CN109004048A - A kind of preparation method of the inorganic perovskite quantum dot film of caesium lead bromine and photovoltaic device based on it - Google Patents

Abstract

The invention discloses a preparation method of a cesium lead bromine inorganic perovskite quantum dot film and a photovoltaic device based on it, which is to synthesize _CsPbBr3 inorganic perovskite quantum dots through a high-temperature heat injection method, and wash and centrifuge through methyl acetate After purification, it is dispersed in n-octane solution, and then through multiple times of spin coating and high temperature annealing, the quantum dots are formed into a thin film, which is used as the light absorption layer of the photovoltaic device. The thickness of the _CsPbBr3 thin film prepared by the method of the present invention can be precisely controlled, thereby obtaining optimal light absorption capacity and improving the photoelectric conversion efficiency of solar cells; the preparation process of the present invention is simple, does not require inert atmosphere protection, and does not require expensive equipment and equipment, and is especially suitable for the preparation of Large-volume, low-cost solar cells are conducive to promoting the development and application of inorganic perovskite solar cells.

Description

A kind of preparation method of cesium lead bromine inorganic perovskite quantum dot thin film and photonics based on it Volt devices

technical field

The invention relates to the application of cesium-lead-bromine inorganic perovskite quantum dots to prepare photovoltaic devices, and belongs to the field of preparation technology of thin-film solar cell photovoltaic devices.

Background technique

Perovskite cell is a new type of solar cell with perovskite thin film material as the light absorption layer, generally expressed as AMX ₃ , where A represents a cation, commonly methylamine (MA), methylamine (FA) and cesium (Cs) Wait. In recent years, organic-inorganic hybrid perovskite solar cells have attracted widespread attention in the photovoltaic industry due to their excellent photoelectric properties, but they face a serious problem, namely poor thermal stability and easy decomposition at high temperatures. This makes it difficult for organic-inorganic hybrid perovskite solar cells to be applied in practical production.

The poor thermal stability of organic-inorganic hybrid perovskite solar cells is mainly caused by organic groups that are easily decomposed by heat and easy to absorb moisture in the air. Therefore, replacing organic groups with more stable inorganic ions Cs is expected to solve the problem of calcium The stability problem of titanium battery.

In recent years, a new type of inorganic cesium-lead-bromide perovskite material (CsPbBr ₃ ) has attracted extensive attention of researchers due to its excellent photoelectric performance, good thermal stability, and water-oxygen stability. However, due to the low solubility of bromine-containing precursor materials in common solvents (such as dimethyl sulfoxide, N,N-dimethylformamide), it is difficult to prepare dense films by the traditional one-step solution method, and due to The low concentration of the precursor leads to a thin film of the light absorbing layer after spin coating, which is not conducive to the full absorption of sunlight, and the film has various defects. In addition, organic small molecule materials such as spiro-OMeTAD or P3HT are usually used in the preparation of perovskite solar cells as hole transport materials. Such materials are not only expensive, but also sensitive to moisture in the air due to their poor thermal stability due to their organic materials.

Therefore, the development of low-cost preparation techniques for high-quality _CsPbBr3 thin films is of great significance for obtaining efficient and stable inorganic perovskite solar cells. Compared with physical vapor deposition preparation processes such as vacuum evaporation with expensive equipment and complicated process, the preparation of CsPbBr ₃ thin films by solution method has the advantages of low cost, simple equipment, fast film formation rate, and the film thickness and morphology can be controlled at the molecular scale. Therefore, it is particularly important to develop a low-cost, simple process, and good stability all-air solution preparation technology for CsPbBr ₃ thin film materials.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a preparation method of cesium lead bromine inorganic perovskite quantum dot film and a photovoltaic device based on it.

The present invention adopts following technical scheme for realizing the purpose of the invention:

The invention first discloses a method for preparing a cesium lead bromine inorganic perovskite quantum dot film, which is characterized in that it comprises the following steps:

Step 1, Synthesis of _CsPbBr3 Inorganic Perovskite Quantum Dots

(1) Synthesis of cesium oleate precursor

Add 0.5g of cesium carbonate, 2mL of oleic acid and 50mL of 1-octadecene into a three-necked flask, vacuumize and ventilate nitrogen for 3 times to remove water and oxygen, then raise the temperature to 120°C and stir for 20-40 minutes to obtain cesium oleic acid Salt precursor solution, stored in nitrogen, kept at 70°C, for later use;

(2) Synthesis of CsPbBr ₃ quantum dots

Add 0.7g of lead bromide and 50mL of 1-octadecene to another three-necked flask, stir at a constant temperature of 120°C for one hour, then add 5mL of oleic acid and 5mL of oleyl ammonium, and continue to stir until the lead bromide is completely dissolved; then raise the temperature to At 170°C, inject 8mL of the cesium oleate precursor solution synthesized in step (1), wait for 5 seconds and then cool to room temperature in an ice bath to obtain the mother solution of CsPbBr ₃ quantum dots;

(3) Purification of CsPbBr ₃ quantum dots

Methyl acetate is mixed with the mother liquor of _CsPbBr3 quantum dots obtained in step (2) in a volume ratio of 2:1, centrifuged at 8000rpm for 5min, and the precipitate is dispersed in 5mL n-octane to obtain _CsPbBr3 quantum dots solution;

Step 2, preparation of _CsPbBr3 inorganic perovskite quantum dot film

Spin-coating and annealing: Take 45 μL of the _CsPbBr3 quantum dot solution synthesized in step (1) and spin-coat it on a clean substrate at a spin-coating speed of 2000 rpm for 40 s, and then place it on a heated substrate at 250 ° C for 5 min for annealing. Remove and cool to room temperature;

The steps of spin coating and annealing are performed multiple times to obtain a CsPbBr ₃ inorganic perovskite quantum dot film with a desired thickness. The "spin-coating and annealing" step is performed once, and the thickness of the film is 40-60nm.

In specific implementation, the amount of each of the above materials can be scaled up in equal proportions.

Preferably, the number of spin-coating and annealing steps in step 2 is 3-5 times, and the thickness of the obtained film at this time is optimal when used as a photovoltaic device.

The present invention also discloses a photovoltaic device based on CsPbBr ₃ inorganic perovskite quantum dot thin film, as shown in Figure 1, it is sequentially deposited on the surface of FTO conductive glass with a dense layer TiO ₂ as an electron transport layer, as a light absorption layer The CsPbBr ₃ inorganic perovskite quantum dot film, and the C electrode as the positive and negative electrodes. Its preparation steps are as follows:

(1) In order to prevent the short circuit of the battery caused by the pinching of the film when testing the battery, the surface of the FTO conductive glass is partially etched, specifically: the surface of the FTO conductive glass is divided into a deposition area and a non-deposition area, and the local uniformity in the deposition area Spread zinc powder on the surface, then drop 2M HCl on the zinc powder and etch for 5 minutes;

Clean and dry the etched FTO conductive glass (clean the etched FTO conductive glass sequentially with soapy water, acetone, and ethanol for 20 minutes, then blow dry with _N2 , and then use a UV-ozone cleaning machine to clean for 20 minutes) , get clean FTO conductive glass.

( ₂ ) Deposit dense layer TiO in the deposition area of FTO conductive glass surface as electron transport layer;

( ₃ ) form CsPbBr3 inorganic perovskite quantum dot film on described electron transport layer with above-mentioned preparation method, as light absorbing layer;

(4) Scrape-coat C electrode on the non-deposited area of the FTO conductive glass surface as a negative electrode, and scrape-coat C electrode on the light-absorbing layer as a positive electrode. After scraping, put the battery on a heating platform at 150°C After heating for 30 minutes, a photovoltaic device based on the CsPbBr ₃ inorganic perovskite quantum dot thin film is obtained.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. Compared with the commonly used organic-inorganic hybrid perovskite solar cells, the present invention can effectively avoid the cumbersome glove box operation and expensive vacuum evaporation equipment investment in the preparation of current perovskite solar cells, and achieve high-quality, The low-cost preparation of stable perovskite light-absorbing layer films is especially suitable for the preparation of large-volume, low-cost solar cells, which is conducive to promoting the development and application of inorganic perovskite solar cells.

2. Compared with the CsPbBr ₃ film prepared by the traditional one-step solution method, the film prepared by using CsPbBr ₃ perovskite quantum dots is denser, and the thickness of the film can be controlled by multiple spin coating methods during preparation, thereby obtaining the optimal The light absorption ability improves the photoelectric conversion efficiency of solar cells, and solves the problem that the film thickness of solar cell devices cannot be precisely controlled.

3. Use carbon electrodes to replace noble metal electrodes such as gold or silver used in the traditional preparation of perovskite solar cells: First, carbon electrodes have the ability to collect holes, avoiding the use of small organic molecule materials such as spiro-OMeTAD or P3HT, thereby avoiding Influence of Instability of Organic Hole Transport Layers on Cell Efficiency. Second, the price of carbon electrodes is lower than that of gold, silver, platinum and other precious metals, and the content of carbon in nature far exceeds these precious metals, which avoids waste of resources and reduces costs. Third, the process of carbon electrodes is relatively simple, which is conducive to industrial actual production.

Description of drawings

Fig. 1 is the structural representation of the perovskite solar cell based on _CsPbBr3 inorganic perovskite quantum dot film;

Fig. 2 is the transmission electron microscope (TEM) photo of the CsPbBr made in embodiment ₁₃ quantum dots;

Fig. 3 is the surface scanning electron micrograph (SEM) of the CsPbBr made in embodiment ₁ thin film;

Fig. 4 is the cross-sectional scanning electron micrograph (SEM) of the _CsPbBr film obtained in embodiment 1;

Fig. 5 is the current density-voltage (JV) characteristic curve of the perovskite solar cell based on _CsPbBr thin film in embodiment 1;

Fig. 6 is the cross-section scanning electron micrograph (SEM) of the _CsPbBr film obtained in embodiment 2;

Fig. 7 is the current density-voltage (JV) characteristic curve of the perovskite solar cell based on _CsPbBr thin film in embodiment 2;

Fig. 8 is the cross-section scanning electron micrograph (SEM) of the CsPbBr film obtained in embodiment ₃ ;

9 is the current density-voltage (JV) characteristic curve of the perovskite solar cell based on the CsPbBr ₃ thin film in Example 3.

Detailed ways

In order to make the above objects, features and advantages of the present invention more obvious and comprehensible, specific implementations of the present invention will be described in detail below in conjunction with examples. The following content is only an example and description of the concept of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the concept of the invention Or beyond the scope defined in the claims, all should belong to the protection scope of the present invention.

Example 1

The present embodiment prepares CsPbBr ₃ inorganic perovskite quantum dot films and solar cells based on them as follows:

Step 1, Synthesis of _CsPbBr3 Inorganic Perovskite Quantum Dots

(11) Synthesis of cesium oleate precursor

Add 0.5g of cesium carbonate, 2mL of oleic acid and 50mL of 1-octadecene into a three-necked flask, vacuumize and ventilate nitrogen for 3 times to remove water and oxygen, then raise the temperature to 120°C and stir for 30 minutes to obtain the precursor of cesium oleate Bulk solution, stored in nitrogen, kept at 70°C, for later use;

(12) Synthesis of CsPbBr ₃ quantum dots

Add 0.7g of lead bromide and 50mL of 1-octadecene to another three-necked flask, stir at a constant temperature of 120°C for one hour, then add 5mL of oleic acid and 5mL of oleyl ammonium, and continue to stir until the lead bromide is completely dissolved; then raise the temperature to At 170°C, quickly inject 8mL of cesium oleate precursor solution synthesized in step (11), wait for 5 seconds and immediately cool to room temperature in an ice bath to obtain the mother solution of CsPbBr ₃ quantum dots;

(13) Purification of _CsPbBr3 quantum dots

Methyl acetate is mixed with the mother liquor of the _CsPbBr3 quantum dots obtained in step (12) in a volume ratio of 2:1, centrifuged at 8000rpm for 5min, and the precipitate is dispersed in 5mL n-octane to obtain the _CsPbBr3 quantum dot solution; Fig. 2 It is a transmission electron microscope (TEM) photo of the CsPbBr ₃ quantum dots prepared in this example, and the size of the quantum dots is 9nm.

2. Preparation of CsPbBr ₃ inorganic perovskite quantum dot solar cells:

(21) Cut the FTO conductive glass into a small piece of 20mm×15mm, and divide it into two parts with a width of 15mm and a width of 5mm, which are respectively used as the deposition area and the non-deposition area. Then the 5 mm width of the deposition area away from the non-deposition area was used as an etching area. Stick the tape on the part of the non-etched area, and leak out the etched area. Spread zinc powder evenly on the etching area, drop 2M HCl solution on the laid zinc powder, and etch for 5 minutes. The etched FTO conductive glass was ultrasonically cleaned with soapy water, acetone, and ethanol for 20 minutes, then dried with _N2 , and then cleaned with a UV-ozone cleaner for 20 minutes to obtain a clean FTO conductive glass.

(22) Deposit dense layer _TiO in the FTO conductive glass surface deposition area as the electron transport layer: first get 1g 75% bis(acetylacetonate) diisopropyl titanate isopropanol solution (wt %) and add to 10.3g Form a 0.15mol/L TiO ₂ precursor solution in n-butanol, take 2-3 drops of the above solution and add it dropwise to the non-etching area on the surface of the clean FTO conductive glass, spin-coat at 2000rpm for 40s, remove the substrate, and dry at 135°C for 10min , and then sintered at 500°C for 30min; after sintering, the substrate was treated with 40mmol/L TiCl ₄ aqueous solution at 70°C for 30min, and then sintered at 500°C for 30min to obtain a dense layer of TiO ₂ .

(23) Spin coating and annealing: Take 45 μL of the CsPbBr ₃ quantum dot solution synthesized in step (1) and spin coat it on the dense layer TiO ₂ at a spin coating speed of 2000 rpm and a spin coating time of 40 s, then place it on a heated substrate at 250 °C Anneal for 5 minutes, remove and cool to room temperature;

The above steps of spin coating and annealing were performed 5 times to obtain a CsPbBr ₃ inorganic perovskite quantum dot film.

Fig. 3 is a scanning electron microscope photograph of the surface of the CsPbBr ₃ film prepared in this example. It can be seen that the film obtained in this example is uniform and dense, and the grain size is relatively large. Fig. 4 is a cross-sectional scanning electron microscope photograph of the CsPbBr ₃ thin film prepared in this example. It can be seen that after 5 times of spin coating, the thickness of the film obtained in this example is about 280nm.

(4) Take the FTO conductive glass that has been coated with CsPbBr ₃ light-absorbing layer, stick the place where the back electrode does not need to be coated with tape, and then apply the conductive carbon paste to the area where the tape is not pasted with a scraper. After the battery was heated on a heating platform at 150°C for 30 minutes, the adhesive tape was removed to complete the preparation of the carbon electrode, and a perovskite solar cell device was obtained.

Carry out performance test to the perovskite photovoltaic device that present embodiment is made: test temperature is 25 ℃; Relative humidity is 30%; The spectral irradiance of light source is 100mW/m2, and has standard AM1.5 solar spectral irradiance distributed. After testing, the current density-voltage (J-V) characteristic curve of the battery is shown in FIG. 5 .

Example 2

In this embodiment, a _CsPbBr thin film and a solar cell based on it are produced in the same manner as in Example 1, the difference is only that the spin coating and annealing steps are performed three times in step (23), as shown in Figure 6, the film thickness is about 170nm. After testing, the film produced in this embodiment is uniform and dense, and the JV characteristic curve of the corresponding solar cell is shown in FIG. 7 .

Example 3

In this embodiment, a CsPbB _r3 thin film and a solar cell based on it are produced in the same manner as in Example 1, the difference is only that the spin coating and annealing steps are performed once in step (23), as shown in Figure 8, the film thickness is about 55nm. After testing, the film produced in this embodiment is uniform and dense, and the JV characteristic curve of the corresponding solar cell is shown in FIG. 9 .

The above are only exemplary embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention Inside.

Claims (4)

1. a kind of preparation method of the inorganic perovskite quantum dot film of caesium lead bromine, characterized by the following steps:

Step 1, CsPbBr₃The synthesis of inorganic perovskite quantum dot

(1) synthesis of the oleate presoma of caesium

0.5g cesium carbonate, 2mL oleic acid and 50mL 1- octadecylene are added in three-neck flask, vacuumizes 3 water removals repeatedly of logical nitrogen Oxygen is then heated at 120 DEG C and is stirred 20-40 minutes, obtains the oleate precursor solution of caesium, be stored in nitrogen, heat preservation It is 70 DEG C, spare；

(2)CsPbBr₃The synthesis of quantum dot

0.7g lead bromide and 50mL1- octadecylene are added in another three-necked flask, constant temperature stirring one hour at 120 DEG C, so 5mL oleic acid and 5mL oil ammonium are added afterwards, continues stirring and is all dissolved to lead bromide；170 DEG C are then heated to, 8mL step is injected (1) the oleate precursor solution of the caesium synthesized by, ice bath is cooled to room temperature after waiting 5 seconds, obtains CsPbBr₃The mother of quantum dot Liquid；

(3)CsPbBr₃The purifying of quantum dot

By methyl acetate and step (2) CsPbBr obtained₃2:1 is mixed the mother liquor of quantum dot by volume, 8000rpm centrifugation Precipitating is dispersed in 5mL normal octane by 5min, i.e. acquisition CsPbBr₃Quantum dot solution；

Step 2, CsPbBr₃The preparation of inorganic perovskite quantum dot film

Spin coating and annealing: CsPbBr synthesized by 45 μ L steps (1) is taken₃Quantum dot solution is spin-coated in clean substrate, spin coating speed Degree is 2000rpm, spin-coating time 40s, is subsequently placed in 250 DEG C and heats the substrate annealing 5min, removes and be cooled to room temperature；

It operates that the spin coating is multiple with annealing steps, that is, obtains the CsPbBr of required thickness₃Inorganic perovskite quantum dot film.

2. preparation method according to claim 1, it is characterised in that: operate the spin coating and annealing steps in step 2 Number is 3-5 times.

3. a kind of photovoltaic device based on the inorganic perovskite quantum dot film of caesium lead bromine, it is characterised in that: the photovoltaic device is The compacted zone TiO as electron transfer layer is sequentially depositing in FTO conductive glass surface₂, wanted with right as light absorbing layer CsPbBr obtained by preparation method described in asking any one of 1~2₃Inorganic perovskite quantum dot film and as positive negative electricity The C electrode of pole.

4. a kind of preparation method of photovoltaic device as claimed in claim 3, which comprises the steps of:

(1) FTO conductive glass surface is divided into crystallizing field and non-deposited area, in the upper zinc of local uniform tiling of the crystallizing field Powder etches 5min then by the HCl drop of 2M on zinc powder；By the cleaning of FTO electro-conductive glass, the drying after etching；

(2) in the crystallizing field deposition compact layer TiO of FTO conductive glass surface₂As electron transfer layer；

(3) CsPbBr is formed on the electron transport layer with preparation method of any of claims 1 or 2₃Inorganic perovskite quantum Point film, as light absorbing layer；

(4) it is scraped on the light absorbing layer in the non-deposited area of FTO conductive glass surface blade coating C electrode as negative electrode It applies C electrode and is used as positive electrode, battery is placed on on 150 DEG C of warm table heating 30min to get being based on after blade coating CsPbBr₃The photovoltaic device of inorganic perovskite quantum dot film.