CN101950687B - Preparation method of blanket type light anode for dye sensitized solar cell - Google Patents

Abstract

The invention discloses a method for preparing a carpet-type photoanode for dye-sensitized solar cells, belonging to the technical field of solar cells. The carpet-type photoanode adds a layer of carpet-type structure-titanium dioxide nanowire array film on the basis of the existing porous titanium dioxide nanocrystal film photoanode for dye-sensitized solar cells. Due to the existence of titanium dioxide nanowire arrays, more fuel sensitizers can be adsorbed; at the same time, due to the greatly reduced porous titanium dioxide nanocrystal grain interface, the grain boundary energy barrier to be overcome by electron transfer is reduced, thereby accelerating the photogenerated electrons in dye molecules- Effective separation of hole pairs; and the porous titanium dioxide nanocrystalline film at the bottom can effectively reduce the generation of leakage current and dark current; therefore, the carpet photoanode for dye-sensitized solar cells provided by the invention has higher photoelectric conversion efficiency. The preparation method is simple, the reaction condition is mild, and the process is safe and reliable.

Description

A kind of preparation method of carpet photoanode for dye-sensitized solar cell

technical field

The invention belongs to the technical field of solar cells, and relates to a photoanode (working electrode) of a dye-sensitized solar cell and a preparation method thereof.

Background technique

Energy is the most basic driving force for the development and economic growth of the entire world, and the basis for human survival. At present, humans mainly use primary energy, including coal, oil, natural gas and other resources. After nearly a hundred years of human consumption, these non-renewable resources have been consumed in large quantities and are facing the danger of being exhausted. It is imperative to develop new renewable energy sources, which mainly include solar energy, wind energy, geothermal energy, biomass energy, hydrogen energy, etc., among which solar energy has the greatest application potential. One of the important ways to develop and utilize solar energy is to use solar cells to convert light energy into electrical energy. According to the different materials used in solar cells, they can be divided into crystalline silicon solar cells, amorphous silicon solar cells and dye-sensitized solar cells. Among them, dye-sensitized solar cells have the advantages of relatively simple preparation process and low price, and have obvious price advantages compared with traditional silicon cells.

A dye-sensitized solar cell is mainly composed of a nanoporous semiconductor film (photoanode) adsorbed with a dye sensitizer, a redox electrolyte, and a counter electrode. Compared with traditional silicon solar cells, the biggest feature of dye-sensitized solar cells is that the absorption of light and the generation and transportation of electrons are completed by two parts of the cell. The dye sensitizer absorbs sunlight, and the photoanode and electrolyte are responsible for electron and hole transport, respectively. The dye sensitizer is excited by sunlight, and the electrons transition from the ground state to the excited state; the dye molecules in the excited state inject electrons into the conduction band of the semiconductor, and the electrons in the conduction band are transported to the photoanode (working electrode) in the nanocrystalline network , into the external circuit; the dye that lost electrons is reduced by the reducing agent in the electrolyte (mainly I ^- ions), so that the dye is regenerated, and at the same time the reducing agent in the electrolyte is oxidized (mainly I ₃ ^- ); Oxidizing ions (mainly I ₃ ^- ) diffuse to the counter electrode to obtain electrons, so that the electrolyte is regenerated, thus completing a cycle of photocurrent.

The basic structure of the photoanode of the existing dye-sensitized solar cell is a porous titanium dioxide nanocrystalline film made on the surface of a transparent conductive glass, and the dye sensitizer is adsorbed on the surface of the porous titanium dioxide nanocrystalline film. In the existing dye-sensitized solar cell photoanode, in the porous titanium dioxide nanocrystalline film responsible for charge separation and electron transport, due to the existence of a large amount of interface resistance between titanium dioxide nanocrystalline grains, an energy barrier for electron transfer will be formed, limiting The rapid migration of oxide conduction band electrons in the oxide porous network film makes the photogenerated electron-hole pairs in the dye molecules unable to be effectively separated, which restricts the improvement of the photoelectric conversion efficiency of dye-sensitized solar cells. In order for dye-sensitized solar cells to eventually replace silicon solar cells, in addition to their cost advantages, improving their photoelectric conversion efficiency is a key technical bottleneck that must be broken through.

Contents of the invention

The invention provides a carpet-type photoanode for a dye-sensitized solar cell, which adds a layer of carpet-type structure on the basis of the existing porous titanium dioxide nanocrystalline film photoanode for a dye-sensitized solar cell, that is, A layer of titanium dioxide nanowire array film is added to the surface of the porous titanium dioxide nanocrystalline film, so that more dye sensitizers can be adsorbed, and at the same time, the porous titanium dioxide nanocrystalline grain interface is greatly reduced, so that the particle interface that electrons must pass through in the titanium dioxide nanowire transmission This greatly reduces the grain boundary energy barrier to be overcome by electron transfer, and accelerates the effective separation of photogenerated electron-hole pairs in dye molecules. And the nanoporous film at the bottom of the structure can effectively reduce the generation of leakage current and dark current, so the new structured solar is expected to significantly improve the photoelectric conversion efficiency of dye-sensitized cells. The invention also provides a preparation method of the carpet-type photoanode for the dye-sensitized solar cell.

The technical scheme that the present invention takes is as follows:

A kind of carpet photoanode for dye-sensitized solar cell, as shown in Figure 1, comprises conductive glass 5, porous titanium dioxide nanocrystalline film 4 and carpet structure layer 3, porous titanium dioxide nanocrystalline film 4 is positioned at conductive glass 5 and carpet type Between the structural layers 3. The carpet structure layer is a layer of titanium dioxide nanowire array film adsorbed with a dye sensitizer.

A preparation method for a dye-sensitized solar cell carpet photoanode, comprising the steps of:

Step 1: Prepare titanium dioxide colloid.

Step 2: Preparation of titanate nanowire array film.

Put the metal titanium plate in a strong alkali solution (NaOH or KOH) at 100-200 ° C for 1-50 hours to form a layer of titanate nanowire array film on the surface of the metal titanium plate, that is, titanium-based titanate nanowires. wire array film; then put the titanium-based titanate nanowire array film into dilute hydrochloric acid solution and fully soak until the white film on the surface is detached from the substrate, and the obtained white film is the titanate nanowire array film.

Step 3: gluing - bonding - sintering - adsorption.

First, coat the titanium dioxide colloid prepared in step 1 on the surface of the conductive glass; then bond the titanate nanowire array film obtained in step 2 on the titanium dioxide colloid, dry and sinter at 200-600°C to obtain a porous titanium dioxide nanocrystalline film and a composite film of a titanium dioxide nanowire array film; finally, the composite film is soaked in a dye sensitizer solution to absorb the dye sensitizer to obtain the final carpet-type photoanode for the dye-sensitized solar cell.

It should be noted that, among the above technical solutions:

1) The titanium dioxide colloid described in step 1 can be commercially available P25 titanium dioxide colloid, or can be prepared by the hydrothermal synthesis method; if the hydrothermal synthesis method is used for self-preparation, the preparation process is as follows: tetraethylpropyl titanate [Ti( i-OC ₃ H ₇ ) ₄ ], nitric acid (HNO ₃ ), glacial acetic acid (CH ₃ COOH) and deionized water (H ₂ O) as raw materials, control Ti(i-OC ₃ H ₇ ) ₄ , HNO ₃ , The molar ratio of CH ₃ COOH to H ₂ O is 1:2.8:1:76; first dissolve Ti(i-OC ₃ H ₇ ) ₄ in H ₂ O, add CH ₃ COOH under vigorous stirring, and then Slowly add HNO ₃ ; then heat the reaction system to 80°C and transfer it to an autoclave for hydrothermal reaction at a temperature of 150-300°C and a pressure of 0-330Mpa to obtain a titanium dioxide sol; finally, remove water from the titanium dioxide sol by vacuum After the treatment, a polymer surfactant is added to adjust the viscosity to obtain viscous titanium dioxide colloid.

2) The reaction mechanism of the preparation of titanate nanowire array film in step 2: the metal titanium plate forms a sheet-like titanate under the action of high-concentration sodium hydroxide, and the sheet-like titanate gradually proceeds along the [101] direction Curl, and finally form a titanate nanowire array, in which the chemical reaction is Ti+NaOH→Na ₂ Ti _x O _2x+1 +H ₂ ; Sodium ions are ion-exchanged with hydrogen ions in hydrochloric acid to obtain titanate nanowire arrays; the reaction is: Na ₂ Ti _x O _2x+1 +HCl→H ₂ Ti _x O _2x+1 +NaCl

3) During the sintering process in step 3, titanate nanowire arrays lose water to form titania nanowire arrays, and the reaction is: H ₂ Ti _x O _2x+1 →TiO ₂ +H ₂ O

The beneficial effects of the present invention are:

Compared with the traditional porous titanium dioxide nanocrystalline photoanode film, the carpet-type photoanode for dye-sensitized solar cells provided by the present invention adds a layer of carpet-type structure-titanium dioxide on the basis of the existing photoanode for dye-sensitized solar cells. nanowire array film, so that more dye sensitizers can be adsorbed; at the same time, due to the greatly reduced porous titanium dioxide nanograin interface, the grain interface through which electrons are transported in titanium dioxide nanowires is greatly reduced, which greatly reduces The grain boundary energy barrier to be overcome by electron transfer, thereby accelerating the effective separation of photogenerated electron-hole pairs in dye molecules; finally, the porous titanium dioxide nanocrystalline film at the bottom of the carpet-type photoanode for dye-sensitized solar cells provided by the invention can Effectively reduce the generation of leakage current and dark current. In summary, the carpet-type photoanode for dye-sensitized solar cells provided by the invention has higher photoelectric conversion efficiency (experimental tests prove that the dye-sensitized The photoelectric conversion efficiency of the dye-sensitized solar cell is more than 10% higher than that of the dye-sensitized solar cell assembled under the same conditions using the existing porous titanium dioxide nanocrystalline photoanode); and the preparation method is simple, the reaction conditions are mild, and the process Safe and reliable.

Description of drawings

Fig. 1 is a schematic structural diagram of a carpet-type photoanode for a dye-sensitized solar cell provided by the present invention. Among them, 5 is conductive glass, 4 is porous titanium dioxide nanocrystal film, and 3 is titanium dioxide nanowire array film.

Fig. 2 is a schematic diagram of the structure of a dye-sensitized solar cell using a carpet-type photoanode for a dye-sensitized solar cell of the present invention. Among them: 1 is the counter electrode; 2 is the electrolyte (iodine base)

Fig. 3 is an SEM image of a carpet-type photoanode for a dye-sensitized solar cell of the present invention.

Fig. 4 is a photocurrent-voltage curve diagram of a dye-sensitized solar cell using a carpet-type photoanode for a dye-sensitized solar cell of the present invention.

Detailed ways

The preparation process of the carpet-type photoanode for dye-sensitized solar cells described in the following examples is not to further limit the present invention, but for the convenience of comparison and testing, a specific embodiment is given to illustrate the technology of the present invention Effect. It should be noted that all carpet-type photoanodes for dye-sensitized solar cells that are specifically prepared according to or substantially according to the technical solutions described in the foregoing summary of the invention can solve the technical problems described in the present invention and can achieve the technical effects described in the present invention. .

Embodiment one

Put the high-purity titanium plate into 8M NaOH solution at 150°C and react for 24 hours to prepare a titanium-based titanate nanowire array film, and put the resulting titanium-based titanate nanowire array film into 0.05mol/L Fully soak in dilute hydrochloric acid until the white film on the surface is separated from the substrate to obtain a titanate nanowire array film; apply a layer of sticky P25 titanium oxide colloid on the surface of transparent conductive glass by scraping, and then coat the titanate nanowires The array film is bonded to the surface of the titanium dioxide colloid, and after drying, it is sintered at 300°C for 50 minutes to obtain a composite film of the porous titanium dioxide nanocrystal film and the titanium dioxide nanowire array film; finally, the composite film is soaked in 4×10 ^-4 mol/L Soak in the organic solution of the dye for 8 hours to obtain the final carpet-type photoanode for the dye-sensitized solar cell.

The prepared dye-sensitized solar cell carpet photoanode was assembled into a cell with iodine/lithium iodide electrolyte and platinum-coated conductive glass counter electrode, and the photoelectric performance test was carried out. The test results are shown by the solid line in Figure 3. It can be calculated that the short-circuit current of the carpet-type photoanode cell for dye-sensitized solar cells described in this embodiment is 15.2mA/cm ² , and the open-circuit voltage is 0.71V. The fill factor is 0.608, and the photoelectric conversion efficiency is 6.58%.

comparative example

The porous titanium dioxide nanocrystalline photoanode was prepared by using the same P25 titanium dioxide colloid as in the example, and assembled into a battery with an iodine/lithium iodide electrolyte and a platinum-coated conductive glass counter electrode, and the photoelectric performance was tested. Its test result is shown in the dotted line in Fig. 3, it can be calculated that the short-circuit current of the porous titanium dioxide nanocrystalline photoanode cell for dye-sensitized solar cells described in the comparative example is 13.5mA/cm ² , and the open-circuit voltage is 0.70V, The fill factor is 0.600, and the photoelectric conversion efficiency is 5.67%. It can be seen that the short-circuit current of the battery adopting the carpet-type photoanode for dye-sensitized solar cells provided by the invention is increased by 12%, and the photoelectric conversion efficiency is increased by 14%.

Claims (4)

1. the preparation method of a used by dye sensitization solar battery blanket type light anode comprises the steps:

Step 1: prepare colloidal tio 2;

Step 2: the preparation of metatitanic acid nano-wire array film;

The strong base solution that metallic titanium plate is put into 100～200 ℃ reacted 1～50 hour, thereby generated one deck titanate nano-wire array film, i.e. titanium base titanate nano-wire array film in pickling metal titanium plate; Then titanium base titanate nano-wire array film is put into dilute hydrochloric acid solution and fully soak, white film and substrate up to the surface break away from, and the white film that obtains is exactly the metatitanic acid nano-wire array film;

Step 3: gluing-bonding-sintering-absorption;

At first at the prepared colloidal tio 2 of conductive glass surface coating step 1; Metatitanic acid nano-wire array film with step 2 gained is bonded in above the colloidal tio 2 then, obtains the laminated film of poriferous titanium dioxide nano-crystal film and nano-wire array film of titanium dioxide after drying in 200～600 ℃ of following sintering; At last laminated film is soaked in absorbing dye sensitizer in the dye sensitization agent solution, obtains final used by dye sensitization solar battery blanket type light anode.

2. the preparation method of used by dye sensitization solar battery blanket type light anode according to claim 1 is characterized in that, strong base solution described in the step 2 is NaOH or KOH solution.

3. the preparation method of used by dye sensitization solar battery blanket type light anode according to claim 1 is characterized in that, colloidal tio 2 described in the step 1 is commercially available P25 colloidal tio 2.

4. the preparation method of used by dye sensitization solar battery blanket type light anode according to claim 1, it is characterized in that, colloidal tio 2 described in the step 1 prepares voluntarily for adopting hydrothermal synthesis method, and its preparation process is as follows: adopt metatitanic acid tetrem propyl ester [Ti (i-OC ₃H ₇) ₄], nitric acid (HNO ₃), glacial acetic acid (CH ₃COOH) and deionized water (H ₂O) be raw material, control Ti (i-OC ₃H ₇) ₄, HNO ₃, CH ₃COOH and H ₂The mol ratio of O is 1: 2.8: 1: 76; At first with Ti (i-OC ₃H ₇) ₄Be dissolved in H ₂Among the O, the powerful stirring adds CH down ₃COOH slowly adds HNO more while stirring ₃Then reaction system is heated to 80 ℃ and change in the autoclave, hydro-thermal reaction under the pressure condition of 150～300 ℃ temperature and 0～330Mpa obtains TiO 2 sol; At last TiO 2 sol is added high molecular surfactant after vaccum dewatering is handled and regulate viscosity, obtain thick colloidal tio 2.

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