An organic solar cell based on PFN-Br modified atomic layer deposition tin oxide, and a preparation method and application thereof

Abstract

The application discloses an organic solar cell based on PFN-Br modified atomic layer deposition tin oxide and a preparation method and application thereof, and the organic solar cell comprises, from bottom to top, a transparent conductive substrate, an electron transport layer, an interface modification layer, an active layer, a hole transport layer and a metal back electrode, wherein the material of the electron transport layer is ALD-SnO2, and the material of the interface modification layer is PFN-Br. The solar cell can fundamentally improve the thermal stability of the device.

Description

Technical Field

[0001] This invention relates to the field of organic optoelectronic devices, specifically to an interface modification technique for organic solar cells, and particularly to an organic photovoltaic device based on PFN-Br modified atomic layer deposition of tin oxide, its preparation method, and its application. Background Technology

[0002] Organic solar cells (OSCs) have attracted widespread attention due to their wide availability of materials, solution-processability, and lightweight flexibility. The electron transport layer (ETL) plays a crucial role in improving the morphology of the active layer, enhancing device stability, strengthening interface transport, and improving carrier collection. Atomic layer deposition (ALD) technology can fabricate dense, uniform, and precisely controllable thickness metal oxide thin films (such as SnO2). Its excellent electron mobility, suitable energy levels, and low defect state density make it an ideal ETL choice for high-performance OSCs, especially suitable for device structures requiring precise control of interface thickness and morphology.

[0003] Patent application CN121728956A discloses a highly stable electron transport layer and a perovskite solar cell. The electron transport layer is fabricated by depositing a fullerene (C0.05) layer onto a substrate on which a hole transport layer and a perovskite thin film layer have been prepared. 60 ); in C 60 A layer of graphitic carbon nitride (g-C3N4) is spin-coated onto the top; finally, an atomic layer deposition (ALD-SnO2) layer of tin oxide is deposited. g-C3N4 exhibits good electrical conductivity and, without affecting electron transport, can fill C... 60 Some gaps between ALD-SnO2 and C can also react with C. 60 The interaction between ALD and SnO2 leads to a tighter bond and improved interface stability. The highly stable electron transport layer prepared in this invention, when applied to perovskite solar cell devices, significantly improves the stability of perovskite solar cells.

[0004] Patent application CN116156910A discloses a highly stable perovskite solar cell with a water vapor barrier and its preparation method. The highly stable perovskite solar cell with a water vapor barrier comprises, from bottom to top: an ITO substrate, an electron transport layer, a perovskite absorber layer, a hole transport layer, a buffer layer, a water vapor barrier layer, and a gold electrode. The preparation method of the highly stable perovskite solar cell with a water vapor barrier specifically includes the following steps: Step 1: Prepare the ITO substrate; Step 2: Prepare the electron transport layer; Step 3: Prepare the perovskite precursor solution; Step 4: Prepare the perovskite absorber layer; Step 5: Prepare the hole transport layer precursor solution; Step 6: Prepare the hole transport layer; Step 7: Prepare the buffer layer; Step 8: Prepare the water vapor barrier layer; Step 9: Prepare the gold electrode.

[0005] However, although the aforementioned patent applications show that rigid perovskite solar cell devices based on ALD-SnO2 ETL can achieve high photoelectric conversion efficiency in the initial state, when applied to wide-bandgap organic photovoltaic materials (such as the PM6:FTCC-Br system), a significant drop in device voltage occurs due to work function mismatch. Furthermore, the devices exhibit significant stability issues under thermal stress conditions; under isothermal aging at 85 °C, the efficiency degradation rate is significantly faster than that of ZnO ETL devices prepared by traditional sol-gel high-temperature annealing. This severely limits the potential of ALD-SnO2 in practical applications. The poor thermal stability stems from the limited oxidation capacity of the precursor oxygen source (H2O) in the ALD-SnO2 process, which cannot completely oxidize all metal precursor molecules. This leads to insufficient coordination numbers in the Sn-O bonds and unavoidable microscopic defects on the film surface (such as oxygen vacancies, dangling bonds, and Sn-source organic ligands). These defect states become strong charge recombination centers under thermal excitation. Meanwhile, the interfacial energy level matching and physical adhesion between SnO2 and the upper organic active layer are prone to deterioration during thermal cycling, leading to increased interfacial resistance and performance degradation. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing organic solar cells based on ALD-SnO2 electron transport layers, such as their unsuitability for wide bandgap acceptors and poor thermal stability, and to provide an organic solar cell with a simple device structure that can fundamentally improve the thermal stability of the device.

[0007] This invention provides an organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide, the structure of which, from bottom to top, comprises: Transparent conductive substrate; An electron transport layer, wherein the material of the electron transport layer is ALD-SnO2; An interface modification layer, wherein the material of the interface modification layer is PFN-Br; Active layer; Hole transport layer; And a metal back electrode.

[0008] The PFN-Br interface modification layer provided by this invention has two main functions. One function is to passivate surface defects, specifically targeting microscopic defects on the surface of the ALD-SnO2 thin film, as detailed below: The amino groups and bromide ions at the ends of the PFN-Br molecular chains can undergo strong coordination or electrostatic interactions with positively charged micro-defects on the ALD-SnO2 surface (such as oxygen vacancies, dangling bonds, and Sn-sourced organic ligands), effectively "stitching up" dangling bonds and significantly reducing the surface state density. This chemical passivation remains stable under thermal stress, suppressing thermally induced defect activation and nonradiative charge recombination.

[0009] Another function is to optimize the interface energy level of ALD-SnO2, which is explained in detail below: PFN-Br forms a fixed-orientation interfacial dipole layer on the SnO2 surface, effectively reducing the work function of SnO2 and optimizing its alignment with the energy level of the lowest unoccupied molecular orbital (LUMO) of the active layer, thus promoting the formation of ohmic contacts. More importantly, this dipole layer structure is stable and can "anchor" the interfacial energy level during high-temperature aging, preventing an increase in the electron extraction barrier caused by changes in the material's work function or energy band structure.

[0010] Another function is to enhance interfacial adhesion and stress buffering: PFN-Br, as an organic molecular layer, has excellent physical compatibility and chemical affinity with the upper organic active layer, forming a smooth transition from the inorganic ETL to the organic active layer. This enhances the mechanical adhesion between the interfaces, and the flexible layer can buffer the internal stress caused by the difference in the thermal expansion coefficients of the materials in each layer, effectively preventing microcracks or delamination at high temperatures.

[0011] Preferably, the thickness of the interface modification layer is 3-5 nm. If the thickness is too large, the series resistance of the device will increase significantly, charge extraction will be difficult, and an S-curve will easily appear.

[0012] Preferably, the PFN-Br is a compound having the following structure: .

[0013] Preferably, the transparent conductive substrate is glass plated with indium tin oxide (ITO) or indium zinc oxide (IZO).

[0014] Preferably, the active layer is made of one or more of PM6: BTP-eC9, PM6: COTIC-4F, PM6: L8BO, and PM6: FTCC-Br.

[0015] Preferably, the hole transport layer is molybdenum trioxide (MoO3).

[0016] Preferably, the metal back electrode is silver (Ag) or aluminum (Al).

[0017] On the other hand, the present invention also provides a method for fabricating an organic photovoltaic device based on PFN-Br modified atomic layer deposition of tin oxide, comprising: (1) Cleaning and pretreatment of the transparent conductive substrate; (2) Atomic deposition of SnO2 on the transparent conductive substrate of step (1) forms an electron transport layer; (3) A PFN-Br solution with a concentration of 0.2-0.3 mg / mL is spin-coated onto the electron transport layer in step (2) by a solution method, and then annealed to form an interface modification layer; (4) An active layer, a hole transport layer and a metal back electrode are sequentially formed on the interface modification layer.

[0018] Preferably, the specific steps of step (3) are as follows: PFN-Br was dissolved in trifluoroethanol to obtain a PFN-Br solution, which was then spin-coated onto an electron transport layer at a speed of 2000-5000 rpm for 20-40 seconds, followed by annealing at 80-120 °C for 5-15 minutes.

[0019] This invention utilizes the fact that trifluoroethanol can better dissolve PFN-Br, allowing PFN-Br to be uniformly dispersed in the solvent. By adjusting the rotation speed and the concentration of the PFN-Br solution, an interface modification layer of appropriate thickness is obtained. Annealing at 100°C for 5 minutes removes residual solvent. At the same time, annealing provides kinetic energy for the PFN-Br molecular chains to rearrange, allowing them to move to a more balanced and ordered position.

[0020] Preferably, the precursor for atomic layer deposition of SnO2 is tetra(dimethylamino)tin and deionized water.

[0021] Preferably, a hole transport layer and a metal back electrode are sequentially formed on the active layer by vacuum evaporation.

[0022] On the other hand, the present invention also provides the application of the organic solar cell in an organic photovoltaic device with indoor soft light.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Optimization of efficiency of indoor soft light devices: PFN-Br modification adjusts the work function of ALD-SnO2 to form a good ohmic contact with the wide bandgap material, which usually improves the fill factor (FF) and open-circuit voltage of the device. VOC This will improve efficiency, resulting in higher or comparable initial efficiency.

[0024] (2) Leap in thermal stability: PFN-Br modification not only improves stability but also enhances the thermal stability of the device. In the continuous aging test under a nitrogen atmosphere at 85°C, the device using the structure of this invention (ALD-SnO2 / PFN-Br) showed a significant improvement in the time required for its power conversion efficiency (PCE) to decay to 80% of its initial value (T). 80 This represents a significant improvement compared to the control device without PFN-Br modification (ALD-SnO2 directly contacts the active layer).

[0025] (3) Simple process and strong applicability: The PFN-Br layer can be formed by room temperature spin coating and low temperature annealing. The process is simple and perfectly compatible with the mainstream solution method for preparing active layers. This technical solution is highly versatile and applicable to a variety of efficient donor-acceptor active layer systems.

[0026] (4) Solving specific technical bottlenecks: This invention addresses the key stability shortcomings of high-performance ALD-SnO2 ETL in applications, providing a clear and effective technical path for developing organic solar cells with both high efficiency and high stability. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an organic solar cell device with a PFN-Br interface modification layer in an embodiment of the present invention.

[0028] Figure 2 shows the thermal stability aging test curves (normalized PCE versus time) of the PM:BTP-eC9 device of Comparative Example 1 (without PFN-Br) and Example 1 (with PFN-Br).

[0029] Figure 3 This is a comparison of the energy level arrangement diagram at the SnO2 / active layer interface in Comparative Example 1 and Example 1, drawn using UPS testing.

[0030] Figure 4 The indoor soft light devices (PM6: FTCC-Br) prepared using different electron transport layers, as provided in Comparative Examples 1, 2, and 1, were tested under AM1.5G sunlight. JV Curve comparison.

[0031] Figure 5 The device (PM6: FTCC-Br) using PFN-Br / SnO2 as the electron transport layer provided in Example 1 was tested under low light conditions at a 3000k 1000 lux LED light source. JV curve.

[0032] Figure 6 The device (PM6: FTCC-Br) prepared by passivating SnO2 with PFN-Br at a concentration of 1 mg / mL, as provided in Comparative Example 3, was tested under AM1.5G sunlight. JV curve. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0034] The present invention proposes a process for passivating the ALD-SnO2 interface using PFN-Br. This strategy effectively fills surface defect states, regulates the interface energy level arrangement, and enhances the mechanical adhesion of the interface. As a result, it significantly improves thermal stability while achieving adjustable interface work function, representing a significant technological breakthrough in this field.

[0035] A specific embodiment of the present invention provides an organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide, such as... Figure 1 As shown, from bottom to top, it includes a transparent substrate (transparent base), a transparent conductive oxide electrode (ITO), an electron transport layer (ALD-SnO2), an interface modification layer (PFN-Br), an active layer, a hole transport layer (MoO3), and a metal back electrode (Ag).

[0036] A 150 nm transparent conductive layer of ITO on a rigid substrate has a sheet resistance of 12 Ohm and a transmittance of 92%. The electron transport layer is an atomic layer deposition ALD-SnO2 with a thickness of 20 nm.

[0037] The active layer is PM6:BTP-eC9, with a thickness of 100-150 nm.

[0038] The hole transport layer is vacuum-deposited MoO3 with a thickness of 5-15 nm.

[0039] The metal back electrode is silver, with a thickness of 50-100 nm.

[0040] Example 1 The specific steps of the method for fabricating organic solar cells based on PFN-Br modified atomic layer deposition of tin oxide provided in this embodiment are as follows: (1) Substrate cleaning: The patterned ITO conductive glass was ultrasonically cleaned in detergent, deionized water, acetone and isopropanol for 20 minutes each, dried with nitrogen, and then treated with ultraviolet ozone for 15 minutes.

[0041] (2) Deposition of the ALD-SnO2 electron transport layer: The treated ITO substrate was placed in an atomic layer deposition apparatus. Tetra(dimethylamino)tin (TDMASn) was used as the tin source, and deionized water was used as the oxygen source. The substrate temperature was set to 90 °C, and a TDMASn pulse, inert gas purging, H2O pulse, and inert gas purging were sequentially introduced to form a deposition cycle. By controlling the number of cycles, a SnO2 film with a thickness of approximately 20 nm was deposited.

[0042] (3) Preparation of PFN-Br interface modification layer: Prepare a PFN-Br trifluoroethanol solution with a concentration of 0.25 mg / mL. Spin-coat the above solution onto the SnO2 film surface at a speed of 3000 rpm for 30 seconds, and then place the sample on a hot stage at 100 ℃ for annealing for 10 minutes to form an ultrathin modification layer with a thickness of about 3-5 nm.

[0043] (4) Preparation of the active layer: For normal devices, a PM6:BTP-eC9 donor-acceptor system was used. The polymer donor PM6 and the small molecule acceptor BTP-eC9 were dissolved in chlorobenzene at a weight ratio of 1:1.2, and 10 mg / mL of 1,3,5-trichlorobenzene was added as an additive, resulting in a total donor-acceptor concentration of 22 mg / mL. The active layer solution was spin-coated onto the PFN-Br modified layer at a speed of 2500 rpm for 30 seconds to form a film of approximately 100 nm. For indoor soft light devices, a PM6:FTCC-Br donor-acceptor system was used, with a donor-acceptor mass ratio of 1:1. Chlorobenzene was used as the solvent, and 10 mg / mL of 1,3,5-trichlorobenzene was added as an additive, resulting in a total donor-acceptor concentration of 20 mg / mL. The active layer solution was spin-coated onto the PFN-Br modified layer at a speed of 2000 rpm for 30 seconds to form a film of approximately 100 nm.

[0044] (5) Preparation of hole transport layer and back electrode: The sample was transferred to a vacuum evaporation chamber and deposited at a pressure below 1×10⁻⁶. ⁻5 Under the condition of Pa, an 8 nm thick MoO3 layer was sequentially thermally evaporated and deposited as a hole transport layer, and a 120 nm thick silver (Ag) layer was deposited as a back electrode.

[0045] A 150 nm transparent conductive layer of ITO on a rigid substrate has a sheet resistance of 12 Ohm and a transmittance of 92%. The electron transport layer is an atomic layer deposition ALD-SnO2 with a thickness of 20 nm.

[0046] The active layer is PM6:BTP-eC9, with a thickness of 110 nm.

[0047] The hole transport layer is a vacuum-deposited MoO3 layer with a thickness of 8 nm.

[0048] The metal back electrode is silver and has a thickness of 120 nm.

[0049] The electron donor material provided in this embodiment is PM6 polymer, and the electron acceptor material is BTP-eC9, with a PM6:BTP-eC9 ratio of 1:1.2 (wt / w). The structure of the prepared rigid organic solar cell device is glass / ITO / ALD-SnO2 / PFN-Br / PM6:BTP-eC9 / MoO3 / Ag.

[0050] Example 2 Compared with Example 1, in step (3), the concentration of the PFN-Br trifluoroethanol solution is 0.3 mg / mL.

[0051] Comparative Example 1 Unlike Example 1, the active layer was directly prepared on the ALD-SnO2 electron transport layer, and the PFN-Br interface modification layer was not prepared.

[0052] Comparative Example 2 Unlike Comparative Example 1, ZnO was atomically deposited on the transparent conductive substrate in step (1) to form an electron transport layer.

[0053] Comparative Example 3 Unlike Example 1, in step (3), the concentration of the PFN-Br trifluoroethanol solution was 1 mg / mL, and the thickness of the PFN-Br interface modification layer was 10 nm.

[0054] like Figure 2 The image shows a comparison between an organic solar cell without an interface modification layer (Comparative Example 1) and an organic solar cell with an interface modification layer (Example 1). Clearly, the organic solar cell with the interface modification layer exhibits significantly improved thermal stability.

[0055] like Figure 3 and Figure 4 As shown, the solar cells prepared in Example 1, Comparative Example 1 and Comparative Example 2 are compared. The change in the work function of ALD-SnO2 after passivation with PFN-Br makes the conduction band bottom of the electron transport layer match the LUMO of the wide bandgap acceptor material (FTCC-Br), and the prepared indoor soft light device exhibits a normal open circuit voltage.

[0056] like Figure 5 As shown, the solar cell prepared in Example 1, i.e. the device made of ALD-SnO2 after passivation with PFN-Br, still exhibits good photoelectric performance under low light.

[0057] like Figure 6As shown, in the solar cell prepared in Comparative Example 3, the high concentration of PFN-Br leads to a more significant interfacial doping effect. PFN-Br, as a polyelectrolyte, undergoes strong intermolecular interactions with the acceptor material, resulting in the transfer of electrons from PFN-Br to the acceptor.

Claims

1. An organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide, characterized in that, Its structure, from bottom to top, includes: Transparent conductive substrate; An electron transport layer, wherein the material of the electron transport layer is ALD-SnO2; An interface modification layer, wherein the material of the interface modification layer is PFN-Br; Active layer; Hole transport layer; And a metal back electrode.

2. The organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide according to claim 1, characterized in that, The thickness of the interface modification layer is 3-5 nm.

3. The organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide according to claim 1, characterized in that, The transparent conductive substrate is glass coated with indium tin oxide or indium zinc oxide.

4. The organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide according to claim 1, characterized in that, The active layer is made of one or more of the following materials: PM6: BTP-eC9, PM6: COTIC-4F, PM6: L8BO, and PM6: FTCC-Br.

5. The organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide according to claim 1, characterized in that, The hole transport layer is molybdenum trioxide.

6. The organic solar cell based on PFN-Br modified atomic layer deposition of tin oxide according to claim 1, characterized in that, The metal back electrode is made of silver or aluminum.

7. A method for fabricating an organic photovoltaic device by PFN-Br modified atomic layer deposition of tin oxide according to any one of claims 1-6, characterized in that, include: (1) Cleaning and pretreatment of the transparent conductive substrate; (2) Atomic deposition of SnO2 on the transparent conductive substrate of step (1) forms an electron transport layer; (3) A PFN-Br solution with a concentration of 0.2-0.3 mg / mL is spin-coated onto the electron transport layer in step (2) by a solution method, and then annealed to form an interface modification layer; (4) An active layer, a hole transport layer and a metal back electrode are sequentially formed on the interface modification layer.

8. The method for fabricating an organic photovoltaic device by PFN-Br modified atomic layer deposition of tin oxide according to claim 7, characterized in that, The specific steps of step (3) are as follows: PFN-Br was dissolved in trifluoroethanol to obtain a PFN-Br solution, which was then spin-coated onto an electron transport layer at a speed of 2000-5000 rpm for 20-40 seconds, followed by annealing at 80-120 °C for 5-15 minutes.

9. The method for fabricating an organic photovoltaic device by PFN-Br modified atomic layer deposition of tin oxide according to claim 7, characterized in that, The precursors for atomic layer deposition of SnO2 are tetra(dimethylamino)tin and deionized water.

10. The application of the organic solar cell according to any one of claims 1-6 in an organic photovoltaic device for indoor soft light.

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