CN110452363B

CN110452363B - Organic solar cell and preparation method thereof

Info

Publication number: CN110452363B
Application number: CN201810428556.9A
Authority: CN
Inventors: 周惠琼; 杨朔
Original assignee: National Center for Nanosccience and Technology China
Current assignee: National Center for Nanosccience and Technology China
Priority date: 2018-05-07
Filing date: 2018-05-07
Publication date: 2022-03-04
Anticipated expiration: 2038-05-07
Also published as: CN110452363A

Abstract

The invention belongs to the field of organic solar cells, and particularly relates to an organic solar cell and a preparation method thereof. The invention provides application of a spirobifluorene polymer, which can be used as an organic solar cell anode interface material. The material can be formed on conductive glass in situ by a polymer monomer by adopting a CV method. And the thickness of the formed film can be regulated and controlled in the film forming process. The polymer provided by the invention is used as an anode interface layer to be applied to an organic solar cell, and can obtain higher current and show more dominant bimolecular recombination compared with PEDOT/PSS. And the polymer monomer of the invention forms a neutral polymer film after forming a film by an electrochemical method. Neutral interface layer, relative to acidic PEDOT: PSS has two advantages: 1. the corrosion of the acid to the electrode is reduced; 2. if the active layer material contains basic groups, the neutral interface layer can avoid interface acid-base reaction with the active layer material. Moreover, the preparation method is simple and easy to implement.

Description

Organic solar cell and preparation method thereof

Technical Field

The invention belongs to the field of organic solar cells, and particularly relates to an organic solar cell and a preparation method thereof.

Background

As a clean and cheap sustainable energy source, Organic Photovoltaic (OPVs) cells have been developed greatly and have achieved a series of remarkable results for decades since their development.

OPVs use the photovoltaic effect as a basic principle, generate hole-electron pairs by using solar radiation, and then separate the hole-electron pairs into carriers which respectively enter the positive electrode and the negative electrode, thereby achieving the purpose of converting solar energy into electric energy. Among them, the interface material plays an important role in battery performance. Because the interface material plays roles of carrier transmission, counter exciton blocking and the like in the battery, the interface material has the following characteristics: (1) forming ohmic contact with the electrode and the active layer; (2) having appropriate energy levels to select exciton transport; (3) the conductivity is excellent; (4) the physical stability is good.

In the existing research on OPVs, an aqueous solution of a conductive polymer (Poly (3,4-ethylenedioxythiophene): Poly (phenylenesulfinate), abbreviated as PEDOT: PSS) is often used as an anode interface material for transporting holes. The PEDOT and PSS have the advantages of conductivity controllability, good work function matching, simple process and the like, so that the PEDOT and PSS become a relatively common anode interface material. But the ITO film has the characteristics of acidity and water absorption, and is easy to cause the corrosion of an ITO electrode. In addition, it has been reported that the electron blocking material can be used as an electrode to collect electrons, so the ability of blocking electrons is not questioned.

In addition, P-type Transition Metal Oxides (TMOs) are also commonly used as anode interface materials, such as MoO₃、V₂O₅NiO, etc. TMOs have good light transmission in visible and infrared regions, so that photons can reach the active layer to generate excitons. In addition, the conduction band is higher than the LUMO energy level of most donor and acceptor materials, and electrons are effectively blocked. However, the formation of TMOs films typically requires completion by a vacuum thermal evaporation process. Not only the cost is sharply increased, but also it cannot be applied to a printing process in mass production. In recent years, some scholars report the process of spin-coating TMOs film by solution-gel method, so that the TMOs film can be further applied. However, light absorption in the visible region still limits its popularity.

Conjugated Microporous Polymers (CMPs) are a class of Polymers with a wide range of pi-conjugation. The unique structure of the molecule enables the molecule to show a series of excellent properties, such as fluorescence, neutrality, work function controllability, electron transfer and the like. It is these advantages that CMPs are receiving more and more attention and research, and are applied to anode interface materials of OPVs, and a series of remarkable results are obtained.

Therefore, there is a need to develop a new anode interface material for organic solar cells to overcome the disadvantages of the prior art.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and an electrochemically synthesized polymer film is used as a hole transport layer and applied to an organic solar cell to improve the current situation that an ITO electrode is corroded due to the acidity of PEDOT (Poly ethylene styrene) PSS. The bimolecular complexation is enhanced while maintaining equivalent performance.

In order to achieve the purpose, the invention provides the following technical scheme:

the polymer is used as an anode interface material of an organic solar cell, wherein the polymer is obtained by polymerizing one or more compounds shown in the following formula I,

wherein the content of the first and second substances,

R1-R8, which may be the same or different, are independently selected from H, heteroaryl;

the heteroaryl group is a monovalent monocyclic, bicyclic or tricyclic aromatic ring system: having 5 to 20 ring atoms and comprising 1 to 5 heteroatoms independently selected from N, O and S, such as "5-14 membered heteroaryl". The "5-to 14-membered heteroaryl" is a monovalent monocyclic, bicyclic or tricyclic aromatic ring system having 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 ring atoms, in particular 5 or 6 or 9 or 10 carbon atoms, and which contains 1 to 5, preferably 1 to 3 heteroatoms independently selected from N, O and S, and, in addition, may be benzo-fused in each case. In particular, the heteroaryl group is selected from thienyl, furyl, pyrrolyl, oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl, indazolyl, indolyl, isoindolyl, pyridyl, carbazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl and the like.

The heteroaryl group is preferably a pyridyl group, a carbazolyl group, a thienyl group, a pyrrolyl group, a furyl group.

Preferably, the formula I is 2,2 ', 7, 7' -tetracarbazolyl-9, 9-spirobifluorene.

According to the invention, the polymer is prepared by Cyclic Voltammetry (CV method for short).

The invention also provides an organic solar cell, which comprises an anode and an anode interface layer, wherein the anode interface layer is the polymer.

According to the invention, the thickness of the polymer may be 10-100nm, for example 30-90 nm.

According to the present invention, the solar cell includes: the anode comprises a substrate, an anode interface layer, a photoactive layer and a cathode.

According to the invention, the substrate may be a glass substrate, the anode, photoactive layer, cathode may be any known to those skilled in the art, for example, the anode is ITO and the photoactive layer may be PTB7-Th: PC₇₁BM, the cathode may be aluminum.

The invention also provides a preparation method for preparing the organic solar cell, which comprises the following steps:

(1) dissolving a compound shown in a formula I and a supporting electrolyte in a solvent to prepare a mixed solution;

(2) the compound of formula I is polymerized in situ on the anode by Cyclic Voltammetry (hereinafter abbreviated CV).

According to the present invention, in the step (1),

the supporting electrolyte may be any electrolyte that does not participate in this electrochemical reaction, such as one or more of tetraethylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium perchlorate, such as tetrabutylammonium perchlorate;

the solvent may be an organic solvent, preferably a polar organic solvent, and may be selected from one or more of acetonitrile, N-dimethylformamide, hexamethylphosphoramide, methanol, ethanol, acetic acid, isopropanol, pyridine, tetramethylethylenediamine, acetone, triethylamine, N-butanol, dioxane, tetrahydrofuran, methyl formate, tributylamine, methyl ethyl ketone, chloroform, ethyl acetate, trioctylamine, dimethyl carbonate, diethyl ether, isopropyl ether, N-butyl ether, trichloroethylene, diphenyl ether, and dichloromethane;

for example, the solvent may be selected from a mixed solution of dichloromethane and acetonitrile; the volume ratio of the dichloromethane to the acetonitrile in the mixed solution can be 1: 1-10: 1, and preferably 2: 1-9: 1;

the concentration of the compound of formula I in the solution may be 0.01-2mmol/L, preferably 0.1-1 mmol/L;

the concentration of the supporting electrolyte in the solution can be 0.01-2mmol/L, preferably 0.1-1 mmol/L;

according to the present invention, in the step (2),

the cyclic voltammetry uses a three-electrode system of an electrochemical workstation, and the reference electrode of the three-electrode system can be Ag⁺Ag electrode, Hg²⁺an/Hg electrode or a hydrogen electrode, preferably Ag⁺an/Ag electrode;

the sweep cut-off voltage of the cyclic voltammetry may be 0.4-1.8V, preferably 0.7-1.5V;

the number of scans of the cyclic voltammetry may be 1-4, e.g. 1, 2, 3, 4;

the invention has the beneficial effects that:

the invention provides application of a spirobifluorene polymer, which can be used as an organic solar cell anode interface material. The material can be formed on conductive glass in situ by a polymer monomer by adopting a CV method. And in the film forming process, the thickness of the formed film can be regulated and controlled by controlling the solution concentration, the scanning cut-off voltage, the scanning times and other factors.

The polymer provided by the invention is used as an anode interface layer to be applied to an organic solar cell, and can obtain higher current and show more dominant bimolecular recombination compared with PEDOT/PSS. And the polymer monomer of the invention forms a neutral polymer film after forming a film by an electrochemical method. Neutral interface layer, relative to acidic PEDOT: PSS has two advantages: 1. the corrosion of the acid to the electrode is reduced; 2. if the active layer material contains basic groups, the neutral interface layer can avoid interface acid-base reaction with the active layer material.

The preparation method is simple and feasible.

Drawings

FIG. 1 is a graph of data obtained from successive CV scans of electrodeposition in example 1.

FIG. 2 is a graph showing the final film thickness as fitted to different scanning times in example 1.

Fig. 3 is a data image obtained by measuring the energy level of the CMP film by the CV method in example 1.

Fig. 4 is a J-V characteristic curve obtained when CMP films of different thicknesses are used in an organic solar cell in example 1.

FIG. 5 shows J measured at different light intensities in the examples_scFitting image to light intensity.

Detailed Description

The invention is described in further detail below with reference to the figures and examples. It will be appreciated by those skilled in the art that the scope of the present invention is not limited to the following examples. In light of the above disclosure, it is within the scope of the present invention to provide several variations and modifications of the above examples without departing from the technical features and scope of the present invention. The drugs referred to in the following examples are commercially available unless otherwise specified.

Example 1

Organic compound monomer 2,2 ', 7, 7' -tetracarbazolyl-9, 9-spirobifluorene (abbreviated as SpCz) is prepared into a film poly (2,2 ', 7, 7' -tetracarbazolyl-9, 9-spirobifluorene) (abbreviated as PSpCz) by a CV method.

(1) Dissolving 2,2 ', 7, 7' -tetracarbazolyl-9, 9-spirobifluorene (abbreviated as SpCz) and tetrabutylammonium perchlorate (abbreviated as TBAP) serving as a supporting electrolyte in dichloromethane and acetonitrile (volume ratio is 7:3) to form a mixed solution, wherein the concentration of the SpCz is 0.1mmol/L, and the concentration of the TBAP is 0.1 mol/L;

(2) the polymer film was prepared by CV method using three-electrode system. Wherein the parameters are set as follows:

scanning range: 0-1.4V; scanning rate: 0.05V/s;

the scanning times are as follows: 1, 2, 3; precision: 1E-5 (A/V);

removing small molecules remained on the surface of the polymer film by spin coating dichloromethane, and constructing PTB7-Th PC by subsequent processes of spin coating, thermal evaporation and the like₇₁BM organic solar cells.

The results and descriptions of the related experiments are as follows:

FIG. 1 is a graph obtained by the CV method. During the first scan, a distinct peak appears at 1.29V, indicating that the carbazolyl group is oxidized to form a film, and thereafter the carbazolyl group continues to polymerize on the already formed polymer film, so that no peak is shown here.

FIG. 2 is a graph showing the relationship between the film thickness and the number of scans, and the relationship between the film thickness and the number of scans was approximately in a direct proportional relationship by data fitting, and the proportionality coefficient was 30 nm/cycle. The results show that the method achieves film thickness control.

Figure 3 is a CV scan image of the polymer. This result was obtained by immersing the formed polymer film in a pure electrolyte (TBAP) solution and performing CV scanning. From this result, the energy level of the polymer film obtained was: HOMO is-5.18 eV, and LUMO is-3.79 eV.

FIG. 4 is a graph of J-V parameters obtained after applying polymer films of different thicknesses to OPVs. It can be seen that at a thickness of 60nm, comparable levels to PEDOT: PSS are achieved, and V is_ocAnd J_scAll are slightly improved. Specific values are shown in table 1.

TABLE 1 detailed parameter table of J-V characteristic curve

FIG. 5 shows the variation light intensity test J_scAnd (4) data. Fitting this set of data, it can be seen that when the polymer film is used as an anode interface material, J_scPSS, which is linear in light intensity and has a slope closer to 1 than PEDOT, indicates that it exhibits slightly more dominant bimolecular complexation.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The application of the polymer in the anode interface material of the organic solar cell is characterized in that the polymer is obtained by polymerizing one or more compounds shown as the following formula I,

formula I

Wherein the content of the first and second substances,

R1-R8 are the same or different and are independently selected from H and carbazolyl;

the polymer is prepared by cyclic voltammetry.

2. An organic solar cell comprising an anode and an anode interfacial layer, wherein the anode interfacial layer is the polymer of claim 1.

3. The organic solar cell according to claim 2, wherein the polymer has a thickness of 30-90 nm;

the solar cell includes: the anode comprises a substrate, an anode interface layer, a photoactive layer and a cathode.

4. The organic solar cell of claim 3, wherein the substrate is a glass substrate, the anode is ITO, and the photoactive layer is PTB7-Th PC₇₁BM, and the cathode is aluminum.

5. A method for preparing the organic solar cell according to any one of claims 2 to 4, comprising the steps of:

(1) dissolving a compound of formula I according to claim 1 and a supporting electrolyte in a solvent to prepare a mixed solution;

(2) the compound of formula I is polymerized in situ on the anode by cyclic voltammetry.

6. The production method according to claim 5, wherein in the step (1), the supporting electrolyte is one or more of tetraethylammonium hexafluorophosphate, tetraethylammonium tetrafluoroborate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, tetrabutylammonium perchlorate.

7. The method according to claim 5, wherein in the step (1), the solvent is an organic solvent selected from the group consisting of acetonitrile, N-dimethylformamide, hexamethylphosphoramide, methanol, ethanol, acetic acid, isopropanol, pyridine, tetramethylethylenediamine, acetone, triethylamine, N-butanol, dioxane, tetrahydrofuran, methyl formate, tributylamine, methyl ethyl ketone, chloroform, ethyl acetate, trioctylamine, dimethyl carbonate, diethyl ether, isopropyl ether, N-butyl ether, trichloroethylene, diphenyl ether, and dichloromethane.

8. The production method according to claim 5, wherein in the step (1), the solvent is selected from a mixed solution of dichloromethane and acetonitrile; the volume ratio of dichloromethane to acetonitrile in the mixed solution is 1: 1-10: 1.

9. The preparation method according to claim 8, wherein the volume ratio of dichloromethane to acetonitrile in the mixed solution is 2:1 to 9: 1.

10. The process according to claim 5, wherein in step (1), the concentration of the compound of formula I in the solution is 0.01 to 2 mmol/L.

11. The production method according to claim 5, wherein in the step (1), the concentration of the supporting electrolyte in the solution is 0.01 to 2 mmol/L.

12. The process according to claim 5, wherein in step (1), the concentration of the compound of formula I in the solution is from 0.1 to 1 mmol/L; the concentration of the supporting electrolyte in the solution is 0.1-1 mmol/L.

13. The method for preparing according to claim 5, wherein, in the step (2), the cyclic voltammetry uses a three-electrode system of an electrochemical workstation, and a reference electrode of the three-electrode system is Ag⁺Ag electrode, Hg²⁺a/Hg electrode or a hydrogen electrode.

14. The method according to claim 5, wherein in the step (2), the sweep cut-off voltage of the cyclic voltammetry is 0.4 to 1.8V;

the number of scanning times of the cyclic voltammetry is 1-4.

15. The method according to claim 5, wherein in the step (2), the sweep cut-off voltage of the cyclic voltammetry is 0.7 to 1.5V;

the number of scans of the cyclic voltammetry is 1, 2, 3 or 4.