CN109872877B

CN109872877B - ZnO photo-anode of dye-sensitized solar cell and preparation method thereof

Info

Publication number: CN109872877B
Application number: CN201910149578.6A
Authority: CN
Inventors: 史彦涛; 李燕茜
Original assignee: Zhejiang Saishi Technology Co ltd; Jiangsu Saiqing Technology Co ltd
Current assignee: Zhejiang Saishi Technology Co ltd; Jiangsu Saiqing Technology Co ltd
Priority date: 2019-02-28
Filing date: 2019-02-28
Publication date: 2021-04-13
Anticipated expiration: 2039-02-28
Also published as: CN109872877A

Abstract

The invention provides a ZnO photo-anode of a dye-sensitized solar cell, which is characterized in that ZnO Nanoparticles (NP), ZnO nanosheet-based multilevel structures (NSHS) and ZnO Nanorods (NR) with relatively small particle sizes are respectively synthesized by a room-temperature solid-phase reaction, an ultrasonic synthesis method and a solution growth method, and are directly coated on conductive glass in a scraping manner according to the advantage that the ZnO nanoparticles with relatively small particles have relatively large specific surface area so as to adsorb dye as much as possible. According to the high one-dimensional crystallinity of the ZnO nano-rod, the surface electron recombination is less, and the ZnO nano-rod is compounded with the double-layer film, so that the far-end excited electrons can be smoothly transmitted to the surface of the conductive glass.

Description

ZnO photo-anode of dye-sensitized solar cell and preparation method thereof

Technical Field

The invention belongs to the field of new energy materials and devices, and particularly relates to a ZnO photo-anode of a dye-sensitized solar cell and a preparation method thereof.

Background

In the current society, with the continuous consumption of fossil energy, environmental pollution is more serious, which causes a series of ecological environment problems, and therefore, the development of novel clean and safe energy is urgent. Solar energy, as a renewable resource, has the advantages that other conventional energy sources cannot be compared with the renewable resource, and is often considered as a novel clean energy source with the highest development value. Dye-sensitized solar cells (DSSCs) can directly convert light energy into electrical energy by the photoelectric effect. The DSSC is mainly composed of a semiconductor film photoanode, a dye photosensitizer, an electrolyte containing a redox couple, and a counter electrode. Compared with the traditional solar cell, the DSSC has the advantages of long service life of the cell, which can reach 15-20 years, simple preparation process, low cost, easy large-scale popularization, rich material sources, no toxicity, no harm and environmental friendliness. In DSSCs, the photoanode has the function of collecting excited electrons, and the dye is excited by light and transported to a conductive substrate through a semiconducting porous membrane in the photoanode. The semiconductor porous film on the one hand provides an attachment point for the dye and on the other hand is connected with the conductive substrate, which plays a crucial role in the generation of current and thus ultimately affects the photoelectric conversion efficiency of the cell. The photo-anode material which is currently being studied relatively much and well is TiO 2. However, TiO2 has poor electron-excited transport ability, and is prone to cause recombination of excited electrons, thereby causing energy waste, and the like, so in the current research, modification of the electron-excited transport ability is mostly performed, thereby causing the preparation process to become complicated, the cost to be further increased, and limiting large-scale application of TiO 2-based DSSC to a certain extent. Therefore, the development of new nanocrystalline materials, such as ZnO nanomaterials, to replace TiO2 is a necessary choice. Compared with TiO2, the ZnO nano material has the advantages of rich raw materials, rich appearance, easy preparation and the like.

Disclosure of Invention

To solve the problems set forth in the background art described above. The invention provides a ZnO photo-anode of a dye-sensitized solar cell and a preparation method thereof.

A ZnO photo-anode of a dye-sensitized solar cell is composed of ZnO nanoparticles, a ZnO nanosheet-based multilevel structure and ZnO nanorods, wherein the ZnO nanoparticles are directly coated on conductive glass in a scraping mode, the ZnO nanorods grow in situ, and then the ZnO nanoparticles and the ZnO nanosheet-based multilevel structure are sequentially coated on the conductive glass in a scraping mode to obtain a nanoparticle/nanosheet-based multilevel structure/nanorod composite photo-anode film.

Preferably, the ZnO nanoparticles are synthesized by a room temperature solid phase method, zinc nitrate hexahydrate and sodium hydroxide are ground by a mortar until the reaction is sufficient, then deionized water is centrifugally washed to be neutral, and then a certain amount of deionized water is added to be uniformly dispersed to be used as the slurry 1.

Preferably, the ZnO nanosheet-based multilevel structure is synthesized by an ultrasonic chemical method, a zinc nitrate aqueous solution and a sodium hydroxide aqueous solution are synthesized under stirring and ultrasonic waves, after complete reaction, deionized water is centrifugally washed to be neutral, then a certain amount of solution mixed with ethanol and water in equal amount is added, and the solution is dispersed to be used as the slurry 2.

Preferably, the ZnO nano-rod is grown in situ, slurry 1 is sequentially coated on conductive glass by a blade coating method, and is placed in Zn (NO) after heat treatment after film forming₃)₂In growth liquid prepared from HMT, growing in a drying oven at 90 ℃, drying in the drying oven after taking out, and sensitizing in N719 ethanol solution.

The application also provides a preparation method of the ZnO photo-anode of the dye-sensitized solar cell, which comprises the steps of sequentially coating the slurry 1 of claim 2 on conductive glass by a blade coating method, carrying out heat treatment after film formation, and then placing the conductive glass on Zn (NO)₃)₂In growth liquid prepared from HMT, growing in a 90 ℃ oven, taking out, drying in the oven, sensitizing in N719 ethanol solution, sequentially coating slurry 1 and slurry 2 on conductive glass by a coating method, performing heat treatment, and placing in Zn (NO)₃)₂And growing in a growth solution prepared from HMT to finally obtain the nano-particle/nano-sheet-based hierarchical structure/nano-rod composite photo-anode film.

The application also provides a dye-sensitized solar cell with ZnO as a photo-anode, wherein Pt is used as a counter electrode, ZnO is used as the photo-anode, a diaphragm is added in the middle to prevent short circuit, a sandwich structure is formed, then electrolyte is added, and packaging is carried out, namely the dye-sensitized solar cell with the anode is obtained.

In the invention, ZnO Nanoparticles (NP), ZnO nanosheet-based multilevel structures (NSHS) and ZnO Nanorods (NR) with relatively small particle sizes are respectively synthesized by a room-temperature solid-phase reaction, an ultrasonic synthesis method and a solution growth method, and are directly coated on conductive glass in a scraping way according to the advantage that the ZnO nanoparticles with relatively small particles have relatively large specific surface area so as to absorb as much dye as possible, and are used for a light scattering layer of a photo-anode according to the good light scattering characteristics of nanosheet-based multilevel spheres, so that light which is not utilized by a first layer of nanoparticle film is scattered back and reused. According to the high one-dimensional crystallinity of the ZnO nano-rod, the surface electron recombination is less, and the ZnO nano-rod is compounded with the double-layer film, so that the far-end excited electrons can be smoothly transmitted to the surface of the conductive glass. Finally, the photo-anode film compounded by nano particles/nano sheet-based multilevel structures/nano rods is obtained and is used as DSSC, N719 dye is used as a sensitizing agent, electrolyte is added, Pt is used as a counter electrode, and a dye-sensitive battery is assembled. The J-V performance was tested. Finally, the stable and high-efficiency ZnO photo-anode film is obtained. The invention can obtain a stable and efficient novel counter electrode material.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an SEM image of a ZnO photo-anode with a multi-level structure;

FIG. 2 is an XRD pattern of NP, NP/NSHS and NP/NSHS/NR based ZnO photoanodes;

FIG. 3 is a J-V curve of cells corresponding to different composite ZnO photo-anodes;

FIG. 4 is a graph of light scattering curves for photoanodes of different configurations;

FIG. 5 is EIS maps of corresponding cells of (A, B) different photoanodes.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Firstly synthesizing ZnO Nanoparticles (NP) and ZnO nanosheet-based multilevel structures (NSHS), synthesizing nanoparticles with small particles by a room-temperature solid-phase method, putting 10.0g of zinc nitrate hexahydrate and 5.0g of sodium hydroxide into a mortar, grinding for 20min until the reaction is sufficient, then centrifugally washing the mixture to be neutral by deionized water, then adding a certain amount of deionized water, and uniformly dispersing the mixture to obtain slurry 1. Synthesizing a nanosheet-based multilevel structure by an ultrasonic chemical method, synthesizing 200ml of 0.08M zinc nitrate aqueous solution and 200ml of 0.4M sodium hydroxide aqueous solution under stirring and ultrasonic waves, after complete reaction, centrifugally washing the mixture to be neutral by deionized water, adding a certain amount of mixed solution of ethanol and water in equal amount, and dispersing the mixed solution to be used as slurry 2. Then growing ZnO nano-rods (NR) in situ and preparing ZnO-based photo-anodes with NP/NSHS/NR multilevel structures, coating the slurry 1 on conductive glass in sequence by a blade coating method, forming films, performing heat treatment at 250 ℃, and placing the films in growth solution prepared from Zn (NO3)2/HMT, wherein the concentration of the growth solution is 1, 5, 12 and 25mM in sequence in order to find the optimal concentration for growing the nano-rods. Growing for 3h in an oven at 90 ℃. After taking out, the membrane was dried in an oven at 120 ℃ and sensitized in 0.5mM N719 ethanol for 2 hours (the resulting photo-anode membranes were designated NP-1, NP-5, NP-12, NP-25, respectively, and the untreated photo-anode was designated NP). And testing the performance to obtain the optimal concentration of the growth liquid, then blade-coating the slurry 1 and the slurry 2 on the conductive glass in sequence by a blade coating method, carrying out heat treatment, and placing the conductive glass in the optimal growth liquid for growth. Finally obtaining the NP/NSHS/NR composite ZnO-based photo-anode.

From FIG. 1, NSHS ZnO (a and b) with a nanosheet multilevel structure, an interface diagram (c) of a composite membrane NP/NSHS/NR and a partial enlarged diagram (d) thereof, and FIG. 2 is an XRD diagram of the NP, NP/NSHS and NP/NSHS/NR-based ZnO photo-anode, the crystallinity of the nano-membrane NSHS/NR-based ZnO photo-anode is good and corresponds to a standard peak of ZnO (JCPDS 36-1451). Therefore, it can be seen from the present example that the ZnO photoanode material can be successfully prepared by simple solid phase reaction, ultrasonic synthesis and in-situ growth.

Example 2

ZnO is used as a photo-anode, Pt is used as a counter electrode, a diaphragm is added in the middle to prevent short circuit, a sandwich structure is formed, then electrolyte is added, and packaging is carried out, wherein the electrolyte consists of acetonitrile solution of 0.1M LiI, 0.1M I2, 0.6M DMPII and 0.45M NMBI. And then carrying out electrical property test. FIG. 3 shows the J-V curve corresponding to a ZnO-based photoanode DSSC. Meanwhile, the battery performance parameters corresponding to the most efficient battery are shown in table 1.

Figure 5 shows J-V curves representing different composite ZnO photoanodes. From the above data, the photoelectric conversion efficiency of the composite electrode NP/NSHS/NR-based DSSC is higher than that of the NP/NSHS-based cell, and the reason for this is probably because the nanorod NR establishes a fast excited electron transport channel in the photo-anode film, thereby reducing the electron recombination during the transport process. Thereby increasing efficiency, while NP/NSHS based cells are superior to NP based cells. Combining the light scattering pattern spectra of the ZnO films with different structures in fig. 4, it can be known that the NSHS with the nanosheet multilevel structure has an excellent light scattering effect, and as the middle second layer film of the photo-anode, the NSHS can scatter light which is not absorbed by the first layer film back to be reused, so that the utilization rate of sunlight is increased. The embodiment shows that the new ZnO material has good photoelectric conversion efficiency as a dye-sensitized solar light anode.

Example 3

To further explore the reason for the improvement of the photoelectric conversion efficiency of the corresponding cell. EIS impedance test and fitting are carried out on the battery to obtain the charge recombination impedance Rrec and the charge transfer impedance Rtr, and the charge transfer impedance Rtr is shown in figure 5. Since the electron recombination and transfer processes will coincide at high bias, we chose lower bias (-0.6V to-0.8V). FIGS. 5A and B are graphs of EIS electrochemical impedances measured at-0.8V and-0.6V respectively, from which it can be seen that the load transfer impedance and the recombination impedance show a decreasing trend as the bias voltage increases. In substantial agreement with theory. In fig. 5, the second semi-circle middle blue number in a and B represents the frequency f, and we can estimate the corresponding electron lifetime according to the formula tn 1/wk 1/2 pi f, wherein the electron lifetime of the NP/NSHS-based photo-anode film is higher than that of the NP/NSHS/NR-based photo-anode film, so that the growth amount of NR requires the optimal growth solution concentration, i.e. 5 mM.

From the above examples, the present invention respectively adopts simple room temperature solid phase reaction, ultrasonic chemical synthesis, and in situ growth method to synthesize ZnO nanoparticles NP, nanoplatelet-based multilevel structure NSHS, nanorod NR. And testing the advantages and the disadvantages of different ZnO nano structures by means of SEM, light scattering, electrochemical impedance EIS and the like. NSHS has good light scattering performance, while NR has good electron transmission performance, and in order to fully utilize the respective advantages, a scheme for preparing a ZnO photo-anode film with an NP/NSHS/NR multi-level structure is designed. The cell is assembled by putting the nano-particle NP-based photo-anode with smaller particles into growth solutions with different concentrations for in-situ growth treatment, the electrochemical impedance EIS and J-V test results are utilized to optimize the concentration of the growth solution to be 5mM, then the NP/NSHS-based photo-anode is treated by the in-situ growth method of the growth solution with the concentration of 5mM, and finally the high-efficiency NP/NSHS/NR-based composite multi-level structure ZnO photo-anode film can be successfully synthesized by SEM observation, and the photoelectric efficiency of the ZnO-based dye-sensitive cell can reach 5.79%. The invention achieves good effect and excellent battery performance, and achieves the purpose of the invention.

Claims

1. A ZnO photo-anode of a dye-sensitized solar cell is characterized in that: the photoanode consists of ZnO nanoparticles, a ZnO nanosheet-based multilevel structure and ZnO nanorods, wherein the ZnO nanoparticles are directly coated on conductive glass in a scraping manner, the ZnO nanorods grow in situ, then the ZnO nanoparticles and the ZnO nanosheet-based multilevel structure are sequentially coated on the ZnO nanorods in a scraping manner, and the ZnO nanorods are placed on 5mM Zn (NO)₃）₂Growing in a growth solution prepared from HMT to obtain a nano-particle/nano-sheet-based hierarchical structure/nano-rod composite photo-anode film;

synthesizing the ZnO nanoparticles by a room temperature solid phase method, grinding zinc nitrate hexahydrate and sodium hydroxide by a mortar until the reaction is sufficient, then centrifugally washing the mixture by deionized water until the mixture is neutral, then adding a certain amount of deionized water, and uniformly dispersing the mixture to obtain slurry 1;

the ZnO nanosheet-based multilevel structure is synthesized by an ultrasonic chemical method, a zinc nitrate aqueous solution and a sodium hydroxide aqueous solution are synthesized under the conditions of stirring and ultrasonic waves, after complete reaction, deionized water is centrifugally washed to be neutral, then a certain amount of solution mixed with ethanol and water in equal amount is added, and the solution is dispersed to be used as slurry 2;

the ZnO nano-rod adopts an in-situ growth method, slurry 1 is sequentially coated on conductive glass by a blade coating method, and is placed in Zn (NO) after heat treatment after film forming₃）₂In growth liquid prepared from HMT, growing in a drying oven at 90 ℃, drying in the drying oven after taking out, and sensitizing in N719 ethanol solution.

2. A method for preparing a ZnO photoanode of a dye-sensitized solar cell according to claim 1, wherein the method comprises the following steps: sequentially coating the slurry 1 on conductive glass by a blade coating method, performing heat treatment after film forming, and then placing in Zn (NO)₃）₂In growth liquid prepared from HMT, growing in a 90 ℃ oven, taking out, drying in the oven, sensitizing in N719 ethanol solution, sequentially coating slurry 1 and slurry 2 on ZnO nanorod by blade coating method, heat treating, and placing in 5mM Zn (NO)₃）₂And growing in a growth solution prepared from HMT to finally obtain the nano-particle/nano-sheet-based hierarchical structure/nano-rod composite photo-anode film.

3. A dye-sensitized solar cell with ZnO as a photo-anode is characterized in that: and Pt is used as a counter electrode, the ZnO photo-anode disclosed in claim 1 or the ZnO photo-anode prepared by the method disclosed in claim 2 is used as a photo-anode, a diaphragm is added in the middle to prevent short circuit, a sandwich structure is formed, then electrolyte is added, and the dye-sensitized solar cell of the anode is obtained by packaging.