CN104952963A - A preparation method of TiO2-ZnO heterojunction nanorods for perovskite solar cells - Google Patents

Abstract

The invention relates to the preparation of a TiO ₂ -ZnO nanorod composite material and its application in perovskite solar cells. In this method, a glass substrate coated with FTO (SnO ₂ :F) coated with a dense layer of TiO ₂ is used as a substrate, a ZnO nanorod array is grown by a hydrothermal method, and a perovskite solar cell is prepared by a two-step method. The process of the method is simple, and the prepared TiO ₂ -ZnO nanorod array is applied to a perovskite solar cell, and its short-circuit current reaches 23.57mA/cm ² .

Description

A preparation method of TiO2-ZnO heterojunction nanorods for perovskite solar cells

technical field

The invention relates to the preparation of a TiO ₂ -ZnO heterojunction nanorod composite material and its application in perovskite solar cells.

Background technique

With the rapid growth of the world economy and the further acceleration of the industrialization process, the demand for energy in modern society has increased dramatically. The research on solar cells is changing with each passing day. The earliest developed crystalline silicon solar cells are limited due to their high cost. Due to the low production cost of dye-sensitized solar cells, people gradually began to study dye-sensitized solar cells, but liquid dye-sensitized solar cells Due to the disadvantages of easy leakage of electrolyte, difficulty in encapsulation, and short circuit, the application of batteries has also been limited. Then researchers gradually shifted their attention to solid-state sensitized solar cells. From the end of 2012, perovskite solar cells have The new breakthrough has attracted great attention of researchers, and its efficiency has gradually increased to 19.3%. However, the existence of defects in this type of cell and the recombination of electrons and holes make the short-circuit current significantly lower than that of silicon-based solar cells.

At present, perovskite solar cells mainly use _TiO2 as the photoanode to prepare planar or mesoporous perovskite solar cells. Some researchers also use ZnO particles or zinc oxide nanorods as mesoporous layers to prepare perovskite solar cells. In 2013, Dianyi Liu et al. prepared a layer of ZnO thin film on ITO (In ₂ O ₃ :Sn) as a photoanode to prepare a perovskite solar cell by spin coating method, and its short-circuit current reached 20.4 mA/cm ² . In 2014, Dae-Yong Son et al. used zinc oxide nanorods to prepare perovskite solar cells, and the short-circuit current reached 20.92 mA/cm ² . The short-circuit current of a solar cell has a lot to do with the structure of each interface in the cell. Therefore, reducing electron-hole recombination and improving short-circuit current are crucial to the performance of the device.

The present invention uses a hydrothermal method to prepare TiO ₂ -ZnO nanorod composite material, which is applied to perovskite solar cells. Using this composite structure, the recombination of electrons and holes is reduced, thereby improving the short circuit of perovskite solar cells. Current, the short-circuit current reached 23.6 mA/cm ² .

Invention content

The object of the present invention is to provide a method for preparing TiO ₂ -ZnO heterojunction nanorods used in perovskite solar cells.

A method for preparing TiO ₂ -ZnO heterojunction nanorods for perovskite solar cells, characterized in that the specific steps of the method are:

a. Put the glass substrate coated with FTO (SnO ₂ :F) in water, acetone, ethanol, and isopropanol for 30 minutes, then wash it in ethanol, and dry it with nitrogen gas for later use.

b. Dissolve 35 μL of hydrochloric acid solution (2 M) in 2.53 mL of ethanol to form a hydrochloric acid alcohol solution, then add 2.53 mL of ethanol into a clean glass bottle, add the rotor and stir on the stirrer, and quickly add 369 μL of tetraisocyanate Titanium propoxide, then added dropwise to the prepared hydrochloric acid alcohol solution to obtain a colorless and clear solution.

c. Spin-coat the solution prepared in step b onto the clean glass substrate coated with FTO (SnO ₂ :F) obtained in step a, and dry it in an oven, and then coat it with FTO (SnO 2 :F) ₂ : The glass substrate in F) was annealed in a tube furnace at 500 °C for 30 min. After the temperature of the tube furnace dropped to room temperature, the sample was taken out to obtain a dense layer of TiO ₂ .

d. Dissolve equimolar zinc nitrate hexahydrate and hexamethylenetetramine in deionized water at a concentration of 35 mM, and put the glass substrate coated with FTO (SnO ₂ :F) with a dense layer in step c Substrates were immersed in the precursor solution, face down, heated at 90 ℃ for 180 min. Finally, the glass substrate coated with FTO (SnO ₂ :F) was taken out, and the grown ZnO nanorods were rinsed with deionized water and ethanol. times and blow dry with a hair dryer.

e. Put the ZnO nanorods obtained in step d in a tube furnace at 450 °C for 30 min and anneal for 30 minutes. After the temperature of the tube furnace drops to room temperature, take out the sample, and finally obtain TiO ₂ -ZnO nanorods.

The characteristics and advantages of the inventive method are as follows:

The invention adopts the hydrothermal method to prepare the TiO ₂ -ZnO nanorod array, the top size of the ZnO nanorod array is reduced, and the porosity is larger. Compared with ZnO nanorod arrays prepared by the traditional hydrothermal method using ZnO as seed crystals, TiO ₂ -ZnO nanorod arrays were applied in CH3NH3PbI3 perovskite solar cells, and the short-circuit current was significantly improved, reaching 23.6 mA/cm ² .

Description of drawings

The left image in Figure 1 is the front scanning electron microscope image of the TiO ₂ -ZnO nanorod array; the right image is the side scanning electron microscope image of the TiO ₂ -ZnO nanorod array.

Fig. 2 is the X-ray diffraction pattern of the TiO ₂ -ZnO nanorod array.

Fig. 3 is the IV curve of the perovskite solar cell prepared by the TiO ₂ -ZnO nanorod array.

Open circuit voltage: the output voltage value of the solar cell when the solar cell is placed under the light source of 100 mW/cm ² and the two ends are open.

Short-circuit current: It is the current flowing through both ends of the solar cell when the output end is short-circuited when the solar cell is placed under the irradiation of a standard light source.

Fill factor: Another important parameter of a solar cell is the fill factor FF, which is the ratio of the maximum output power to the product of the open circuit voltage and the short circuit current. FF is an important index to measure the output characteristics of solar cells. It represents the characteristics of the maximum power that the solar cells can output when they are under the optimal load. The larger the value, the greater the output power of the solar cells. The value of FF is always less than l. In fact, due to the influence of series resistance and parallel resistance, the value of the actual solar cell fill factor is lower than the ideal value given by the above formula. Series and parallel resistors have a great influence on the fill factor. The larger the series resistance, the more the short-circuit current drops, and the more the fill factor decreases; the smaller the parallel resistance, the greater the current, the more the open circuit voltage drops, and the more the fill factor decreases. .

Photoelectric conversion efficiency: The conversion efficiency of a solar cell refers to the maximum energy conversion efficiency when an optimal load resistor is connected to the external circuit, which is equal to the ratio of the output power of the solar cell to the energy incident on the surface of the solar cell. The photoelectric conversion efficiency of a solar cell is an important parameter to measure the quality and technical level of the cell. It is related to the structure, junction characteristics, material properties, operating temperature, radiation damage of radioactive particles, and environmental changes of the cell.

Detailed ways

Specific embodiments of the present invention are now described in the following.

Example 1

Concrete preparation steps of the present invention are as follows:

(1) The glass substrate coated with FTO (SnO ₂ :F) was placed in water, acetone, ethanol, and isopropanol for 30 min, respectively, and then rinsed in ethanol and dried with nitrogen for later use.

(2) Dissolve 35 μL of hydrochloric acid solution (2 M) in 2.53 mL of ethanol to make hydrochloric acid alcohol solution, then add 2.53 mL of ethanol into a clean glass bottle, add the rotor and stir on the stirrer, and quickly add 369 μL of four Titanium isopropoxide was then added dropwise to the prepared alcoholic hydrochloric acid solution to obtain a colorless and clear solution. the

(3) Spin-coat the solution prepared in step b onto the clean glass substrate coated with FTO (SnO ₂ :F) obtained in step a, and dry in an oven, and then coat the glass substrate coated with FTO (SnO 2 :F) The glass substrate of SnO ₂ :F) was annealed in a tube furnace at 500 °C for 30 min. After the temperature of the tube furnace dropped to room temperature, the sample was taken out to obtain a dense layer of TiO ₂ .

(4) Dissolve equimolar zinc nitrate hexahydrate and hexamethylenetetramine in deionized water at a concentration of 35 mM, and put the glass coated with FTO (SnO ₂ :F) with a dense layer in step c The substrate was immersed in the precursor solution, face down, and heated at 90 °C for 180 min. Finally, the glass substrate coated with FTO (SnO ₂ :F) was taken out, and the grown ZnO nanorods were rinsed with deionized water and ethanol. Several times, and blow dry with a hair dryer.

(5) Put the ZnO nanorods obtained in step d in a tube furnace for annealing at 450 °C for 30 min. After the temperature of the tube furnace dropped to room temperature, take out the sample, and finally obtain TiO ₂ -ZnO nanorods.

The samples prepared in the above examples were characterized and tested for photoelectric conversion performance through instrumental detection, and the results are as follows:

1. It can be seen from Figure 1 that the TiO ₂ -ZnO nanorod array is hydrothermally heated for 180 min, and the nanorod length can reach about 500 nm.

2. It can be seen from Figure 2 that TiO ₂ -ZnO nanorods and nanorods are all typical hexagonal wurtzite structures, and the diffraction peaks appear at 2θ=31.75°, 34.39°, 36.24°, 47.54°, 62.86° respectively corresponding to ZnO The (100), (002), (101), (102), (103) crystal planes of the wurtzite structure are consistent with the standard value of bulk ZnO (JCPDS card 36-1451).

Asterisks represent the diffraction peaks of glass substrates coated with FTO (SnO ₂ :F).

3. As shown in Figure 3, the perovskite solar cells assembled with ZnO nanorod arrays prepared with TiO ₂ as seed crystals have a short-circuit current as high as 23.57 mA/cm ² . But its open-circuit voltage is not ideal, only reached about 0.6V, there is still a lot of room for improvement, and further optimization is needed.

Claims (1)

1. one kind for perovskite solar cell TiO ₂the preparation method of-ZnO heterojunction nanometer rods, is characterised in that to have following preparation process and step:

A kind of TiO for perovskite solar cell ₂the preparation method of-ZnO heterojunction nanometer rods, is characterised in that the concrete steps of the method are:

A. FTO(SnO will be coated with ₂: F) glass baseplate be put in each ultrasonic 30 min in water, acetone, ethanol, isopropyl alcohol successively, be then put in ethanol and rinse, and dry up with nitrogen for subsequent use;

B. get 35 μ L hydrochloric acid solutions (2 M) to be dissolved in 2.53 mL ethanol and to be made into hydrochloric acid alcoholic solution, 2.53 mL ethanol are added again in clean vial, add rotor to be placed on blender and to stir, and add 369 μ L titanium tetraisopropylates fast, and then dropwise add the hydrochloric acid alcoholic solution prepared, obtain the solution of achromaticity and clarification;

C. the solution that step b prepares, be spun to the clean of step a gained and be coated with FTO(SnO ₂: F) glass baseplate on, and to dry in an oven, then being coated with FTO(SnO ₂: F) glass baseplate to be put in tube furnace 500 DEG C of annealing 30 min, be down to after room temperature until tube furnace temperature and take out sample, obtain TiO ₂compacted zone;

D. get equimolar zinc nitrate hexahydrate and hexa is dissolved in deionized water, concentration is 35 mM, is coated with FTO(SnO what complete compacted zone in step c ₂: F) glass baseplate be dipped in this precursor liquid, face down, 90 DEG C of hydro-thermal 180 min. finally take out and are coated with FTO(SnO ₂: F) glass baseplate, the ZnO nanorod grown with deionized water and alcohol flushing for several times, and dries up with hair-dryer;

E. the ZnO nanorod obtained in steps d to be put in tube furnace 450 DEG C of annealing 30 min. to be down to after room temperature until tube furnace temperature and to take out sample, finally to obtain TiO ₂-ZnO nanorod.