Perovskite solar cell based on hole transport layer solvent engineering and preparation method

Abstract

The invention discloses a perovskite solar cell based on hole transport layer solvent engineering and a preparation method thereof. The preparation method comprises the following steps: preparing a hole transport layer precursor solution of the perovskite solar cell by using a mixed solvent of chlorobenzene (CB), ethyl acetate (EA) and 4-tert-butylpyridine (TBP); the optimal solvent formula is obtained by regulating and controlling the solvent proportion, and the high-quality organic hole transport layer thin film is prepared by using the spin-coating method, so that the efficiency and the stability of the perovskite solar cell are greatly improved, and the high-performance perovskite solar cell is further obtained. A new thought and a new method are provided for promoting industrial production and commercial application of the perovskite solar cell.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell fabrication technology, specifically relating to a perovskite solar cell based on hole transport layer solvent engineering and its fabrication method. Background Technology

[0002] As a third-generation solar cell, perovskite solar cells have seen a significant increase in photoelectric conversion efficiency (PCE) over the past decade, rising from an initial 3.8% to 26.1%, potentially matching or even surpassing crystalline silicon cells. Compared to crystalline silicon cells, perovskite solar cells offer advantages such as lower production costs and the ability to operate normally in low-light conditions, including cloudy or rainy days. Among various perovskite solar cells, the organic small molecule Spiro-OMeTAD is a commonly used hole transport material, achieving high PCE efficiency. Typically, LiTFSI and TBP are added to this hole transport layer. LiTFSI assists in the oxidation of Spiro-OMeTAD by oxygen, while TBP promotes the dissolution of LiTFSI in the hole transport layer precursor solution. However, TBP forms a complex with PbI2, promoting perovskite decomposition. As a liquid component in perovskite solar cells, TBP's volatility makes it prone to corroding and decomposing the perovskite, posing a challenge to device stability. Studies have shown that TBP reduces oxidized Spiro-OMeTAD, leading to problems such as low carrier mobility. The addition of TBP also partially transforms Spiro-OMeTAD from an amorphous state to a crystalline state; this mixed crystalline and amorphous structure degrades the conductivity of the hole transport layer. TBP was originally intended to dissolve LiTFSI, and research indicates that ethyl acetate can effectively dissolve LiTFSI without corroding perovskite. In summary, the additive TBP in Spiro-OMeTAD affects device performance, and it is feasible to completely or partially replace TBP with ethyl acetate to dissolve LiTFSI. This invention shields or reduces the negative effects of TBP in perovskite solar cells, such as corrosion of perovskite and reduction of oxidized Spiro-OMeTAD, thereby improving cell stability and further advancing its industrial production and commercialization.

[0003] CN201810903957.5 discloses a method for preparing inorganic perovskite solar cells based on the synergistic effect of gradient annealing and antisolvent, as well as the prepared inorganic perovskite solar cells. This method is a low-temperature, easy-to-prepare, low-cost, and highly efficient perovskite solar cell. The perovskite layer is formed using a solution spin-coating method with gradient annealing and antisolvent treatment, resulting in a smoother, more uniform, more efficient, and more stable film. Compared to commonly used one-step annealing and toxic antisolvent methods, gradient annealing produces a denser film and a purer phase. The use of a green antisolvent eliminates the need for traditional toxic antisolvents, effectively reducing environmental pollution. Furthermore, in terms of microstructure, the antisolvent-treated film achieves micron-level grain size with minimal grain boundaries, thus suppressing defect states and ensuring the thermal and humidity stability of the perovskite film.

[0004] CN2020110134648 discloses a method for preparing a perovskite thin film, comprising the following steps: 1) spin-coating a perovskite solution onto the semiconductor layer of a substrate having a semiconductor layer, wherein the solvent of the perovskite solution is one or more of DMF, DMSO, and γ-GBL; 2) adding an inversion solvent before the spin-coating is completed; 3) after the spin-coating is completed, annealing the substrate in a gas environment with a pressure of 0.1-10 MPa at 80-120°C for 5-60 minutes to obtain a perovskite thin film. Summary of the Invention

[0005] The purpose of this invention is to provide a perovskite solar cell based on organic hole transport layer solvent engineering and its preparation method, so as to improve the poor stability of current perovskite solar cells based on TBP-added Spiro-OMeTAD hole transport layers.

[0006] The present invention adopts the following technical solution: a perovskite solar cell based on organic hole transport layer solvent engineering, which includes, from bottom to top, a transparent substrate, a transparent electrode, an electron transport layer TiO2 or SnO2 (20nm-200nm), a perovskite light-absorbing layer (300nm-700nm), a hole transport layer based on solvent engineering (100nm-300nm), and a metal electrode (80nm-100nm). The hole transport layer is prepared by dissolving Spiro-OMeTAD and LiTFSI solutes in a mixed solvent of chlorobenzene and ethyl acetate and then coating it with an organic hole transport layer solution; the thickness ranges from 100nm to 300nm.

[0007] The transparent electrode is made of FTO or ITO.

[0008] The perovskite uses ABX3 material (A=Cs, MA, FA; B=Pb, Sn, X=I, Br, Cl) as the perovskite light-absorbing layer.

[0009] Preparation includes the following steps: A: Deposit an FTO or ITO thin film on a glass substrate to form a transparent electrode, or directly use FTO or ITO glass; B: A dense TiO2 or SnO2 layer is deposited on the transparent electrode as an electron transport layer by screen printing or spray pyrolysis process, with a thickness ranging from 20nm to 200nm. C: The perovskite material grown on the electron transport layer is grown by spin coating, scraping, or spraying, and then the solvent in the perovskite material precursor solution is removed by evaporation and annealing. The thickness ranges from 300nm to 700nm. D: An organic hole transport layer solution is coated on the perovskite light-absorbing layer, and a hole transport layer with a thickness of 100nm-300nm is obtained by spin coating. Electrodes are then deposited on the layer to obtain a perovskite solar cell. The organic hole transport layer coating solution consists of a main solvent and a trace solvent. The main solvent is a mixed solution of chlorobenzene and ethyl acetate, with chlorobenzene accounting for 50%-99% of the main solvent by volume, and the remaining main solvent being ethyl acetate. TBP is added as a trace solvent at a volume of less than 3% of the main solvent. The solutes are 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) and lithium bis(trifluoromethanesulfonylimide) (LiTFSI). The thickness of the dense layer is controlled by adjusting the concentration of the dense layer slurry, the number of printing passes, and the duration of spraying. The LiTFSI is first dissolved in an acetonitrile solution and then added to the hole transport layer solution.

[0010] Step D, regarding the preparation of the organic hole transport layer solution, involves adding different proportions of solvent to Spiro-OMeTAD and LiTFSI solutes, stirring at 20°C-30°C for 6-24 hours, and allowing it to stand until it reaches thermodynamic stability to obtain the hole transport layer solution. The spin-coating process for the hole transport layer is as follows: 38-50 μL of the hole transport layer precursor solution is spin-coated onto the substrate at a rotation speed of 3000 rpm, an acceleration of 3000 rpm / s, and a spin-coating time of 30 s.

[0011] Beneficial Effects: This invention obtains different hole transport layer solvent formulations by adjusting the solvent ratio, and prepares high-quality hole transport layer films using spin coating to fabricate perovskite solar cells with good stability. This method introduces ethyl acetate, an additive with good solubility for Spiro-OMeTAD (LiTFSI), into the main solvent chlorobenzene. This reduces or eliminates the adverse effects of the original additive TBP on the perovskite layer, such as corrosion and reduction of the oxidized Spiro-OMeTAD, thus constructing a high-quality hole transport layer as a carrier transport channel. This improves the stability of the perovskite solar cell, increasing humidity stability by more than 200 hours while maintaining an efficiency of approximately 80% or more of the initial state, resulting in a perovskite solar cell with good stability. Figure 1 As shown, the introduction of ethyl acetate alleviates and improves the corrosion and decomposition of perovskite solar cells, thus enhancing their stability. This will provide new ideas and methods for promoting the further industrial production and commercial application of perovskite solar cells. The perovskite thin film prepared by the method of this invention exhibits excellent stability and is suitable for commercialization as a perovskite solar cell. Attached Figure Description

[0012] Figure 1. (a) and (b) show the macroscopic morphology of the battery after 200 h and 600 h, respectively, for the control group containing TBP; (c) and (d) show the macroscopic morphology of the battery after 200 h and 600 h, respectively, for the experimental group after 200 h and 600 h, respectively, for the group using EA instead of TBP. Figure 2 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0013] In this implementation example, as shown in the figure, the perovskite solar cell structure based on organic hole transport layer solvent engineering includes, from bottom to top, a transparent substrate 6, a transparent electrode 5, an electron transport layer TiO2 or SnO2 4, a perovskite light-absorbing layer 3, a hole transport layer 2 based on solvent engineering, and a metal electrode 1.

[0014] Transparent substrate materials can be made of transparent materials such as glass.

[0015] Transparent electrodes, deposited on a substrate, also serve to transport electrons. The material can be commonly used transparent electrode materials such as FTO or ITO, and commercially available FTO or ITO glass (integrated with the transparent substrate) can be used directly.

[0016] The perovskite uses ABX3 material (A=Cs, MA, FA; B=Pb, Sn, X=I, Br, Cl) as the perovskite light-absorbing layer, with a thickness ranging from 300nm, 500, or 700nm.

[0017] The hole transport layer is prepared by dissolving Spiro-OMeTAD and LiTFSI solutes in a mixed solvent of chlorobenzene and ethyl acetate to form an organic hole transport layer solution with a thickness ranging from 100 nm to 300 nm.

[0018] To effectively extract photogenerated electrons, a TiO2 or SnO2 layer is deposited on a transparent electrode as an electron transport layer. To reduce or avoid the negative effects of the Spiro-OMeTAD additive TBP, an organic hole transport layer solution is prepared by optimizing the solvent ratio and using a mixed solvent of chlorobenzene and ethyl acetate to dissolve the Spiro-OMeTAD and LiTFSI solutes. The hole transport layer is then prepared by spin coating and other methods.

[0019] The metal electrode is a gold electrode or a silver electrode.

[0020] The fabrication method of perovskite solar cells based on organic hole transport layer solvent engineering includes the following steps: A: Deposit an FTO or ITO thin film on a glass substrate to form a transparent electrode, or commercially available FTO or ITO glass can be used directly; B: A dense TiO2 or SnO2 layer is deposited on the transparent electrode as an electron transport layer by screen printing or spray pyrolysis. The thickness of the dense layer can be controlled by adjusting the concentration of the dense layer paste, the number of printing passes, the duration of spraying, etc. C: Perovskite material is grown as a light-absorbing layer by spin coating, blade coating, spray coating, etc., with the solvent removed from the perovskite material precursor solution by evaporation, annealing and other methods. The thickness of the perovskite material as a light-absorbing layer is 300nm, 500nm and 700nm. D: An organic hole transport layer solution is coated onto a perovskite light-absorbing layer, and a hole transport layer is obtained by spin coating. Electrodes are then deposited onto this layer to obtain a perovskite solar cell. The chlorobenzene constitutes 50%-99% of the main solvent by volume, with the remainder being ethyl acetate. TBP is used as a trace solvent, added at a level slightly more than 0% or 1% or 2% of the main solvent volume. The organic hole transport layer solution can have a thickness ranging from 100 nm, 200 nm, to 300 nm. In this invention, FTO or ITO on a glass substrate serves as the transparent electrode, TiO2 or SnO2 layer serves as the electron transport layer, and perovskite layer serves as the light-absorbing layer. Due to energy level matching, under illumination, photogenerated electrons in the perovskite material move to the TiO2 electron transport layer and are collected at the FTO or ITO transparent electrode. Photogenerated holes then move to the metal electrode through the hole transport layer with optimized solvent ratio, thus forming a fully functional perovskite solar cell. This perovskite solar cell based on organic hole transport layer solvent engineering objectively reduces or avoids the adverse effects of the original Spiro-OMeTAD additive TBP on the perovskite layer, such as corrosion and reduction of oxidized Spiro-OMeTAD. It constructs a high-quality hole transport layer as a carrier transport channel, thereby obtaining a perovskite solar cell with good stability, enabling further industrial production and commercial application of perovskite solar cells.

[0021] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that they do not depart from the spirit of the technical solutions of the present invention and should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A perovskite solar cell based on organic hole transport layer solvent engineering, characterized in that, From bottom to top, it includes a transparent substrate, a transparent electrode, an electron transport layer of TiO2 or SnO2, a perovskite light-absorbing layer, a hole transport layer based on solvent engineering, and a metal electrode. The hole transport layer is prepared by dissolving Spiro-OMeTAD and LiTFSI solutes in a mixed solvent of chlorobenzene and ethyl acetate to form an organic hole transport layer solution and then coating it. The transparent electrode is made of FTO or ITO, and the perovskite is made of ABX3 as the perovskite light-absorbing layer.

2. The perovskite solar cell based on organic hole transport layer solvent engineering according to claim 1, characterized in that, The electron transport layer TiO2 or SnO2 has a thickness of 20nm-200nm, the perovskite light-absorbing layer has a thickness of 300nm-700nm, the hole transport layer based on solvent engineering has a thickness of 100nm-300nm, and the metal electrode has a thickness of 80nm-100nm.

3. The perovskite solar cell based on organic hole transport layer solvent engineering according to claim 1, characterized in that, In ABX3, A is any one of Cs, MA, and FA; B is any one of Pb and Sn; and X is any one of I, Br, and Cl.

4. A method for preparing the perovskite solar cell according to claim 1, characterized in that, Includes the following steps: A: Deposit an FTO or ITO thin film on a glass substrate to form a transparent electrode, or directly use FTO or ITO glass; B: A dense TiO2 or SnO2 layer is deposited on the transparent electrode as an electron transport layer by screen printing or spray pyrolysis process, with a thickness ranging from 20nm to 200nm. C: The perovskite material grown on the electron transport layer is grown by spin coating, scraping, or spraying, and then the solvent in the perovskite material precursor solution is removed by evaporation and annealing. The thickness ranges from 300nm to 700nm. D: An organic hole transport layer solution is coated on the perovskite light-absorbing layer, and a hole transport layer with a thickness of 100nm-300nm is obtained by spin coating. Electrodes are then deposited on the layer to obtain a perovskite solar cell. The organic hole transport layer coating solution consists of a main solvent and a trace solvent. Chlorobenzene accounts for 50%-99% of the volume of the main solvent, with the remaining main solvent being ethyl acetate. 4-tert-butylpyridine (TBP) is added as a trace solvent, with an addition amount within 3% of the main solvent volume. The solutes are 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) and lithium bis(trifluoromethanesulfonylimide) (LiTFSI). The thickness of the dense layer is controlled by adjusting the concentration of the dense layer slurry, the number of printing passes, and the duration of spraying. The LiTFSI is first dissolved in an acetonitrile solution and then added to the hole transport layer solution.

5. The method for preparing perovskite solar cells by solvent preparation according to claim 4, characterized in that, The chlorobenzene has a volume percentage of 95% in the main solvent, the ethyl acetate has a volume percentage of 5%, and the amount of trace solvent TBP added is 0. Alternatively, the volume percentage of chlorobenzene in the main solvent is 90%, the volume percentage of ethyl acetate is 10%, and the amount of trace solvent TBP added is 0. Alternatively, the volume percentage of chlorobenzene in the main solvent is 80%, the volume percentage of ethyl acetate is 20%, and the amount of trace solvent TBP added is 0. Alternatively, the volume percentage of chlorobenzene in the main solvent is 70%, the volume percentage of ethyl acetate is 30%, and the amount of trace solvent TBP added is 0. Alternatively, the volume percentage of chlorobenzene in the main solvent is 60%, the volume percentage of ethyl acetate is 40%, and the amount of trace solvent TBP added is 0. Alternatively, the volume percentage of chlorobenzene in the main solvent is 75%, the volume percentage of ethyl acetate is 25%, and the amount of trace solvent TBP added is 3% of the volume of the main solvent.

6. The method for preparing perovskite solar cells by solvent preparation according to claim 4, characterized in that, The preparation process of the organic hole transport layer is as follows: Spiro-OMeTAD is added to a solvent, stirred at 20°C-30°C for 6-24 hours, and allowed to stand until it reaches a thermodynamically stable state to obtain the hole transport layer solution.

7. The method for preparing perovskite solar cells by solvent preparation according to claim 4, characterized in that, The process of coating an organic hole transport layer on a substrate using spin coating is as follows: the hole transport layer precursor solution is 38-50 μL spin-coated on the substrate, the spin speed is 3000-4500 rpm, the acceleration is 1000-3000 rpm / s, and the spin coating time is 10-30 s.

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