Preparation methods and applications of cobalt sulfide / tin dioxide composite thin films and their dye-sensitized solar cells

Abstract

This invention relates to the field of electrode material preparation technology, and discloses a method for preparing a stable and transparent cobalt sulfide / tin dioxide composite film and its application. The preparation method includes: Step 1, washing and drying conductive glass; Step 2, placing cobalt chloride hexahydrate and thioacetamide into an ethanol solution and stirring to obtain a mixture; Step 3, immersing the conductive glass treated in Step 1 into the mixture and heating to obtain a cobalt sulfide film; Step 4, mixing and diluting stannous chloride dihydrate and ethanol to obtain a precursor solution; Step 5, spin-coating the precursor solution onto the cobalt sulfide film and curing it to obtain the cobalt sulfide / tin dioxide composite film. This invention solves the problems of easy decomposition and instability of cobalt sulfide films in high humidity air by spin-coating the tin dioxide precursor solution onto the surface of the cobalt sulfide film. Furthermore, the preparation method is simple and the reaction time is short, which is of great significance for alleviating the energy crisis and environmental problems.

Description

Technical Field

[0001] This invention relates to the field of electrode material preparation technology, and in particular to a method for preparing a stable and transparent cobalt sulfide / tin dioxide composite film and its application in dye-sensitized solar cells. Background Technology

[0002] Solar energy, with its abundant resources, wide distribution, and environmental friendliness, has become a research hotspot in the energy field. In dye-sensitized solar cells, the noble metal platinum, with its excellent conductivity and catalytic activity, is the most commonly used counter electrode material. However, platinum suffers from limited resources, high cost, and limitations in Ig... - / I3 - The corrosive nature of electrolyte systems has spurred extensive research into alternative, abundant counter electrode materials that can replace precious metals. These materials include carbon materials, conductive polymers, selenides, transition metal sulfides, and alloys. Among these, transition metal sulfides are gaining increasing attention due to their good stability and excellent electrocatalytic performance.

[0003] In the exploration of non-platinum counter electrode materials, cobalt sulfide nanomaterials have attracted considerable attention due to their excellent electrocatalytic performance. As a member of the transition metal sulfide family, cobalt sulfide not only possesses the common characteristics of nanomaterials but also exhibits good performance in optical and electrical aspects, making it an excellent counter electrode material. Electrochemical testing results show that cobalt sulfide counter electrodes have good electrocatalytic activity, comparable to that of platinum electrodes. Recently, cobalt sulfide with different morphologies and phases has been prepared using hydrothermal, solvothermal, electroplating, and electrodeposition methods, achieving good photovoltaic performance in dye-sensitized solar cells. However, most of these preparation processes require cumbersome and complex experimental procedures or harsh preparation conditions. Meanwhile, low-temperature preparation techniques for chalcogenide thin films have rapidly developed. However, cobalt sulfide thin films prepared using low-temperature techniques suffer from easy decomposition and poor stability under high humidity environments, severely restricting the widespread application of dye-sensitized solar cells. Summary of the Invention

[0004] Objective of the Invention: Addressing the problems existing in the prior art, this invention provides a method for preparing a stable and transparent cobalt sulfide / tin dioxide composite thin film and its application. By spin-coating a tin dioxide precursor solution onto the surface of a cobalt sulfide thin film, a stable and transparent cobalt sulfide / tin dioxide composite thin film is prepared. This method solves the problems of easy decomposition and instability of cobalt sulfide thin films in high humidity air, and has the advantages of simple preparation method, low cost, and short reaction time. This invention is of great significance for alleviating the energy crisis and environmental problems.

[0005] Technical solution: This invention provides a method for preparing a stable and transparent cobalt sulfide / tin dioxide composite thin film, comprising the following steps:

[0006] Step 1: Clean and dry the conductive glass;

[0007] Step 2: Add cobalt chloride hexahydrate and thioacetamide to anhydrous ethanol solution and stir until homogeneous to obtain a mixture;

[0008] Step 3: Place the conductive glass treated in Step 1 into the mixed solution and heat at a constant temperature to obtain a cobalt sulfide thin film;

[0009] Step 4: Mix and dilute stannous chloride dihydrate and anhydrous ethanol to obtain the precursor solution;

[0010] Step 5: Spin-coat the precursor solution onto the cobalt sulfide film, and cure it to obtain a cobalt sulfide / tin dioxide composite film.

[0011] Preferably, in step four, the concentration of the precursor solution is 0.9–1.1 mmol / mL.

[0012] Furthermore, in step five, the curing treatment is a high-temperature curing treatment at 180℃~240℃ for 0.5~1.5 hours.

[0013] Preferably, in step two, the molar ratio of cobalt chloride hexahydrate to thioacetamide is 1:0.8-1.2.

[0014] Furthermore, in step two, the constant temperature heating is performed at 80℃~90℃ for 5~7 hours.

[0015] Preferably, in step one, the conductive glass is indium tin oxide conductive glass or fluorine-doped tin oxide conductive glass.

[0016] Preferably, in step one, the cleaning process involves sequentially washing with a cleaning agent, deionized water, and anhydrous ethanol.

[0017] The present invention also provides an application of the cobalt sulfide / tin dioxide composite thin film prepared according to any one of the above methods in dye-sensitized solar cells.

[0018] The present invention also provides a dye-sensitized solar cell: assembled from a photoanode, an electrolyte and a counter electrode, wherein the counter electrode is a cobalt sulfide / tin dioxide composite thin film prepared according to any one of the above methods. Beneficial effects

[0019] The advantages of the preparation method of the present invention are that the preparation process is simple and easy to operate, the raw materials are readily available and low in toxicity, and the cost is low, which greatly reduces the overall cost of dye-sensitized solar cells.

[0020] This invention prepares a tin dioxide film on the surface of a cobalt sulfide film using a simple low-temperature heat treatment technique. Stable and long-term-storeable transparent cobalt sulfide / tin dioxide composite film can be prepared without harsh experimental conditions.

[0021] Compared to cobalt sulfide films prepared at low temperatures and those subjected to heat treatment, this invention effectively inhibits cobalt sulfide decomposition, enhancing its stability and improving its electrocatalytic performance. Generally, cobalt sulfide films prepared at low temperatures have poor crystallinity and are prone to decomposition in high-humidity environments. Although high-temperature heat treatment can effectively improve the crystallinity of nanomaterials, the electrocatalytic activity of cobalt sulfide films prepared at low temperatures also decreases during high-temperature heat treatment. While high-temperature heat treatment enhances the crystallinity of the cobalt sulfide film, it also leads to thermal decomposition and self-aggregation, thus affecting its electrocatalytic performance. Therefore, by curing a tin dioxide film onto the surface of a cobalt sulfide film prepared at low temperatures, not only can the thermal decomposition and self-aggregation of the cobalt sulfide film be inhibited, but its crystallinity can also be enhanced, thereby improving its electrocatalytic performance.

[0022] This invention provides a stable and transparent cobalt sulfide / tin dioxide composite thin film counter electrode. Dye-sensitized solar cells assembled from this electrode exhibit excellent photovoltaic performance and have great application potential. Attached Figure Description

[0023] Figure 1 The figures show the photocurrent density-voltage curves of dye-sensitized solar cells prepared by each thin film in Embodiment 4 and Comparative Examples 1-2 of the present invention.

[0024] Figure 2 The graphs show the stability of the photoelectric conversion efficiency of dye-sensitized solar cells prepared by each thin film in Embodiment 4 and Comparative Examples 1-2 of the present invention, wherein the storage environment of the battery device is above 60% humidity.

[0025] In this diagram, curve A corresponds to a platinum electrode, curve B corresponds to a cobalt sulfide film prepared directly without any treatment, curve C corresponds to a cobalt sulfide film after heat treatment, and curve D corresponds to a cobalt sulfide / tin dioxide film prepared in Embodiment 4 of this invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] Implementation Method 1

[0028] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0029] 2) Weigh 35.7 mg of cobalt chloride hexahydrate and 11.3 mg of thioacetamide in a 1:1 molar ratio, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution and put it in a drying oven to be heated at 80°C for 6 hours.

[0030] 3) Using anhydrous ethanol as a solvent, take 10 mL of the solvent and add 112.8 mg of stannous chloride dihydrate to the solvent. Stir well to prepare a 0.05 mol / mL tin dioxide solution. Then take 0.1 mL of the 0.05 mol / mL tin dioxide solution and mix it with 4.9 mL of anhydrous ethanol. Dilute to a 1 mmol / mL tin dioxide precursor solution.

[0031] 4) Remove the FTO substrate from step 2), rinse it with anhydrous ethanol, dry it, and place it in a spin coater. Add the 1 mmol / mL tin dioxide precursor solution prepared in step 3), and spin coat it at 3000 rpm for 30 seconds. Then, cure the spin-coated FTO substrate at 200°C for 1 hour to obtain a stable and transparent cobalt sulfide / tin dioxide film, which can then be stored in air.

[0032] Implementation Method 2

[0033] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0034] 2) Weigh out 35.7 mg of cobalt chloride hexahydrate and 9.0 mg of thioacetamide at a molar ratio of 1:0.8, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution, and put it in a drying oven to be heated at 90°C for 5 hours.

[0035] 3) Using anhydrous ethanol as a solvent, take 10 mL of the solvent and add 112.8 mg of stannous chloride dihydrate to the solvent. Stir well to prepare a 0.05 mol / mL tin dioxide solution. Then take 0.09 mL of the 0.05 mol / mL tin dioxide solution and mix it with 4.91 mL of anhydrous ethanol. Dilute to prepare a 0.9 mmol / mL tin dioxide precursor solution.

[0036] 4) Remove the FTO substrate from step 2), rinse it with anhydrous ethanol, dry it, and place it in a spin coater. Add the 0.9 mmol / mL tin dioxide precursor solution prepared in step 3), and spin coat it at 3000 rpm for 30 seconds. Then, cure the spin-coated FTO substrate at 180°C for 0.5 hours to obtain a stable and transparent cobalt sulfide / tin dioxide film, which can then be stored in air.

[0037] Implementation Method 3

[0038] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0039] 2) Weigh 35.7 mg of cobalt chloride hexahydrate and 13.6 mg of thioacetamide at a molar ratio of 1:1.2, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution, and put it in a drying oven to heat at 80°C for 7 hours.

[0040] 3) Using anhydrous ethanol as a solvent, take 10 mL of the solvent and add 112.8 mg of stannous chloride dihydrate to the solvent. Stir well to prepare a 0.05 mol / mL tin dioxide solution. Then take 0.11 mL of the 0.05 mol / mL tin dioxide solution and mix it with 4.89 mL of anhydrous ethanol. Dilute to prepare a 1.1 mmol / mL tin dioxide precursor solution.

[0041] 4) Remove the FTO substrate from step 2), rinse it with anhydrous ethanol, dry it, and place it in a spin coater. Add the 1.1 mmol / mL tin dioxide precursor solution prepared in step 3), and spin coat it at 3000 rpm for 30 seconds. Then, cure the spin-coated FTO substrate at 240°C for 1.5 hours to obtain a stable and transparent cobalt sulfide / tin dioxide film, which can then be stored in air.

[0042] Implementation Method 4

[0043] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0044] 2) Weigh 35.7 mg of cobalt chloride hexahydrate and 11.3 mg of thioacetamide in a 1:1 molar ratio, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution and put it in a drying oven to be heated at 80°C for 6 hours.

[0045] 3) Using anhydrous ethanol as a solvent, take 10 mL of the solvent and add 112.8 mg of stannous chloride dihydrate to the solvent. Stir well to prepare a 0.05 mol / mL tin dioxide solution. Then take 0.1 mL of the 0.05 mol / mL tin dioxide solution and mix it with 4.9 mL of anhydrous ethanol. Dilute to a 1 mmol / mL tin dioxide precursor solution.

[0046] 4) Remove the FTO substrate from step 2), rinse it with anhydrous ethanol, dry it, and place it in a spin coater. Add the 1 mmol / mL tin dioxide precursor solution prepared in step 3), and spin coat it at 3000 rpm for 30 seconds. Then, cure the spin-coated FTO substrate at 210°C for 1 hour to obtain a stable and transparent cobalt sulfide / tin dioxide film, which can then be stored in air.

[0047] 5) Using the above-mentioned cobalt sulfide / tin dioxide thin film as the counter electrode, and N719-sensitized titanium dioxide thin film as the photoanode, and reacting it with a film containing I... - / I3 - The electrolyte of the redox couple was assembled into a dye-sensitized solar cell, and its photocurrent density-voltage curve is shown in the figure. Figure 1 As shown in D. Comparative Example 1

[0048] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0049] 2) Weigh 35.7 mg of cobalt chloride hexahydrate and 11.3 mg of thioacetamide in a 1:1 molar ratio, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution and put it in a drying oven to be heated at 80°C for 6 hours.

[0050] 3) After heating is complete, remove the FTO substrate and dry it at room temperature to obtain the cobalt sulfide thin film prepared at low temperature.

[0051] 4) Using the above-mentioned cobalt sulfide thin film as the counter electrode and the N719-sensitized titanium dioxide thin film as the photoanode, and reacting it with a film containing I... - / I3 - The electrolyte of the redox couple was assembled into a dye-sensitized solar cell, and its photocurrent density-voltage curve is shown in the figure. Figure 1 As shown in B.

[0052] 5) For comparison, a commercially available platinum electrode was used as a reference electrode. The photocurrent density-voltage curve of a dye-sensitized solar cell constructed from it is shown below. Figure 1 As shown in Figure A. Comparative Example 2

[0053] 1) The FTO conductive glass is cleaned in sequence with cleaning agent, deionized water and anhydrous ethanol, and then dried to obtain a clean FTO substrate.

[0054] 2) Weigh 35.7 mg of cobalt chloride hexahydrate and 11.3 mg of thioacetamide in a 1:1 molar ratio, dissolve them in 15 mL of anhydrous ethanol, and stir well. Place the clean FTO substrate with the conductive side down in the prepared solution and put it in a drying oven to be heated at 80°C for 6 hours.

[0055] 3) After heating is complete, remove the FTO substrate and cure it at 210°C for 1 hour to obtain a heat-treated cobalt sulfide film.

[0056] 4) Using the above-mentioned cobalt sulfide thin film as the counter electrode and the N719-sensitized titanium dioxide thin film as the photoanode, and reacting it with a film containing I / I3 - The electrolyte of the redox couple was assembled into a dye-sensitized solar cell, and its photocurrent density-voltage curve is shown in the figure. Figure 1 As shown in C.

[0057] A battery device based on the cobalt sulfide / tin dioxide thin film prepared in Embodiment 4, Comparative Examples 1-2, and a battery device based on a platinum electrode were compared. Figure 1 The photocurrent density-voltage curves of four different dye-sensitized solar cells with different counter electrodes are shown. It can be seen that the photoelectric conversion efficiency of the platinum electrode-based device is 4.82%, and the photocurrent density is 11.24 mA·cm⁻¹. -2 The open-circuit voltage is 0.66V, and the fill factor is 0.65. Figure 1 As shown in curve A, the photoelectric conversion efficiency of the battery device based on cobalt sulfide thin film is 4.38%, and the photocurrent density is 9.77 mA·cm⁻¹. -2 The open-circuit voltage is 0.69V, and the fill factor is 0.65. Figure 1 The B curve is shown in the figure. The photoelectric conversion efficiency of the battery device based on the heat-treated cobalt sulfide thin film is 3.41%, and the photocurrent density is 8.09 mA·cm. -2 The open-circuit voltage is 0.68V, and the fill factor is 0.62. Figure 1 The C-curve is shown in the figure. The photoelectric conversion efficiency of the battery device based on cobalt sulfide / tin dioxide thin film is 4.58%, and the photocurrent density is 10.42 mA·cm⁻¹. -2The open-circuit voltage is 0.72V, and the fill factor is 0.61. Figure 1 The D curve is shown in the figure. Therefore, the prepared cobalt sulfide / tin dioxide thin film has good electrocatalytic activity, comparable to that of a platinum electrode; the dye-sensitized solar cell assembled from it also has good photovoltaic performance, and the photoelectric conversion efficiency of the cell device is comparable to that of the cell device based on the platinum electrode.

[0058] Will Figure 1 Dye-sensitized solar cells B, C, and D were placed in an environment with 60% humidity. The photocurrent density-voltage curves were measured to analyze the changes in their photoelectric conversion efficiency. In Comparative Example 1, the cobalt sulfide film, placed directly in 60% humidity air without any treatment, initially exhibited high photoelectric conversion efficiency, but its storage time was short and its stability was poor. In Comparative Example 2, the cobalt sulfide film after heat treatment initially had lower device efficiency than Comparative Example 1, but its efficiency increased after a period of rest. However, its photoelectric conversion efficiency still decreased after prolonged storage, indicating that the cobalt sulfide film did not simultaneously exhibit good electrocatalytic performance and stability. In contrast, in Example 4, a tin dioxide precursor solution was spin-coated onto the surface of the cobalt sulfide film to obtain a cobalt sulfide / tin dioxide film. Initially, the device efficiency was higher than that of Comparative Examples 1 and 2, and it still maintained a stable and high device efficiency after 96 hours of storage. The experimental results show that after treatment by the method of this invention, the stability of the cobalt sulfide film is significantly improved, which can effectively improve the photoelectric conversion efficiency of dye-sensitized solar cells and has great application potential.

[0059] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a stable and transparent cobalt sulfide / tin dioxide composite thin film, characterized in that, Includes the following steps: Step 1: Clean and dry the conductive glass; Step 2: Add cobalt chloride hexahydrate and thioacetamide to anhydrous ethanol solution and stir until homogeneous to obtain a mixture; Step 3: Place the conductive glass treated in Step 1 into the mixed solution and heat it at a constant temperature to obtain a cobalt sulfide thin film; the constant temperature heating temperature is 80℃~90℃. Step 4: Mix and dilute stannous chloride dihydrate and anhydrous ethanol to obtain the precursor solution; Step 5: Spin-coat the precursor solution onto the cobalt sulfide film, and cure it to obtain a cobalt sulfide / tin dioxide composite film; the curing temperature is 180℃~240℃. The cobalt sulfide / tin dioxide composite film is the counter electrode material for dye-sensitized solar cells.

2. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step four, the concentration of the precursor solution is 0.9–1.1 mmol / mL.

3. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step five, the curing process takes 0.5 to 1.5 hours.

4. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step two, the molar ratio of cobalt chloride hexahydrate to thioacetamide is 1:0.8-1.

2.

5. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step three, the constant temperature heating is performed at 80℃~90℃ for 5~7 hours.

6. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step one, the conductive glass is indium tin oxide conductive glass or fluorine-doped tin oxide conductive glass.

7. The method for preparing cobalt sulfide / tin dioxide composite thin films according to claim 1, characterized in that: In step one, the cleaning process involves sequentially washing with a cleaning agent, deionized water, and anhydrous ethanol.

8. The application of a cobalt sulfide / tin dioxide composite thin film prepared by any one of claims 1 to 7 in dye-sensitized solar cells.

9. A dye-sensitized solar cell, characterized in that: It is assembled from a photoanode, an electrolyte, and a counter electrode, wherein the counter electrode is a cobalt sulfide / tin dioxide composite film prepared by any one of claims 1 to 7.

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