Photoelectronic device based on single crystal homogeneous structure and application thereof

Abstract

The invention provides an optoelectronic device based on a single-crystal homogeneous structure and application of the optoelectronic device. The optoelectronic device comprises crystal materials with different gel concentrations, different gel embedding areas are introduced into a single crystal in an asymmetric embedding mode, a single crystal homojunction is constructed, and the homojunction device achieves the self-driven photoelectric response characteristic. And transverse and longitudinal optoelectronic devices based on the single crystal homojunction are constructed. Different from a single crystal photoconductive symmetrical structure device prepared only by using a traditional solution method, the optoelectronic device does not need extra bias voltage to ensure normal work of the device, and a photodiode structure similar to a traditional inorganic semiconductor homojunction can be realized; the asymmetric structure embedded by the gel enables the photoelectric device to have the current-voltage characteristic similar to that of a traditional semiconductor homojunction diode, can effectively perform photoelectric conversion, and can be widely applied to photoelectric detectors and other photoelectric devices.

Description

Technical Field

[0001] The 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. Through different doping concentrations or crystal structures, a built-in electric field or space charge region is formed. The existence of this electric field causes the bending of the energy band and forms a potential barrier. This barrier controls the flow of carriers in the device to form an interface with special electrical properties. In modern semiconductor technology, homojunction is the most common structure and plays an important role in many electronic and optoelectronic devices, such as diodes, transistors, solar cells, and semiconductor lasers. In the existing commonly used single crystal silicon homojunction preparation process, processes such as thermal diffusion and ion implantation are often used, and the whole process involves material growth, doping control, interface quality, heat treatment, etc. Its application range for semiconductor single crystals is limited, the whole process has high energy consumption, and it is not suitable for some existing solution methods for preparing single crystals.

[0003] By growing single crystals through the gel method and embedding the gel network into semiconductor single crystals, a large area of ​​gel semiconductor crystal contact interface can be introduced 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 can effectively introduce the interface interaction between the gel material and the single crystal, thus providing new possibilities for device performance optimization. In addition, the formation of gel single crystal composite materials will not affect some basic properties of the single crystal, such as lattice constant and optical absorption.

[0004] Previously, gel single crystal composite materials were mainly used to construct optoelectronic devices with heterojunction structures, which were applied in fields such as photoelectric detection and solar cells. However, methods for preparing homojunction optoelectronic devices using gel network embedding have not yet been proposed. Therefore, there are still certain challenges in achieving stable gel embedding to construct homojunction optoelectronic devices based on single crystals. 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 objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0007] In a first aspect of the present invention, there is provided 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 of the connection 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 methods, 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 of the 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, and can also be selected according to 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%~0.6w / v%; if the first gel and the second gel are both agarose gel, then 0.3w / v%≤second gel concentration<first gel concentration≤0.6w / v%, and the greater 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 0-60, or 0.01-55, or 0.1-45, or 0.3-40, or 5-30, or 10-20, 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 crystal in the gel network by setting different gel concentrations and / or types in the first crystal layer and the second crystal layer in the photoelectric crystal layer. This method is different from the single crystal photoconductive symmetrical structure device prepared by the traditional solution method (such as evaporation crystallization method, cooling crystallization method or anti-solvent diffusion crystallization method without gel), and does not require additional bias voltage to ensure the normal operation of the device, and can achieve a photodiode structure similar to the traditional inorganic semiconductor homojunction. This gel-embedded asymmetric structure enables the optoelectronic device to have a current-voltage characteristic similar to that of a traditional semiconductor homojunction diode, can effectively perform photoelectric conversion, and can be widely used in photodetectors and other optoelectronic devices.

[0027] The regulation of the work function of the crystal by the asymmetric gel comes from the different types or proportions of the internal gel groups in the asymmetric gel. The different types or proportions of the gel groups embedded in the single crystal will produce different dipole effects on the crystal, and then have different effects on the work function of the crystal; taking sodium metasilicate gel as an example, it contains silicon hydroxyl groups and silicon oxygen silicon bonds inside. It is speculated that the main role in sodium metasilicate gel is silicon oxygen silicon bonds. Therefore, at the same gel concentration, the higher the content of silicon oxygen silicon bonds, the greater the effect on its work function. Similarly, the situation in agarose is similar, but the main role is played by hydroxyl groups. The higher the gel concentration, the higher the content of hydroxyl groups per unit volume, and the greater the effect on the work function of the crystal. Taking lead iodide grown in agarose gel as an example, in two regions of the single crystal, different proportions of hydroxyl groups and carbon oxygen carbon bonds can form a homojunction, that is, a higher proportion of hydroxyl groups or hydroxyl concentrations exist in one region, while the proportion or concentration of hydroxyl groups in the adjacent region is lower, so that the two regions can be connected to form 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 some embodiments, the concentration of the sodium metasilicate gel is 3 to 20 w / v%. Within this concentration range, the work function of the lead iodide single crystal will also increase continuously with the increase of the gel concentration, and the overall energy band structure will move downward. However, at high gel concentrations, the work function changes discontinuously and non-monotonic, and the crystal growth time will also be greatly extended.

[0030] In some embodiments, the concentration of the agarose gel is 0.3 w / v% to 0.6 w / v%; within this concentration range, the work function of lead iodide will also continuously decrease with the increase of gel concentration, and the overall energy band structure will move upward. However, at a high gel concentration of more than 0.6 w / v%, the crystal morphology will rapidly deteriorate and no longer grow flaky hexagonal crystals, and the crystal growth time will also be greatly extended.

[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 certain embodiments, the inorganic single crystal comprises: PbI 2 , PbS, inorganic perovskites (such as CsPbX 3 etc.), KDP, copper (such as Cu 2 O, Cu 2S, etc.), ZnO, some 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 comprises: an organic-inorganic hybrid perovskite single crystal, such as MAPbX 3 ,PEAPbX 3 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 aggregate to a certain extent, supersaturation occurs, nucleation and crystallization occur, and a gel single crystal composite material is obtained.

[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 the reactants for producing single crystals in gel, and then slowly cooling to form nuclei and crystallize 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 a first gel layer or a second gel layer, based on which a first crystal layer or a second crystal layer grown in the first gel or the second gel can be obtained; the gel can also be a multilayer gel including a first gel layer and a second gel layer, wherein the first gel layer and the second gel layer can be arranged alternately in sequence, and a 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 a gel single crystal composite material containing two gel concentrations embedded can be obtained at one time, and a 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 not containing reactants, or can be gel layers containing reactants.

[0041] For example, the gel diffusion method for preparing gel single crystal composite materials often uses a U-tube method or adds a blank gel layer at the interface of a gel-solution containing different reactants to prepare single crystal materials, wherein 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 includes 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 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 a lead iodide single crystal or a perovskite material will also increase continuously with the increase in gel concentration, and the overall energy band structure will move downward. However, in the case of high gel concentration, the work function changes discontinuously 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%, 5 w / v%, 10 w / v%, and 15 w / v%.

[0045] In certain embodiments, if agarose hydrogel is used to prepare a single crystal material by a gel growth method, the concentration of the agarose hydrogel is 0.3w / v% to 0.6w / v%; within this concentration range, the work function of lead iodide will also decrease continuously with the increase of gel concentration, and the overall band structure will move upward. However, at high gel concentrations above 0.6w / v%, the crystal morphology deteriorates rapidly and no longer grows lamellar hexagonal crystals, and the crystal growth time will also be greatly extended. The gel concentration of the agarose hydrogel can also be 0.3w / v% to 0.4w / v%, 0.4w / v% to 0.6w / v%, and can also be 0.3w / v%, 0.4w / v%, 0.5w / v%, and 0.6w / 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 aggregate to a certain extent, supersaturation occurs, nucleation and crystallization occur, and a gel-embedded single crystal material is obtained.

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

[0048] In certain embodiments, the U-tube method includes adding two reactant solutions to the two ends of the U-tube, and adding a layer of blank gel containing no reactants to the middle part 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 interface of a gel-solution 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 on 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, react slowly 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, and 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 with gel layers of different gel concentrations alternately distributed.

[0052] In some embodiments, the multilayer includes 2 layers or more, and can also be 2 to 20 layers, or can also 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 a gel single crystal composite material, the amount of each component is adjusted according to the selected single crystal growth position; 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 experimental conditions; wherein the blank gel can be a single-layer or 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] Take the above-mentioned U-tube method as an example; the volume ratio of the blank gel to the two reactant solutions is 1:0.8-1.2.

[0055] If it is necessary to generate single crystals in a gel containing reactants, one or more reactant solutions can be made into gel solutions, and a blank gel can be added between the reactant solutions to adjust the reaction rate. In this case, the amount of blank gel used is small to avoid the blank gel layer being too thick. 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 a multi-layer gel. 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.

[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 there is no gel embedded in the pure single crystal material.

[0057] The present invention uses the gel method to prepare the gel single crystal composite material, and uses the characteristics of the gel method growth to introduce a large area of ​​the gel network and the single crystal contact interface while maintaining the long-range order of the single crystal, so as to achieve the uniform doping of the single crystal by the gel network. In addition, the embedding of gel networks with different concentrations and / or components is used to achieve the purpose of continuous regulation of the work function of the semiconductor single crystal, and the asymmetric embedding of gel networks with different concentrations and / or components into the single crystal is used to prepare homojunctions and optoelectronic devices.

[0058] The present invention is further described 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 the first gel or the second gel, respectively, and growing them in a constant temperature and light-proof environment, then taking out 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 junction of the first gel and the second gel in a constant temperature and light-proof environment, then taking out the single crystal located at the junction of the first gel and the second gel, cleaning the surface of the single crystal, and drying 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 first gel layer and the second gel layer from the gel, cleaning the surface of the single crystal, and drying the multilayer gel to obtain a photoelectric crystal layer comprising the first crystal layer and the second crystal layer; wherein the multilayer gel has two or more layers, wherein the first gel layer and the second gel layer are arranged alternately 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 in 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, it is not limited thereto, wherein the iodine-containing compound may be an aqueous solution without gel, or an iodine-containing compound gel containing a first gel and an iodine-containing compound gel containing a second gel; the lead-containing compound may also be a lead-containing compound aqueous solution, and the iodine-containing compound may be an iodine-containing compound gel containing a first gel and an iodine-containing compound gel containing a second gel. As long as at least one of the reactants is a reactant gel containing the first gel and a reactant gel containing the second gel, it is acceptable. As long as the photoelectric crystal layer containing the first crystal layer and the second crystal layer can be taken out from the crystal at the junction of the first gel and the second gel.

[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 and letting it stand (which can be replaced by other containers) to form a sodium metasilicate hydrogel, respectively adding a lead compound aqueous solution and an iodine compound aqueous solution on both sides of the sodium metasilicate hydrogel in the U-shaped tube, growing the mixture in a constant temperature and light-proof environment, then taking out a single crystal from the gel, cleaning the surface of the single crystal, and drying the mixture to obtain a 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, mainly through the acid solution reacting with 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 adopts the U-tube method to prepare sodium metasilicate hydrogel-lead iodide single crystal material. It can also prepare single crystal material by adding a blank gel layer at the interface of gel-solution 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 gel concentration in the sodium metasilicate hydrogel is 3 w / v% to 20 w / v%, wherein the gel concentration refers to the concentration of sodium metasilicate, based on the solution after the sodium metasilicate aqueous solution and the acetic acid aqueous solution are mixed. Taking a 10 w / v% gel concentration as an example, specifically, 5 g of sodium metasilicate pentahydrate is fully dissolved in 25 mL of ultrapure water, and then mixed with 25 mL of acetic acid aqueous solution; wherein the concentration of the acetic acid aqueous 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 (NH 4 I); preferably potassium iodide.

[0072] In certain embodiments, the lead-containing compound comprises lead nitrate (Pb(NO 3 ) 2 ), lead acetate ((CH 3 COO 2 Pb); preferably lead acetate.

[0073] In certain embodiments, the standing time is 12-48 hours, 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 also be 5-10 v / v% acetic acid, it may also 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 forming the single crystal include a methylamine compound and a PbX 2 , 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 PbX 2 , wherein X is a halogen element, specifically Cl (chlorine), Br (bromine) or I (iodine).

[0084] The present invention further provides sodium metasilicate hydrogel-MAPbBr 3The preparation method of a single crystal material comprises: 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 to both sides of the multilayer gel layer respectively, growing in a constant temperature and light-proof environment, then taking out a single crystal from the interface of the multilayer gel, cleaning the surface of the single crystal, and drying to obtain a sodium metasilicate hydrogel-lead iodide single crystal material.

[0085] In certain embodiments, the gel is formed by mixing a gel aqueous solution and an acid solution having different concentrations and then standing.

[0086] In some embodiments, the concentration of the lead bromide solution is 0.5 to 2 mol / L; it can 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 perovskite single crystal composite material embedded in the gel 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 prepared, the single crystal reactants include phenylethylamine iodide and lead iodide; if a methylamine lead bromide single crystal is prepared, the single crystal reactants include methylamine bromide and lead bromide.

[0096] In some embodiments, the concentration of iodinated phenylethylamine in the gel solution is 0.1-0.4 mol / L, and can 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 some embodiments, the concentration of lead iodide in the gel solution is 0.05-0.2 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 anti-solvent comprises dichloromethane or toluene.

[0100] In certain embodiments, the volume ratio of the gel solution to the anti-solvent is 1:1-5; 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 pure phenethylamine lead iodide single crystal, comprising mixing a phenethylamine lead iodide single crystal reactant and a solvent, heating and then cooling to obtain a pure phenethylamine 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 (PbI 2 ).

[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 and 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 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 lead iodide single crystal material) by evaporation and 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; it 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, it can also be 180-200°C, it can also be 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, a method for preparing an agarose hydrogel-lead iodide single crystal material for preparing a lateral single crystal homojunction device is exemplarily provided, comprising (c1) or (c2):

[0116] (c1) preparing agarose gels containing lead compounds respectively including a first gel and a second gel, preparing a plurality of agarose gel layers containing lead compounds including the first gel and the second gel in a container, pouring the first gel (agarose gel) on the upper layer of the agarose gel layers containing lead compounds, and then pouring the second gel (agarose gel) containing iodine compounds, and placing the agarose gel in a constant temperature and light-proof environment for growth after complete gelation; then taking out a crystal from the interface of the gel layers of the first gel and the second gel, cleaning the crystal surface, and drying to obtain a photoelectric crystal layer including 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 0.3w / v% to 0.6w / v%, wherein the gel concentration refers to the concentration of agarose in any agarose hydrogel solution, including agarose hydrogel solution, iodine-containing compound agarose hydrogel solution, and lead-containing compound hydrogel solution. The agarose gel concentration can be continuously changed from 0.3w / v% to 0.6w / v%, and the work function of lead iodide will also continuously decrease with the increase of gel concentration, and the overall energy band structure will move upward. However, at high gel concentrations above 0.6w / v%, the crystal morphology deteriorates rapidly and no longer grows lamellar hexagonal crystals, and the crystal growth time will also be greatly extended.

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

[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 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.

[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 containing a lead compound comprises 2-5 v / v% ethylenediamine, 8-15 v / v% acetic acid, 0.2-0.4 mol / L of the lead 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 some embodiments, the first electrode and the second electrode are each selected from transparent electrodes (such as ITO (indium tin oxide), FTO, IZO (indium zinc oxide) and SnO 2 ), a transparent electrode modified with 2PACz or poly-2PACz, a metal (such as Ag, Cu, Au, Al, Mo, W, Cr, Ti and Nd), 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 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 min, or 1 to 3 min, or 1, 2, 3, 4, or 5 min.

[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, taking 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, taking the substrate as a reference, when the first crystal layer and the second crystal layer in the crystal layer are connected up and down, they can be used to construct a vertical optoelectronic device.

[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, it is a vertical optoelectronic device.

[0136] In certain preferred embodiments, taking 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 some 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, taking 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 at the upper left or upper right.

[0141] In certain preferred embodiments, when constructing a lateral optoelectronic device, taking 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] Exemplarily, 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 transparent electrode modified with 2PACz, 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 (e.g., metallic silver) on the optoelectronic crystal layer.

[0143] Specifically, in the present invention, in order to prepare vertical and horizontal homojunction single crystal devices, the present invention adopts the following two methods. To construct a vertical homojunction optoelectronic device, a gel single crystal composite material obtained by transferring growth in different gel concentrations can be used to construct a vertical homojunction single crystal device with gel distribution, or a gel composite single crystal can be used as a template to in-situ grow a single crystal without gel doping using a traditional solution method that does not involve gel, including evaporation crystallization, cooling crystallization, or anti-solvent diffusion crystallization to construct a vertical homojunction single crystal device.

[0144] The vertical homojunction device adopts a device structure in which the bottom electrode is a transparent electrode. In addition, the lead iodide single crystals grown in different gel concentrations are transferred to the transparent electrode, and the transferred crystals are cleaned and thinned with single crystal tape in advance so that the single crystals can better contact the transparent electrode and the crystals can contact each other. Finally, in a vacuum environment, a layer of metal is thermally evaporated on it as the top electrode. The final structure from bottom to top is: the first electrode / PbI 2 (First Gel) / PbI 2 (Second gel) / Second electrode or First electrode / PbI 2 (Second Gel) / PbI 2 The basic structure of the longitudinal photodetector is (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 then a first electrode and a second electrode are respectively fixed on both sides or the upper left and upper right of the photoelectric crystal layer, wherein the first electrode and the second electrode are respectively in contact with the first crystal layer and the second crystal layer in the photoelectric crystal layer.

[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 also cleaned using single crystal tape, and then a gold electrode is prepared by thermal evaporation on both sides or above the gel with differential concentration distribution inside the single crystal, and finally a metal electrode / PbI 2 (Second Gel) / PbI 2 (First gel) / metal electrode or metal electrode / PbI 2 (First Gel) / PbI 2 (Second gel) / metal electrode lateral photodetector basic structure. Or use the shadow effect of thermal evaporation to prepare asymmetric gold and silver electrodes, and finally construct Ag / PbI 2 (low gel concentration) / PbI 2 (High gel concentration) / Au lateral photodetector basic 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 the 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 the present invention can also be used in optoelectronic devices and high-energy ray detectors. Obviously, such applications are all attributed to the change in the band structure of the gel-doped lead iodide single crystal, and a homojunction is formed with an undoped lead iodide single crystal or a lead iodide single crystal embedded with a higher concentration of gel, and has good self-driven photoelectric response performance. The present invention uses gel doping to change the band properties of the lead iodide semiconductor, so that it can be used in a homojunction photoelectric detector.

[0153] Beneficial effects:

[0154] Previously, gel single crystal composite materials were mainly used to construct optoelectronic devices with heterojunction structures, and were applied to fields such as photoelectric detection and solar cells. Methods for preparing homojunction optoelectronic devices using gel network embedding had not yet been proposed. The present invention introduces different gel embedding regions into a single crystal by an asymmetric embedding method 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 the single crystal photoconductive symmetrical structure device prepared by the traditional solution method, the optoelectronic device of the present invention does not require an additional bias voltage to ensure the normal operation of the device, and can realize a photodiode structure similar to the traditional inorganic semiconductor homojunction. This gel-embedded asymmetric structure enables the optoelectronic device to have a current-voltage characteristic similar to that of a traditional semiconductor homojunction diode, can effectively perform photoelectric conversion, and can be widely used 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 The left picture is a schematic diagram of the growth device for the bidirectional diffusion growth of lead iodide single crystals by sodium metasilicate gel, the middle picture is a schematic diagram of the growth device for the growth of lead iodide single crystals by agarose gel or a multilayer agarose gel with alternating concentration distribution, and the right picture is a schematic diagram of the growth device for the bidirectional diffusion growth of lead iodide single crystals by agarose gel or a multilayer agarose gel with alternating concentration distribution.

[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 ITO / PbI 2 (High gel concentration) / PbI 2 Schematic diagram of (solution-grown / low gel concentration) / Ag homojunction photodetector.

[0160] Figure 5 Au / PbI 2 (low gel concentration) / PbI 2 Schematic diagram of (high gel concentration) / Au single crystal homojunction photodetector.

[0161] Figure 6 Au / PbI 2 (low gel concentration) / PbI 2 (High gel concentration) / Ag single crystal homojunction photodetector, where the left picture is a schematic diagram of the asymmetric electrode evaporation method, and the right picture is a schematic diagram of Au / PbI 2 (low gel concentration) / PbI 2 Schematic diagram of (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 8 This is the current density-voltage curve of the gel single crystal photodetector prepared in Example 2.

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

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

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

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

[0168] Fig.13 The gel single crystals prepared in Example 6 are shown in the left picture. The left picture is MAPbBr 3 (MA: methylamine) crystal, the right picture is PEA 2 PbI 4 (PEA: phenylethylamine) single crystal. DETAILED DESCRIPTION

[0169] The following is a description of the implementation of the present invention by means of specific embodiments. Those 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 protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

[0171] When the embodiments give 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 can 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 grasp of the prior art by those skilled in the art and the record 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 can also be used to realize the present invention.

[0172] like Figure 1 As 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 connected 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 is not in contact with the second electrode 3; 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 object 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 realize 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 semiconductor single crystals by a gel method, realizes 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 realize 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 the present invention can also be used in optoelectronic devices and high-energy ray detectors. Obviously, such applications are all attributed to the change in the band structure of the gel-doped lead iodide single crystal, and a homojunction is formed with an undoped lead iodide single crystal or a lead iodide single crystal embedded with a higher concentration of gel, and has good self-driven photoelectric response performance. The present invention uses gel doping to change the band properties of the lead iodide semiconductor, so that it can be used in a homojunction photoelectric detector.

[0176] The present invention adopts a solution method to prepare a homojunction device, and the embedded gel network of different concentrations can realize continuous regulation of the work function of the lead iodide single crystal, and its energy level structure can be regulated by changing the gel concentration, and has better homojunction quality. In addition, the patterned distribution of the gel inside the artificially manufactured single crystal can effectively construct a built-in electric field, which is 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 the 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, 1w / v% means that 100mL of solution contains 1g of a substance.

[0178] In the present invention, the gel volume involved refers to the ungelled gel volume. The room temperature mentioned in the present invention is the common 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 crystal, sodium metasilicate aqueous solution and acetic acid aqueous solution are first configured. In this embodiment, taking 10w / v% gel concentration as an example, 5g of sodium metasilicate pentahydrate is fully dissolved in 25mL of ultrapure water; then 25mL of 13v / v% acetic acid aqueous solution is configured, and the metasilicic acid solution is slowly added dropwise into 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, stir for 10 minutes and pour it into a U-shaped tube at 20°C and let it stand for 24-48 hours until it is completely gelled, and the amount added is to cover the bent part of the U-shaped tube.

[0183] The gel concentration is not limited to 10 w / v%. The preparation process of other gel concentrations is the same as the above process, but 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 gel concentration of 15 w / v%, 7.5 g of sodium metasilicate pentahydrate and a 19.5 v / v% acetic acid aqueous solution concentration are used, and the other contents remain unchanged; the gel concentration 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 2-8mm ( Figure 3b).

[0187] The growth process of 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 change continuously from 3w / v% to 20w / v%, and the work function of the lead iodide will also increase 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, in the case of higher gel concentration, the work function changes discontinuously and non-monotonic, and the crystal growth time will be extended.

[0188] (3) Traditional solution growth of 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 substrate

[0191] ITO needs to be cleaned before use. The cleaning agents used to clean ITO are hellmanex III alkaline detergent, deionized water, ethanol, acetone, and isopropanol, respectively, and ultrasonic cleaning is performed for 20 minutes each. Dry 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 torn off the single crystal surface on both sides using single crystal Scott tape, so that the single crystal surface is exposed to fresh surface, and the overall thickness of the crystal is reduced to micron level, about tens of microns to hundreds of microns.

[0194] (6) Crystal transfer

[0195] After wetting the crystal obtained in step (5) with anhydrous ethanol, drop it on the ITO conductive glass substrate and air dry it for 1 hour until the crystal naturally adheres to the substrate. Then, 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 to form an upper and lower stacked structure, namely ITO / PbI 2 (High gel concentration) / PbI 2 (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 ITO / PbI 2 (High gel concentration) / PbI 2(low gel concentration) structure.

[0197] (7) Evaporation of metal electrodes

[0198] Under vacuum conditions, ITO / PbI 2 (High gel concentration) / PbI 2 A layer of metallic silver with a thickness of about 100 nm is thermally evaporated as the top electrode (grown by traditional solution method). 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 / PbI 2 (High gel concentration) / PbI 2 (traditional solution growth) / Ag, structure such as 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 a current density-voltage curve is plotted.

[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 fully dissolve 5g of sodium metasilicate pentahydrate in 25ml of ultrapure water. Then prepare 25ml of 13v / v% acetic acid aqueous solution, and slowly drop the metasilicic acid solution into the acetic acid aqueous solution during mixing, and keep the acetic acid solution stirring and keep the ice water bath cooling. 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 is to cover the bent part of the U-shaped tube.

[0206] (2) Growth of Gel Composite Single Crystals

[0207] The gel obtained in the previous step is added with an aqueous solution of lead acetate (containing 10v / v% 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 at 20°C for growth. The concentrations of lead acetate and potassium iodide in the aqueous solution of lead acetate and the aqueous solution of potassium iodide are both 0.4mol / L. After one month of growth, the gel is destroyed, the crystal is taken out of the gel, the surface is repeatedly rinsed with ethanol, and then the crystal is dried in a vacuum oven at 40°C for 8 to 12 hours to obtain a yellow flaky lead iodide gel composite single crystal, the crystal size of which is generally 2-8mm. The growth process of other gel concentrations is the same as the above process. The gel concentration can also be continuously changed from 3w / v% to 20w / v% to set up the experiment, and the work function of lead iodide will also increase continuously with the increase of gel concentration, and the overall band structure will move downward, so the required gel concentration can be selected according to the energy level structure and work function required by the device. However, in the case of high gel concentration, the work function change is discontinuous and non-monotonic, and the crystal growth time will be 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 lead iodide pure single crystals were obtained.

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

[0211] ITO needs to be cleaned before use. The cleaning agents used to clean ITO are hellmanexⅢ alkaline detergent, deionized water, ethanol, acetone, and isopropanol, respectively, and ultrasonic cleaning is performed for 20 minutes. Dry in an oven for use. The glass substrate containing ITO needs to be strictly cleaned before use and dried in an oven for use; then the ITO is treated with oxygen plasma for 2 minutes, and then soaked in a 1mg / ml 2PACz methanol solution for 8 hours, then cleaned with methanol, and blown dry with a nitrogen gun for use. The energy level structure of the bottom electrode of ITO modified with 2PACz will be deeper, so it is more compatible with 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) is repeatedly torn off the single crystal surface on both sides using single crystal Scott tape, so that the single crystal surface is exposed to fresh surface and the overall thickness of the crystal is reduced to micrometer level.

[0214] (6) Crystal transfer

[0215] After wetting the crystal obtained in step (5) with anhydrous ethanol, drop it on the ITO conductive glass substrate and air dry it for 1 hour until the crystal naturally adheres to the substrate. Then, 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 to form an upper and lower stacked structure, namely, ITO (2PACz modified) / PbI 2 (High gel concentration) / PbI 2 Of course, the crystal in step (3) can also be replaced with a single crystal grown at another gel concentration in step (5) to form ITO (2PACz modified) / PbI 2 (High gel concentration) / PbI 2 (low gel concentration) structure.

[0216] (7) Evaporation of metal electrodes

[0217] Under vacuum conditions, ITO (2PACz modified) / PbI 2 (High gel concentration) / PbI 2 A layer of metallic silver with a thickness of about 100 nm is thermally evaporated on the top electrode (grown by traditional solution method) at an evaporation rate of 0.01 nm / s at the initial evaporation rate, which is increased to 0.05 nm / s after the silver thickness reaches 2.5 nm. The resulting vertical device structure is ITO (2PACz modified) / PbI 2 (High gel concentration) / PbI 2 (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 plotted.

[0220] The results are as follows Figure 8 As shown in the figure, the results show that there is an obvious rectification effect in the dark state, an obvious photoelectric response under illumination, the relationship between voltage and current is nonlinear, the photocurrent is improved under forward bias, and there is a certain open circuit voltage. At 0V, there is also an obvious photocurrent, and there is a certain short-circuit current, indicating that the homojunction detector can work in self-driven mode. And 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 photoelectric detector is as follows:

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

[0224] A mixed solution containing 6v / v% ethylenediamine, 20v / v% acetic acid, and 0.4mol / L lead acetate is prepared. Then, a 0.6w / v% agarose aqueous solution is prepared, 0.6g agarose powder is added to 100mL deionized water, and a 0.6w / v% agarose hydrogel is obtained after microwave boiling and stirring. The mixed solution of lead acetate and the 0.6w / v% agarose hydrogel are mixed in equal volumes to obtain a lead acetate agarose solution containing 3v / v% ethylenediamine, 10v / v% acetic acid, 0.2mol / L lead acetate, and 0.3w / v% agarose. A certain volume of the lead acetate agarose solution is poured into a beaker and placed at room temperature to form a gel after cooling.

[0225] (2) Preparation of multilayer gel

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

[0227] (3) Growth of Gel Composite Single Crystals

[0228] Agarose sol was prepared in a similar manner, and a 0.6w / v% 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-layer lead acetate agarose gel in step (1) was 1:7, and then an agarose hydrogel containing 0.4mol / L potassium iodide of the same volume as the four-layer lead acetate agarose gel was poured onto the uppermost layer. After complete gelation, the gel was placed in a constant temperature and light-proof environment for growth. 3v / v% ethylenediamine neutralized with acetic acid was still added to all the above gel components and solutions. Finally, a gel distribution structure from bottom to top was formed: 0.3w / v%-0.6w / v% alternating distribution (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 crystal was taken out from the interface of the gel layer with alternating distribution of 0.3w / v%-0.6w / v%-0.3w / v%-0.6w / v% with 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] Moreover, the work function of the lead iodide single crystal can change continuously according to the gel concentration. The agarose gel concentration can change continuously from 0.3w / v% to 0.6w / v%. The work function of the lead iodide will also decrease continuously with the increase of gel concentration, and the overall energy band structure will move upward. Therefore, in actual situations, the required gel concentration can be selected according to the energy level structure and work function required by the device. However, at high gel concentrations above 0.6w / v%, the crystal morphology deteriorates rapidly and no longer grows flaky hexagonal crystals, and the crystal growth time will be greatly extended.

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

[0231] The sheet-like gel single crystal obtained in (3), wherein the crystal grown at the interface of 0.3w / v% and 0.6w / v% gel distribution, can be used for subsequent homojunction preparation. The single crystal surface is repeatedly torn off using single crystal Scott tape, so that the single crystal surface is exposed to fresh surface, and the overall thickness of the crystal is reduced to micron level.

[0232] (5) Crystal transfer

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

[0234] (6) Evaporation of metal electrodes

[0235] 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 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, which is increased to 0.05nm / s after the gold thickness reaches 2.5nm. The final lateral device structure is Au (upper left) / PbI 2 (low gel concentration) / PbI 2 (Gel concentration is high) / Au (upper right), the structure is as follows 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. Because the current area of ​​the lateral device cannot be calibrated, only the current is obtained, and the current-voltage curve is plotted. The results are shown in the figure below. Fig. 9As 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 photoelectric detector is as follows:

[0240] (1) Preparation of gel

[0241] When using agarose hydrogel to prepare lead iodide single crystals, you can also prepare multiple layers of blank agarose hydrogel first, pour it into a culture dish, and remove excess gel on both sides after gelation. Prepare a 0.6w / v% agarose hydrogel solution, add 0.6g agarose powder to 100mL deionized water, boil it in a microwave and stir it evenly to obtain an agarose sol with a concentration of 0.6w / v%, which is poured into a culture dish. Prepare an agarose sol with a concentration of 0.3w / v% in the same way, and add the sol to the top of the gel. All prepared agarose hydrogel solutions contain 3v / v% ethylenediamine. Similarly, four layers of agarose gel with alternating concentrations of 0.3w / v% and 0.6w / v% can be prepared in a culture dish, and the volume of each layer of gel is 1:1. After the gel is complete, remove the excess gel on both sides to leave room for adding solutions on both sides.

[0242] (2) Growth of Gel Composite Single Crystals

[0243] 0.4 mol / L aqueous lead acetate solution (containing 10 v / v% acetic acid) and 0.4 mol / L aqueous potassium iodide solution with the same volume as the four layers of agarose gel are added to both sides, and all prepared solutions (such as aqueous lead acetate solution and aqueous potassium iodide solution) contain 3 v / v% ethylenediamine neutralized by acetic acid, and then placed in a constant temperature and dark environment for growth. After growing for one month, the gel is destroyed, and the crystal is taken out from the distribution interface of 0.3 w / v% and 0.6 w / v% gel with tweezers, and the surface is repeatedly rinsed with ethanol, and then the crystal is dried in a 40°C vacuum oven to obtain a yellow flaky lead iodide gel composite single crystal, and the crystal size is generally 1-3 mm.

[0244] Moreover, the work function of the lead iodide single crystal can change continuously according to the gel concentration. The agarose gel concentration can change continuously from 0.3w / v% to 0.6w / v%. The work function of the lead iodide will also decrease continuously with the increase of gel concentration, and the overall energy band structure will move upward. Therefore, in actual situations, the required gel concentration combination can be selected according to the energy level structure and work function required by the device. However, at high gel concentrations above 0.6w / v%, the crystal morphology deteriorates rapidly and no longer grows flaky hexagonal crystals, and the crystal growth time will also be greatly extended.

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

[0246] The sheet-like gel single crystal is obtained by step (2), wherein the crystal grown at the interface of 0.3w / v% and 0.6w / v% gel distribution can be used for subsequent homojunction preparation. The single crystal surface is repeatedly torn off using single crystal Scott tape to expose a fresh surface of the single crystal surface, and the overall thickness of the crystal is reduced to micrometer level.

[0247] (4) Crystal transfer

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

[0249] (5) Evaporation of metal electrodes

[0250] 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 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: the initial evaporation rate is 0.01nm / s, and it is increased to 0.05nm / s after the gold thickness reaches 2.5nm. The final lateral device structure is Au (upper left) / PbI 2 (low gel concentration) / PbI 2 (Gel concentration is high) / Au (upper right).

[0251] (6) Evaporation of metal electrodes

[0252] 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 and to perform a response test on the relevant photodiode. There was an obvious photoelectric response under illumination and a certain open circuit voltage. At 0V, there was also an obvious photocurrent and a certain short circuit current.

[0253] Example 5

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

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

[0256] Prepare a mixed solution containing 6v / v% ethylenediamine, 20v / v% acetic acid, and 0.4mol / L lead acetate. Then prepare a 0.6w / v% agarose hot solution, add 0.6g agarose powder to 100mL deionized water, boil in microwave and stir evenly to obtain a 0.6w / v% agarose sol. Mix the mixed solution of lead acetate and the 0.6w / v% agarose hot sol in equal volumes to obtain a 0.3w / v% agarose sol containing 3v / v% ethylenediamine, 10v / v% acetic acid, and 0.2mol / L lead acetate. Take a certain volume of the mixed sol and pour it into a beaker, and place it at room temperature to cool and form a gel.

[0257] (2) Preparation of multilayer gel

[0258] After the sol in (1) is 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 0.3 w / v%-0.6 w / v%-0.3 w / v%-0.6 w / v% agarose gel containing 0.2 mol / L lead acetate in alternating concentrations can be prepared in a beaker, and the volume of each layer of gel is the same.

[0259] (3) Growth of Gel Composite Single Crystals

[0260] Agarose sol was prepared in a similar manner, and blank agarose hydrogel was poured on the upper layer of the gel obtained in (2), wherein the volume ratio of blank agarose hydrogel to four layers of agarose gel containing lead acetate was 1:7; then, 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 on the top layer, and after complete gelation, it was placed in a constant temperature and light-proof environment for growth. 3v / v% ethylenediamine neutralized with acetic acid was still added to all the above gel components and solutions. Finally, the following gel distribution structure from bottom to top was formed: 0.3w / v%-0.6w / v% alternating distribution (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 taken out from the interface of the gel layers with different gel concentrations with tweezers, and the surface was repeatedly rinsed with ethanol. The crystals were then dried in a 40°C vacuum oven to obtain yellow flaky lead iodide gel composite single crystals, the crystal size of which was generally 2-5 mm. The agarose gel concentration can be continuously changed from 0.3w / v% to 0.6w / v%, and the work function of lead iodide will also continuously decrease with the increase of gel concentration, and the overall energy band structure will move upward. However, at high gel concentrations above 0.6w / v%, the crystal morphology deteriorates rapidly and no longer grows flaky hexagonal crystals, and the crystal growth time will also be greatly extended.

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

[0262] The sheet-like gel single crystal obtained in (3), wherein the crystal grown at the interface of 0.3w / v% and 0.6w / v% gel distribution, can be used for subsequent homojunction preparation. The single crystal surface is repeatedly torn off using single crystal Scott tape, so that the single crystal surface is exposed to fresh surface, and the overall thickness of the crystal is reduced to micron level.

[0263] (5) Crystal transfer

[0264] The crystals obtained in (4) were fixed on a glass substrate with 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 caused 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 top 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) / PbI 2 (low gel concentration) / PbI 2 (Gel concentration is high) / Ag (upper right), e.g. 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 Fig.10 As shown, there is an obvious photoelectric response under illumination 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. And due to the presence of gold / silver asymmetric electrodes, due to the better matching of the work functions of the electrodes on both sides, its open circuit voltage will be improved to a certain extent, further enhancing its photodiode effect.

[0270] Example 6

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

[0272] (1) Preparation of organosiloxane gel

[0273] Preparation of PEA with 10 v / v% (10.23 w / v%) organosiloxane gel 2 PbI 4 Taking (PEA: phenylethylamine) single crystal as an example, 0.475ml of tetramethoxysilane and 0.025ml of trimethoxyphenylsilane were added to 3.375ml of 1,4-butyrolactone, followed by 0.125ml of 55wt% hydroiodic acid aqueous solution. After heating at 90℃ for one hour, 0.8mmol of PEAI (phenylethylamine iodide) and 0.4mmol of lead iodide were added. The mixture was heated at 90℃ for one hour until completely dissolved, and then the solution was completely cooled. 15 microliters of ethylenediamine were 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) on the upper side of 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, take the crystals out of the gel, repeatedly rinse the surface with dichloromethane, and then dry the crystals in a vacuum oven at 40°C for 8 hours to obtain flake PEA 2 PbI 4 -Gel composite single crystal ( Fig.13 ). The growth process of other gel concentrations is the same as the above process. Only the concentration of tetramethoxysilane and trimethoxyphenylsilane is changed, or other siloxane monomers such as (3-aminopropyl)trimethoxysilane can be added as needed.

[0276] The growth of other types of perovskite single crystals only requires replacing the above-mentioned PEAI and lead iodide with corresponding components and suitable solvents. 3 To grow single crystals of MA (methylamine), it is necessary to replace the hydroiodic acid in the gel synthesis process with hydrobromic acid, change the components to MABr (methylammonium bromide) and lead bromide, and change the solvent to DMF.

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

[0278] 0.498g PEAI powder, 0.461g PbI 2The 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 washing with dichloromethane, flake PEA was obtained. 2 PbI 4 Single crystal.

[0279] (4) Device preparation

[0280] PEA 2 PbI 4 The two-dimensional perovskite can also be repeatedly torn off the single crystal surface on both sides using single crystal Scott tape as shown in the above lead iodide single crystal. The single crystal surface is exposed to fresh surface, and the overall thickness of the crystal is reduced to micrometer level. Then the crystal is transferred to the ITO electrode using the same method as in Example 1. The related photodetector can also be carried out, and the vertical device structure is ITO / PEA 2 PbI 4 (High gel concentration) / PEA 2 PbI 4 (Traditional solution growth) / Ag.

[0281] (5) Testing

[0282] 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 480nm laser illumination and to perform a response test on the relevant photodiode. There was an obvious photoelectric response under illumination and a certain open circuit voltage. At 0V, there was also an obvious photocurrent and a certain short circuit current.

[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] Preparation of MAPbBr using sodium metasilicate gel 3When single crystal, first prepare sodium metasilicate solution and hydrobromic acid aqueous solution. In this embodiment, take 5w / v% gel concentration as an example, first fully dissolve 3g of sodium metasilicate pentahydrate in 20mL ultrapure water; then prepare 40mL of 48wt% hydrobromic acid solution, slowly drop the metasilicate solution into the hydrobromic acid solution during mixing, and keep stirring the hydrobromic acid solution. 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 is half of the bent part of the U-shaped tube. Subsequently, 10w / v% gel is prepared in the same way, added to the top of the completely gelled 5w / v% gel, and the amount added is to cover the bent part of the U-shaped tube, so that two layers of gel of 5w / v% / 10w / v% are configured, and the volume of each layer of gel is the same.

[0287] (2) Crystal growth

[0288] Add the same volume of lead bromide solution (using 48wt% hydrobromic acid as solvent) and methylammonium bromide solution (using 48wt% hydrobromic acid as solvent) as the two layers of gel in step (1) on both sides of the U-shaped tube, and place it in a constant temperature and dark environment for growth. The concentration of lead bromide solution (using 48wt% hydrobromic acid as solvent) and methylammonium bromide solution (using 48wt% hydrobromic acid as solvent) are both 1mol / L. After growing at 20℃ in a constant temperature and dark environment for one and a half months, the gel is destroyed, the crystal is taken out from the interface of the two layers of gel, the surface is repeatedly rinsed with dichloromethane, and then the crystal is dried in a vacuum oven at 40℃ for 8h to obtain orange block MAPbBr 3 Gel composite single crystal ( Fig.13 ).

[0289] (3) Device preparation and testing

[0290] Among them, MAPbBr 3 The 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 lead iodide single crystal. The single crystal surface is exposed to a fresh surface, and the overall thickness of the crystal is reduced to the micron level. To make the electrodes laterally distributed 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 respectively placed on the upper left and upper right of the single crystal. 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 final device structure is Au (upper left) / MAPbBr 3 (low gel concentration) / MAPbBr 3(Gel concentration is high) / Au (upper right). The device is placed in a vacuum probe station, and the left and right electrodes are scanned using a Keythley semiconductor analyzer to obtain the dark current and the photocurrent under 480nm laser illumination and perform the response test of the relevant photodiode. There is an obvious photoelectric response under illumination and a certain open circuit voltage. At 0V, there is also an obvious 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 crystal, first prepare sodium metasilicate aqueous solution and acetic acid aqueous solution. Taking 10w / v% gel concentration as an example, first fully dissolve 5g of sodium metasilicate pentahydrate in 25ml ultrapure water. Then prepare 25ml of 13v / v% acetic acid aqueous solution, and slowly drop the metasilicic acid solution into the acetic acid aqueous solution during mixing, and keep the acetic acid solution stirring and keep the ice water bath cooling. 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, and the amount added is to cover the bent part of the U-shaped tube.

[0295] (2) Growth of Gel Composite Single Crystals

[0296] Taking the growth in 10w / v% gel concentration as an example, the gel obtained in the previous step is 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 is 0.4mol / L. After growing for one month, the gel is destroyed, the crystal is taken out of the gel, the surface is repeatedly rinsed with ethanol, and then the crystal is dried in a 40°C vacuum oven to obtain a yellow flaky lead iodide gel composite single crystal, the crystal size of which is generally 2-8mm. The growth process of other gel concentrations is also the same as the above process.

[0297] (4) Cleaning of ITO substrate

[0298] ITO needs to be cleaned before use. The cleaning agents used to clean ITO are alkaline detergent, deionized water, ethanol, acetone, and isopropanol, respectively, and ultrasonic cleaning is performed for 20 minutes each. Dry in an oven for later use.

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

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

[0301] (6) Crystal transfer

[0302] After wetting the crystal obtained in (5) with anhydrous ethanol, drop it on the ITO conductive glass substrate and let it air dry for 1 hour until the crystal naturally adheres to the substrate. 2 (gel composite) structure.

[0303] (7) Evaporation of metal electrodes

[0304] Under vacuum conditions, ITO / PbI 2 A layer of metallic silver with a thickness of about 100 nm was thermally evaporated on the (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 resulting vertical device structure was ITO / PbI 2 (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 Fig.11 As shown in the results, it has obvious photoelectric response under light. Fig.11 As shown, there is no rectification effect in the dark state or under illumination.

[0307] Comparative Example 2

[0308] (1) Preparation of gel

[0309] Prepare a mixed solution containing 6v / v% ethylenediamine, 20v / v% acetic acid, and 0.4mol / L lead acetate. Then prepare a 0.6w / v% agarose hot solution, add 0.6g agarose powder to 100mL deionized water, boil in microwave and stir evenly to obtain a 0.6w / v% agarose sol. Mix the mixed solution of lead acetate and the 0.6w / v% agarose hot sol in equal volumes to obtain a 0.3w / v% agarose sol containing 3v / v% ethylenediamine, 10v / v% acetic acid, and 0.2mol / L lead acetate. Take a certain volume of the mixed sol and pour it into a beaker, and place it at room temperature to cool and form a gel.

[0310] (2) Growth of Gel Composite Single Crystals

[0311] Prepare the agarose sol in a similar manner. Pour a blank agarose hydrogel on top of the gel obtained in (1), where the volume ratio of the blank agarose to the agarose gel obtained in step (1) is 1:7. Subsequently, pour a 0.4 mol / L potassium iodide agarose hydrogel with the same volume as the gel obtained in step (1) on the top layer. After complete gelation, place it in a constant temperature and light-shielded environment for growth. The same ethylenediamine neutralized with acetic acid as in step (1) is still added to all the above gel components and solutions. Finally, the following gel distribution structure from bottom to top is formed: 0.3 w / v% gel (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 growing for one month, break the gel and use tweezers to take out the crystals from the lead acetate gel layer ( Figure 3 c), rinse the surface repeatedly with ethanol, and then dry the crystals in a vacuum oven at 40 °C to obtain yellow flaky lead iodide gel composite single crystals, and the crystal size is generally 2 - 5 mm.

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

[0313] For the flaky gel single crystal obtained in (2), repeatedly tear the surface of the single crystal with a single crystal scott tape to expose a fresh surface of the single crystal.

[0314] (4) Transfer of the crystal

[0315] Fix the crystal obtained in (4) on a glass substrate with tape.

[0316] (5) Evaporation of the metal electrode

[0317] Under vacuum conditions, use a mask plate to thermally evaporate a layer of metal gold with a thickness of about 100 nm on the crystal as the electrode. The evaporation rate is that the initial evaporation rate is 0.01 nm / s, and after the gold thickness reaches 2.5 nm, it is increased to 0.05 nm / s. The final obtained lateral device structure is Au / PbI 2 (gel single crystal composite material) / Au.

[0318] (6) Testing

[0319] Place the device in a vacuum probe station, apply a scanning voltage to the left and right electrodes to obtain the dark current and photocurrent under illumination, and draw the current-voltage curve results as shown in Fig.12 shown. It has an obvious photoelectric response under illumination. But as Fig.12 shown, it has no rectifying effect in both the dark state and under illumination.

[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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still 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 of the connection 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 is not in contact with the second electrode; 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; The first gel and the second gel have different gel types and / or gel concentrations.

2. The optoelectronic device according to claim 1, characterized in that When the first gel and the second gel are of the same gel type, the concentration of the second gel is less than the concentration 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, characterized in that 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; Preferably, the concentration of the first gel is 0.3-60 w / v%; and / or, the concentration of the second gel is 0.3-60 w / v%; Preferably, 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.

4. The optoelectronic device according to claim 1, characterized in that: 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; Preferably, the inorganic single crystal includes PbI2, PbS, inorganic perovskite, KDP, cuprous, ZnO, and transition metal sulfide crystals; Preferably, the organic single crystal comprises fullerene, anthracene or an organic semiconductor crystal; Preferably, the organic-inorganic hybrid single crystal comprises an organic-inorganic hybrid perovskite single crystal; Preferably, the organic-inorganic hybrid perovskite single crystal includes MAPbX3 and PEAPbX3, wherein X is a halogen element.

5. The optoelectronic device according to claim 3, characterized in that: The gel concentration of the sodium metasilicate gel is 3 to 20 w / v%; Preferably, the gel concentration of the agarose gel is 0.3-0.6 w / v%; Preferably, the silicone gel has a gel concentration of 5 to 20 w / v%.

6. The optoelectronic device according to claim 1, characterized in that: Methods for preparing gel single crystal composite materials by gel growth include gel diffusion method, gel anti-solvent diffusion method or gel cooling method; Preferably, 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, to obtain a gel single crystal composite material prepared by gel growth; and / or, 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; and / or, The gel cooling method comprises: dissolving the reactants for producing single crystals in gel, and then slowly cooling to form nuclei and crystallize to obtain a gel single crystal composite material; Preferably, the gel is a single-layer gel or a multi-layer gel; Preferably, the multi-layer gel is a multi-layer gel comprising a first gel layer and a second gel layer. Preferably, 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.

7. The optoelectronic device according to claim 6, characterized in that: 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; Preferably, the iodine-containing compound comprises potassium iodide, sodium iodide or ammonium iodide; Preferably, the lead-containing compound includes lead nitrate and lead acetate; Preferably, when the single crystal is a MAPbX3 single crystal, the reactants for generating the single crystal include a methylamine-containing compound and PbX2, wherein X is a halogen element; Preferably, when the single crystal is PEAPbX3, the reactants for generating the single crystal include a phenylethylamine-containing compound and PbX2, wherein X is a halogen element.

8. The optoelectronic device according to claim 7, characterized in that: The first electrode and the second electrode are transparent electrodes, metals or metal alloys; Preferably, the transparent electrode comprises ITO, FTO, IZO or SnO2; Preferably, the transparent electrode further comprises a transparent electrode modified with 2PACz or Poly-2PACz; Preferably, the metal includes Ag, Cu, Au, Al, Cr or Ti; Preferably, the first electrode and the second electrode are different and / or the same.

9. The method for preparing the optoelectronic device according to any one of claims 1 to 8, comprising: 1) connecting the first crystal layer and the second crystal layer to prepare a crystal layer including a homojunction; 2) Preparing a first electrode and a second electrode on the first crystal layer and the second crystal layer in the crystal layer respectively, to complete the preparation of the optoelectronic device.

10. Use of the optoelectronic device according to any one of claims 1 to 8 in the field of photodetectors, solar cells, phototransistors, light-emitting diodes or high-energy ray detection.

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