An AgBiS2 quantum dot solar cell and its fabrication method

Abstract

The application relates to the field of solar cells, and particularly discloses an AgBiS2 quantum dot solar cell and a preparation method thereof. The method comprises the following steps: preparing an Au thin film or an Ag thin film on conductive glass, then preparing a TiO2 nanorod array as an electron transport layer, and depositing AgBiS2 quantum dots on the electron transport layer as a light absorption layer; and depositing a hole transport layer and a metal electrode layer on the light absorption layer. In the AgBiS2 quantum dot solar cell, the Au thin film or the Ag thin film can excite local surface plasmon resonance, enhance the near-field intensity of incident light in a wide spectral range, and form complementarity with the absorption range of the AgBiS2 quantum dots, so that the capture efficiency of the light absorption layer for long-wave band photons is effectively improved, and the short-circuit current density and the photoelectric conversion efficiency of the device are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell materials technology, specifically a method for preparing AgBiS2 quantum dot solar cells. Background Technology

[0002] Quantum dot solar cells have become an important development direction for third-generation photovoltaic technology due to their advantages such as tunable bandgap, solution-processability, and multiexciton effects. Combining quantum dots with one-dimensional oxide nanorod arrays can construct heterojunction structures with direct charge transport channels, effectively promoting the separation and collection of photogenerated carriers. However, due to the contradiction between carrier diffusion length and light absorption depth in quantum dot films, the thickness of the quantum dot light-absorbing layer in practical devices is usually limited to within a few hundred nanometers, resulting in insufficient light-trapping capability in the near-infrared band, severely restricting further improvements in short-circuit current density and photoelectric conversion efficiency. To overcome this bottleneck, surface plasmon resonance technology has been introduced into the field of solar cells: when metal (such as Ag, Au) nanostructures are photoexcited, their surface free electrons undergo collective oscillation, generating a highly localized enhanced electromagnetic field, which can significantly improve the light absorption efficiency of surrounding light-absorbing materials. Existing research often uses randomly distributed metal nanoparticles or island-like films on transparent conductive electrodes as plasmon scattering centers, utilizing their localized surface plasmon resonance effect to enhance light-trapping capability. However, conventional methods for preparing metal nanoparticles, such as chemical synthesis followed by spin coating, suffer from problems such as wide particle size distribution, uneven coverage, and poor compatibility with subsequent solution-based film-forming processes. Furthermore, charge recombination losses at the interface between metal nanoparticles and electrodes often offset some of the light absorption gain. Summary of the Invention

[0003] To address the aforementioned shortcomings, this invention proposes an AgBiS2 quantum dot solar cell and its fabrication method. Gold and silver thin films are directly deposited on the surface of conductive glass as a surface plasmon structure layer. The aim is to precisely control the subsequent annealing temperature and film thickness to excite strong localized surface plasmon resonances in the obtained gold and silver films. This enhances the near-field intensity of incident light over a wide spectral range, complementing the absorption range of AgBiS2 quantum dots. This significantly increases the capture probability of long-wavelength photons by the quantum dot layer, improving the external quantum efficiency and short-circuit current density of the device. This provides a simple and efficient plasmon light management strategy for high-performance array quantum dot solar cells.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides an AgBiS2 quantum dot solar cell, the structure of which includes: Conductive glass; A plasmonic layer disposed on the conductive glass, wherein the plasmonic layer is an Au thin film or an Ag thin film; The TiO2 nanorod array disposed on the plasmon layer serves as an electron transport layer. An AgBiS2 quantum dot light-absorbing layer disposed on the TiO2 nanorod array; Hole transport layer disposed on the AgBiS2 quantum dot light-absorbing layer; And a metal electrode layer disposed on the hole transport layer.

[0005] This invention further provides a method for preparing the AgBiS2 quantum dot solar cell, comprising the following steps: (1) Prepare Au or Ag thin films as plasmon layers on conductive glass; (2) Prepare TiO2 nanorod arrays as electron transport layers on Au or Ag films; (3) Deposit AgBiS2 quantum dots as a light-absorbing layer on the electron transport layer; (4) Deposit a hole transport layer on the light-absorbing layer; (5) A metal electrode layer is deposited on the hole transport layer to obtain an AgBiS2 quantum dot solar cell.

[0006] Preferably, in step (1), the Au film or Ag film is prepared by vacuum evaporation and then annealed at 100-300°C for 2-60 minutes.

[0007] Preferably, in step (1), the thickness of the Au film or Ag film is 10 to 100 nm.

[0008] Preferably, in step (2), the TiO2 nanorod array is prepared by a hydrothermal method. The preparation process is as follows: concentrated hydrochloric acid and deionized water are mixed at a volume ratio of 1:1, tetrabutyl titanate is added and stirred evenly to obtain a solution A with a tetrabutyl titanate concentration of 0.02-0.04 mol / L; sodium chloride is added to hydrochloric acid until sodium chloride reaches saturation, tetrabutyl titanate is added and stirred evenly to obtain a solution B with a tetrabutyl titanate concentration of 0.02-0.04 mol / L; a conductive glass coated with a plasmon layer is placed in a high-pressure vessel with the conductive side facing down, 20-40 mL of solution A is added, and the hydrothermal reaction is carried out at 110-190℃ for 2-6 h, then 20-40 mL of solution B is added, and the hydrothermal reaction is continued at 110-190℃ for 5-15 h; the sample is taken out and washed with deionized water to obtain the TiO2 nanorod array.

[0009] Preferably, in step (3), the AgBiS2 quantum dots are prepared by hot injection method. The preparation process is as follows: 4 mmol of bismuth acetate, 3.2 mmol of silver acetate, 40 mL of oleic acid and 15 mL of octadecene are mixed in a three-necked flask, oxygen and moisture are removed by vacuuming, and the mixture is heated and stirred at 80-120°C for 1-3 hours; then 5 mL of sulfur source precursor solution is rapidly injected, wherein the sulfur source precursor solution is an octadecene solution of 5 mmol of hexamethyldisiloxane; the reactants are cooled in an ice-water bath and purified by centrifugation to obtain AgBiS2 quantum dots.

[0010] Preferably, in step (3), the AgBiS2 quantum dots are deposited by spin coating, and the concentration of the spin coating solution is 20-300 mg / mL.

[0011] Preferably, in step (4), the hole transport layer is Spiro-MeOTAD (2,2',7,7'-tetra(4-methoxyphenyl)-9,9'-spirodifluorene).

[0012] Preferably, in step (5), the metal electrode layer is a gold electrode or a silver electrode.

[0013] The advantages and positive effects of this invention are reflected in: This invention fabricates a uniform and dense Au or Ag thin film on the surface of conductive glass by precisely controlling the subsequent annealing temperature and film thickness. After annealing, this film can excite strong localized surface plasmon resonances, significantly enhancing the near-field intensity of incident light over a wide spectral range. This characteristic complements the absorption range of AgBiS2 quantum dots themselves, greatly improving the quantum dot layer's ability to capture long-wavelength photons, thereby significantly improving the short-circuit current density and photoelectric conversion efficiency of the device. Attached Figure Description

[0014] Figure 1 These are transmission electron microscope images of AgBiS2 quantum dots; Figure 2 This is the X-ray diffraction pattern of AgBiS2 quantum dots; Figure 3 This is a schematic diagram of the device structure of the AgBiS2 quantum dot solar cell provided in the embodiments of the present invention; Figure 4 These are the normalized absorption curves of Au films annealed at different temperatures in each embodiment; Figure 5 These are the JV curves of AgBiS2 quantum dot solar cells in various embodiments and comparative examples. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0016] Example 1 This embodiment prepares AgBiS2 quantum dot solar cells according to the following steps: (1) Vacuum vapor deposit a 20 nm thick Au film on a clean FTO conductive glass; anneal the conductive glass with Au film at 200°C for 5 minutes.

[0017] (2) Concentrated hydrochloric acid and deionized water were mixed at a volume ratio of 1:1. An appropriate amount of tetrabutyl titanate was added and stirred evenly to obtain a solution A with a tetrabutyl titanate concentration of 0.03 mol / L. An appropriate amount of sodium chloride was added to the hydrochloric acid until the sodium chloride reached saturation. Tetrabutyl titanate was added and stirred evenly to obtain a solution B with a tetrabutyl titanate concentration of 0.03 mol / L. A conductive glass coated with a plasmon layer was placed in an autoclave with the conductive side facing down. 28 mL of solution A was added, and the reaction was carried out hydrothermally at 150℃ for 4 h. Then 28 mL of solution B was added, and the reaction was continued hydrothermally at 150℃ for 10 h. After the reaction was completed, the sample was taken out and washed with deionized water to obtain a TiO2 nanorod array.

[0018] (3) Mix 4 mmol bismuth acetate, 3.2 mmol silver acetate, 40 mL oleic acid, and 15 mL octadecene in a three-necked flask, remove oxygen and moisture under vacuum, and heat and stir at 100°C for 2 hours; then quickly inject 5 mL of sulfur source precursor solution (octadecene solution containing 5 mmol hexamethyldisiloxane), and cool the reaction mixture in an ice-water bath; centrifuge at 4500 rpm for 5 minutes, discard the supernatant, add acetone, centrifuge again at 4500 rpm for 5 minutes, and repeat the operation once more to obtain AgBiS2 quantum dots. Disperse the AgBiS2 quantum dots in DMF solution to obtain an AgBiS2 quantum dot dispersion with a concentration of 150 mg / mL, and spin-coat it onto a TiO2 nanorod array to form an absorbing layer. The transmission electron microscope image and X-ray diffraction pattern of the AgBiS2 quantum dots prepared in this example are shown below. Figure 1 , Figure 2 As shown.

[0019] (4) Spin-coating Spiro-MeOTAD solution onto the light-absorbing layer to form a hole transport layer.

[0020] (5) A 60 nm thick Au electrode is deposited on the hole transport layer to obtain an AgBiS2 quantum dot solar cell, the structure of which is as follows: Figure 3 As shown.

[0021] Example 2 This embodiment prepares an AgBiS2 quantum dot solar cell, which has basically the same process steps as that in Example 1, except that the annealing temperature of the Au thin film in step (1) is 250°C.

[0022] Example 3 This embodiment prepares an AgBiS2 quantum dot solar cell, which has basically the same process steps as that in Example 1, except that the annealing temperature of the Au thin film in step (1) is 300℃.

[0023] Comparative Example This comparative example prepared an AgBiS2 quantum dot solar cell, which had basically the same process steps as Example 1, except that an Au thin film was not deposited on the conductive glass, and a TiO2 nanorod array was directly deposited.

[0024] The absorption spectra of the Au thin films prepared in each embodiment were measured, and the results are as follows: Figure 4 As shown, Au films obtained at different annealing temperatures all exhibit obvious plasmon resonance characteristics, especially in the long wavelength region, where the absorption spectrum is significantly broadened.

[0025] In AM1.5, the effective area of ​​the active layer is 0.04 cm². 2 Photovoltaic tests were conducted on the AgBiS2 quantum dot solar cells prepared in each embodiment and comparative example under the specified conditions. The JV curves are shown in the figure below. Figure 5 As shown. The comparative battery short-circuit current is 12.27 mA / cm. 2 The open-circuit voltage was 0.429 V, the fill factor was 0.482, and the photoelectric conversion efficiency was 2.54%. Compared with the comparative example, all embodiments showed significant improvements in short-circuit current density, with Embodiment 1 showing the largest improvement at 17.51 ​​mA / cm². 2 The open-circuit voltage was 0.429 V, the fill factor was 0.479, and the photoelectric conversion efficiency was 3.60%; the short-circuit current of the battery in Example 2 was 15.99 mA / cm². 2 The open-circuit voltage was 0.422 V, the fill factor was 0.491, and the photoelectric conversion efficiency was 3.31%; the short-circuit current of the battery in Example 3 was 14.14 mA / cm². 2 The open-circuit voltage was 0.424 V, the fill factor was 0.505, and the photoelectric conversion efficiency was 3.02%. These results indicate that surface plasmons generated by the Au thin film improved the short-circuit current density and photoelectric conversion efficiency of the AgBiS2 solar cell.

[0026] The above description is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Simple changes or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention all fall within the scope of protection of the present invention.

Claims

1. An AgBiS2 quantum dot solar cell, characterized in that, include: Conductive glass; A plasmonic layer disposed on the conductive glass, wherein the plasmonic layer is an Au thin film or an Ag thin film; The TiO2 nanorod array disposed on the plasmon layer serves as an electron transport layer. An AgBiS2 quantum dot light-absorbing layer disposed on the TiO2 nanorod array; Hole transport layer disposed on the AgBiS2 quantum dot light-absorbing layer; And a metal electrode layer disposed on the hole transport layer.

2. The AgBiS2 quantum dot solar cell as described in claim 1, characterized in that, The thickness of the Au or Ag film is 10–100 nm.

3. A method for preparing an AgBiS2 quantum dot solar cell as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Prepare Au or Ag thin films as plasmon layers on conductive glass; (2) Prepare TiO2 nanorod arrays as electron transport layers on Au or Ag films; (3) Deposit AgBiS2 quantum dots as a light-absorbing layer on the electron transport layer; (4) Deposit a hole transport layer on the light-absorbing layer; (5) A metal electrode layer is deposited on the hole transport layer to obtain an AgBiS2 quantum dot solar cell.

4. The preparation method according to claim 3, characterized in that, In step (1), the Au film or Ag film is prepared by vacuum evaporation and then annealed at 100-300°C for 2-60 minutes.

5. The preparation method according to claim 3, characterized in that, In step (2), the TiO2 nanorod array is prepared by a hydrothermal method. The preparation process is as follows: concentrated hydrochloric acid and deionized water are mixed at a volume ratio of 1:1, tetrabutyl titanate is added and stirred evenly to obtain a solution A with a tetrabutyl titanate concentration of 0.02-0.04 mol / L; sodium chloride is added to hydrochloric acid until sodium chloride reaches saturation, tetrabutyl titanate is added and stirred evenly to obtain a solution B with a tetrabutyl titanate concentration of 0.02-0.04 mol / L; conductive glass coated with a plasmon layer is placed in an autoclave with the conductive side facing down, 20-40 mL of solution A is added, and the hydrothermal reaction is carried out at 110-190℃ for 2-6 h, then 20-40 mL of solution B is added, and the hydrothermal reaction is continued at 110-190℃ for 5-15 h; the sample is taken out and washed with deionized water to obtain the TiO2 nanorod array.

6. The preparation method according to claim 3, characterized in that, In step (3), the AgBiS2 quantum dots are prepared by hot injection method. The preparation process is as follows: 4 mmol of bismuth acetate, 3.2 mmol of silver acetate, 40 mL of oleic acid and 15 mL of octadecene are mixed in a three-necked flask, oxygen and moisture are removed by vacuuming, and the mixture is heated and stirred at 80-120°C for 1-3 hours; then 5 mL of sulfur source precursor solution is rapidly injected, which is a 5 mmol solution of hexamethyldisiloxane in octadecene; the reactants are cooled in an ice-water bath and purified by centrifugation to obtain AgBiS2 quantum dots.

7. The preparation method according to claim 3 or 6, characterized in that, In step (3), the AgBiS2 quantum dots are deposited by spin coating, and the concentration of the spin coating solution is 20-300 mg / mL.

8. The preparation method according to claim 3, characterized in that, In step (4), the hole transport layer is Spiro-MeOTAD.

9. The preparation method according to claim 3, characterized in that, In step (5), the metal electrode layer is a gold electrode or a silver electrode.

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