An optoelectronic device based on single crystal homogeneous structure and its application

Abstract

The present invention provides an optoelectronic device based on a single crystal homogeneous structure and its application. The optoelectronic device includes crystal materials with different gel concentrations. Different gel embedding areas are introduced into the single crystal by asymmetric embedding to construct a single crystal homojunction, and the homojunction device realizes self-driven photoelectric response characteristics; and constructs lateral and vertical optoelectronic devices based on the single crystal homojunction. Unlike single crystal photoconductive symmetrical structure devices prepared only by traditional solution methods, the optoelectronic device of the present invention does not require additional bias voltage to ensure the normal operation of the device, and can realize a photodiode structure similar to a traditional inorganic semiconductor homojunction; this gel-embedded asymmetric structure enables the optoelectronic device to have current-voltage characteristics similar to traditional semiconductor homojunction diodes, can effectively perform photoelectric conversion, and can be widely used in photodetectors and other optoelectronic devices.

Description

Technical Field

[0001] The present invention relates to the fields of novel composite material preparation and optoelectronic technology, and in particular to an optoelectronic device based on a single crystal homogeneous structure and its application. Background Art

[0002] A semiconductor single crystal homojunction is an interface structure composed of different regions of the same semiconductor material. Differences in doping concentration or crystal structure create a built-in electric field or space charge region. The presence of this electric field causes energy band bending, forming a potential barrier. This barrier controls the flow of carriers in the device, forming an interface with unique electrical properties. In modern semiconductor technology, homojunctions are the most common structure and play an important role in many electronic and optoelectronic devices, such as diodes, transistors, solar cells, and semiconductor lasers. However, the existing commonly used single crystal silicon homojunction preparation process often uses processes such as thermal diffusion and ion implantation, and the entire process involves material growth, doping control, interface quality, and heat treatment. Its applicability to semiconductor single crystals is limited, the entire process consumes a lot of energy, and it is not suitable for some existing solution-based single crystal preparation processes.

[0003] By growing single crystals through the gel method and embedding the gel network into semiconductor single crystals, it is possible to introduce a large-area gel-semiconductor crystal contact interface while maintaining the long-range order of the single crystal. This method not only does not affect the long-range order of the single crystal itself in terms of crystal structure, but also effectively introduces interfacial interactions between the gel material and the single crystal, thus providing new possibilities for optimizing device performance. In addition, the formation of the gel-single crystal composite material does not affect some basic properties of the single crystal, such as lattice constant and optical absorption.

[0004] Previously, gel single-crystal composite materials were primarily used to construct heterojunction optoelectronic devices for applications such as photodetection and solar cells. However, methods for fabricating homojunction optoelectronic devices using gel network embedding have not yet been proposed. Therefore, achieving stable gel embedding to construct homojunction optoelectronic devices based on single crystals remains challenging. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an optoelectronic device based on a single crystal homogeneous structure to solve the problems in the prior art.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention is achieved through the following technical solutions.

[0007] A first aspect of the present invention provides an optoelectronic device based on a single crystal homojunction, the optoelectronic device comprising a first electrode, a photoelectric crystal layer, and a second electrode;

[0008] The photoelectric crystal layer includes a first crystal layer and a second crystal layer;

[0009] The first crystal layer is connected to the second crystal layer, and the interface between the connected layers forms a homojunction;

[0010] One of the first electrode and the second electrode is connected to the first crystal layer, and the other is connected to the second crystal layer;

[0011] The first electrode is not in contact with the second electrode;

[0012] The first crystal layer is a gel single crystal composite material grown in a first gel;

[0013] The second crystal layer is a pure single crystal material or a gel single crystal composite material grown in a second gel;

[0014] The first gel and the second gel have different gel types and / or gel concentrations.

[0015] In certain embodiments, when the first gel and the second gel are of the same gel type, the concentration of the second gel is less than that of the first gel;

[0016] In some of the embodiments, when the first gel and the second gel are of different types, the concentration of the second gel is less than or equal to the concentration of the first gel;

[0017] The single crystals in the first crystal layer and the second crystal layer are of the same type and are connected to form a homojunction.

[0018] In some embodiments, the first gel and the second gel are independently selected from one or more of sodium metasilicate gel, silicone gel, dextran gel, polyacrylamide gel, agarose gel, and semiconductor gel.

[0019] In certain preferred embodiments, the concentration of the first gel is 0.3 w / v% to 60 w / v%; it can also be 0.3 w / v% to 30 w / v%, or it can also be 30 w / v% to 60 w / v%.

[0020] In certain preferred embodiments, the gel concentration of the second gel is 0.3 w / v% to 60 w / v%; it can also be 0.3 w / v% to 30 w / v%, or it can also be 30 w / v% to 60 w / v%.

[0021] In the present invention, the difference between the first crystal layer and the second crystal layer is only that one grows in the first gel and the other grows in the second gel, and other conditions remain the same.

[0022] The present invention can be completed as long as the types or concentrations of the first gel and the second gel are different. They can also be selected based on the principles of device design and work function matching. For example, taking agarose gel as an example, its concentration suitable for single crystal growth is 0.3w / v% to 0.6w / v%. If the first gel and the second gel are both agarose gels, then 0.3w / v%≤second gel concentration<first gel concentration≤0.6w / v%, and the larger the difference in concentration between the first gel and the second gel, the better.

[0023] The concentration difference between the first gel and the second gel is 0 to 60, or 0.01 to 55, or 0.1 to 45, or 0.3 to 40, or 5 to 30, or 10 to 20, or 0.1, 0.3, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60; within a reasonable range, on the basis of ensuring the performance of the single crystal, the greater the concentration difference, the more conducive it is to having current-voltage characteristics similar to those of a traditional semiconductor homojunction diode.

[0024] In the present invention, the gel single crystal composite material is a composite structure formed by combining a gel network with a single crystal material.

[0025] In the present invention, the pure single crystal material is a single crystal material without gel embedding prepared by a non-gel crystal growth method; for example, it can be prepared by an evaporation crystallization method, a cooling crystallization method, or an anti-solvent diffusion crystallization method that does not involve gel.

[0026] The present invention achieves asymmetric embedding of the gel network into the crystal by setting different gel concentrations and / or types in the first and second crystal layers of the photoelectric crystal layer. This method differs from single-crystal photoconductive symmetrical structure devices prepared by traditional solution methods (such as evaporation crystallization methods that do not involve gel, cooling crystallization methods, or anti-solvent diffusion crystallization). It does not require an additional bias voltage to ensure normal operation of the device and can achieve a photodiode structure similar to that of a traditional inorganic semiconductor homojunction. This gel-embedded asymmetric structure gives the optoelectronic device current-voltage characteristics similar to those of a traditional semiconductor homojunction diode, enabling efficient photoelectric conversion and finding widespread application in photodetectors and other optoelectronic devices.

[0027] The ability of asymmetric gels to modulate the work function of crystals stems from the different types or ratios of gel groups within the asymmetric gel. These differences in the types or ratios of gel groups embedded in a single crystal produce different dipole interactions, and thus, different effects on the crystal's work function. For example, sodium metasilicate gel contains silanol groups and silanol-oxygen-silicon bonds. It is speculated that silanol-oxygen-silicon bonds are the primary agents in sodium metasilicate gels. Therefore, at the same gel concentration, a higher silanol-oxygen-silicon bond ratio has a greater influence on the work function. Similarly, the situation in agarose gel is similar, but hydroxyl groups play a primary role. Higher gel concentrations increase the hydroxyl content per unit volume, further impacting the crystal's work function. For example, in lead iodide grown in agarose gel, different ratios of hydroxyl groups to carbon-oxygen-carbon bonds within two regions of a single crystal can form a homojunction. Specifically, one region has a higher ratio or concentration of hydroxyl groups, while an adjacent region has a lower ratio or concentration of hydroxyl groups. Connecting these two regions creates a homojunction.

[0028] In certain embodiments, the gel comprises one or more of sodium metasilicate gel, silicone gel, dextran gel, polyacrylamide gel, agarose gel, and semiconductor gel.

[0029] In certain embodiments, the sodium metasilicate gel concentration is 3 to 20 w / v%. Within this concentration range, the work function of the lead iodide single crystal increases continuously with increasing gel concentration, shifting the overall band structure downward. However, at higher gel concentrations, the work function change is discontinuous and non-monotonic, and the crystal growth time is significantly prolonged.

[0030] In certain embodiments, the agarose gel concentration is between 0.3 w / v% and 0.6 w / v%. Within this concentration range, the work function of lead iodide decreases continuously with increasing gel concentration, shifting the overall band structure upward. However, at gel concentrations above 0.6 w / v%, the crystal morphology rapidly deteriorates, and hexagonal flake crystals no longer grow. Furthermore, crystal growth time is significantly prolonged.

[0031] In certain embodiments, the silicone gel has a gel concentration of 5 to 20 w / v%.

[0032] In certain embodiments, the single crystals in the first gel single crystal composite material and the single crystals in the second gel single crystal composite material include inorganic single crystals, organic single crystals, or organic-inorganic hybrid single crystals.

[0033] In some embodiments, the inorganic single crystal includes: PbI2, PbS, inorganic perovskites (such as CsPbX3, etc.), KDP, cuprous (such as Cu2O, Cu2S, etc.), ZnO, certain transition metal sulfides (such as SnS), etc.

[0034] In certain embodiments, the organic single crystal includes fullerene, anthracene, and other organic semiconductor crystals.

[0035] In certain embodiments, the organic-inorganic hybrid single crystal includes: an organic-inorganic hybrid perovskite single crystal, such as MAPbX3, PEAPbX3, etc.; wherein X is a halogen element, specifically Cl (chlorine), Br (bromine) or I (iodine).

[0036] In certain embodiments, the preparation method of the gel single crystal composite material includes: a gel diffusion method, a gel anti-solvent diffusion method or a gel cooling method.

[0037] The gel diffusion method includes: diffusing the reactants for producing single crystals into the gel to react, and when the reaction products accumulate to a certain extent, they become supersaturated, nucleate and crystallize to obtain a gel single crystal composite material.

[0038] The gel anti-solvent diffusion method comprises: dissolving the reactants for producing single crystals in gel, then adding anti-solvent, nucleating and crystallizing to obtain gel single crystal composite materials.

[0039] The gel cooling method comprises: dissolving reactants for producing single crystals in gel, then slowly cooling, nucleating and crystallizing to obtain a gel single crystal composite material.

[0040] In the preparation method of the gel single crystal composite material, the gel can be a single-layer gel, such as the first gel layer or the second gel layer, based on which the first crystal layer or the second crystal layer grown in the first gel or the second gel can be obtained; the gel can also be a multi-layer gel including the first gel layer and the second gel layer, wherein the first gel layer and the second gel layer can be arranged alternately in sequence, and the photoelectric crystal layer including the first crystal layer and the second crystal layer can be taken out at the interface between the first gel layer and the second gel layer, so that the gel single crystal composite material containing two gel concentrations embedded can be obtained at one time, and the photoelectric crystal layer including the first crystal layer and the second crystal layer can be prepared only once; wherein the first gel layer and the second gel layer can be gel layers that do not contain reactants, or can be gel layers that contain reactants.

[0041] For example, the gel diffusion method for preparing gel single crystal composite materials often uses the U-tube method or adds a blank gel layer at the gel-solution interface containing different reactants to prepare single crystal materials, where the role of the blank gel is to reduce the diffusion rate and the concentration of reactants in the gel.

[0042] In certain embodiments, the solvent of the gel comprises water or an organic solvent.

[0043] In certain embodiments, the organic solvent comprises one or more of methanol, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), dichloromethane (DCM), and 1,4-butyrolactone.

[0044] In certain embodiments, if a sodium metasilicate hydrogel is used to prepare a single crystal material by a gel growth method, the gel concentration of the sodium metasilicate hydrogel is 3 to 20 w / v%. Within this concentration range, the work function of materials such as lead iodide single crystals or perovskite materials will also continuously increase with increasing gel concentration, and the overall band structure will shift downward. However, at high gel concentrations, the work function change is discontinuous and non-monotonic, and the crystal growth time will also be greatly extended. The gel concentration of the sodium metasilicate hydrogel can also be 5 to 15 w / v%, 10 to 15 w / v%, 5 to 10 w / v%, 8 to 12 w / v%, or 5 w / v%, 10 w / v%, or 15 w / v%.

[0045] In certain embodiments, when agarose hydrogel is used to prepare a single crystal material through a gel growth method, the concentration of the agarose hydrogel is 0.3 w / v% to 0.6 w / v%. Within this concentration range, the work function of lead iodide, for example, will continuously decrease with increasing gel concentration, and the overall band structure will shift upward. However, at high gel concentrations above 0.6 w / v%, the crystal morphology rapidly deteriorates, and flaky hexagonal crystals no longer grow, and the crystal growth time is also greatly prolonged. The gel concentration of the agarose hydrogel can also be 0.3 w / v% to 0.4 w / v%, 0.4 w / v% to 0.6 w / v%, and 0.3 w / v%, 0.4 w / v%, 0.5 w / v%, or 0.6 w / v%.

[0046] In certain embodiments, the method for preparing a single crystal material in the gel specifically includes: diffusing the reactants for producing single crystals into the gel to react, and when the reaction products accumulate to a certain extent, supersaturation occurs, nucleation and crystallization occur, and a gel-embedded single crystal material is obtained.

[0047] The preparation method of single crystal material in gel mostly adopts U-tube method or adds a blank gel at the interface of gel-solution containing different reactants to prepare single crystal material, wherein the blank gel plays the role of reducing the diffusion rate and the concentration of reactants in the gel.

[0048] In certain embodiments, the U-tube method comprises adding two reactant solutions to both ends of the U-tube, and adding a layer of blank gel containing no reactants to the middle portion of the U-tube; as the reactant solutions diffuse, the two reactants meet and react in the blank gel to generate a supersaturated solution, thereby precipitating crystals; and obtaining a gel single crystal composite material.

[0049] In certain embodiments, the specific steps of adding a blank gel layer at the gel-solution interface containing different reactants to prepare a single crystal material include: dissolving one reactant in the gel, and after the gel solidifies, adding a solution of another reactant to its surface; in order to slow down the reaction rate, a layer of blank gel without reactants can be added between the reactant solution and the gel; the reactants diffuse into the gel, slowly react and precipitate crystals; and obtaining a gel single crystal composite material.

[0050] In certain embodiments, the gel is a single-layer gel or a multi-layer gel, wherein the multi-layer gel comprises gel layers with different gel concentrations; wherein the gel may be a gel that does not contain reactants or a gel that contains reactants.

[0051] Exemplarily, the method for preparing the multilayer gel includes: preparing gel solutions containing reactants or not containing reactants with different gel concentrations, and after forming a layer of gel, adding a second layer or multiple layers of gel thereon to form a multilayer gel; achieving a multilayer gel in which gel layers with different gel concentrations are alternately distributed.

[0052] In some embodiments, the multilayer includes 2 or more layers, and can also be 2 to 20 layers, or can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 20 layers.

[0053] When using the gel method to produce gel single crystal composite materials, the amount of each component is adjusted according to the growth position of the selected single crystal; if it is necessary to generate a single crystal in a gel that does not contain a reactant (i.e., a blank gel), the volume ratio of the blank gel to the reactant is 1:0.8-1.2; it can also be 1:0.9, 1:1 or 1:1.1; preferably 1:1; it can be appropriately adjusted according to the experimental conditions; the blank gel can be a single layer or a multi-layer gel, and if it is a multi-layer gel, the volume ratio between each layer of gel is also 1:0.8-1.2; preferably 1:1; if the blank gel is a multi-layer gel, the volume of the blank gel is the total volume of the multi-layer gel.

[0054] For example, the above-mentioned U-tube method is used; the volume ratio of the blank gel to the two reactant solutions is 1:0.8-1.2.

[0055] If it is desired to form single crystals in a gel containing reactants, one or more reactant solutions can be used as gel solutions, and a blank gel can be added between the reactant solutions to adjust the reaction rate. In this case, a smaller amount of blank gel is used to avoid an excessively thick blank gel layer. The volume ratio of the blank gel to the gel containing reactants is 1:5-10, and can also be 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. The volume ratio between the reactant solutions is 1:0.8-1.2, preferably 1:1. The gel containing reactants can be a single layer or multiple layers. If it is a multilayer gel, the volume ratio between each gel layer is also 1:0.8-1.2, preferably 1:1.

[0056] In certain embodiments, the preparation method of the pure single crystal material includes evaporation crystallization, cooling crystallization or anti-solvent diffusion crystallization without gel, wherein the pure single crystal material has no gel embedded in it.

[0057] The present invention utilizes a gel method to prepare a gel single crystal composite material. The characteristics of gel growth are exploited to introduce a large-area gel network into the contact interface with the single crystal while maintaining the long-range order of the single crystal, achieving uniform doping of the single crystal with the gel network. Furthermore, by embedding gel networks of varying concentrations and / or compositions, the work function of the semiconductor single crystal can be continuously controlled. Furthermore, by asymmetrically embedding gel networks of varying concentrations and / or compositions into the single crystal, homojunctions and optoelectronic devices can be prepared.

[0058] The present invention is further explained by taking lead iodide single crystal as an example;

[0059] The method for preparing the gel-lead iodide single crystal material comprises (b1), (b2) or (b3):

[0060] (b1) placing an aqueous solution of a lead compound and an aqueous solution of an iodine compound on both sides of a first gel or a second gel, respectively, and growing the single crystal in a constant temperature and light-proof environment, then removing the single crystal from the gel, cleaning the surface of the single crystal, and drying to obtain a first crystal layer or a second crystal layer;

[0061] (b2) placing a lead-containing compound and an iodine-containing compound on both sides of the first gel or the second gel, respectively, wherein one of the lead-containing compound and the iodine-containing compound comprises the first gel, the second gel, and one is an aqueous solution or comprises the second gel; growing the single crystal at the interface of the first gel and the second gel in a constant temperature and light-proof environment, then removing the single crystal located at the interface of the first gel and the second gel, cleaning the surface of the single crystal, and drying the single crystal to obtain a photoelectric crystal layer comprising the first crystal layer and the second crystal layer;

[0062] (b3) preparing a multilayer gel, wherein the multilayer gel comprises a first gel layer and a second gel layer, adding an aqueous solution of a lead compound and an aqueous solution of an iodine compound to both sides of the multilayer gel, respectively, placing the multilayer gel in a constant temperature and light-proof environment for growth, then taking out a single crystal located at the junction of the gel layers of the first gel layer and the second gel from the gel, cleaning the surface of the single crystal, and drying the gel to obtain a photoelectric crystal layer comprising the first crystal layer and the second crystal layer; wherein the multilayer gel is two or more layers, wherein the first gel layer and the second gel layer are alternately arranged in sequence.

[0063] Exemplarily, (b2) may be: placing a lead-containing compound and an iodine-containing compound on both sides of the gel of the first gel, respectively, wherein the lead-containing compound includes a lead-containing compound gel containing the first gel and a lead-containing compound gel containing the second gel; the iodine-containing compound includes an iodine-containing compound gel containing the second gel; wherein the lead-containing compound may also be a lead-containing compound gel that may be two or more layers, wherein the lead-containing compound gel containing the first gel and the lead-containing compound gel containing the second gel may be arranged alternately in sequence; growing under a constant temperature and light-proof environment, then taking out the crystal located at the junction of the gel layers of the first gel and the second gel, cleaning the crystal surface, and drying to obtain a photoelectric crystal layer containing the first crystal layer and the second crystal layer.

[0064] However, this is not limiting. The iodine-containing compound can be an aqueous solution without gel, or an iodine-containing compound gel comprising a first gel and an iodine-containing compound gel comprising a second gel. The lead-containing compound can also be an aqueous solution of a lead-containing compound, and the iodine-containing compound can be an iodine-containing compound gel comprising a first gel and an iodine-containing compound gel comprising a second gel. Any method is acceptable as long as at least one of the reactants is a reactant gel comprising the first gel and a reactant gel comprising the second gel. As long as a photoelectric crystal layer comprising a first crystal layer and a second crystal layer can be removed from the crystal at the interface between the first and second gels, the method is acceptable.

[0065] The present invention further provides a method for preparing a sodium metasilicate hydrogel-lead iodide single crystal material, comprising: mixing a sodium metasilicate aqueous solution and an acid solution, pouring the mixture into a U-shaped tube (which can be replaced by other containers) and allowing the mixture to stand to form a sodium metasilicate hydrogel; adding a lead-containing compound aqueous solution and an iodine-containing compound aqueous solution to both sides of the sodium metasilicate hydrogel in the U-shaped tube, respectively; growing the mixture in a constant temperature and light-proof environment; then removing the single crystal from the gel, cleaning the surface of the single crystal, and drying the mixture to obtain the sodium metasilicate hydrogel-lead iodide single crystal material.

[0066] In certain embodiments, the gel concentration in the sodium metasilicate hydrogel is 3 w / v% to 20 w / v%.

[0067] In certain embodiments, the volume ratio of the sodium metasilicate aqueous solution to the acid solution is 1:0.5-5; it can also be 1:0.5-2; it can also be 1:2-5; it can also be 1:1-3; but it is not limited thereto and can be selected according to actual conditions. It is mainly through the reaction of the acid solution with the sodium metasilicate to form orthosilicic acid, and then the orthosilicic acid is dehydrated and condensed into a gel network.

[0068] In certain embodiments, the acid solution includes an aqueous acetic acid solution, an aqueous hydrobromic acid solution, or the like.

[0069] This example mainly uses the U-tube method to prepare sodium metasilicate hydrogel-lead iodide single crystal material. It can also prepare single crystal materials by adding a blank gel layer at the gel-solution interface containing different reactants, such as preparing lead iodide single crystal material by adding a metasilicic acid hydrogel at the interface of sodium metasilicate hydrogel containing lead compound and aqueous solution containing iodine compound.

[0070] In certain embodiments, the sodium metasilicate hydrogel has a gel concentration of 3 w / v% to 20 w / v%, where the gel concentration refers to the concentration of sodium metasilicate, measured based on a solution obtained by mixing an aqueous sodium metasilicate solution with an aqueous acetic acid solution. For example, a gel concentration of 10 w / v% is prepared by first dissolving 5 g of sodium metasilicate pentahydrate in 25 mL of ultrapure water and then mixing with 25 mL of an aqueous acetic acid solution; the concentration of the aqueous acetic acid solution is 10 to 20 v / v%.

[0071] In certain embodiments, the iodine-containing compound comprises potassium iodide (KI), sodium iodide (NaI), or ammonium iodide (NH4I); preferably, potassium iodide.

[0072] In certain embodiments, the lead-containing compound includes lead nitrate (Pb(NO3)2) or lead acetate ((CH3COO)2Pb); preferably lead acetate.

[0073] In certain embodiments, the standing time is 12-48 hours, or 12-24 hours, or 24-48 hours, but is not limited thereto, and is based on the formation of a gel state.

[0074] In certain embodiments, the lead acetate aqueous solution further comprises 5-15 v / v% acetic acid; it may be 5-10 v / v% acetic acid, it may be 10-15 v / v% acetic acid, or it may be 5, 10, or 15 v / v% acetic acid.

[0075] In certain embodiments, the concentration of the lead compound aqueous solution is 0.2-0.4 mol / L; it can also be 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L.

[0076] In certain embodiments, the concentration of the aqueous solution of the iodine-containing compound is 0.2-0.4 mol / L; it can also be 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L.

[0077] In some embodiments, the crystal growth time in the gel is 20-40 days; it can also be 20-30 days, 30-40 days, 25-35 days, or 20 days, 25 days, 30 days, 35 days, or 40 days; preferably 30 days; but it is not limited thereto and can be adjusted according to the single crystal material.

[0078] In some embodiments, the temperature of crystal growth in the gel is 15-35°C; it can also be 15-25°C, it can also be 25-35°C, it can also be 15°C, 16°C, 17°C, 18°C, 18°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 30°C, 35°C.

[0079] In certain embodiments, the drying is vacuum drying.

[0080] In certain embodiments, the drying temperature is 35-45°C; it can also be 35-40°C, or 40-45°C, or it can be 35°C, 40°C, or 45°C.

[0081] In certain embodiments, the drying time is 6 to 10 hours; it can also be 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0082] In certain embodiments, when the single crystal is a MAPbX3 single crystal, the reactants for generating the single crystal include a methylamine compound and PbX2, wherein X is a halogen element, specifically Cl (chlorine), Br (bromine) or I (iodine).

[0083] In certain embodiments, when the single crystal is a PEAPbX3 single crystal, the reactants for generating the single crystal include a phenylethylamine compound and PbX2, wherein X is a halogen element, specifically Cl (chlorine), Br (bromine) or I (iodine).

[0084] The present invention further provides a method for preparing a sodium metasilicate hydrogel-MAPbBr3 single crystal material, comprising: adding a multilayer gel containing gel layers of different concentrations into a U-shaped tube, then adding a lead bromide solution and a methylamine bromide solution on both sides of the multilayer gel layer, respectively, growing the material under a constant temperature and light-proof environment, then removing the single crystal from the interface of the multilayer gel, cleaning the surface of the single crystal, and drying the material to obtain a sodium metasilicate hydrogel-lead iodide single crystal material.

[0085] In certain embodiments, the gel is formed by mixing aqueous gel solutions and acid solutions of different concentrations and then allowing the mixture to stand.

[0086] In certain embodiments, the concentration of the lead bromide solution is 0.5 to 2 mol / L; it may also be 0.5, 1, 1.5 or 2 mol / L.

[0087] In certain embodiments, the concentration of the methylammonium bromide solution is 0.5 to 2 mol / L; it may also be 0.5, 1, 1.5 or 2 mol / L.

[0088] In certain embodiments, the solvent of the lead bromide solution and the methylammonium bromide solution is a hydrobromic acid solution.

[0089] In certain embodiments, the concentration of the hydrobromic acid solution is 35-60 wt %; it can also be 40-55 wt %; it can also be 35, 40, 45, 48, 50, 55 or 60 wt %.

[0090] The present invention also provides a method for preparing a gel-embedded perovskite single crystal composite material, comprising:

[0091] The single crystal reactant is evenly dissolved in the gel solution and allowed to stand for gelation; after adding the anti-solvent, the solution is grown at a constant temperature and away from light, and then the gel is destroyed, the crystal material in the gel is taken out, and the gel-embedded perovskite single crystal composite material is taken out.

[0092] In certain embodiments, the gel comprises one or more of sodium metasilicate gel, silicone gel, dextran gel, polyacrylamide gel, agarose gel, and semiconductor gel; preferably silicone gel.

[0093] In certain embodiments, the siloxane includes tetramethoxysilane and trimethoxyphenylsilane.

[0094] In certain embodiments, the solvent of the silicone gel is an organic solvent.

[0095] In certain embodiments, corresponding reactants can be selected according to the type of single crystal to be synthesized. For example, if a phenylethylamine lead iodide single crystal is to be prepared, the single crystal reactants include phenylethylamine iodide and lead iodide; if a methylamine lead bromide single crystal is to be prepared, the single crystal reactants include methylamine bromide and lead bromide.

[0096] In certain embodiments, the concentration of iodinated phenylethylamine in the gel solution is 0.1 to 0.4 mol / L, and may also be 0.1 mol / L, 0.16 mol / L, 0.2 mol / L, 0.3 mol / L or 0.4 mol / L;

[0097] In certain embodiments, the concentration of lead iodide in the gel solution is 0.05 to 0.2 mol / L; it can also be 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.15 mol / L, or 0.2 mol / L.

[0098] In certain embodiments, the gel solution further comprises 0.2-0.5 wt % of hydroiodic acid, wherein the concentration of hydroiodic acid is 50-70 wt %; preferably, it further comprises 0.005-0.02 v / v % of ethylenediamine.

[0099] In certain embodiments, the antisolvent comprises dichloromethane or toluene.

[0100] In certain embodiments, the volume ratio of the gel solution to the antisolvent is 1:1 to 5; it can also be 1:1, 1:2, 1:3, 1:4 or 1:5.

[0101] In certain embodiments, the present invention also provides a method for preparing a pure phenylethylamine lead iodide single crystal, comprising mixing a phenylethylamine lead iodide single crystal reactant and a solvent, heating, and then cooling to obtain a pure phenylethylamine lead iodide single crystal.

[0102] In certain embodiments, the reactants of the phenylethylamine lead iodide single crystal are phenylethylamine ammonium iodide (PEAI) and lead iodide (PbI2).

[0103] In certain embodiments, the solvent is hydroiodic acid, preferably 50 wt.% to 70 wt.% of hydroiodic acid.

[0104] In certain embodiments, the mass volume ratio of the phenylethylamine ammonium iodide to the solvent is 0.05 g / mL to 0.15 g / mL; it can also be 0.06 g / mL, 0.07 g / mL, 0.07968 g / mL, 0.09 g / mL, 0.0996 g / mL, 0.11 g / mL, 0.11952 g / mL, 0.12 g / mL, 0.13 g / mL or 0.14 g / mL.

[0105] In certain embodiments, the mass volume ratio of the lead iodide to the solvent is 0.05 g / mL to 0.15 g / mL; it can also be 0.06 g / mL, 0.07376 g / mL, 0.08 g / mL, 0.0922 g / mL, 0.1 g / mL, 0.11064 g / mL, 0.12 g / mL, 0.13 g / mL or 0.14 g / mL.

[0106] In certain embodiments, the heating temperature is 80-140°C; it can also be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C or 140°C.

[0107] In certain embodiments, the heating time is 4 to 8 hours; it can also be 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0108] In certain embodiments, the cooling is specifically cooling to room temperature at a rate of 0.5-2°C per hour.

[0109] The present invention can also prepare pure single crystal materials (such as lead iodide single crystal materials) by traditional solution methods such as evaporation crystallization method without gel, cooling crystallization method or anti-solvent diffusion crystallization.

[0110] In certain embodiments, the step of preparing the second crystal (such as a lead iodide single crystal material) by evaporation crystallization includes: heat-treating the lead iodide solution, cooling it to room temperature, and washing it to obtain the second crystal.

[0111] In certain embodiments, the concentration of the lead iodide solution is 5 to 10 mg / mL; and can also be 5, 6, 7, 8, 9, or 10 mg / mL.

[0112] In certain embodiments, the heat treatment temperature is 160-200°C; it can also be 160-180°C, or 180-200°C, or 160°C, 170°C, 180°C, 190°C, or 200°C.

[0113] In certain embodiments, the heat treatment time is 4 to 10 hours, or 4 to 8 hours, or 6 to 20 hours, or 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0114] For example, to construct a lateral homojunction single crystal, a multilayer gel can be constructed first. If the single crystal is grown at the interface of different gel concentration distributions constructed in advance, the grown gel single crystal can construct a difference in gel concentration distribution in the horizontal direction.

[0115] Thus, an exemplary method for preparing an agarose hydrogel-lead iodide single crystal material for preparing a lateral single crystal homojunction device is provided, comprising (c1) or (c2):

[0116] (c1) preparing agarose gels containing a lead compound comprising a first gel and a second gel, respectively; preparing a plurality of agarose gel layers containing the lead compound comprising the first gel and the second gel in a container; pouring the first gel (agarose gel) on the upper layer of the plurality of agarose gel layers containing the lead compound; and subsequently pouring the second gel (agarose gel) containing the iodine compound; and after complete gelation, placing the resulting mixture in a constant temperature and light-proof environment for growth; and then removing a crystal from the interface between the first gel and the second gel layers, cleaning the crystal surface, and drying the resulting mixture to obtain a photoelectric crystal layer comprising the first crystal layer and the second crystal layer;

[0117] (c2) preparing agarose gel solutions with different agarose concentrations, preparing an agarose gel layer including a first gel and a second gel in a container, adding an aqueous solution of a lead compound and an aqueous solution of an iodine compound to both sides of the agarose gel layer, respectively, placing the solution in a constant temperature and light-proof environment for growth, then taking out the crystal from the gel interface between the first gel and the second gel, cleaning the crystal surface, and drying the solution to obtain a photoelectric crystal layer including the first crystal layer and the second crystal layer.

[0118] In certain embodiments, the gel concentration in the agarose hydrogel is 0.3 w / v% to 0.6 w / v%, wherein the gel concentration refers to the concentration of agarose in any agarose hydrogel solution, including agarose hydrogel solutions, iodine-containing agarose hydrogel solutions, and lead-containing compound hydrogel solutions. The agarose gel concentration can be continuously varied from 0.3 w / v% to 0.6 w / v%, and the work function of lead iodide also continuously decreases with increasing gel concentration, and the overall energy band structure shifts upward. However, at high gel concentrations above 0.6 w / v%, the crystal morphology deteriorates rapidly, and lamellar hexagonal crystals no longer grow, and the crystal growth time is also greatly prolonged.

[0119] In certain embodiments, to ensure the normal morphological growth of lead iodide single crystals in agarose gel, a certain amount of ethylenediamine is added to all of the above gel components and solutions (such as agarose hydrogel solution, lead-containing compound solution (including lead-containing compound hydrogel solution and lead-containing compound aqueous solution), and iodine-containing compound solution (including iodine-containing compound hydrogel solution and iodine-containing compound aqueous solution); the concentration of ethylenediamine is 2-5 v / v%, and can also be 2, 3, 4, or 5 v / v%; the concentration of acetic acid is 8-15 v / v%, and can also be 8, 9, 10, 11, 12, 13, 14, or 15 v / v%. The addition of ethylenediamine is used to reduce the nucleation density and enable two-dimensional growth of crystals; ethylenediamine is only required to be added to agarose gel; if the crystal growth in sodium metasilicate gel itself is good enough, ethylenediamine is not required.

[0120] In certain embodiments, the concentration of the lead-containing compound in the lead-containing compound aqueous solution or the lead-containing compound agarose gel is 0.2-0.4 mol / L; it can also be 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L.

[0121] In certain embodiments, the concentration of the iodine-containing compound in the agarose gel containing the iodine-containing compound or the iodine-containing compound aqueous solution is 0.2-0.4 mol / L; it can also be 0.2 mol / L, 0.3 mol / L, or 0.4 mol / L.

[0122] If the concentration of the lead-containing compound or iodine-containing compound is too low, the growth is slow and the crystals are small. If the concentration is too high, the nucleation density in the system is too high and the crystal morphology deteriorates.

[0123] In certain embodiments, the agarose gel solution of the lead-containing compound comprises 2-5 v / v% ethylenediamine, 8-15 v / v% acetic acid, 0.2-0.4 mol / L of the lead-containing compound, and 0.3-0.6 w / v% agarose.

[0124] In certain embodiments, the agarose gel solution containing an iodine compound comprises 2-5 v / v% ethylenediamine, 8-15 v / v% acetic acid, 0.2-0.4 mol / L iodine-containing compound, and 0.3-0.6 w / v% agarose.

[0125] In certain embodiments, the first electrode and the second electrode are each selected from a transparent electrode (e.g., ITO (indium tin oxide), FTO, IZO (indium zinc oxide) and SnO2), a transparent electrode modified with 2PACz or poly-2PACz, a metal (e.g., Ag, Cu, Au, Al, Mo, W, Cr, Ti and Nd), or an alloy containing at least one of these metals (Al alloys such as Al-Nd, Cu alloys such as Cu-Mn, etc.); the first electrode and the second electrode may be the same or different; preferably, they are different.

[0126] In certain embodiments, the preparation method of the 2PACz or poly-2PACz modified transparent electrode material is: treating the transparent conductive material with oxygen plasma, then immersing it in a 2PACz solution, washing, and drying.

[0127] In certain embodiments, the treatment time is 1 to 5 minutes, or 1 to 3 minutes, or 1, 2, 3, 4, or 5 minutes.

[0128] In certain embodiments, the concentration of the 2PACz solution is 0.5-2 mg / mL; it can also be 0.5, 1, 1.5, or 2 mg / mL.

[0129] In certain embodiments, the soaking time is 6-10 hours; it can also be 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0130] In certain embodiments, the solvent of the 2PACz solution is an organic solvent, preferably methanol.

[0131] In certain embodiments, the optoelectronic device further comprises a substrate, and the crystal layer, the first electrode and / or the second electrode are fixed on the substrate.

[0132] In some preferred embodiments, the first electrode is connected to a first crystal layer among the crystal layers, and the second electrode is connected to a second crystal layer among the crystal layers.

[0133] In certain embodiments, with the substrate as a reference, the first crystal layer and the second crystal layer in the crystal layer are connected vertically, horizontally, or alternately.

[0134] In certain preferred embodiments, with the substrate as a reference, the first crystal layer and the second crystal layer in the crystal layer can be used to construct a vertical optoelectronic device when connected up and down.

[0135] In certain preferred embodiments, taking the substrate as a reference, when the first electrode and the second electrode are located on the upper and lower sides of the crystal layer, a vertical optoelectronic device is formed.

[0136] In certain preferred embodiments, with the substrate as a reference, when the first crystal layer and the second crystal layer in the crystal layer are connected left and right, a lateral optoelectronic device is constructed.

[0137] In certain embodiments, taking the substrate as a reference, when the first electrode and the second electrode are located on the left and right sides of the crystal layer, it is a vertical optoelectronic device.

[0138] In certain preferred embodiments, when constructing a lateral optoelectronic device, taking the substrate as a reference, when the thickness of the first crystal layer is at the millimeter level or above, the first electrode is located on the left or right side of the first crystal layer.

[0139] In certain preferred embodiments, when constructing a lateral optoelectronic device, taking the substrate as a reference, when the thickness of the second crystal layer is at the millimeter level or above, the second electrode is located on the left or right side of the first crystal layer.

[0140] In certain preferred embodiments, when constructing a lateral optoelectronic device, with the substrate as a reference, when the thickness of the first crystal layer is micrometer-level or less, the first electrode is located above the first crystal layer, preferably in the upper left or upper right position.

[0141] In certain preferred embodiments, when constructing a lateral optoelectronic device, with the substrate as a reference, when the second crystal layer is micrometer-sized or smaller, the second electrode is located above the second crystal layer, preferably in the upper left or upper right.

[0142] Illustratively, the present invention provides a method for constructing a vertical optoelectronic device: transferring a first crystal layer and a second crystal layer onto a transparent electrode or a 2PACz-modified transparent electrode, wherein the first crystal layer and the second crystal layer are connected up and down to form a photoelectric crystal layer, wherein the first crystal layer is located above or below the second crystal layer; finally, in a vacuum environment, thermally evaporating a layer of metal electrode (such as metallic silver) on the optoelectronic crystal layer.

[0143] Specifically, the present invention employs the following two methods to prepare vertical and horizontal homojunction single crystal devices. To construct vertical homojunction optoelectronic devices, a gel single crystal composite material grown in different gel concentrations can be transferred to construct a vertical homojunction single crystal device. Alternatively, a gel composite single crystal can be used as a template to in situ grow a gel-free single crystal using conventional solution methods that do not involve gels, including evaporation crystallization, cooling crystallization, or anti-solvent diffusion crystallization.

[0144] The bottom electrode of the vertical homojunction device is a transparent electrode. In addition, lead iodide single crystals grown in different gel concentrations are transferred onto the transparent electrode. The transferred crystals are first cleaned and thinned with single crystal tape to ensure better contact between the single crystal and the transparent electrode, as well as between the crystals. Finally, a layer of metal is thermally evaporated on it in a vacuum environment to form the top electrode. Finally, the basic structure of the vertical photodetector is constructed, which is as follows from bottom to top: first electrode / PbI2 (first gel) / PbI2 (second gel) / second electrode or first electrode / PbI2 (second gel) / PbI2 (first gel) / second electrode.

[0145] Exemplarily, the present invention provides a method for constructing a lateral optoelectronic device: a first crystal layer and a second crystal layer grown in a first gel and a second gel are laterally connected to form a photoelectric crystal layer and transferred onto the substrate; the first single crystal is located on the left or right side of the second single crystal; and a first electrode and a second electrode are fixed on both sides or the upper left and upper right of the photoelectric crystal layer, respectively, wherein the first electrode and the second electrode are in contact with the first crystal layer and the second crystal layer in the photoelectric crystal layer, respectively.

[0146] The first electrode and the second electrode are preferably metal electrodes; preferably, the metal materials of the first electrode and the second electrode are the same or different, preferably the metal materials of the first electrode and the second electrode are different; when the metal materials of the first electrode and the second electrode are different, the asymmetric effect of the optoelectronic device is further enhanced.

[0147] In order to construct a lateral homojunction single crystal, a patterned distribution of gel concentration can be first constructed. If the single crystal is grown at the interface of different gel concentration distributions constructed in advance, the grown gel single crystal will construct a difference in gel concentration distribution in the lateral direction, thereby preparing a lateral single crystal homojunction device.

[0148] For example, a lateral single-crystal homojunction device is similarly cleaned using single-crystal tape. Gold electrodes are then deposited on either side or above the surface of the gel with differential concentration distribution within the single crystal using thermal evaporation. Finally, a lateral photodetector structure of metal electrode / PbI2 (second gel) / PbI2 (first gel) / metal electrode or metal electrode / PbI2 (first gel) / PbI2 (second gel) / metal electrode is constructed. Alternatively, asymmetric gold and silver electrodes are fabricated using the shadow effect of thermal evaporation, ultimately constructing a Ag / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Au lateral photodetector structure.

[0149] In some embodiments, the conditions of the thermal evaporation include: the evaporation rate is: the initial evaporation rate is 0.005-0.02 nm / s, and it is increased to 0.04-0.7 nm / s after the electrode thickness reaches 1-4 nm; however, thermal evaporation of fixed electrodes is widely used in many fields and is a conventional technology that can be selected and optimized according to specific needs.

[0150] In certain embodiments, the substrate includes a glass substrate, a stainless steel plate substrate, or a flexible stainless steel belt substrate.

[0151] The present invention also provides use of the optoelectronic device as described above as a photodetector, a photosensitive transistor, a high-energy ray detector or a light-emitting diode.

[0152] The gel-embedded lead iodide single crystal and its homojunction device described in this invention can also be used in optoelectronic devices and high-energy radiation detectors. This application is clearly due to the altered band structure of the gel-doped lead iodide single crystal, which forms a homojunction with an undoped lead iodide single crystal or a lead iodide single crystal embedded with a higher concentration of gel, resulting in excellent self-driven photoelectric response performance. The present invention utilizes gel doping to alter the band properties of the lead iodide semiconductor, enabling its use in homojunction photodetectors.

[0153] Beneficial effects:

[0154] Previously, gel single crystal composite materials were mainly used to construct optoelectronic devices with heterojunction structures, and were applied in fields such as photoelectric detection and solar cells. A method for preparing homojunction optoelectronic devices by using gel network embedding had not yet been proposed. The present invention introduces different gel embedding areas in the single crystal through asymmetric embedding to construct a single crystal homojunction, and the homojunction device realizes self-driven photoelectric response characteristics; and constructs lateral and vertical optoelectronic devices based on single crystal homojunctions.

[0155] Unlike conventional solution-processed single-crystal photoconductive symmetrical structures, the optoelectronic device of this invention requires no additional bias voltage to ensure proper operation, enabling a structure similar to that of a conventional inorganic semiconductor homojunction photodiode. This gel-embedded asymmetric structure imparts current-voltage characteristics similar to those of conventional semiconductor homojunction diodes, enabling efficient photoelectric conversion and broad application in photodetectors and other optoelectronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0156] Figure 1 This is a structural diagram of the optoelectronic device of the present invention; wherein 1: first electrode, 2: photoelectric crystal layer, 21: first crystal layer, 22: second crystal layer, 3: second electrode.

[0157] Figure 2 Schematic diagram of a gel single crystal growth apparatus. The left figure shows a schematic diagram of a growth apparatus for bidirectional diffusion growth of lead iodide single crystals using sodium metasilicate gel. The middle figure shows a schematic diagram of a growth apparatus for lead iodide single crystals using agarose gel or multiple layers of agarose gel with alternating concentration distributions. The right figure shows a schematic diagram of a growth apparatus for bidirectional diffusion growth of lead iodide single crystals using agarose gel or multiple layers of agarose gel with alternating concentration distributions.

[0158] Figure 3 These are optical microscope images of lead iodide gel single crystals. a is a single crystal grown by the traditional solution method, b is a single crystal grown by sodium metasilicate hydrogel, c is a single crystal grown in agarose gel, and d is a single crystal grown at the interface of alternating concentration distribution of agarose gel and the marked position is the asymmetric embedding interface position of the gel.

[0159] Figure 4 Schematic diagram of ITO / PbI2 (high gel concentration) / PbI2 (solution growth / low gel concentration) / Ag homojunction photodetector.

[0160] Figure 5 Schematic diagram of Au / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Au single crystal homojunction photodetector.

[0161] Figure 6 This is an Au / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Ag single crystal homojunction photodetector. The left picture is a schematic diagram of the asymmetric electrode evaporation method, and the right picture is a schematic diagram of the Au / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Ag single crystal homojunction photodetector.

[0162] Figure 7 This is the current density-voltage curve of the gel single crystal photodetector prepared in Example 1.

[0163] Figure 8This is the current density-voltage curve of the gel single crystal photodetector prepared in Example 2.

[0164] Figure 9 This is the current-voltage curve of the gel single crystal photodetector prepared in Example 3.

[0165] Figure 10 This is the current-voltage curve of the gel single crystal photodetector prepared in Example 5.

[0166] Figure 11 This is the current density-voltage curve of the gel single crystal photodetector prepared in Comparative Example 1.

[0167] Figure 12 This is the current-voltage curve of the gel single crystal photodetector prepared in Comparative Example 2.

[0168] Figure 13 These are pictures of the gel single crystals prepared in Example 6. The left picture is a MAPbBr3 (MA: methylamine) crystal, and the right picture is a PEA2PbI4 (PEA: phenylethylamine) single crystal. DETAILED DESCRIPTION

[0169] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0170] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0171] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0172] like Figure 1As shown, the present invention provides an optoelectronic device; the optoelectronic device includes a first electrode 1, a photoelectric crystal layer 2 and a second electrode 3; the photoelectric crystal layer 2 includes a first crystal layer 21 and a second crystal layer 22; the first crystal layer 21 is connected to the second crystal layer 22, and the connection interface forms a homojunction; the first electrode 1 and the second electrode 3 are respectively connected to the first crystal layer 21 and the second crystal layer 22 in the photoelectric crystal layer 3; the first electrode 1 and the second electrode 3 are not in contact; wherein the first crystal layer 21 is a gel single crystal composite material grown in a first gel, and the second crystal layer 22 is a pure single crystal material or a gel single crystal composite material grown in a second gel; the gel type and / or gel concentration of the first gel and the second gel are different.

[0173] Exemplarily, the optoelectronic device may include a first electrode 1, a photoelectric crystal layer 2, and a second electrode 3 in sequence, and the first electrode 1 and the second electrode 3 are respectively located on both sides of the photoelectric crystal layer; however, the first electrode 1 and the second electrode 3 are not limited to the two sides of the photoelectric crystal layer 2, and the positions of the first electrode 1 and the second electrode 3 can be adjusted according to the thickness of the first crystal layer 21 and the second crystal layer 22 in the photoelectric crystal layer 2, as long as the first electrode 1 and the second electrode 3 are respectively connected to the first crystal layer 21 and the second crystal layer 22 in the photoelectric crystal layer 2.

[0174] The purpose of the present invention is to provide a gel-doped single crystal, wherein the schematic diagram of the gel method single crystal growth device can be referred to Figure 2 , but not limited to this. The embedded gel network is used to achieve continuous regulation of the work function of the single crystal. And the regulation law of the gel on the single crystal is used to apply it to the homojunction photodetector. In order to obtain a gel-embedded single crystal composite material, the present invention grows a semiconductor single crystal by a gel method, achieves a relatively uniform embedding of the gel network into the semiconductor single crystal, and changes the energy band structure of the single crystal. The gel network is asymmetrically embedded to achieve patterned embedding of the single crystal, construct a single crystal homojunction, and the homojunction device realizes self-driven photoelectric response characteristics.

[0175] The gel-embedded lead iodide single crystal and its homojunction device described in this invention can also be used in optoelectronic devices and high-energy radiation detectors. This application is clearly due to the altered band structure of the gel-doped lead iodide single crystal, which forms a homojunction with an undoped lead iodide single crystal or a lead iodide single crystal embedded with a higher concentration of gel, resulting in excellent self-driven photoelectric response performance. The present invention utilizes gel doping to alter the band properties of the lead iodide semiconductor, enabling its use in homojunction photodetectors.

[0176] The present invention adopts a solution method to prepare a homojunction device. The embedded gel network of different concentrations can realize continuous regulation of the work function of the lead iodide single crystal. The energy level structure can be regulated by changing the gel concentration, and the homojunction quality is improved. In addition, the patterned distribution of the gel inside the artificially manufactured single crystal can effectively construct a built-in electric field. Compared with the photoconductive type photodetector of the lead iodide single crystal without gel embedding (Han, Mingming, Jiamin Sun, Luozhen Bian, Zhou Wang, Lei Zhang, Yanxue Yin, Zhaofeng Gao, Journal of Materials Chemistry C 2018, 6, 5746-5753; Wang, Yaguang, Lin Gan, Junnian Chen, Rui Yang, Tianyou Zhai, Science Bulletin, 2017, 62, 1654-1662; Zhu, Xinghua, Peihua Wangyang, Hui Sun, Dingyu Yang, Xiuying Gao, Haibo Tian, ​​Materials Letters, 2017, 193, 101-104), the gel single crystal homojunction constructed by the present invention can separate photogenerated carriers in the absence of bias, so the homojunction device can realize the function of photoelectric detection in the self-driven mode.

[0177] The unit w / v involved in the present invention refers to the ratio of mass to volume, wherein the unit of mass is g and the unit of volume is mL, expressed in grams per milliliter (g / mL); for example, 1 w / v% means that 1 g of a substance is contained in 100 mL of solution.

[0178] In the present invention, the gel volume involved refers to the volume of ungelled gel. The room temperature mentioned in the present invention is the conventional understanding of room temperature in the art, generally referring to 10-30°C.

[0179] Example 1

[0180] This embodiment provides a method for preparing a gel single crystal longitudinal photodetector based on an ITO bottom electrode, which is specifically as follows:

[0181] (1) Preparation of gel

[0182] When using sodium metasilicate hydrogel to prepare lead iodide single crystals, sodium metasilicate aqueous solution and acetic acid aqueous solution are first configured. In this embodiment, taking a 10w / v% gel concentration as an example, 5g of sodium metasilicate pentahydrate is first fully dissolved in 25mL of ultrapure water; then 25mL of a 13v / v% acetic acid aqueous solution is configured, and the metasilicic acid solution is slowly added dropwise to the acetic acid aqueous solution during mixing, and the acetic acid solution is kept stirred and cooled in an ice-water bath. After the addition is completed, it is stirred for 10 minutes and then poured into a U-shaped tube at 20°C and allowed to stand for 24-48 hours until it is completely gelled, and the amount added is such that it does not cover the bend of the U-shaped tube.

[0183] The gel concentration is not limited to 10 w / v%. The preparation process for other gel concentrations is the same as the above process, except that the mass of sodium metasilicate pentahydrate is increased or decreased accordingly, and the concentration of the acetic acid aqueous solution is also increased or decreased proportionally. For example, for a 15 w / v% gel concentration, 7.5 g of sodium metasilicate pentahydrate and a 19.5 v / v% acetic acid aqueous solution concentration are used, with all other factors remaining unchanged. The gel concentrations in other embodiments can also be adjusted according to this method.

[0184] Subsequent experiments took growth in a gel concentration of 10 w / v% as an example.

[0185] (2) Growth of gel composite single crystals

[0186] Add equal volumes of lead acetate aqueous solution (containing 10v / v% acetic acid) and potassium iodide aqueous solution to the gel obtained in the previous step on both sides of the U-shaped tube, and place it in a constant temperature and dark environment at 20°C for growth. The concentrations of lead acetate in the lead acetate aqueous solution and potassium iodide in the potassium iodide aqueous solution are both 0.4 mol / L. After growing for one month, the gel is destroyed, and the crystals are taken out of the gel with tweezers. The surface is repeatedly rinsed with ethanol, and then dried in a vacuum oven at 40°C for 8 hours to obtain yellow flaky lead iodide gel composite single crystals. The crystal size (i.e., the widest part of the hexagonal crystal) is generally 2-8 mm ( Figure 3 b).

[0187] The growth process for other gel concentrations is the same as the above process. In addition, the work function of the lead iodide single crystal can change continuously according to the gel concentration. The gel concentration can be continuously changed from 3w / v% to 20w / v%. The work function of lead iodide also increases continuously with the increase of gel concentration, and the overall energy band structure moves downward. Therefore, the required gel concentration can be selected according to the energy level structure and work function required by the device. However, at higher gel concentrations, the work function change is discontinuous and non-monotonic, and the crystal growth time will be extended.

[0188] (3) Traditional solution-grown single crystals

[0189] 0.3 g of lead iodide powder and 30 mL of ultrapure water were sealed in a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, kept at 180 ° C for 6 hours, and then naturally cooled to room temperature. After rinsing with deionized water and ethanol, yellow flaky lead iodide pure single crystals ( Figure 3 a).

[0190] (4) Cleaning of ITO (Indium Tin Oxide) glass substrates

[0191] ITO needs to be cleaned before use. The cleaning agents used for cleaning ITO are Hellmanex III alkaline detergent, deionized water, ethanol, acetone, and isopropyl alcohol, respectively. Ultrasonic cleaning is performed for 20 minutes each. The ITO is then dried in an oven for later use.

[0192] (5) Pretreatment of gel composite single crystal

[0193] The sheet-like gel single crystal obtained in step (2) is repeatedly peeled off on both sides of the single crystal surface using single crystal Scott tape to expose fresh surfaces of the single crystal surface and reduce the overall thickness of the crystal to micron level, about tens to hundreds of microns.

[0194] (6) Crystal transfer

[0195] After wetting the crystal obtained in step (5) with anhydrous ethanol, it was dropped onto an ITO conductive glass substrate and allowed to air dry for 1 hour until the crystal naturally adhered to the substrate. Subsequently, the crystal obtained in step (3) was wetted using the same method and naturally adhered to the top of the gel composite single crystal, forming a top-to-bottom stacked structure, i.e., ITO / PbI2 (high gel concentration) / PbI2 (traditional solution grown) structure.

[0196] The crystal in step (3) can also be replaced with a single crystal grown at another gel concentration in step (5) to form a structure of ITO / PbI2 (high gel concentration) / PbI2 (low gel concentration).

[0197] (7) Evaporation of metal electrodes

[0198] Under vacuum conditions, a layer of metallic silver with a thickness of about 100 nm is thermally evaporated on ITO / PbI2 (high gel concentration) / PbI2 (traditional solution growth) as the top electrode. The evaporation rate is: the initial evaporation rate is 0.01 nm / s, and it is increased to 0.05 nm / s after the silver thickness reaches 2.5 nm. The final vertical device structure is ITO / PbI2 (high gel concentration) / PbI2 (traditional solution growth) / Ag, as shown in the following figure. Figure 4 shown.

[0199] (8) Testing

[0200] The vertical device prepared in step (7) is placed in a vacuum probe station, and a scanning voltage is applied to the upper and lower electrodes using a Keythley semiconductor analyzer to obtain the dark current and the photocurrent under 450nm laser illumination; and the current density-voltage curve is drawn.

[0201] The results are as follows Figure 7 As shown, the results show that the longitudinal device has an obvious photoelectric response under light, the relationship between voltage and current is nonlinear, its photocurrent is improved under forward bias, and there is a certain open-circuit voltage. At 0V, there is also an obvious photocurrent and a certain short-circuit current, indicating that the homojunction detector can work in self-driven mode.

[0202] Example 2

[0203] A method for preparing an asymmetric gel single crystal longitudinal photodetector based on a 2PACz-modified ITO bottom electrode is as follows:

[0204] (1) Preparation of gel

[0205] When using sodium metasilicate hydrogel to prepare lead iodide single crystals, first prepare sodium metasilicate aqueous solution and acetic acid aqueous solution. Taking 10w / v% gel concentration as an example, first dissolve 5g of sodium metasilicate pentahydrate in 25ml of ultrapure water. Then prepare 25ml of 13v / v% acetic acid aqueous solution, and slowly add the metasilicic acid solution dropwise into the acetic acid aqueous solution while mixing, and keep the acetic acid solution stirring and cooling in an ice-water bath. After the addition is completed, stir for 10 minutes and pour it into a U-shaped tube at 20℃ and let it stand for 24-48 hours until it is completely gelled. The amount added should not exceed the bend of the U-shaped tube.

[0206] (2) Growth of gel composite single crystals

[0207] The gel obtained in the previous step was added to both sides of the U-shaped tube with equal volumes of lead acetate aqueous solution (containing 10 v / v% acetic acid) and potassium iodide aqueous solution, respectively, and placed in a constant temperature and dark environment at 20°C for growth. The concentrations of lead acetate and potassium iodide in the lead acetate aqueous solution and potassium iodide aqueous solution were both 0.4 mol / L. After one month of growth, the gel was destroyed, the crystals were removed from the gel, the surface was repeatedly rinsed with ethanol, and then the crystals were dried in a 40°C vacuum oven for 8 to 12 hours to obtain yellow flaky lead iodide gel composite single crystals, whose crystal size was generally 2-8 mm. The growth process for other gel concentrations was the same as the above process. The experiment could also be set up by continuously changing the gel concentration from 3 w / v% to 20 w / v%. The work function of lead iodide also increased continuously with the increase of gel concentration, and the overall band structure shifted downward. Therefore, the required gel concentration can be selected according to the energy level structure and work function required for the device. However, at high gel concentrations, the work function change was discontinuous and non-monotonic, and the crystal growth time was also greatly extended.

[0208] (3) Traditional solution method for growing single crystals without gel

[0209] 0.3 g of lead iodide powder and 30 mL of ultrapure water were sealed in a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, kept at 180 °C for 6 hours, and then naturally cooled to room temperature. After rinsing with deionized water and ethanol, yellow flaky pure single crystals of lead iodide were obtained.

[0210] (4) Cleaning and modification of ITO substrate.

[0211] ITO needs to be cleaned before use. The cleaning agents used for cleaning ITO are, in order, Hellmanex III alkaline detergent, deionized water, ethanol, acetone, and isopropanol, each ultrasonically cleaned for 20 minutes. The ITO substrate is then oven-dried before use. The ITO substrate is then treated with oxygen plasma for 2 minutes, then immersed in a 1 mg / ml 2PACz solution in methanol for 8 hours. The substrate is then rinsed with methanol and dried with a nitrogen gun. The 2PACz-modified ITO bottom electrode has a deeper energy level structure, better matching the work function of the lead iodide single crystal.

[0212] (5) Pretreatment of gel composite single crystal

[0213] The sheet-like gel single crystal obtained in step (2) was repeatedly peeled off on both sides of the single crystal surface using single crystal Scott tape to expose fresh surfaces of the single crystal surface and reduce the overall thickness of the crystal to micrometer level.

[0214] (6) Crystal transfer

[0215] After wetting the crystal obtained in step (5) with anhydrous ethanol, drop it on an ITO conductive glass substrate and air dry it for 1 hour until the crystal naturally adheres to the substrate. Subsequently, the crystal obtained in step (3) is wetted in the same way and naturally adheres to the upper part of the gel composite single crystal, forming a top-bottom stacked structure, i.e., ITO (2PACz modified) / PbI2 (high gel concentration) / PbI2 (traditional solution method growth). Of course, the crystal in step (3) can also be replaced with a single crystal grown at another gel concentration in step (5), forming a structure of ITO (2PACz modified) / PbI2 (high gel concentration) / PbI2 (low gel concentration).

[0216] (7) Evaporation of metal electrodes

[0217] Under vacuum conditions, a layer of metallic silver with a thickness of about 100 nm was thermally evaporated on ITO (2PACz modified) / PbI2 (high gel concentration) / PbI2 (traditional solution grown) as the top electrode. The evaporation rate was: the initial evaporation rate was 0.01 nm / s, and it was increased to 0.05 nm / s after the silver thickness reached 2.5 nm. The final vertical device structure was ITO (2PACz modified) / PbI2 (high gel concentration) / PbI2 (solution grown) / Ag.

[0218] (8) Testing

[0219] The device was placed in a vacuum probe station, and a scanning voltage was applied to the upper and lower electrodes using a Keythley semiconductor analyzer to obtain the dark current and the photocurrent under 450nm laser illumination; the current density-voltage curve was drawn.

[0220] The results are as follows Figure 8 As shown in the results, there is a significant rectification effect in the dark state and a clear photoelectric response under illumination. The relationship between voltage and current is nonlinear. Under forward bias, its photocurrent is slightly increased and a certain open-circuit voltage is present. At 0V, there is also a significant photocurrent and a certain short-circuit current, indicating that the homojunction detector can operate in a self-driven mode. In addition, due to the better energy level alignment of the 2PACz-modified ITO electrode, its photocurrent rectification effect is more significant.

[0221] Example 3

[0222] A method for preparing an asymmetric gel single crystal lateral homojunction photodetector is as follows:

[0223] (1) Preparation of the first layer of gel

[0224] A mixed solution containing 6 v / v% ethylenediamine, 20 v / v% acetic acid, and 0.4 mol / L lead acetate was prepared. A 0.6 w / v% agarose aqueous solution was then prepared. 0.6 g of agarose powder was added to 100 mL of deionized water, microwaved, and stirred to obtain a 0.6 w / v% agarose hydrogel. Equal volumes of the lead acetate mixed solution and the 0.6 w / v% agarose hydrogel were mixed to obtain a lead acetate agarose solution containing 3 v / v% ethylenediamine, 10 v / v% acetic acid, 0.2 mol / L lead acetate, and 0.3 w / v% agarose. A certain volume of the lead acetate agarose solution was poured into a beaker and allowed to cool at room temperature to form a gel.

[0225] (2) Preparation of multilayer gel

[0226] After the sol in (1) is completely gelled, a lead acetate agarose solution containing 3 v / v% ethylenediamine, 10 v / v% acetic acid, 0.2 mol / L lead acetate, and 0.6 w / v% agarose is prepared in the same manner. This sol is added to the top of the gel in (1) to prepare four layers of gel with alternating concentrations of 0.3 w / v%-0.6 w / v%-0.3 w / v%-0.6 w / v%. The volume of each layer of gel is the same, but can be adjusted according to specific circumstances. Similarly, multiple layers of agarose gel containing 0.2 mol / L lead acetate can be prepared in a beaker with alternating concentrations of 0.3 w / v% and 0.6 w / v%.

[0227] (3) Growth of gel composite single crystals

[0228] Agarose sol was prepared in a similar manner. A 0.6 w / v% blank agarose hydrogel was poured onto the upper layer of the gel obtained in step (2). The volume ratio of the blank agarose hydrogel to the four-layer lead acetate agarose gel in step (1) was 1:7. Then, an agarose hydrogel containing 0.4 mol / L potassium iodide of the same volume as the four-layer lead acetate agarose gel was poured onto the upper layer. After complete gelation, the gel was placed in a constant temperature and dark environment for growth. 3 v / v% ethylenediamine neutralized with acetic acid was still added to all the above gel components and solutions. Finally, the following gel distribution structure was formed from bottom to top: 0.3 w / v%-0.6 w / v% alternating distribution (containing 0.2 mol / L lead acetate), 0.6 w / v% (blank gel), 0.3 w / v% (containing 0.4 mol / L potassium iodide) agarose gel. After one month of growth, the gel was broken and the crystal was removed from the interface of the gel layer with alternating distribution of 0.3w / v%-0.6w / v%-0.3w / v%-0.6w / v% using tweezers. The surface was repeatedly rinsed with ethanol and then dried in a vacuum oven at 40°C to obtain yellow flaky lead iodide gel composite single crystals. The crystal size was generally 2-5mm ( Figure 3 d).

[0229] Furthermore, the work function of a single lead iodide crystal can vary continuously depending on the gel concentration. The agarose gel concentration can be continuously varied from 0.3 w / v% to 0.6 w / v%. The work function of lead iodide also decreases continuously with increasing gel concentration, shifting the overall energy band structure upward. Therefore, in practical applications, the desired gel concentration can be selected based on the device's desired energy level structure and work function. However, at high gel concentrations above 0.6 w / v%, the crystal morphology rapidly deteriorates, and hexagonal flake crystals no longer grow. Furthermore, the crystal growth time is significantly prolonged.

[0230] (4) Pretreatment of gel composite single crystal

[0231] The sheet-like gel single crystal obtained in (3) is used for subsequent homojunction preparation. The crystal grown at the interface between the 0.3 w / v% and 0.6 w / v% gel distributions is used. The surface of the single crystal is repeatedly peeled off using single crystal Scott tape to expose a fresh surface, and the overall thickness of the crystal is reduced to the micron level.

[0232] (5) Crystal transfer

[0233] The crystals obtained in (4) were fixed on a glass substrate with adhesive tape, and the interface formed by the gel distribution was marked.

[0234] (6) Evaporation of metal electrodes

[0235] In order to make the electrodes distributed laterally on both sides of the interface caused by the distribution of gel in the crystal, the first electrode and the second electrode are placed on the upper left and upper right of the single crystal respectively because the crystal is relatively thin. Under vacuum conditions, a layer of metal gold with a thickness of about 100nm is thermally evaporated on the crystal using a mask plate as an electrode. The evaporation rate is 0.01nm / s at the initial evaporation rate. After the gold thickness reaches 2.5nm, it is increased to 0.05nm / s. The final lateral device structure is Au (upper left) / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Au (upper right), as shown in the structure. Figure 5 .

[0236] (7) Testing

[0237] The device was placed in a vacuum probe station, and a scanning voltage was applied to the left and right electrodes using a Keythley semiconductor analyzer to obtain the dark current and the photocurrent under 450nm laser illumination. Since the current area of ​​the lateral device cannot be calibrated, only the current is available, and the current-voltage curve is plotted. The results are as follows. Figure 9 As shown, the results show that there is an obvious photoelectric response under light and a certain open-circuit voltage. At 0V, there is also an obvious photocurrent and a certain short-circuit current, indicating that the homojunction detector can work in a self-driven mode.

[0238] Example 4

[0239] A method for preparing an asymmetric gel single crystal lateral homojunction photodetector is as follows:

[0240] (1) Preparation of gel

[0241] When using agarose hydrogel to prepare lead iodide single crystals, you can also first prepare multiple layers of blank agarose hydrogel, pour them into a Petri dish, and remove the excess gel on both sides after gelation. To prepare a 0.6 w / v% agarose hydrogel solution, add 0.6g of agarose powder to 100mL of deionized water, microwave-boil, and stir to obtain a 0.6w / v% agarose sol, which is then poured into a Petri dish. Next, prepare a 0.3w / v% agarose sol using the same method and add it to the top of the gel. All prepared agarose hydrogel solutions contain 3v / v% ethylenediamine. Similarly, four layers of alternating 0.3w / v% and 0.6w / v% agarose gel can be prepared in a Petri dish, with the volume ratio of each layer being 1:1. After gelation is complete, remove the excess gel on both sides to leave space for the addition of the two solutions.

[0242] (2) Growth of gel composite single crystals

[0243] Equal volumes of 0.4 mol / L aqueous lead acetate solution (containing 10 v / v% acetic acid) and 0.4 mol / L aqueous potassium iodide solution were added to both sides of the four-layer agarose gel. All prepared solutions (such as the aqueous lead acetate solution and the aqueous potassium iodide solution) contained 3 v / v% ethylenediamine neutralized with acetic acid. The gels were then placed in a constant temperature, dark environment, and grown. After one month of growth, the gels were broken, and crystals were removed from the interface between the 0.3 w / v% and 0.6 w / v% gels using tweezers. The surface was repeatedly rinsed with ethanol, and the crystals were then dried in a 40°C vacuum oven to obtain yellow flaky lead iodide gel composite single crystals, typically 1-3 mm in size.

[0244] Furthermore, the work function of a single lead iodide crystal can vary continuously depending on the gel concentration. The agarose gel concentration can be continuously varied from 0.3 w / v% to 0.6 w / v%. The work function of lead iodide also decreases continuously with increasing gel concentration, shifting the overall energy band structure upward. Therefore, in practical applications, the desired gel concentration combination can be selected based on the device's desired energy level structure and work function. However, at high gel concentrations above 0.6 w / v%, the crystal morphology rapidly deteriorates, and hexagonal flake crystals no longer grow. Furthermore, the crystal growth time is significantly prolonged.

[0245] (3) Pretreatment of gel composite single crystal

[0246] The resulting sheet-like gel single crystals are obtained by step (2). Crystals grown at the interface between the 0.3 w / v% and 0.6 w / v% gel distributions can be used for subsequent homojunction preparation. The surface of the single crystal is repeatedly peeled off using single crystal Scott tape to expose fresh surfaces, and the overall thickness of the crystal is reduced to the micron level.

[0247] (4) Crystal transfer

[0248] The crystals obtained in step (3) were fixed on a glass substrate with adhesive tape, and the interface formed by the gel distribution was marked.

[0249] (5) Evaporation of metal electrodes

[0250] To ensure the electrodes are distributed laterally on either side of the interface created by the gel distribution within the crystal, the first and second electrodes are placed on the upper left and upper right sides of the single crystal, respectively, due to its thinness. Under vacuum conditions, a layer of approximately 100nm thick gold was thermally evaporated onto the crystal using a mask, serving as the electrodes. The deposition rate was initially 0.01nm / s, increasing to 0.05nm / s after the gold thickness reached 2.5nm. The resulting lateral device structure was Au (upper left) / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Au (upper right).

[0251] (6) Evaporation of metal electrodes

[0252] The device was placed in a vacuum probe station, and a sweep voltage was applied to the left and right electrodes using a Keythley semiconductor analyzer. Dark current and photocurrent under 450nm laser illumination were measured, and the corresponding photodiode response was tested. Under illumination, a clear photoelectric response was observed, with a certain open-circuit voltage. At 0V, a significant photocurrent also appeared, with a certain short-circuit current present.

[0253] Example 5

[0254] A method for preparing an asymmetric gel single crystal lateral homojunction photodetector with an asymmetric electrode is as follows:

[0255] (1) Preparation of the first layer of gel

[0256] A mixed solution containing 6 v / v% ethylenediamine, 20 v / v% acetic acid, and 0.4 mol / L lead acetate was prepared. A 0.6 w / v% agarose hot solution was then prepared. 0.6 g of agarose powder was added to 100 mL of deionized water, microwaved, and stirred to obtain a 0.6 w / v% agarose sol. Equal volumes of the lead acetate mixed solution and the 0.6 w / v% agarose hot sol were mixed to obtain a 0.3 w / v% agarose sol containing 3 v / v% ethylenediamine, 10 v / v% acetic acid, and 0.2 mol / L lead acetate. A certain volume of the mixed sol was poured into a beaker and allowed to cool at room temperature to form a gel.

[0257] (2) Preparation of multilayer gel

[0258] After the sol in (1) has completely gelled, a 0.6 w / v% agarose sol containing 3 v / v% ethylenediamine, 10 v / v% acetic acid, and 0.2 mol / L lead acetate is prepared in the same manner and added to the top of the gel in (1). Similarly, multiple layers of agarose gel containing 0.2 mol / L lead acetate can be prepared in a beaker with alternating concentrations of 0.3 w / v%-0.6 w / v%-0.3 w / v%-0.6 w / v%, with each layer having the same volume.

[0259] (3) Growth of gel composite single crystals

[0260] Agarose sol was prepared in a similar manner, and a blank agarose hydrogel was poured onto the upper layer of the gel obtained in step (2), wherein the volume ratio of the blank agarose hydrogel to the four layers of agarose gel containing lead acetate was 1:7; then, an agarose hydrogel containing 0.4 mol / L potassium iodide of the same volume as the four layers of lead acetate agarose gel in step (2) was poured onto the uppermost layer. After complete gelation, the gel was placed in a constant temperature and dark environment for growth. 3 v / v% ethylenediamine neutralized with acetic acid was still added to all the above gel components and solutions. Finally, the following gel distribution structure was formed from bottom to top: 0.3 w / v%-0.6 w / v% alternating distribution (containing 0.2 mol / L lead acetate), 0.6 w / v% (blank gel), 0.3 w / v% (containing 0.4 mol / L potassium iodide) agarose gel. After one month of growth, the gel was broken and the crystals were removed from the interface of the gel layers at different gel concentrations using tweezers. The surface was repeatedly rinsed with ethanol and then dried in a 40°C vacuum oven to obtain yellow flaky lead iodide gel composite single crystals, typically 2-5 mm in size. The agarose gel concentration can be continuously varied from 0.3 w / v% to 0.6 w / v%, and the work function of lead iodide also decreases continuously with increasing gel concentration, shifting the overall energy band structure upward. However, at high gel concentrations above 0.6 w / v%, the crystal morphology rapidly deteriorates, and hexagonal flaky crystals no longer grow. Furthermore, the crystal growth time is significantly prolonged.

[0261] (4) Pretreatment of gel composite single crystal

[0262] The sheet-like gel single crystal obtained in (3) is used for subsequent homojunction preparation. The crystal grown at the interface between the 0.3 w / v% and 0.6 w / v% gel distributions is used. The surface of the single crystal is repeatedly peeled off using single crystal Scott tape to expose a fresh surface, and the overall thickness of the crystal is reduced to the micron level.

[0263] (5) Crystal transfer

[0264] The crystals obtained in (4) were fixed on a glass substrate with adhesive tape, and the interface formed by the gel distribution was marked.

[0265] (6) Evaporation of metal electrodes

[0266] The electrodes should be distributed laterally on both sides of the interface formed by the distribution of gel in the crystal. Figure 6 As shown, the shadow effect of thermal evaporation is used to evaporate an asymmetric electrode. Under vacuum conditions, a layer of metal gold with a thickness of about 50nm is thermally evaporated on the upper surface as an electrode. The evaporation rate is: the initial evaporation rate is 0.01nm / s, and it is increased to 0.05nm / s after the gold thickness reaches 2.5nm. Then, the evaporation source in another direction is replaced to thermally evaporate a layer of metal silver with a thickness of about 50nm as an electrode. The evaporation rate is, the initial evaporation rate is 0.01nm / s, and it is increased to 0.05nm / s after the silver thickness reaches 2.5nm. The shadow effect can be used to make the electrodes evaporated twice misaligned, and the final lateral device structure is Au (upper left) / PbI2 (low gel concentration) / PbI2 (high gel concentration) / Ag (upper right), as shown Figure 6 shown.

[0267] (7) Testing

[0268] The device was placed in a vacuum probe station, and a scanning voltage was applied to the left and right electrodes using a Keythley semiconductor analyzer to obtain the dark current and the photocurrent under 450nm laser illumination. Because the current area of ​​the lateral device cannot be calibrated, only the current was measured and the current-voltage curve was drawn.

[0269] The results are as follows Figure 10 As shown, under illumination, there is a clear photoelectric response and a certain open-circuit voltage. At 0V, there is also a clear photocurrent and a certain short-circuit current, indicating that the homojunction detector can operate in a self-driven mode. In addition, due to the presence of the asymmetric gold / silver electrodes, the open-circuit voltage is slightly increased due to the better matching of the work functions of the electrodes on both sides, further enhancing the photodiode effect.

[0270] Example 6

[0271] This embodiment provides a method for preparing perovskite single crystals by preparing siloxane gel using an antisolvent diffusion method;

[0272] (1) Preparation of organosiloxane gel

[0273] Taking the preparation of PEA2PbI4 (PEA: phenylethylamine) single crystals with 10v / v% (10.23w / v%) organosiloxane gel as an example, 0.475ml of tetramethoxysilane and 0.025ml of trimethoxyphenylsilane were added to 3.375ml of 1,4-butyrolactone, followed by the addition of 0.125ml of a 55wt% aqueous solution of hydroiodic acid. After heating at 90°C for one hour, 0.8mmol of PEAI (phenylethylamine iodide) and 0.4mmol of lead iodide were added, and the mixture was heated at 90°C for one hour until completely dissolved. The solution was then completely cooled. 15 microliters of ethylenediamine was added to 1ml of 1,4-butyrolactone, and the two solutions were mixed evenly and added to the culture bottle. Finally, the mixture was allowed to stand for gelation.

[0274] (2) Growth of gel composite single crystals

[0275] Pour 15 ml of anti-solvent dichloromethane (or toluene) onto the gel obtained in the previous step. Then place it in a constant temperature and dark environment at 20 ° C for growth. After ten days of growth, destroy the gel, remove the crystal from the gel, rinse the surface repeatedly with dichloromethane, and then dry the crystal in a vacuum oven at 40 ° C for 8 hours to obtain a sheet of PEA2PbI4-gel composite single crystal ( Figure 13 The growth process for other gel concentrations is the same as above, with only the concentrations of tetramethoxysilane and trimethoxyphenylsilane being changed. Alternatively, other siloxane monomers, such as (3-aminopropyl)trimethoxysilane, can be added as needed.

[0276] To grow other types of perovskite single crystals, simply replace the aforementioned PEAI and lead iodide with corresponding components and suitable solvents. For example, to grow MAPbBr3 (MA: methylamine) single crystals, the hydroiodic acid used in the gel synthesis process must be replaced with hydrobromic acid, the components modified to MABr (methylammonium bromide) and lead bromide, and the solvent changed to DMF.

[0277] (3) Traditional solution method for growing single crystals

[0278] 0.498 g of PEAI powder, 0.461 g of PbI2 powder and 5 mL of 57 wt% hydroiodic acid solution were sealed in a 50 mL polytetrafluoroethylene-lined stainless steel autoclave, kept at 100 °C for 6 hours, and then cooled to room temperature at 1 °C per hour. After rinsing with dichloromethane, flaky PEA2PbI4 single crystals were obtained.

[0279] (4) Device preparation

[0280] Among them, the two-dimensional perovskite of the PEA2PbI4 type can also be used as shown in the above-mentioned lead iodide single crystal, using single crystal Scott tape to repeatedly tear off the single crystal surface on both sides. This exposes a fresh surface on the single crystal surface and reduces the overall thickness of the crystal to the micron level. The crystal is then transferred to an ITO electrode using the same method as in Example 1. Related photodetectors can also be made, with a vertical device structure of ITO / PEA2PbI4 (high gel concentration) / PEA2PbI4 (traditional solution growth) / Ag.

[0281] (5) Testing

[0282] The device was placed in a vacuum probe station, and a sweep voltage was applied to the left and right electrodes using a Keythley semiconductor analyzer. Dark current and photocurrent under 480nm laser illumination were measured, and the corresponding photodiode response was tested. Under illumination, a clear photoelectric response was observed, with a certain open-circuit voltage. At 0V, a significant photocurrent also appeared, with a certain short-circuit current present.

[0283] Example 7

[0284] This embodiment provides a method for preparing an asymmetric gel-embedded perovskite single crystal using sodium metasilicate gel; the method comprises the following steps:

[0285] (1) Preparation of multilayer gel

[0286] When using sodium metasilicate gel to prepare MAPbBr3 single crystals, sodium metasilicate solution and hydrobromic acid aqueous solution are first configured. In this embodiment, taking 5w / v% gel concentration as an example, 3g of sodium metasilicate pentahydrate is first fully dissolved in 20mL of ultrapure water; then 40mL of 48wt% hydrobromic acid solution is configured, and the metasilicic acid solution is slowly added dropwise into the hydrobromic acid solution during mixing, and the hydrobromic acid solution is kept stirring. After the dropwise addition is completed, stir for 10 minutes and pour it into a U-shaped tube and let it stand for 24-48 hours until it is completely gelled. The amount added is half of the bend of the U-shaped tube. Subsequently, 10w / v% gel is configured in the same way, added to the top of the completely gelled 5w / v% gel, and the amount added is not enough to cover the bend of the U-shaped tube, so that two layers of gel of 5w / v% / 10w / v% are configured, and each layer of gel has the same volume.

[0287] (2) Crystal growth

[0288] On both sides of the U-shaped tube, lead bromide solution (using 48wt% hydrobromic acid as solvent) and methylamine bromide solution (using 48wt% hydrobromic acid as solvent) of equal volume to the two layers of gel in step (1) were added, and the tube was placed in a constant temperature and dark environment for growth. The concentrations of lead bromide solution (using 48wt% hydrobromic acid as solvent) and methylamine bromide solution (using 48wt% hydrobromic acid as solvent) were both 1 mol / L. After growing at a constant temperature and dark environment of 20°C for one and a half months, the gel was destroyed, and the crystal was taken out from the interface of the two layers of gel. The surface was repeatedly rinsed with dichloromethane, and then the crystal was dried in a vacuum oven at 40°C for 8 hours to obtain an orange block of MAPbBr3 gel composite single crystal ( Figure 13 ).

[0289] (3) Device preparation and testing

[0290] The MAPbBr3 single crystal can also be repeatedly torn off the single crystal surface on both sides using single crystal Scott tape as shown in the above-mentioned lead iodide single crystal. The fresh surface of the single crystal is exposed, and the overall thickness of the crystal is reduced to the micron level. To make the electrodes distributed laterally on both sides of the interface caused by the distribution of gel in the crystal, refer to Example 4. Since the crystal is relatively thin, the first electrode and the second electrode are placed on the upper left and upper right of the single crystal respectively. Under vacuum conditions, a layer of metal gold with a thickness of about 100nm is thermally evaporated on the upper surface of the crystal interface as an electrode. The evaporation rate is , and the initial evaporation rate is 0.01nm / s, which is increased to 0.05nm / s after the gold thickness reaches 2.5nm.

[0291] The resulting device structure is Au (upper left) / MAPbBr3 (low gel concentration) / MAPbBr3 (high gel concentration) / Au (upper right). The device was placed in a vacuum probe station, and a scanning voltage was applied to the left and right electrodes using a Keythley semiconductor analyzer to obtain the dark current and photocurrent under 480nm laser illumination, and the response of the relevant photodiode was tested. Under illumination, there is a clear photoelectric response and a certain open-circuit voltage. At 0V, there is also a clear photocurrent, and there is a certain short-circuit current.

[0292] Comparative Example 1

[0293] (1) Preparation of gel

[0294] When using sodium metasilicate hydrogel to prepare lead iodide single crystals, first prepare a sodium metasilicate aqueous solution and an acetic acid aqueous solution. Taking a 10w / v% gel concentration as an example, first fully dissolve 5g of sodium metasilicate pentahydrate in 25ml of ultrapure water. Then prepare 25ml of a 13v / v% acetic acid aqueous solution. During mixing, slowly add the metasilicic acid solution dropwise into the acetic acid aqueous solution, and keep the acetic acid solution stirring and cooling in an ice-water bath. After the addition is completed, stir for 10 minutes and pour it into a U-shaped tube and let it stand for 24-48 hours until it is completely gelled. The amount added should not exceed the bend of the U-shaped tube.

[0295] (2) Growth of gel composite single crystals

[0296] Taking the growth in a gel concentration of 10w / v% as an example, the gel obtained in the previous step was added with an aqueous solution of lead acetate (containing 10% acetic acid) and an aqueous solution of potassium iodide of equal volume to the gel on both sides of the U-shaped tube, and placed in a constant temperature and dark environment for growth. The concentration of the aqueous solution of lead acetate (containing 10% acetic acid) and the aqueous solution of potassium iodide was 0.4mol / L. After growing for one month, the gel was destroyed, the crystal was taken out of the gel, the surface was repeatedly rinsed with ethanol, and then the crystal was dried in a vacuum oven at 40°C to obtain a yellow flaky lead iodide gel composite single crystal, the crystal size of which was generally 2-8mm. The growth process of other gel concentrations is the same as the above process.

[0297] (4) Cleaning of ITO substrate

[0298] ITO needs to be cleaned before use. The cleaning agents used for cleaning ITO are alkaline detergent, deionized water, ethanol, acetone, and isopropyl alcohol, respectively. Ultrasonic cleaning is performed for 20 minutes each. Dry in an oven and set aside.

[0299] (5) Pretreatment of gel composite single crystal

[0300] The sheet-like gel single crystal obtained in (2) was repeatedly peeled off on both sides of the single crystal surface using single crystal Scott tape, so that the fresh surface of the single crystal was exposed and the overall thickness of the crystal was reduced to micrometer level.

[0301] (6) Crystal transfer

[0302] After wetting the crystals obtained in (5) with anhydrous ethanol, they were dropped onto an ITO conductive glass substrate and allowed to air dry for 1 hour until the crystals naturally adhered to the substrate, forming a laminated structure, namely, an ITO / PbI2 (gel composite) structure.

[0303] (7) Evaporation of metal electrodes

[0304] Under vacuum conditions, a layer of metallic silver with a thickness of about 100 nm was thermally evaporated on ITO / PbI2 (gel composite) as the top electrode. The evaporation rate was: the initial evaporation rate was 0.01 nm / s, and it was increased to 0.05 nm / s after the silver thickness reached 2.5 nm. The final vertical device structure was ITO / PbI2 (gel composite) / Ag.

[0305] (8) Testing

[0306] The device was placed in a vacuum probe station, and a scanning voltage was applied to the upper and lower electrodes to obtain the dark current and the photocurrent under illumination. The current density-voltage curve was drawn with reference to Example 1. The results are shown in Figure 1. Figure 11 As shown in the results, the photoelectric response under light is obvious. Figure 11 As shown, there is no rectification effect in the dark state or under light illumination.

[0307] Comparative Example 2

[0308] (1) Preparation of gel

[0309] A mixed solution containing 6 v / v% ethylenediamine, 20 v / v% acetic acid, and 0.4 mol / L lead acetate was prepared. A 0.6 w / v% agarose hot solution was then prepared. 0.6 g of agarose powder was added to 100 mL of deionized water, microwaved, and stirred to obtain a 0.6 w / v% agarose sol. Equal volumes of the lead acetate mixed solution and the 0.6 w / v% agarose hot sol were mixed to obtain a 0.3 w / v% agarose sol containing 3 v / v% ethylenediamine, 10 v / v% acetic acid, and 0.2 mol / L lead acetate. A certain volume of the mixed sol was poured into a beaker and allowed to cool at room temperature to form a gel.

[0310] (2) Growth of gel composite single crystals

[0311] Agarose sol was prepared in a similar manner, and blank agarose hydrogel was poured onto the upper layer of the gel obtained in step (1), wherein the volume ratio of blank agarose to the agarose gel obtained in step (1) was 1:7; then, agarose hydrogel containing 0.4 mol / L potassium iodide of the same volume as the gel obtained in step (1) was poured onto the top layer, and after complete gelation, it was placed in a constant temperature and dark environment for growth. The same ethylenediamine neutralized with acetic acid as in step (1) was still added to all the above gel components and solutions. Finally, the following gel distribution structure was formed from bottom to top: 0.3w / v% gel (containing 0.2mol / L lead acetate), 0.6w / v% (blank gel), 0.3w / v% (containing 0.4mol / L potassium iodide) agarose gel. After one month of growth, the gel was destroyed and the crystals were removed from the lead acetate gel layer with tweezers ( Figure 3c) repeatedly rinsing the surface with ethanol, and then drying the crystals in a vacuum oven at 40° C. to obtain yellow flaky lead iodide gel composite single crystals, the crystal size of which is generally 2-5 mm.

[0312] (3) Pretreatment of gel composite single crystal

[0313] The sheet-like gel single crystal obtained in (2) was repeatedly peeled off using single crystal Scott tape to expose a fresh surface of the single crystal.

[0314] (4) Crystal transfer

[0315] The crystal obtained in (4) was fixed on a glass substrate with tape.

[0316] (5) Evaporation of metal electrodes

[0317] Under vacuum conditions, a mask was used to thermally evaporate a layer of metal gold with a thickness of about 100 nm on the crystal as an electrode. The initial evaporation rate was 0.01 nm / s, and it was increased to 0.05 nm / s after the gold thickness reached 2.5 nm. The final lateral device structure was Au / PbI2 (gel single crystal composite material) / Au.

[0318] (6) Testing

[0319] The device was placed in a vacuum probe station, and a scanning voltage was applied to the left and right electrodes to obtain the dark current and the photocurrent under illumination. The current-voltage curve was drawn with reference to Example 3. The results are shown in FIG. Figure 12 As shown in Figure 2, it has obvious photoelectric response under light. Figure 12 As shown, there is no rectification effect in the dark state or under light.

[0320] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An optoelectronic device based on a single crystal homojunction, characterized in that: The optoelectronic device comprises a first electrode, a photoelectric crystal layer and a second electrode; The photoelectric crystal layer includes a first crystal layer and a second crystal layer; The first crystal layer is connected to the second crystal layer, and the interface between the connected layers forms a homojunction; One of the first electrode and the second electrode is connected to the first crystal layer, and the other is connected to the second crystal layer; the first electrode and the second electrode are not in contact; The first crystal layer is a gel single crystal composite material grown in a first gel; The second crystal layer is a pure single crystal material or a gel single crystal composite material grown in a second gel; wherein the first gel and the second gel have different gel types and / or gel concentrations; The homojunction is formed by connecting single crystals in the first crystal layer and the second crystal layer.

2. The optoelectronic device according to claim 1, wherein When the first gel and the second gel are of the same gel type, the concentration of the second gel is less than that of the first gel; When the first gel and the second gel are of different types, the concentration of the second gel is less than or equal to the concentration of the first gel.

3. The optoelectronic device according to claim 1, wherein The first gel and the second gel are independently selected from one or more of sodium metasilicate gel, silicone gel, dextran gel, polyacrylamide gel, agarose gel, and semiconductor gel.

4. The optoelectronic device according to claim 1, wherein The single crystal in the gel single crystal composite material includes an inorganic single crystal, an organic single crystal or an organic-inorganic hybrid single crystal.

5. The optoelectronic device according to claim 4, characterized in that The inorganic single crystals include PbI2, PbS, inorganic perovskites, KDP, cuprous, ZnO, and transition metal sulfide crystals; The organic single crystal includes fullerene, anthracene or organic semiconductor crystal; The organic-inorganic hybrid single crystal includes an organic-inorganic hybrid perovskite single crystal.

6. The optoelectronic device according to claim 5, characterized in that The organic-inorganic hybrid perovskite single crystal includes MAPbX3 and PEAPbX3, wherein X is a halogen element.

7. The optoelectronic device according to claim 3, wherein: The gel concentration of the sodium metasilicate gel is 3-20w / v; and / or, the gel concentration of the agarose gel is 0.3-0.6 w / v; And / or, the silicone gel has a gel concentration of 5 to 20 w / v%.

8. The optoelectronic device according to claim 3, wherein The concentration of the first gel is 0.3~60w / v%; and / or, the concentration of the second gel is 0.3~60w / v%; and / or, the solvent of the first gel is water or an organic solvent; and / or, the solvent of the second gel is water or an organic solvent.

9. The optoelectronic device according to claim 6, wherein: Methods for preparing gel single crystal composite materials by gel growth include gel diffusion method, gel anti-solvent diffusion method or gel cooling method.

10. The optoelectronic device according to claim 9, characterized in that The specific steps of the gel diffusion method include: diffusing the reactants for producing single crystals into the gel to react, and when the reaction products aggregate to a certain extent in the gel to produce supersaturation, nucleation and crystallization are performed to obtain a gel single crystal composite material prepared by gel growth; The gel antisolvent diffusion method comprises: dissolving the reactants for producing single crystals in gel, then adding antisolvent to form nuclei and crystallize to obtain gel single crystal composite materials; The gel cooling method comprises: dissolving reactants for producing single crystals in gel, then slowly cooling, nucleating and crystallizing to obtain a gel single crystal composite material.

11. The optoelectronic device according to claim 10, wherein: The gel is a single-layer gel or a multi-layer gel, and the multi-layer gel is a multi-layer gel comprising a first gel layer and a second gel layer.

12. The optoelectronic device according to claim 11, wherein: When the gel is a multi-layer gel, a photoelectric crystal layer including a first crystal layer and a second crystal layer is taken out at the interface between the first gel layer and the second gel layer.

13. The optoelectronic device according to claim 10, wherein: When the single crystal is a lead iodide single crystal, the reactants for producing the single crystal include an iodine-containing compound and a lead-containing compound; When the single crystal is a MAPbX3 single crystal, the reactants for producing the single crystal include a methylamine-containing compound and PbX2, wherein X is a halogen element; When the single crystal is PEAPbX3, the reactants for producing the single crystal include a phenylethylamine compound and PbX2, wherein X is a halogen element.

14. The optoelectronic device according to claim 13, wherein: The iodine-containing compound includes potassium iodide, sodium iodide or ammonium iodide; the lead-containing compound includes lead nitrate and lead acetate.

15. The optoelectronic device according to claim 1, wherein The first electrode and the second electrode are transparent electrodes, metals or metal alloys.

16. The optoelectronic device according to claim 15, wherein: The transparent electrode includes ITO, FTO, IZO or SnO2; the metal includes Ag, Cu, Au, Al, Cr or Ti; And / or, the first electrode and the second electrode are different and / or the same.

17. The optoelectronic device according to claim 15, wherein: The transparent electrode further comprises 2PACz.

18. The optoelectronic device according to claim 15, wherein: The transparent electrode also includes a transparent electrode modified with Poly-2PACz.

19. The method for preparing the optoelectronic device according to any one of claims 1 to 18, comprising the following steps: connecting the first crystal layer and the second crystal layer to prepare a crystal layer including a homojunction; A first electrode is prepared on the first crystal layer in the crystal layer, and a second electrode is prepared on the second crystal layer to complete the preparation of the optoelectronic device.

20. Use of the optoelectronic device according to any one of claims 1 to 18 in the field of photodetectors, solar cells, phototransistors, light-emitting diodes or high-energy ray detection.

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