Hole transport layer with three-layer structure, perovskite solar cell and preparation method thereof

Abstract

The invention discloses a hole transport layer with a three-layer structure, a perovskite solar cell and a preparation method of the perovskite solar cell. The hole transport layer is of a three-layer stacked structure and sequentially comprises an inorganic metal oxide layer, an organic polymer interface modification layer and a self-assembly monomolecular layer from bottom to top. By adopting the three materials with different components, the problem that shape-preserving coverage is difficult to form between the perovskite layer and the substrate in a traditional structure is solved, and meanwhile, the spontaneous oxidation-reduction reaction of high-valence metal cations in the inorganic metal oxide layer and the complex chemical process of deprotonation of the cations in the perovskite layer are effectively inhibited. In addition, through the three-layer structure of the hole transport layer, the interlayer wettability of the solar cell is improved, and crystallization optimization of perovskite is facilitated, so that the defect state density is remarkably reduced, and the non-radiative recombination loss is reduced. Finally, the photoelectric conversion efficiency of the solar cell is improved, and the stability of the device is remarkably enhanced.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology and relates to the improvement and optimization of perovskite solar cells. Specifically, it relates to a three-layer hole transport layer, a perovskite solar cell, and its fabrication method. Background Technology

[0002] Perovskite solar cells (PSCs), as a representative of third-generation photovoltaic power generation technology, have advantages such as abundant raw materials, low manufacturing costs, and rapid improvement in photoelectric conversion efficiency. Their development is of great significance for reducing the cost of photovoltaic power generation and promoting applications such as flexible wearable electronic devices and building-integrated photovoltaics.

[0003] In the evolution of device structures, the inverted (pin) structure has attracted widespread attention due to its low-temperature fabrication process, negligible current hysteresis, and better compatibility with tandem solar cells. Compared to the conventional (nip) structure, the inverted structure exhibits superior operational stability because its charge transport layer and electrode materials can more effectively block ion migration and side reactions between the perovskite layer and the metal electrode. However, the performance of the inverted structure is highly dependent on the quality of the top hole transport layer (HTL).

[0004] Inorganic metal oxides, due to their typically hydrophilic surfaces and good compatibility with perovskite precursor solutions, are conducive to the formation of uniform and dense perovskite films, and their diverse deposition processes have made them the most mainstream hole transport materials. However, non-stoichiometric films prepared from inorganic metal oxides often contain metal vacancies and interstitial oxygen, resulting in some metal ions existing in a high-valence oxidation state to maintain charge balance. These high-valence metal ions possess strong oxidizing and Lewis acidic properties, which are key factors inducing perovskite interface decomposition and device performance degradation.

[0005] Existing technologies propose spin-coating a self-assembled monolayer (SAM) between a hole transport layer constructed from inorganic metal oxides and a perovskite layer. This approach can passivate surface defects in the hole transport layer, modulate energy levels, block direct chemical interactions, and improve wettability. However, the coverage and uniformity of SAMs on the substrate are often difficult to guarantee, which exacerbates the risk of size scaling. Furthermore, SAMs are anchored by chemical bonds, which have weak bonding capabilities. Under long-term thermal stress, light exposure, or humidity conditions, these chemical bonds may hydrolyze or break, causing the SAM layer to desorb from the substrate and leading to complete device failure. In addition, the acidic groups of SAMs may directly contact the perovskite, accelerating the oxidation of iodide ions, the decomposition of formamidinium, and the reduction of lead ions.

[0006] Therefore, there is an urgent need to propose an optimized hole transport layer to improve the operational stability of perovskite solar cells while avoiding the loss of photoelectric conversion efficiency. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a three-layer hole transport layer and a perovskite solar cell, along with its fabrication method. By using a continuous deposition method of three-layer hole transport materials, the invention improves hole extraction at the lower interface, enhances the quality of the buried perovskite, and achieves high stability. This solves the problems of chemical decomposition and lattice analysis of perovskite by high-valence metal cations in inorganic hole transport materials, as well as the low coverage and poor stability of SAMs.

[0008] A three-layer hole transport layer includes an inorganic metal oxide layer, an organic polymer interface modification layer, and a self-assembled monolayer.

[0009] Preferably, the inorganic metal oxide layer is made of NiO. x Any one of CuO2, CuSCN, and V2O5.

[0010] Preferably, the material of the organic polymer interface modification layer is any one of the organic polymers Polymer-4PACZ, Polymer-2PACZ, Polymer-PhPACz, Polymer-4PADCB, and PTAA.

[0011] Preferably, the material of the self-assembled monolayer is any one of Ph-4PACZ, Me-4PACZ, 4PADCB, and 4PABCZ.

[0012] Preferably, the inorganic metal oxide layer has a thickness of 10-15 nm, the organic polymer interface modification layer has a thickness of 5-8 nm, and the self-assembled monolayer has a thickness of 3-5 nm.

[0013] A method for preparing a three-layer hole transport layer involves dissolving an organic polymer and a self-assembled monomolecule in an organic solvent, spin-coating the organic polymer solution onto the surface of an inorganic metal oxide layer for interface modification, and then spin-coating the self-assembled monomolecule solution onto the surface of the organic polymer interface-modified layer to form a self-assembled monolayer.

[0014] Preferably, the organic polymer Polymer-4PACZ is dissolved in a mixed solution of methanol (MeOH) and chloroform (CF), and the self-assembled monomer Ph-4PACZ is dissolved in an ethanol solution. The molecular structures of the polymers Polymer-4PACZ and Ph-4PACZ are shown in formulas (I) and (II), respectively:

[0015] Preferably, an organic polymer solution is spin-coated onto the surface of the inorganic metal oxide layer at 3000 rpm for 30 s, and a self-assembled monomolecule solution is spin-coated onto the surface of the organic polymer interface modification layer at 4000 rpm for 30 s.

[0016] Preferably, the solvent is filtered using a 0.22 μm pore size needle filter before the preparation of the mixed solution.

[0017] A perovskite solar cell with a three-layer hole transport layer includes, from bottom to top, a conductive glass layer, an inorganic metal oxide layer, an organic polymer interface modification layer, a self-assembled monolayer, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer.

[0018] Preferably, the conductive glass layer is ITO or FTO, and the perovskite layer is made of Cs. 0.05 FA 0.95 PbI3, the electron transport layer is made of PCBM or C. 60 The hole blocking layer is made of BCP, and the electrode is made of Ag metal.

[0019] Preferably, an anti-reflective layer of MgF2 is also provided on the back side of the conductive glass layer to reduce solar energy reflection at the battery and increase light absorption. This invention has the following beneficial effects:

[0020] 1. In the three-layer hole transport layer, NiO x With good surface hydrophilicity and roughness adaptability, the organic polymer can fill the microscopic unevenness of the inorganic layer surface to form a continuous and dense intermediate layer. The self-assembled monolayer forms an ordered molecular layer on the polymer surface through chemical adsorption. The synergistic effect of the three-layer structure ensures that the hole transport layer provides conformal coverage of the perovskite layer at the microscale.

[0021] 2. High-valence metal cations in inorganic metal oxide layers possess strong oxidizing properties and Lewis acidity, readily inducing I in perovskite. - Oxidized to I2, FA + Decomposition, Pb 2+ To address the issue of perovskite structure collapse caused by reduction, an organic polymer layer is used as the first physical barrier. This layer isolates the high-valence metal cations from direct contact with the perovskite, blocking the interfacial pathway of redox reactions. Then, through the formation of coordination bonds or chelation interactions between the phosphonic acid and carboxyl groups in the self-assembled monolayer and the high-valence metal cations, a second protective layer is formed, reducing its oxidizing properties. The bilayer structure of polymer and SAMs provides multiple chemical barriers. Even if some SAMs desorb, the polymer layer maintains its protective function, achieving conformal coverage of the perovskite emitting layer on the substrate. Simultaneously, it significantly suppresses potential chemical reactions, ultimately achieving long-term device stability.

[0022] 3. The three-layer structure of the hole transport layer forms a stepped energy level structure, reducing the energy barrier and energy loss of the hole transport path from the perovskite to the electrode, making it smoother. Furthermore, the functional groups in the polymer and SAMs can effectively passivate the uncoordinated Pb at the lower interface of the perovskite. 2+ I - These defects reduce non-radiative recombination and increase the open-circuit voltage of the device. Simultaneously, the thickness of the three-layer hole transport layer is controlled at the nanometer level, preventing significant optical absorption and ensuring the current density generated by the battery. Therefore, the photoelectric conversion efficiency of the device is also improved. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the perovskite solar cell with a three-layer hole transport layer prepared in Example 1;

[0024] Figure 2 These are the JV curves of the solar cells prepared in Example 1 and Comparative Example 1;

[0025] Figure 3 These are the aging test results of the solar cells prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0026] The present invention will be further explained below with reference to the accompanying drawings; it should be understood that the scope of protection of the present invention is not limited thereto.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The reagents, materials, and instruments used are commercially available unless otherwise specified.

[0028] Example 1

[0029] This embodiment provides a perovskite solar cell with a three-layer hole transport layer, such as... Figure 1 As shown, from bottom to top, it includes a conductive glass layer, an inorganic metal oxide layer, an organic polymer interface modification layer, a self-assembled monolayer, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer. The specific preparation steps are as follows:

[0030] Step 1: The conductive glass substrate is ultrasonically cleaned sequentially in glass cleaning solution, deionized water, acetone solution, and anhydrous ethanol for 20 min, and then rapidly dried in an oven. It is then treated in oxygen plasma for 2 min before use.

[0031] Step 2, NiO XDissolved in deionized water, a precursor solution with a concentration of 10 mg / mL was prepared and spin-coated at 2000 rpm onto a conductive glass substrate treated with oxygen plasma for 30 s. Then, it was annealed in air at 150 °C for 15 min and cooled to room temperature to form a NiOx substrate.

[0032] Step 3: Dissolve the organic polymer Polymer-4PACZ in a mixed solution of methanol and chloroform at a volume ratio of 1:1 to prepare a conductive polymer solution with a concentration of 1 mg / mL. Spin-coat the solution onto the surface of the NiOx substrate at 3000 rpm for 30 seconds, anneal at 100°C for 10 minutes, and then cool to form an organic polymer interface modification layer.

[0033] Step 4: Dissolve the self-assembled monomolecular material Ph-4PACZ in ethanol to prepare a self-assembled monomolecular solution with a concentration of 0.5 mg / mL. Spin-coat the solution onto the surface of the organic polymer interface modification layer at 3000 rpm for 30 s, and anneal at 100℃ for 10 min to form a self-assembled monomolecular layer. This yields a three-layer hole transport layer.

[0034] Step 5: Weigh the perovskite component Cs according to the stoichiometric ratio. 0.05 FA 0.95 PbI3 was added with appropriate amounts of PbCl2 and MACl as additives to prepare a perovskite precursor. Then, it was dissolved in a mixed solvent of DMF and DMSO with a volume ratio of 4:1 to prepare a precursor solution with a concentration of 1.6 M.

[0035] On the hole transport layer, 65 μL of precursor solution was statically added dropwise, followed by spin coating at 1000 rpm for 8 s, and then at 5000 rpm for 25 s. 15 s after the second spin coating, 150 μL of chlorobenzene was poured in as an antisolvent. Immediately after both spin coating steps, the mixture was transferred to a hot plate and annealed at 110 °C for 20 min to form a perovskite luminescent layer.

[0036] Step 6: Dissolve PDAI2 solution in isopropanol to prepare a solution with a concentration of 1 mg / mL. Spin-coat the perovskite luminescent layer surface at 5000 rpm for 25 s, and then anneal at 110 °C for 5 min for passivation and deposition treatment.

[0037] Step 7: Sequentially deposit a 40 nm thick layer of C on the passivated perovskite luminescent layer surface at a rate of 0.01 nm / s. 60 An electron transport layer was deposited, followed by an 8 nm thick BCP hole-blocking layer at a rate of 0.01 nm / s, and a 100 nm thick Ag electrode at a rate of 0.05 nm / s. The vacuum level during the deposition process was less than 1 × 10⁻⁶. -4bar.

[0038] Step 8: Evaporate a 100nm thick MgF2 anti-reflection coating on the back side of the conductive glass substrate to obtain the perovskite solar cell.

[0039] Example 2

[0040] This embodiment provides the fabrication of a perovskite solar cell with a three-layer hole transport layer, based on Example 1, using a conductive polymer solution.

[0041] Example 3

[0042] This embodiment provides a method for preparing a perovskite solar cell with a three-layer hole transport layer. Based on Example 2, CuO2 is used to prepare the precursor solution and Me-4PACZ is used to prepare the self-assembled monomolecule solution.

[0043] Example 4

[0044] This embodiment provides the fabrication of a perovskite solar cell with a three-layer hole transport layer. Based on Example 1, a precursor solution is prepared using V2O5.

[0045] Example 5

[0046] This embodiment provides the fabrication of a perovskite solar cell with a three-layer hole transport layer. Based on Example 4, PTAA is used to prepare a conductive polymer solution, and 4PADCB is used to prepare a self-assembled monomolecule solution.

[0047] Comparative Example 1

[0048] Based on Example 1, this comparative example prepares a perovskite solar cell with a hole transport layer modified only by an organic polymer interface as a comparison. From bottom to top, it includes a conductive glass layer, an inorganic metal oxide layer, an organic polymer interface modification layer, a perovskite light-emitting layer, an electron transport layer, a hole blocking layer, and a metal electrode layer.

[0049] The JV curves of the perovskite solar cells prepared in Example 1 and Comparative Example 1 were tested respectively, and the results are as follows: Figure 2 As shown, the perovskite solar cell prepared in Comparative Example 1 has an open-circuit voltage (Voc) of 1.14 V and a short-circuit current (Jsc) of 25.02 mA·cm⁻¹. -2 The fill factor (FF) was 78.43%, and the final power conversion efficiency (PCE) was 22.45%. The perovskite solar cell prepared in Example 1 had an open-circuit voltage (Voc) of 1.16 V and a short-circuit current (Jsc) of 25.02 mA·cm⁻¹. -2The fill factor (FF) was 82.65%, and the final photoelectric conversion efficiency (PCE) was 24.11%. Compared with Comparative Example 1, the short-circuit current of Example 1 did not change significantly, indicating that although the hole transport layer thickness was slightly increased, no additional optical absorption was caused. At the same time, due to the dual chemical modification of organic polymer and monomolecular assembly material, the defects at the perovskite lower interface were effectively passivated, nonradiative recombination was reduced, and the open-circuit voltage and photoelectric conversion efficiency of the device were also improved.

[0050] Unencapsulated solar cells were subjected to a heat aging test at 65°C in a glove box under a nitrogen atmosphere. The results are as follows: Figure 3 As shown, after 1200 hours of heating aging, the photoelectric conversion efficiency of Comparative Example 1 was only 84.97% of the original efficiency; while after 1200 hours of heating aging, Example 1 could still maintain the original efficiency of 96.16%, indicating that the multiple chemical barriers between the polymer and SAMs can ensure the conformal coverage of the perovskite light-emitting layer on the substrate, achieving a significant improvement in stability.

Claims

1. A three-layer hole transport layer, characterized in that: It includes inorganic metal oxide layers, organic polymer interface modification layers, and self-assembled monolayers.

2. The three-layer hole transport layer as described in claim 1, characterized in that: The material of the inorganic metal oxide layer is NiO. x Any one of CuO2, CuSCN, and V2O5.

3. The three-layer hole transport layer as described in claim 1, characterized in that: The material of the organic polymer interface modification layer is any one of the organic polymers Polymer-4PACZ, Polymer-2PACZ, Polymer-PhPACz, Polymer-4PADCB, and PTAA.

4. The three-layer hole transport layer as described in claim 1, characterized in that: The material of the self-assembled monolayer is any one of Ph-4PACZ, Me-4PACZ, 4PADCB, and 4PABCZ.

5. A three-layer hole transport layer as described in any one of claims 1 to 4, characterized in that: The inorganic metal oxide layer has a thickness of 10-15 nm, the organic polymer interface modification layer has a thickness of 5-8 nm, and the self-assembled monolayer has a thickness of 3-5 nm.

6. The method for preparing a three-layer hole transport layer as described in any one of claims 1 to 4, characterized in that: The organic polymer and the self-assembled monomolecules were dissolved in organic solvents respectively. The organic polymer solution was spin-coated onto the surface of the inorganic metal oxide layer for interface modification. Then, the self-assembled monomolecule solution was spin-coated onto the surface of the organic polymer interface modification layer to form a self-assembled monolayer.

7. The method for preparing a three-layer hole transport layer as described in claim 6, characterized in that: The organic polymer Polymer-4PACZ was dissolved in a mixed solution of methanol and chloroform, and the self-assembled monomer Ph-4PACZ was dissolved in an ethanol solution.

8. The method for preparing a three-layer hole transport layer as described in claim 6, characterized in that: An organic polymer solution was spin-coated onto the surface of the inorganic metal oxide layer at 3000 rpm for 30 s, and a self-assembled monomer solution was spin-coated onto the surface of the organic polymer interface modification layer at 4000 rpm for 30 s.

9. The method for preparing a three-layer hole transport layer as described in claim 6, characterized in that: The solvent is filtered using a needle filter before the mixed solution is prepared.

10. A perovskite solar cell with a three-layer hole transport layer, characterized in that: The solar cell is an inverted perovskite solar cell, and its hole transport layer is a three-layer hole transport layer as described in any one of claims 1 to 4.

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