TiO2 / NaYF4: Yb, Er composite material as well as preparation method and application thereof

Abstract

The invention discloses a TiO2 / NaYF4: Yb, Er composite material as well as a preparation method and application thereof. The method comprises the following steps: dispersing titanium dioxide in a sodium hydroxide solution, adding a hydrogen peroxide solution, and carrying out a hydrothermal reaction; carrying out sintering to obtain sea urchin-shaped TiO2; the preparation method comprises the following steps: carrying out hydrothermal reaction on polyvinylpyrrolidone, a Y source, a Yb source, an Er source and an F source in an alcohol-water solution containing NaCl to prepare NaYF4: Yb, Er; the preparation method comprises the following steps: stirring sea urchin-shaped TiO2 and NaYF4: Yb, Er in a solvent to obtain the TiO2 / NaYF4: Yb, Er composite material. According to the invention, by improving the adsorption capacity of the dye and improving the absorption of the dye to light, the light capturing capability of the photo-anode is synergistically improved, the photoelectric conversion efficiency can be improved, and the photo-anode has potential application value in the field of dye-sensitized solar cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of dye-sensitized solar cells, and in particular relates to a TiO2 / NaYF4:Yb, Er composite material and a preparation method and application thereof. Background Art

[0002] With the rapid development of society, the use of non-renewable energy sources, such as fossil fuels, faces challenges such as environmental pollution, climate change, and energy shortages. Solar energy, due to its pollution-free nature and abundant reserves, is considered one of the most promising alternative energy sources. Dye-sensitized solar cells (DSSCs) have garnered significant attention in the development of solar cells due to their high theoretical efficiency, low production cost, environmental friendliness, and the ability to fabricate flexible devices on a large scale.

[0003] DSSCs, based on low-cost nano-titanium dioxide and photosensitizing dyes, mimic the natural process of plants using solar energy for photosynthesis, converting solar energy into electricity. DSSCs primarily consist of a photoanode, an electrolyte, and a counter electrode. The photoanode is primarily composed of conductive glass, a photoanode material, and an adsorbed dye. During operation, the photoanode captures solar energy. Specifically, the dye adsorbed on the photoanode material absorbs solar energy, becoming excited to produce photogenerated electrons. These electrons are then transferred to the photoanode material and then to the conductive glass, forming an electric current that performs external work. The more solar energy captured by the photoanode, the more photogenerated electrons it produces. Therefore, photoanodes with high light-capturing capacity are key to improving the photoelectric conversion efficiency of DSSCs. In DSSCs, because titanium dioxide is a wide-bandgap semiconductor, it can only absorb ultraviolet and short-wavelength visible light, which constitute a relatively small portion of sunlight. However, DSSCs sensitized with dyes can utilize narrow-bandwidth dyes to absorb visible light. In order to further broaden the dye absorption spectrum, rare earth doped upconversion materials are introduced into the photoanode materials. Among them, NaYF4:Yb,Er is a good rare earth doped upconversion material with the ability to absorb infrared light and emit visible light.

[0004] However, the actual efficiency of DSSCs is currently low. Titanium dioxide and NaYF4:Yb,Er are mainly prepared by mixing DSSCs rather than by composite growth. For example: (1) TiO2 powder is mixed evenly with NaYF4:Yb,Er powder, ethyl cellulose and pinene alcohol, and a slurry is obtained after aging. The slurry is then coated on the conductive surface of FTO glass by casting or screen printing, dried and calcined to obtain a NaYF4:Yb,Er modified dye-sensitized solar cell TiO2 photoanode. This TiO2 photoanode improves the light absorption intensity and spectral response range, and the photoelectric conversion efficiency is 1.9% to 2.7%. (2) TiO2 and NaYF4:Yb,Er are mixed into a slurry to prepare a photoanode film; or a NaYF4:Yb,Er photoanode film is coated on the TiO2 photoanode film to form a composite film. In both cases, the distribution is uneven, the dye can only be adsorbed on TiO2, and the distance between NaYF4:Yb,Er and the dye is too far, making energy transfer impossible. In addition, the composite material prepared by TiO2 and NaYF4:Yb,Er in the prior art has a low adsorption capacity for dyes due to its small specific surface area, thus failing to achieve high efficiency. Summary of the Invention

[0005] In response to the above technical problems, the present invention provides a TiO2 / NaYF4:Yb,Er composite material, its preparation method and application. The present invention prepares sea urchin-like TiO2, and then composites TiO2 with NaYF4:Yb,Er to form a composite material with a hierarchical structure, wherein NaYF4:Yb,Er grows on the spines of the sea urchin-like TiO2. After the dye is adsorbed on TiO2, it is also adsorbed on the spines of the sea urchin-like TiO2. As a result, the distance between the dye and NaYF4:Yb,Er is very close, satisfying the conditions for energy transfer, thereby improving the dye's absorption of near-infrared light. The present invention increases the adsorption amount of the dye and simultaneously increases the dye's absorption of light, thereby synergistically improving the light-capturing ability of the photoanode, which can improve the photoelectric conversion efficiency and has potential application value in the field of dye-sensitized solar cells.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In one aspect, the present invention provides a method for preparing a TiO2 / NaYF4:Yb,Er composite material, comprising the following steps:

[0008] (1) dispersing titanium dioxide in a sodium hydroxide solution, adding a hydrogen peroxide solution and performing a hydrothermal reaction; and sintering to obtain sea urchin-shaped TiO2;

[0009] (2) hydrothermally reacting polyvinylpyrrolidone, a Y source, a Yb source, an Er source, and a F source in an alcohol aqueous solution containing NaCl to prepare NaYF4:Yb,Er;

[0010] (3) stirring the sea urchin-shaped TiO2 and NaYF4:Yb,Er in a solvent to obtain the TiO2 / NaYF4:Yb,Er composite material;

[0011] Among them, steps (1) and (2) are performed in no particular order.

[0012] As a preferred embodiment, in step (1), the titanium dioxide is P25 titanium dioxide powder;

[0013] and / or, the concentration of the sodium hydroxide solution is 9 to 11 mol / L;

[0014] and / or, the concentration of the hydrogen peroxide solution is 25% to 35%;

[0015] and / or, the molar ratio of sodium hydroxide to hydrogen peroxide is 13 to 18:1;

[0016] In some specific embodiments, the titanium dioxide is dispersed in the sodium hydroxide solution by alternating magnetic stirring and ultrasonic waves.

[0017] As a preferred embodiment, in step (1), the temperature of the hydrothermal reaction is 145 to 155° C.; the time of the hydrothermal reaction is 85 to 95 minutes;

[0018] In certain specific embodiments, the hydrothermal reaction further includes post-treatments of centrifugation, acid washing, water washing and drying; the acid washing is washing with dilute nitric acid; and the drying is drying at 50-80° C. for 8-24 hours.

[0019] As a preferred embodiment, in step (1), the sintering temperature is 450-480° C.; the sintering time is 2-2.5 hours; and the sintering heating rate is 8-12° C. / min.

[0020] As a preferred embodiment, in step (2), the Y source is a soluble Y salt, such as Y(NO3)3·6H2O, YCl3·6H2O, etc.; the Yb source is a soluble Yb salt, such as Yb(NO3)3·5H2O, YCl3·6H2O, etc.; the Er source is a soluble Er salt, such as Er(NO3)3·5H2O, ErCl3·6H2O, etc.; the F source is a soluble F salt, such as NH4F, NaF, etc.;

[0021] and / or, the molar ratio of Y in the Y source, Yb in the Yb source, Er in the Er source, F in the F source, and NaCl is 0.07-0.08:0.1-0.3:0.01-0.03:6-8:1.5-2.5;

[0022] and / or, the molar ratio of polyvinyl pyrrolidone to NaCl is 2 to 4:1;

[0023] In certain specific embodiments, the molecular weight of the polyvinyl pyrrolidone is 58,000; the amount of the polyvinyl pyrrolidone is the ratio of the mass of polyvinyl pyrrolidone to the molar mass of the repeating unit (C6H9NO);

[0024] and / or, the alcohol aqueous solution is an ethanol aqueous solution;

[0025] And / or, the polyvinyl pyrrolidone is dispersed in an alcohol aqueous solution, and after adding a Y source, a Yb source and an Er source and stirring, NaCl and a F source are added.

[0026] As a preferred embodiment, in step (2), the temperature of the hydrothermal reaction is 175 to 185° C.; the time of the hydrothermal reaction is 16 to 18 hours;

[0027] In some specific embodiments, the hydrothermal reaction further includes post-treatments of washing and drying; the washing is preferably performed with a mixed solution of ethanol and deionized water, preferably with a volume ratio of ethanol to deionized water of 1:1; the washing is performed at a rate of 3000 to 4000 rpm for 10 to 15 minutes each time; the drying is performed at 60 to 80°C for 8 to 12 hours.

[0028] As a preferred embodiment, in step (3), the mass ratio of TiO2 to NaYF4:Yb,Er is 1:0.3-0.6;

[0029] And / or, the stirring temperature is 45-55°C;

[0030] And / or, the stirring treatment time is 1.5 to 2.5 hours;

[0031] and / or, the solvent is acetone;

[0032] In some specific embodiments, post-processing of centrifugation and drying is further included.

[0033] In another aspect, the present invention provides a TiO2 / NaYF4:Yb, Er composite material obtained by the above preparation method.

[0034] In another aspect, the present invention provides the use of the above-mentioned TiO2 / NaYF4:Yb,Er composite material in the preparation of dye-sensitized solar cells;

[0035] Specifically, the application in preparing dye-sensitized solar cell photoanode.

[0036] The above technical solution has the following advantages or beneficial effects:

[0037] The present invention combines the rare earth upconversion material NaYF4:Yb,Er with sea urchin-like TiO2 to prepare a sea urchin-like TiO2 / NaYF4:Yb,Er composite material with a hierarchical structure. (1) The material is further used to prepare a photoanode. After adsorbing the dye, on a microscopic scale, NaYF4:Yb,Er grows on the spines of the sea urchin-like TiO2, and the dye is also adsorbed on the spines of the sea urchin-like TiO2, with NaYF4:Yb,Er being relatively close to the dye. NaYF4:Yb,Er can absorb near-infrared light and emit visible light, and the emitted visible light band is just within the absorption range of the dye. Therefore, the rare earth-doped upconversion material is equivalent to a converter, converting near-infrared light that the dye cannot directly absorb into visible light that the dye can absorb. (2) The sea urchin-like structure is a hierarchical structure with a large specific surface area and more active sites, which can adsorb more dyes, thereby improving the photoanode's light capture ability and thus improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG1 is a microscopic morphology of a sample prepared in Example 1 of the present invention, wherein: Figure 1a This is a transmission electron microscopy image of the sea urchin-like TiO2 / NaYF4:Yb,Er composite material; Figure 1b for Figure 1a High-resolution transmission electron microscopy image of the white dotted box area; Figure 1c This is a transmission electron microscope image of sea urchin-shaped TiO2.

[0039] Figure 2 3. It is the XRD pattern of the sea urchin-shaped TiO2, NaYF4:Yb,Er, and TiO2 / NaYF4:Yb,Er composite materials prepared in Example 1 of the present invention.

[0040] Figures 3a to 3c They are nitrogen analysis diagrams of P25 TiO2, sea urchin-shaped TiO2 prepared in Example 1 of the present invention, and TiO2 / NaYF4:Yb,Er composite material.

[0041] Figure 4 It is the ultraviolet-visible-near infrared absorption spectrum of the sea urchin-shaped TiO2, NaYF4:Yb, Er and TiO2 / NaYF4:Yb, Er composite materials prepared in Example 1 of the present invention.

[0042] Figure 5 The fluorescence spectra of NaYF4:Yb,Er and TiO2 / NaYF4:Yb,Er composite materials prepared in Example 1 of the present invention are shown in FIG.

[0043] Figure 6 This is a diagram of the luminescence mechanism of NaYF4:Yb,Er prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0045] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0046] Example 1:

[0047] (1) Synthesis of sea urchin-like TiO2

[0048] 0.1 g of P25 titanium dioxide powder (P25) was placed in 60 mL of 10 mol / L sodium hydroxide solution, and magnetic stirring and ultrasonication were alternately performed four times for 5 minutes each to fully mix the solution to form a white composite solution. The solution was then slowly transferred to a 50 mL hydrothermal kettle and 4 mL of hydrogen peroxide (purity: 30%) solution was added. The hydrothermal kettle was then placed in an electric blast oven and heated to 150° C., after which a 90-minute timer was started. The hydrothermal kettle was removed after naturally cooling to room temperature, centrifuged at high speed, and then repeatedly washed three times with a 0.2 mol / L dilute nitric acid solution until it became acidic. The solution was then repeatedly washed three times with deionized water to remove any ions in the product. After the product was washed to neutrality, it was transferred to a vacuum drying oven and dried at 60° C. under vacuum for 12 hours. The dried powder was sintered in a muffle furnace at 450° C. for 2 hours at a heating rate of 10° C. / min. Finally, a white solid powder of sea urchin-like TiO2 (TiO2) was obtained.

[0049] (2) Synthesis of NaYF4:Yb,Er

[0050] 0.6 g of polyvinylpyrrolidone (PVP, molecular weight 58000) was dispersed in a mixed solution of 4 mL of deionized water and 16 mL of ethanol and stirred for 10 min; then 0.078 mmol of Y(NO3)36H2O, 0.2 mmol of Yb(NO3)35H2O and 0.02 mmol of Er(NO3)35H2O were added and stirred for 5 min; 2 mmol of NaCl and 7 mmol of NH4F were added and stirred for 20 min to obtain a white liquid; the white liquid was slowly transferred to a 50 mL hydrothermal autoclave; then the hydrothermal autoclave was placed in an electric forced air oven and heated at 180°C for 17 h; after the hydrothermal autoclave was naturally cooled to room temperature, the product was collected by centrifugation, mixed with ethanol and deionized water in a volume ratio of 1:1 and washed three times at 4000 rpm for 15 min each; and then dried at 60°C for 12 h.

[0051] (3) Synthesis of TiO2 / NaYF4:Yb,Er

[0052] 0.3 g of the urchin-like TiO2 powder synthesized in step (1) was dispersed in 200 mL of acetone and ultrasonically vibrated for 15 minutes. Then, the NaYF4:Yb,Er synthesized in step (2) was added. The suspension was then stirred in a 50°C water bath for 2 hours and finally centrifuged and dried to obtain a TiO2 / NaYF4:Yb,Er composite material.

[0053] In this embodiment, NaYF4:Yb,Er is added according to the mass ratio of TiO2 to NaYF4:Yb,Er of 1:0.3, 1:0.4, 1:0.5 and 1:0.6.

[0054] (4) Preparation of photoanode

[0055] 0.3 g of P25 titanium dioxide powder, the urchin-like TiO2 synthesized in this example, and the TiO2 / NaYF4:Yb,Er composite material were mixed with a solution containing 6 g of ethanol, 1 g of terpineol, and 0.5 g of ethyl cellulose, respectively, and stirred for 24 h to form a viscous slurry; the above slurry was scraped onto a clean FTO with a blade, dried at 125°C for 15 min, and this process was repeated three times using the same slurry to obtain a photoanode; calcined at 450°C for 30 min; the photoanode was immersed in a dye (0.4 mmol N719 ethanol solution) for 24 h to fully sensitize it; then the photoanode was removed from the N719 solution and briefly rinsed with anhydrous ethanol to remove the unadsorbed dye to obtain a photoanode.

[0056] FIG1 is a microscopic morphology of the sample prepared in step (1) and step (3) of Example 1 of the present invention; wherein, Figure 1aThis is a transmission electron microscope image of the TiO2 / NaYF4:Yb,Er composite material prepared with a mass ratio of TiO2 and NaYF4:Yb,Er of 1:0.5. Figure 1c The transmission electron microscope image of the sea urchin-shaped TiO2 is shown in Figure 1. It can be seen from the figure that the composite material maintains the sea urchin shape of TiO2, and its size and the length (400nm) and diameter (20nm) of the spines remain basically unchanged; however, there are some black particles near the tip of the TiO2 spines, whose size is close to that of the rare earth material. Figure 1a The black particles in the thorn tip of the TiO2 in the sea urchin composite material in the white dotted frame area were further photographed with high-resolution transmission electron microscopy to obtain lattice fringe images of the two areas. Figure 1b As can be seen from the figure, the measured lattice spacing of the TiO2 spine region is 0.184nm, which matches the spacing of the (200) crystal plane of anatase TiO2. The lattice spacing of the black particles at the tips of the TiO2 spines is 0.174nm, which matches the spacing of the (002) crystal plane of NaYF4:Yb,Er. This proves that the black particles at the tips of the TiO2 spines in the composite material are NaYF4:Yb,Er. Therefore, this example successfully prepared a sea urchin-like TiO2 / NaYF4:Yb,Er composite material with a hierarchical structure.

[0057] Figure 2The XRD patterns of the sea urchin-shaped TiO2 (TiO2), NaYF4:Yb,Er, and the TiO2 / NaYF4:Yb,Er composite material prepared in this example with a mass ratio of TiO2 to NaYF4:Yb,Er of 1:0.5 are shown. As can be seen from the figure, the TiO2 at 25.28, 37.80, 48.05, 53.89, 55.06, 62.69, 68.76, 70.31, and 75.03 degrees correspond to the (101), (004), (200), (105), (211), (204), (116), (220), and (215) crystal planes of anatase TiO2 (JCPDS card No. 21-1272), respectively. This indicates that anatase TiO2 was prepared in this example. NaYF4:Yb,Er at 30.1, 30.8, 43.5, and 53.8 degrees correspond to the (110), (101), (201), and (211) crystal planes of hexagonal NaYF4:Yb,Er (JCPDS card 28-1192), respectively, proving that hexagonal NaYF4:Yb,Er was prepared in this example. In the TiO2 / NaYF4:Yb,Er composite materials, the blue diamond symbols represent the peak positions of TiO2, and the red dots represent the peak positions of NaYF4:Yb,Er. The 2q peaks at 25.28, 37.80, 48.05, 53.89, 55.06, 62.69, 68.76, 70.31 and 75.03 degrees correspond to the (101), (004), (200), (105), (211), (204), (116), (220) and (215) planes of anatase TiO2 (JCPDS card No. 21-1272), respectively; the 2q peaks at 30.1, 30.8, 43.5 and 53.8 degrees correspond to the hexagonal NaYF4:Yb,Er (JCPDS card No. 28-1192) of the (110), (101), (201), and (211) crystal planes. Therefore, the TiO2 / NaYF4:Yb,Er composite material synthesized in this example has both TiO2 peaks and NaYF4:Yb,Er peaks without other impurity peaks, indicating that the TiO2 / NaYF4:Yb,Er composite material was successfully prepared without affecting the crystal phase of the material itself.

[0058] Figures 3a to 3c They are the nitrogen analysis diagrams of P25 TiO2, the sea urchin-like TiO2 (TiO2) synthesized in this example, and the TiO2 / NaYF4:Yb,Er composite material prepared according to the mass ratio of TiO2 to NaYF4:Yb,Er of 1:0.5. According to the experimental results, the specific surface areas of P25, sea urchin-like TiO2, and TiO2 / NaYF4:Yb,Er composite material are calculated to be 42.6m 2 / g, 122.8m 2 / g and 115m 2 / g, it can be seen that the specific surface areas of the sea urchin-shaped TiO2 and TiO2 / NaYF4:Yb,Er composite materials are significantly higher than those of P25, indicating that the TiO2 and TiO2 / NaYF4:Yb,Er composite materials prepared in this example have a hierarchical structure with a large specific surface area.

[0059] Figure 4 The UV-visible-near infrared absorption spectra of the sea urchin-shaped TiO2 (TiO2), NaYF4: Yb, Er and the TiO2 / NaYF4: Yb, Er composite material prepared according to the mass ratio of TiO2 to NaYF4: Yb, Er of 1:0.5 are shown in the figure. As can be seen from the figure, the absorption peak of the sea urchin-shaped TiO2 is around 315nm, and there is no absorption at 450nm-1050nm; NaYF4: Yb, Er has four absorption peaks at 489, 521, 654 and 975nm at 450nm-1050nm, and the first three peaks are respectively 3+ Ionic 4 F 7 / 2 - 4 I 15 / 2 、 2 H 11 / 2 - 4 I 15 / 2 、 4 F 9 / 2 - 4 I 15 / 2 The absorption peak at 975nm is related to the Yb 3+ of 2 F 5 / 2 - 2 F 7 / 2 The absorption spectrum of the TiO2 / NaYF4:Yb,Er composite material has a strong absorption peak around 315nm (corresponding to TiO2) and an absorption peak around 975nm corresponding to NaYF4:Yb,Er,Yb.

[0060] Figure 5 and Figure 6 The fluorescence spectra of NaYF4:Yb,Er synthesized in this example and the TiO2 / NaYF4:Yb,Er composite material prepared according to the mass ratio of TiO2 to NaYF4:Yb,Er of 1:0.5 and the luminescence mechanism diagram of NaYF4:Yb,Er are shown respectively. Figure 5 It can be seen that NaYF4:Yb,Er has fluorescence at 521, 543 and 657nm, which are derived from rare earth Er respectively. 3+ ion2 H 11 / 2 → 4 I 15 / 2 、 4 S 3 / 2 → 4 I 15 / 2 and 4 F 9 / 2 → 4 I 15 / 2 The energy level transition is as follows: Figure 6 Shown: Yb in NaYF4:Yb,Er under near-infrared excitation 3+ exist 2 F 5 / 2 The electron on the energy level absorbs a 980nm photon and then jumps to 2 F 7 / 2 Excited state, transfers energy to the nearby Er 3+ And return to the ground state, making Er 3+ Electrons from the ground state 4 I 15 / 2 Energy level transition to 4 I 11 / 2 energy level, and then receives the energy of the second photon, and 4 I 11 / 2 Energy level transition to 4 F 7 / 2 The lifetime of electrons in this energy level is very short, so they fall back to 2 H 11 / 2 and 4 S 3 / 2 These two energy levels, from this energy level to the ground state 4 I 15 / 2 Energy level, radiating green light of 521nm and 543nm wavelength respectively, releasing energy; for red light of 659nm, it is Er 3+ The electrons from 2 F 9 / 2 Energy level transition to the ground state 4 I 15 / 2 There are two ways to generate energy levels: one is to occupy 4 S 3 / 2 Some electrons in the energy level jump rapidly to 4 F 9 / 2 Energy level, another way is Er 3+ First absorb a photon and transition from the ground state to 4 I 11 / 2 Energy level, and Er 3+ The electrons in 4 I 11 / 2 The energy level lifetime is short, so some electrons fall back to 4 I13 / 2 Energy level, at this energy level 3+ Then absorb a Yb 3+ The transferred photon energy jumps to 2 F 9 / 2 energy level, 2 F 9 / 2 The energy level has a long lifetime and returns to the ground state through transition 4 I 15 / 2 When irradiated, a red light of 659nm is emitted, releasing energy. The fluorescence peak position of TiO2 / NaYF4:Yb,Er is the same as that of NaYF4:Yb,Er, which proves that the TiO2 / NaYF4:Yb,Er composite material is successfully prepared in this embodiment, and the composite of TiO2 and NaYF4:Yb,Er does not affect the fluorescence peak position of NaYF4:Yb,Er. Compared with NaYF4:Yb,Er, the fluorescence intensity of TiO2 / NaYF4:Yb,Er decreases slightly. The possible reason is that TiO2 reflects and scatters the emitted light of NaYF4:Yb,Er. However, the fluorescence of the TiO2 / NaYF4:Yb,Er composite photoanode material is still very strong, and the main fluorescence band is visible light of 510nm-560nm, which matches the visible light absorption band of N719 dye (peak at 530nm). Therefore, it can be used to convert near-infrared light into visible light to enhance the absorption of visible light by N719 dye.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a TiO2 / NaYF4:Yb,Er composite material, characterized in that: The following steps are involved: (1) dispersing titanium dioxide in a sodium hydroxide solution, adding a hydrogen peroxide solution and performing a hydrothermal reaction; Sea urchin-like TiO2 was obtained by sintering; (2) hydrothermally reacting polyvinylpyrrolidone, a Y source, a Yb source, an Er source, and a F source in an alcohol aqueous solution containing NaCl to prepare NaYF4:Yb,Er; (3) stirring the sea urchin-shaped TiO2 and NaYF4:Yb,Er in a solvent to obtain the TiO2 / NaYF4:Yb,Er composite material; Among them, steps (1) and (2) are performed in no particular order.

2. The preparation method according to claim 1, characterized in that In step (1), the titanium dioxide is P25 titanium dioxide powder; and / or, the concentration of the sodium hydroxide solution is 9 to 11 mol / L; and / or, the concentration of the hydrogen peroxide solution is 25% to 35%; And / or, the molar ratio of sodium hydroxide to hydrogen peroxide is 13-18:

1.

3. The preparation method according to claim 1, characterized in that In step (1), the temperature of the hydrothermal reaction is 145 to 155° C.; and the time of the hydrothermal reaction is 85 to 95 minutes.

4. The preparation method according to claim 1, characterized in that In step (1), the sintering temperature is 450-480° C.; the sintering time is 2-2.5 hours; and the sintering heating rate is 8-12° C. / min.

5. The preparation method according to claim 1, characterized in that In step (2), the Y source is a soluble Y salt; the Yb source is a soluble Yb salt; the Er source is a soluble Er salt; and the F source is a soluble F salt. and / or, the molar ratio of Y in the Y source, Yb in the Yb source, Er in the Er source, F in the F source, and NaCl is 0.07-0.08:0.1-0.3:0.01-0.03:6-8:1.5-2.5; and / or, the molar ratio of polyvinyl pyrrolidone to NaCl is 2 to 4:1; and / or, the alcohol aqueous solution is an ethanol aqueous solution; And / or, the polyvinyl pyrrolidone is dispersed in an alcohol aqueous solution, and after adding a Y source, a Yb source and an Er source and stirring, NaCl and a F source are added.

6. The preparation method according to claim 1, characterized in that In step (2), the temperature of the hydrothermal reaction is 175 to 185° C.; and the time of the hydrothermal reaction is 16 to 18 hours.

7. The preparation method according to claim 1, characterized in that In step (3), the mass ratio of TiO2 to NaYF4:Yb,Er is 1:0.3-0.6; And / or, the stirring temperature is 45-55°C; And / or, the stirring treatment time is 1.5 to 2.5 hours; And / or, the solvent is acetone.

8. The TiO2 / NaYF4:Yb,Er composite material obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the TiO2 / NaYF4:Yb,Er composite material according to claim 8 in the preparation of dye-sensitized solar cells.

10. The use according to claim 9, characterized in that Application in the preparation of dye-sensitized solar cell photoanode.

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