An organic solar cell and a method for preparing the same

Abstract

The application discloses an organic solar cell and a preparation method thereof. The organic solar cell device comprises a cathode substrate, a cathode interface layer, an active layer, an anode interface layer and an anode layer. The cathode interface layer material is doped with an organic electron acceptor and ZnO, and the doping volume ratio is 1:1. The application adopts a nanoparticle technology means, successfully dopes hydrophobic organic electron acceptor particles in ZnO as a composite cathode interface layer to prepare the organic solar cell device, thereby improving the contact between the electron transport layer and the active layer, forming the matching of energy levels at the interface, enhancing the charge transport, and finally improving the photoelectric conversion efficiency of the organic solar cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic solar cells, in particular to an organic solar cell doped with an organic electron acceptor and a preparation method thereof. BACKGROUND

[0002] Zinc oxide (ZnO) is widely used as a cathode interface layer in inverted organic solar cells due to its excellent photoelectric performance, good solution processing property and simple processing method. Since ZnO is an inorganic material, it is difficult to form good contact with the organic material of the active layer, and the low charge mobility and large amount of defects on the surface of ZnO also hinder the transmission of electrons. Therefore, it is a research hotspot to modify the ZnO thin film by doping with organic material to improve the performance of the device. However, most of the organic electron acceptor materials are hydrophobic materials and cannot be dissolved in the polar solvent used for preparing the ZnO thin film by sol-gel method. SUMMARY

[0003] The embodiment of the present application aims to provide a preparation method of an organic solar cell, so that the hydrophobic organic electron acceptor material can be dissolved in the polar solvent used for preparing the ZnO thin film by sol-gel method, thereby realizing the organic doping modification of the cathode interface layer material ZnO thin film and significantly improving the photoelectric conversion efficiency of the device.

[0004] The present application provides a preparation method of an organic solar cell, which comprises the following steps:

[0005] providing an ITO substrate, forming a cathode interface layer on the ITO substrate, and forming an active layer on the cathode interface layer;

[0006] forming an anode interface layer on the active layer, and forming an anode layer on the anode interface layer;

[0007] In the step of forming the cathode interface layer on the ITO substrate, the following steps are included:

[0008] preparing a ZnO precursor solution and an organic electron acceptor solution;

[0009] stirring the ZnO precursor solution at a first rotating speed, and adding the organic electron acceptor solution drop by drop into the ZnO precursor solution during the stirring process to form a ZnO nanoparticle precursor solution;

[0010] After the organic electron acceptor solution is added to the ZnO precursor solution, the ZnO nanoparticle precursor solution is heated to a preset temperature and kept at the preset temperature for a first time to obtain a cathode interface layer solution; the cathode interface layer solution is then coated onto the ITO substrate to form a cathode interface layer.

[0011] Furthermore, the organic electron acceptor can be PC. 71 BM or PC 61 One of BM or IT4F.

[0012] Furthermore, the doping volume ratio of the precursor solution to the organic electron acceptor solution is 1:1.

[0013] Furthermore, before stirring the ZnO precursor solution at a first rotational speed, or during stirring the ZnO precursor solution at a first rotational speed, the ZnO precursor solution is heated to bring its temperature to a first temperature; and / or, before adding the organic electron acceptor solution dropwise to the ZnO precursor solution, the organic electron acceptor solution is heated to bring its temperature to a second temperature. The first temperature is higher than room temperature and lower than the second temperature.

[0014] Furthermore, the first temperature is 35-50 degrees Celsius; the second temperature is 60-65 degrees Celsius; the first rotation speed is 1000-1500 rpm; and the preset temperature is 60 degrees Celsius.

[0015] Furthermore, the active layer material is PM6 and L8BO, and the mass ratio of PM6 to L8BO is 1:1.2. And / or, the anode interface layer is MoO3 with a thickness of 10 nm; the anode layer is Ag with a thickness of 100 nm.

[0016] Furthermore, the preparation of the ZnO precursor solution includes: preparing a solution of zinc acetate dihydrate with ethylene glycol monomethyl ether as a solvent and ethanolamine as an additive in air to a concentration of 100 mg / ml; and obtaining the ZnO precursor solution by stirring for a first time, wherein the percentage of ethanolamine added is 2.8%.

[0017] Furthermore, the preparation of the organic electron acceptor solution includes: preparing a first solution with a concentration of 1 mg / ml using chloroform as a solvent; heating the first solution to a second temperature and stirring for a second time to obtain the organic electron acceptor solution.

[0018] Furthermore, the formation of the cathode interface layer on the ITO substrate includes: providing a single ethylene glycol monomethyl ether solution as a first precursor solution, and preparing an organic electron acceptor solution;

[0019] The first precursor solution is stirred at a first rotation speed. During the stirring of the first precursor solution, the organic electron acceptor solution is added dropwise to the first precursor solution to form a first nanoparticle precursor solution.

[0020] After the organic electron acceptor solution is added to the first precursor solution, the first nanoparticle precursor solution is heated to a preset temperature and kept at the preset temperature for a second time. Zinc acetate dihydrate and ethanolamine are added to the first nanoparticle precursor solution and stirred for a third time to obtain a cathode interface layer solution. The cathode interface layer solution is then coated onto the ITO substrate to form a cathode interface layer.

[0021] Furthermore, organic solar cells are prepared using the preparation method described above. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of an organic solar cell 100 provided by the present invention;

[0023] Figure 2 This is a schematic diagram of the fabrication process of an organic solar cell provided in an embodiment of the present invention;

[0024] Figure 3 The images show the dynamic light scattering patterns of different nanoparticles obtained in Examples 1-3 of this invention.

[0025] Figure 4 The graph shows the relationship between current density and voltage for the solar energy devices in comparative examples and Examples 1-3 under illumination conditions.

[0026] Figure label:

[0027] 1-Cathode substrate; 2-Cathode interface layer; 3-Active layer; 4-Anode interface layer; 5-Anode layer. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0031] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0032] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0033] This invention provides an organic solar cell and its fabrication method. By employing nanoparticle technology, a hydrophobic organic electron acceptor is successfully doped into ZnO to form a composite cathode interface layer, thereby improving the contact between the electron transport layer and the active layer and increasing the photoelectric efficiency of the solar cell. Figure 1 The organic solar cell 100 shown includes a cathode substrate 1, a cathode interface layer 2, an active layer 3, an anode interface layer 4, and an anode layer 5. Exemplarily, the organic solar cell 100 is fabricated using the method described below.

[0034] Reference Figure 2 , Figure 2 This is a flowchart illustrating the steps involved in the fabrication of organic solar cells.

[0035] like Figure 2 As shown, the preparation method includes steps S101 to S105.

[0036] Step S101: Provide an ITO substrate.

[0037] For example, the cathode substrate 1 is an ITO substrate.

[0038] The ITO cathode substrate was first ultrasonically cleaned with acetone for 10 minutes, then cleaned with deionized water and detergent for 5 minutes, followed by cleaned with pure water for 5 minutes. This pure water cleaning process was repeated three times. Then, it was cleaned with isopropanol for 10 minutes. Finally, the glass was dried with a nitrogen gun and then irradiated with a UV-ozone machine for 15 minutes to obtain the desired ITO substrate.

[0039] It is understood that the cleaning time depends on the surface area of ​​the cathode substrate. Any equivalent substitutions or changes made by those skilled in the art regarding the cleaning agent or cleaning sequence should be covered within the scope of protection of this invention.

[0040] Step S102: Forming a cathode interface layer on the ITO substrate, wherein forming the cathode interface layer on the ITO substrate includes: preparing a ZnO precursor solution and an organic electron acceptor solution; stirring the ZnO precursor solution at a first rotation speed; during the stirring of the ZnO precursor solution, adding the organic electron acceptor solution dropwise to the ZnO precursor solution to form a ZnO nanoparticle precursor solution; after completing the operation of adding the organic electron acceptor solution to the ZnO precursor solution, heating the ZnO nanoparticle precursor solution to a preset temperature and keeping the ZnO nanoparticle precursor solution at the preset temperature for a first time to obtain a cathode interface layer solution; coating the cathode interface layer solution onto the ITO substrate to form a cathode interface layer.

[0041] For example, organic electron acceptors include PC 61 BM or PC 71 One of BM or IT4F.

[0042] Implementation method 1, the organic electron acceptor is PC 61 BM, cathode interface layer 2 is PC 61 BM: ZnO layer.

[0043] A ZnO precursor solution was prepared, and an organic electron acceptor solution was also prepared. In air, zinc acetate dihydrate was dissolved in ethylene glycol monomethyl ether as a solvent and ethanolamine as an additive to a concentration of 100 mg / mL (ethanolamine addition percentage: 2.8%). After magnetic stirring for 1 h, the ZnO precursor solution was obtained. PC... 61 BM prepared a 1 mg / ml solution using chloroform as a solvent, and obtained PC after magnetic stirring at 60 degrees Celsius for 1 hour. 61 BM solution; Place the ZnO precursor solution on a heated stirrer at 40 degrees Celsius and 1500 rpm. Use a 10 ml syringe to take PC solution at a 1:1 volume ratio with the ZnO precursor solution. 61 BM solution, and the above PC 61BM solution was added dropwise to the ZnO precursor solution. After the addition was complete, stirring was stopped to obtain a ZnO nanoparticle precursor solution. The ZnO nanoparticle precursor solution was heated to 65 degrees Celsius and allowed to evaporate for 2 hours to obtain the cathode interface layer solution.

[0044] Finally, a cathode interface layer solution was spin-coated onto the surface of the ITO cathode substrate 1 treated in step S101 to obtain a cathode interface layer 2. The spin-coating speed was 3000-4000 rpm and the spin-coating time was 30 s. After spin-coating, the substrate was annealed at 200 degrees for 30 min.

[0045] It is important to note that during the dropwise addition process, the ZnO precursor solution must be kept at a temperature above room temperature but below the boiling point of chloroform (61.2 degrees Celsius). Exceeding this range will cause rapid particle agglomeration, resulting in particles larger than nanometers, negatively impacting the final device efficiency. The organic electron acceptor solution temperature needs to be close to the boiling point of chloroform, maintained at 60-65 degrees Celsius. Too low a temperature may accelerate particle agglomeration, while too high a temperature may cause the ethylene glycol methyl ether in the ZnO precursor solution to evaporate, affecting the final zinc oxide concentration. Furthermore, residual chloroform can also affect zinc oxide crystallization. Therefore, after stopping stirring following the dropwise addition, the temperature of the ZnO nanoparticle precursor solution needs to be raised to 60-65 degrees Celsius. This allows the chloroform solvent in the organic electron acceptor solution to evaporate until the liquid level is almost the same as the initial ZnO precursor solution level, without any agglomeration, thus obtaining the cathode interface layer solution.

[0046] Understandably, the evaporation time of chloroform solvent depends on the amount of solvent used.

[0047] In embodiment 2, unlike the first embodiment, the organic electron acceptor is PC. 71 BM, that is, the cathode interface layer 2 is PC. 71 BM: ZnO layer.

[0048] In embodiment 3, unlike the first embodiment, the organic electron acceptor is IT4F, that is, the cathode interface layer 2 is an IT4F:ZnO layer.

[0049] In some embodiments, such as Embodiment 4, a single ethylene glycol monomethyl ether solution is used as the precursor solution, and an organic electron acceptor solution is prepared to which PC... 61 BM prepared a 1 mg / ml solution using chloroform as a solvent, and obtained PC after magnetic stirring at 60 degrees Celsius for 1 hour. 61 BM solution; Place the single ethylene glycol monomethyl ether solution on a heated stirrer at 40 degrees Celsius and 1500 rpm, and use a 10 ml syringe to take a 1:1 volume ratio of the above PC solution with the ZnO precursor solution. 61 BM solution, and the above PC 61BM solution was added dropwise to ethylene glycol monomethyl ether solution. After the addition was complete, stirring was stopped to obtain a nanoparticle precursor solution. The nanoparticle precursor solution was heated to 65 degrees Celsius and allowed to evaporate for 2 hours. Zinc acetate dihydrate was then added to bring the concentration of zinc acetate dihydrate in the solution to 100 mg / ml. Ethanolamine was added as an additive at a percentage of 2.8%. The solution was then magnetically stirred for 1 hour to obtain the cathode interface layer solution.

[0050] Finally, a cathode interface layer solution was spin-coated onto the surface of the ITO cathode substrate 1 treated in step S101 to obtain a cathode interface layer 2. The spin-coating speed was 3000-4000 rpm and the spin-coating time was 30 s. After spin-coating, the substrate was annealed at 200 degrees for 30 min.

[0051] It is important to note that during the dropwise addition process, the precursor solution should be kept at a temperature above room temperature but below the boiling point of chloroform (61.2 degrees Celsius). Exceeding this range will cause rapid particle agglomeration, resulting in particles larger than nanometers, which will negatively impact the final device efficiency. The temperature of the organic electron acceptor solution needs to be close to the boiling point of chloroform, maintained at 60-65 degrees Celsius. Too low a temperature may accelerate particle agglomeration, while too high a temperature may cause the ethylene glycol methyl ether in the precursor solution to volatilize, affecting the final zinc oxide concentration. At the same time, the residue of chloroform will also affect the crystallization of zinc oxide. Therefore, after stopping stirring after the dropwise addition, the temperature of the nanoparticle precursor solution needs to be raised to 60-65 degrees Celsius. This is necessary to ensure that the chloroform solvent in the organic electron acceptor solution evaporates to a level almost the same as the liquid level of the precursor solution before the dropwise addition, without any agglomeration. Then, zinc acetate dihydrate and ethanolamine are added, and the solution is magnetically stirred for 1 hour to obtain the cathode interface layer solution.

[0052] Understandably, the evaporation time of chloroform solvent depends on the amount of solvent used.

[0053] Step S103: An active layer is formed on the cathode interface layer.

[0054] For example, the preparation process of active layer 3 is as follows: PM6 and L8BO are dissolved in chloroform in nitrogen, wherein the mass ratio of PM6 to L8BO is 1:1.2, the concentration of PM6 is 7.2 mg / ml, the additive is diiodomethane, and the concentration of diiodomethane is 0.25%. After heating to 40 degrees and magnetically stirring for 30 min, an active layer solution is obtained. Finally, the active layer solution is spin-coated on the surface of cathode interface layer 2 to obtain active layer 3. The spin-coating speed is 3000 rpm, the spin-coating time is 30 s, and after spin-coating, it is annealed at 100 degrees for 5 min.

[0055] Step S104: Form an anode interface layer on the active layer.

[0056] For example, MoO3 is deposited on the surface of the active layer 3 at a rate of 0.05 A / s as the anode interface layer 4, with a thickness of 10 nm.

[0057] Step S105: Form an anode layer on the anode interface layer.

[0058] For example, Ag is deposited on the surface of the anode interface layer 4 at a rate of 0.2-1 A / s as the anode layer 5, with a thickness of 100 nm.

[0059] Comparative Example

[0060] The comparative example was prepared under basically the same conditions as Example 1, except that the cathode interface layer was ZnO and no other materials were doped.

[0061] Figure 3 PC was prepared in Examples 1-3 61 BM, PC 71 Dynamic light scattering patterns measured from BM and IT4F nanoparticles allow observation of PC. 61 BM and PC 71 Both BM and IT4F have nanoparticle sizes around 100 nm, while IT4F has nanoparticle sizes between 300-400 nm. This proves that the present invention does indeed disperse organic electron acceptor materials in the form of nanoparticles in the polar solvent of ZnO through nanoparticle technology.

[0062] Figure 4 Examples 1-3: Organic electron acceptor PC 61 BM, PC 71 The graphs show the current density versus voltage under illumination for organic solar cells with ZnO as the cathode modification layer (BM and IT4F, respectively) and the comparative organic solar cell with ZnO as the cathode modification layer. It can be seen that the short-circuit current density (Jsc) of the comparative organic solar cell with ZnO as the cathode modification layer is 23.07093 mA / cm². 2 Examples 1-3 Organic electron acceptor PC 61 BM, PC 71 Organic solar cells with BM and IT4F-doped ZnO as cathode modification layers have short-circuit current densities (Jsc) of 23.90086 mA / cm². 2 24.80502 mA / cm 2 and 25.50723 mA / cm 2 This indicates that the introduction of organic electron acceptors can effectively improve charge transport efficiency, thereby increasing short-circuit current density.

[0063] Under standard test conditions, the photovoltaic characteristic parameters of Examples 1-3 and the comparative example are shown in Table 1. The comparison shows that the conversion efficiency of the comparative example is 14.49658% (Jsc = 23.07093 mA / cm²). 2 (Voc was 0.8889V, FF was 70.69175%). After incorporating organic electron acceptor nanoparticles, although the open-circuit voltage decreased slightly, the short-circuit current and fill factor increased significantly. The final efficiency was improved by 2.96% (Example 1), 12.11% (Example 2), and 15.53% (Example 3) compared to the original ZnO, respectively. This indicates that the carrier mobility of organic solar cells with organic electron acceptors introduced into the ZnO cathode interface layer is effectively improved.

[0064] Table 1. Photovoltaic characteristic parameters of Examples 1-3 and Comparative Examples

[0065] ETL V oc (V) J SC (mA / cm 2 )]]> Fill Factor (%) Efficiency (%) Comparative Example ZnO 0.8889 23.07093 70.69175 14.49658 Example 1 ZnO:PC 61 BM]] 0.8769 23.90086 71.21797 14.92576 Example 2 ZnO:PC 71 BM]] 0.8731 24.80502 75.04319 16.25178 Example 3 ZnO:IT4F 0.8629 25.50723 76.09133 16.74786

[0066] Compared with existing technologies, this invention successfully incorporates PM through nanoparticle technology. 61 BM, PC 71 Organic electron acceptor materials such as BM and IT4F are uniformly dispersed in ZnO solution in the form of nanoparticles, resulting in n-type doping in the electron transport layer. The organic electron acceptor materials and ZnO particles work in coordination to form a composite inorganic-organic cathode interface layer, which modulates the energy level of the electron transport layer and improves the electron mobility of ZnO. The electron acceptor materials form good contact with the active layer material at the interface. The doping of organic electron acceptor materials also passivates the ZnO layer and reduces its surface defects.

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto.

[0068] Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this invention, based on the technical solution and inventive concept of this invention, shall be covered within the protection scope of this invention.

Claims

1. A method for preparing an organic solar cell, characterized in that, include: An ITO substrate is provided, and a cathode interface layer is formed on the ITO substrate, and an active layer is formed on the cathode interface layer; An anode interface layer is formed on the active layer, and an anode layer is formed on the anode interface layer; The cathode interface layer formed on the ITO substrate includes: A solution containing a ZnO precursor was prepared, and an organic electron acceptor solution was also prepared. The ZnO precursor solution is stirred at a first rotation speed. During the stirring process, the organic electron acceptor solution is added dropwise to the ZnO precursor solution to form a ZnO nanoparticle precursor solution. After the organic electron acceptor solution is added to the ZnO precursor solution, the ZnO nanoparticle precursor solution is heated to a preset temperature and kept at the preset temperature for a first time to obtain the cathode interface layer solution. The cathode interface layer solution is coated onto the ITO substrate to form a cathode interface layer; The organic electron acceptor is selected from PC. 71 BM or PC 61 One of BM or IT4F; Before stirring the ZnO precursor solution at a first rotation speed, or during stirring the ZnO precursor solution at a first rotation speed, the ZnO precursor solution is heated to bring the temperature of the ZnO precursor solution to a first temperature. Before adding the organic electron acceptor solution dropwise to the ZnO precursor solution, the organic electron acceptor solution is heated to bring the temperature of the organic electron acceptor solution to a second temperature. The first temperature is higher than room temperature and lower than the second temperature.

2. The preparation method according to claim 1, characterized in that, The doping volume ratio of the precursor solution to the organic electron acceptor solution is 1:

1.

3. The preparation method according to claim 1, characterized in that, The first temperature is 35-50 degrees Celsius; the second temperature is 60-65 degrees Celsius; the first rotation speed is 1000-1500 rpm; and the preset temperature is 60 degrees Celsius.

4. The preparation method according to claim 1, characterized in that, The active layer material is PM6 and L8BO, and the mass ratio of PM6 to L8BO is 1:1.

2. And / or, the anode interface layer is MoO3 with a thickness of 10 nm; the anode layer is Ag with a thickness of 100 nm.

5. The preparation method according to any one of claims 1-4, characterized in that, The preparation of the ZnO precursor solution includes: In air, zinc acetate dihydrate was prepared into a solution with a concentration of 100 mg / ml using ethylene glycol monomethyl ether as a solvent and ethanolamine as an additive; after stirring for a first time, the ZnO precursor solution was obtained, wherein the percentage of ethanolamine added was 2.8%.

6. The preparation method according to any one of claims 1-4, characterized in that, The preparation of the organic electron acceptor solution includes: The organic electron acceptor was prepared into a first solution with a concentration of 1 mg / ml using chloroform as a solvent; The organic electron acceptor solution is obtained by heating the first solution to a second temperature and stirring for a second time.

7. The preparation method according to claim 1, characterized in that, The cathode interface layer formed on the ITO substrate includes: A single ethylene glycol monomethyl ether solution was provided as the first precursor solution, and an organic electron acceptor solution was prepared. The first precursor solution is stirred at a first rotation speed. During the stirring of the first precursor solution, the organic electron acceptor solution is added dropwise to the first precursor solution to form a first nanoparticle precursor solution. After the organic electron acceptor solution is added to the first precursor solution, the first nanoparticle precursor solution is heated to a preset temperature and kept at the preset temperature for a second time. Zinc acetate dihydrate and ethanolamine are added to the first nanoparticle precursor solution and stirred for a third time to obtain the cathode interface layer solution. The cathode interface layer solution is coated onto the ITO substrate to form a cathode interface layer.

8. An organic solar cell, characterized in that, include: It is prepared by the preparation method described in any one of claims 1-7.

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