancies.

[0054] Among them, the tin vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photo-generated charge captures by the bismuth-based perovskite photonic synaptic transistor.

[0055] It should be noted that during the annealing process, Sn 2+ is oxidized to Sn 4+ , forming Sn vacancies to capture photo-generated electrons, enhancing the optical gating effect, and increasing the carrier lifetime to 50 ns.

[0056] In this specific embodiment, step S3 includes:

[0057] Mix TIPS-pentacene and polystyrene with a concentration of 10 mg / mL each in a volume ratio of 3:1 in chlorobenzene to obtain a second mixed solution; take the second mixed solution and drop-coat it on the bismuth-based perovskite light absorption layer to form the semiconductor channel layer, and then anneal it at 100 °C for 30 min in a nitrogen environment to obtain a bismuth-based perovskite / semiconductor composite film.

[0058] Step S4: Fabricate source and drain electrodes on both sides of the upper surface of the semiconductor channel layer to form a source / drain electrode layer.

[0059] In this specific embodiment, fabricating source and drain electrodes on both sides of the upper surface of the semiconductor channel layer in step S4 to form a source / drain electrode layer includes:

[0060] Use a metal mask to thermally evaporate a 50-nm-thick gold electrode on the semiconductor channel layer as the source and drain electrodes to form a source / drain electrode layer.

[0061] It should be noted that the gold electrode has excellent conductivity and can improve the performance of the bismuth-based perovskite photonic synaptic transistor.

[0062] In this specific embodiment, the silica / silicon substrate is n-type and has a thickness of 100 nm.

[0063] In this specific embodiment, the channel length of the semiconductor channel layer is 80 μm and the width is 200 μm.

[0064] In this specific embodiment, as Figure 3 shown, Figure 3 in (a), using SnI 2 to delay CsBi 3 I10 Schematic diagram of the crystallization rate, where Sn in (a) 2+ competes with Bi 3+ to slow down the crystallization rate of CsBi 3 I 10 .

[0065] (b) is the schematic diagram of the device structure and the energy level diagram of enhancing the photo-generated charge capture by Sn vacancies. In (b), the Sn vacancies can bind photo-generated charges, thereby causing a stronger optical gating effect and improving the carrier lifetime.

[0066] In a specific application scenario, by comparing the CsBi with and without the addition of SnI 2 I 3 I 10 comparative experiments are used to show the improvement of the performance of the bismuth-based perovskite photo-synaptic transistor in the embodiments of the present invention. As Figure 4 shown, Figure 4 in, (a) is the CsBi 3 I 10 precursor, (b) is the CsBi with the addition of SnI 2 I 3 I 10 precursor, (c) is the photos of the CsBi 3 I 10 film and the CsBi 2 I 3 I 10 film with the addition of SnI 3 I 10 after spin coating on a glass substrate and then undergoing 10-minute post-treatment: vacuum pumping, annealing at 60 °C, and annealing at 100 °C. (d) is the optical microscope image of the CsBi 2 I 3 I 10 film and (e) is the optical microscope image of the CsBi 2 I

[0067] In a specific application scenario, by comparing the experiments of different annealing temperatures of the CsBi 2 I 3 I 10 film with the addition of SnI Figure 5 shown, the addition of SnI 2 I 3 I 10The ultraviolet-visible absorption spectra of the film after spin coating on a glass substrate and then undergoing post-treatment for 10 minutes: vacuum pumping, annealing at 60 °C, and annealing at 100 °C are as Figure 5 shown in (f), and the X-ray diffraction spectra are as Figure 5 shown in (g). By comparing the three cases of vacuum pumping, annealing at 60 °C, and annealing at 100 °C in (f) and (g), it can be found that the CsBi 3 I 10 film performance of annealing at 100 °C is greater than that of annealing at 60 °C and greater than that of vacuum pumping (without annealing). Because more Sn vacancies are formed during annealing at 100 °C, which can capture more photo-generated electrons of bismuth-based perovskite, causing a stronger optical gating effect, accelerating the exciton separation of bismuth-based perovskite photo-synaptic transistors to improve the device's photoelectric conversion efficiency and expand the device's conductance change range.

[0068] In the embodiments of the present invention, the crystallization process of bismuth-based perovskite is regulated by adding tin iodide. By using the Lewis acid additive tin iodide, divalent tin ions compete with cesium ions of cesium iodide to form a complex, thereby slowing down the crystallization rate of the bismuth-based film, realizing the controllability of the crystallization process of bismuth-based perovskite, improving the film formation uniformity and the quality of its heterojunction interface, being beneficial to improving the photo-generated charge transport efficiency to enhance the device's ability to adjust to optical signals and increasing the conductance change range, and realizing the improvement of the image recognition accuracy of bismuth-based perovskite photo-synaptic transistors.

[0069] In the embodiments of the present invention, some divalent tin ions in the bismuth-based perovskite light absorption layer are oxidized to tetravalent tin ions during annealing treatment to form Sn vacancies. The Sn vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photo-generated charge captures of bismuth-based perovskite photo-synaptic transistors. The embodiments of the present invention utilize the Sn vacancies to capture photo-generated electrons of bismuth-based perovskite, causing a stronger optical gating effect, and the carrier lifetime is increased to 50 ns, accelerating the exciton separation of bismuth-based perovskite photo-synaptic transistors to improve the device's photoelectric conversion efficiency and expand the device's conductance change range.

[0070] In summary, the embodiments of the present invention effectively expand the device's conductance change range by controlling the crystallization of bismuth-based perovskite to improve the film formation uniformity and using Sn vacancies to capture photo-generated charges to increase the carrier lifetime.

[0071] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0072] Each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and reference can be made to the relevant parts of the method embodiments for the relevant content.

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A bismuth-based perovskite optical synapse transistor, characterized in that: The bismuth-based perovskite photosynaptic transistor has a layered structure, which includes, from bottom to top, a silicon dioxide / silicon substrate layer, a bismuth-based perovskite light absorption layer that is first doped with stannous iodide and then annealed to form tin vacancies, a semiconductor channel layer, and a source / drain electrode layer; the source / drain electrode layer includes a source electrode and a drain electrode that are respectively arranged on both sides of the upper surface of the semiconductor channel layer; wherein, in the stage of doping the stannous iodide, the bismuth-based perovskite light absorption layer improves the solubility of cesium iodide and bismuth iodide in the precursor and the film crystal quality by adding the stannous iodide; in the stage of annealing the bismuth-based perovskite light absorption layer, part of the divalent tin ions in the bismuth-based perovskite light absorption layer are oxidized by DMSO solvent during the annealing process to form tetravalent tin ions to generate tin vacancies, and the tin vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photogenerated charges captured by the bismuth-based perovskite photosynaptic transistor.

2. A method for preparing a bismuth-based perovskite optical synapse transistor, characterized in that: The bismuth-based perovskite optical synapse transistor according to claim 1, wherein the method comprises: Step S1, dissolving cesium iodide and bismuth iodide in a mixed solvent of DMF and DMSO in a first ratio, and adding a corresponding preset amount of stannous iodide to obtain a first mixed solution; wherein the DMF is N,N-dimethylformamide, the DMSO is dimethyl sulfoxide, and the stannous iodide is used to increase the solubility of cesium iodide and bismuth iodide in the precursor; Step S2, spin-coating the first mixed solution on a silicon dioxide / silicon substrate to form a bismuth-based perovskite film doped with stannous iodide, wherein the stannous iodide is used to regulate the crystallization rate of the bismuth-based perovskite film and improve the crystallization quality of the bismuth-based perovskite film; annealing the bismuth-based perovskite film to break the unstable tin-iodine bond so that part of the divalent tin ions are oxidized by the DMSO solvent during the annealing process to form tetravalent tin ions to generate tin vacancies; wherein the tin vacancies in the bismuth-based perovskite light absorption layer are used to increase the number of photogenerated charges captured by the bismuth-based perovskite photosynaptic transistor; Step S3, preparing a semiconductor channel layer on the bismuth-based perovskite light absorption layer; Step S4: preparing a source electrode and a drain electrode on the upper surface of the semiconductor channel layer to form a source / drain electrode layer.

3. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: The concentration of the first mixed solution is 0.15M, and the ratio of bismuth to tin is Cs(Bi 1-x Sn x )3I 10 Chemical formula calculation, x is adjusted between 0-0.

4.

4. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: The step S2 comprises: Step S201, washing the silicon dioxide / silicon substrate with acetone, isopropanol and deionized water respectively; treating the silicon dioxide / silicon substrate with oxygen plasma to improve the hydrophilicity of the surface of the silicon dioxide / silicon substrate; Step S202, placing the silicon dioxide / silicon substrate in a nitrogen atmosphere, setting the spin coating speed to 3000 rpm; dropping the first mixed solution on the silicon dioxide / silicon substrate and spin coating to form a film; Step S203, annealing the spin-coated silicon dioxide / silicon substrate in a nitrogen atmosphere at a temperature of 100-150° C. for a first annealing time of 20-40 min to break the tin-iodine bond, regulate the crystallization rate of the bismuth-based perovskite film, and at the same time, oxidize part of the divalent tin ions through the DMSO solvent during the annealing process to form tetravalent tin ions to generate tin vacancies.

5. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: In the step S3, a semiconductor channel layer is prepared on the bismuth-based perovskite light absorption layer, comprising: TIPS-pentacene and polystyrene, both with a concentration of 10 mg / mL, are mixed in chlorobenzene in a volume ratio of 3:1 to obtain a second mixed solution; the second mixed solution is drop-coated on the bismuth-based perovskite light absorption layer to form the semiconductor channel layer, and then annealed at 100°C for 30 minutes in a nitrogen environment to obtain a bismuth-based perovskite / semiconductor composite film.

6. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: In the step S4, source electrodes and drain electrodes are prepared on both sides of the upper surface of the semiconductor channel layer to form a source / drain electrode layer, including: A gold electrode with a thickness of 50 nm is thermally evaporated on the semiconductor channel layer using a metal mask as the source electrode and the drain electrode to form a source / drain electrode layer.

7. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: In the step S4, the semiconductor channel layer and the source / drain electrode layer are prepared by depositing corresponding materials.

8. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: The silicon dioxide / silicon substrate is of n-type and has a thickness of 100 nm.

9. The method for preparing a bismuth-based perovskite optical synapse transistor according to claim 2, characterized in that: The channel length of the semiconductor channel layer is 80 μm and the width is 200 μm.

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