An organic solar cell based on a high-thermal-conductivity network structure and a preparation method thereof

Abstract

This invention relates to the field of photovoltaic device technology, specifically to an organic solar cell based on a high thermal conductivity network structure and its fabrication method. The organic solar cell device structure, from bottom to top, includes a transparent conductive substrate, a hole transport layer, an organic active layer, an electron transport layer, and a metal electrode. The organic active layer is composed of a polymer donor PM6, a non-fullerene acceptor Y6, and a liquid crystal molecule CA6OB. Under the induction of a thermal annealing process, the liquid crystal molecule CA6OB undergoes an in-situ free radical polymerization reaction and transforms into the liquid crystal polymer PCA6OB, thereby constructing a high thermal conductivity three-dimensional interpenetrating network structure within the bulk heterojunction active layer. This network structure allows for precise control of the vertical component distribution of the donor and acceptor materials, significantly enhancing the orderliness and crystallinity of molecular stacking. Through the synergistic effect of thermal management and morphology control, the photoelectric conversion efficiency and long-term thermal stability of the organic solar cell device are simultaneously improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic device technology, specifically to an organic solar cell based on a high thermal conductivity network structure and its fabrication method. Background Technology

[0002] Organic solar cells, as a novel photovoltaic technology geared towards a low-carbon future, have demonstrated enormous application potential in the energy sector due to their unique advantages. This technology utilizes organic semiconductor materials as the core photosensitive layer, boasting significant advantages such as abundant raw material sources, low manufacturing costs, and the ability to perform large-area printing processing using solution methods. Organic solar cells have irreplaceable application value in scenarios such as power supply for flexible electronic devices, building-integrated photovoltaics (BIPV), and indoor low-light power generation, making them one of the important directions in current new energy materials research.

[0003] With the rapid development of materials science, the emergence of non-fullerene acceptor materials has greatly promoted the improvement of energy conversion efficiency in organic solar cells. In particular, the binary system based on polymer donor PM6 and non-fullerene acceptor Y6, with its excellent spectral response range and charge transport characteristics, has enabled the energy conversion efficiency of the device to break through the 20% mark. This highly efficient bulk heterojunction system, through precise energy level matching and morphology control, achieves efficient exciton separation and transport, and has become a focus of attention in academia and industry.

[0004] Despite record-breaking photoelectric conversion efficiencies, organic solar cells still face significant challenges in terms of thermal stability during practical applications. The active layer of a bulk heterojunction is typically thermodynamically metastable, and during long-term operation, Joule heating or heat accumulation due to ambient temperature fluctuations are inevitable. This thermal effect accelerates phase separation and morphological degradation of the donor and acceptor materials within the active layer, exacerbates nonradiative recombination processes, and ultimately leads to irreversible degradation of the device's photovoltaic performance. How to effectively dissipate internal heat and lock in the microstructure of the active layer while maintaining high efficiency has become a critical technical challenge hindering the commercial application of organic solar cells. Summary of the Invention

[0005] This invention aims to address the problem of insufficient thermal stability often associated with high efficiency in existing organic solar cells, and provides an organic solar cell based on a high thermal conductivity network structure and its fabrication method. This invention achieves a synergistic improvement in both photoelectric conversion efficiency and thermal stability by introducing polymerizable liquid crystal molecules to construct a highly thermally conductive three-dimensional interpenetrating network in situ within the active layer.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: an organic solar cell based on a high thermal conductivity network structure, wherein the device structure of the organic solar cell comprises, from bottom to top: a transparent conductive substrate, a hole transport layer, an organic active layer, an electron transport layer, and a metal electrode; The organic active layer comprises a polymer donor PM6, a non-fullerene electron acceptor Y6, and a liquid crystal molecule CA6OB; wherein the chemical structural formulas of the polymer donor PM6, the non-fullerene electron acceptor Y6, and the liquid crystal molecule CA6OB are as follows: ; ; .

[0007] Preferably, the organic solar cell is a forward device structure, and its specific stacked structure from bottom to top is as follows: ITO glass substrate, PEDOT:PSS hole transport layer, organic active layer, PDINN electron transport layer and metal Ag cathode.

[0008] Preferably, the organic active layer is a bulk heterojunction thin film comprising polymer donor PM6, non-fullerene electron acceptor Y6, and liquid crystal molecule CA6OB.

[0009] Preferably, the proportions of each component in the organic active layer are as follows: the mass ratio of polymer donor PM6 to non-fullerene electron acceptor Y6 is 1:1.15-1.25; the added mass of liquid crystal molecule CA6OB is 1.5% to 2.5% of the total mass of polymer donor PM6 and non-fullerene electron acceptor Y6.

[0010] Preferably, the mass ratio of polymer donor PM6 to non-fullerene electron acceptor Y6 in the organic active layer is 1:1.2, and the added mass of liquid crystal molecule CA6OB is preferably 2% of the total mass of polymer donor PM6 and non-fullerene electron acceptor Y6.

[0011] This invention also provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure, comprising the following steps: Step 1: Substrate cleaning The ITO glass sheet was ultrasonically cleaned in a series of solutions: detergent, deionized water, acetone, and isopropanol. After cleaning, the ITO glass sheet was surface treated using a plasma cleaner. Step 2: Prepare the hole transport layer PEDOT:PSS solution was coated onto the surface of a treated ITO glass sheet using a static spin coating process, followed by a heating and annealing process to form a PEDOT:PSS hole transport layer. Step 3: Preparation of the organic active layer The polymer donor PM6, the non-fullerene electron acceptor Y6, and the liquid crystal molecule CA6OB were dissolved together in chloroform solvent according to a set ratio. The mixed solution was transferred to a glove box under a nitrogen atmosphere and heated and stirred. 30 minutes before the start of the spin coating process, 0.5% by volume of 1-CN additive was added to the mixed solution. Subsequently, the mixed solution was spin-coated onto the surface of the PEDOT:PSS hole transport layer and annealed to form a bulk heterojunction organic active layer. The mass ratio of PM6 to Y6 was 1:1.15-1.25, and the mass of CA6OB was 1.5% to 2.5% of the total mass of PM6 and Y6. Step 4: Fabrication of the electron transport layer PDINN material was dissolved in methanol solvent to prepare a precursor solution. The PDINN solution was then coated onto the surface of the organic active layer using a dynamic spin coating process to form an electron transport layer. Step 5: Electrode Deposition The device is fabricated by depositing a metallic Ag electrode onto the PDINN electron transport layer using a vapor deposition process.

[0012] Preferably, in step two, the rotation speed of the static spin coating is 4500-5500 rpm; the temperature of the heating annealing treatment is between 145-155℃, and the annealing time is maintained at 15-20 minutes.

[0013] Preferably, in step three, the total solute concentration in the mixed solution used to prepare the bulk heterojunction organic active layer is controlled between 15 mg / mL and 17 mg / mL.

[0014] Preferably, in step three, the spin coating speed is 3000-4000 rpm; the annealing temperature after spin coating is set to 90-120℃, and the annealing time is 5 minutes.

[0015] Preferably, in step four, the concentration range of the PDINN methanol solution is 0.5-1.5 mg / mL; the spin coating speed during the dynamic spin coating process is 2000-3000 rpm, and the spin coating time is 25 seconds.

[0016] This invention provides an organic solar cell based on a high thermal conductivity network structure and its fabrication method. It has the following beneficial effects: 1. This invention introduces the liquid crystal molecule CA6OB with polymerizable groups into the organic active layer, and induces its in-situ free radical polymerization reaction using a thermal annealing process to transform it into the liquid crystal polymer PCA6OB. This constructs a highly thermally conductive three-dimensional interpenetrating network structure at the donor-acceptor interface and in the bulk phase. The presence of this network structure significantly improves the thermal conductivity of the blend film, providing an efficient heat dissipation channel for the heat generated during device operation. It effectively avoids active layer morphology collapse and excessive phase aggregation caused by heat accumulation, thereby greatly enhancing the long-term thermal stability of the device under high-temperature conditions.

[0017] 2. This invention utilizes the unique self-assembly properties of the liquid crystal molecule CA6OB and its polymers to precisely control the microstructure and vertical component distribution of the PM6:Y6 bulk heterojunction, promoting the orderly stacking of donor and acceptor molecules and improving crystallinity. This optimized microstructure reduces the density of trapped states during carrier transport, lowers non-radiative recombination losses, and achieves a synergistic balance between electron and hole mobility, thereby significantly improving exciton dissociation efficiency and charge collection efficiency, resulting in a dual improvement in device fill factor and short-circuit current density.

[0018] 3. The fabrication strategy employed in this invention achieves a significant leap in photoelectric conversion efficiency through simple additive engineering without altering the complexity of the original device manufacturing process. Experimental data shows that, at the optimal doping ratio, the device's energy conversion efficiency increases from 16.55% in the basic system to 18.35%, and it maintains excellent performance output even after 1000 hours of thermal aging testing. This method successfully solves the bottleneck problem of achieving both efficiency and stability in the field of organic solar cells, providing a reliable technical path for fabricating high-efficiency, long-life organic photovoltaic devices. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the forward device structure of the organic solar cell of the present invention; Figure 2 A comparison of surface roughness using atomic force microscopy (AFM) of thin films made from liquid crystal molecule CA6OB and liquid crystal polymer PCA6OB in this invention; Figure 3 This is a bar chart comparing the thermal conductivity and thermal diffusivity of PM6, Y6, and CA6OB films in the organic solar cell of this invention. Figure 4 This is a comparison chart of the current density-voltage (JV) characteristic curves of the devices based on PM6:Y6 and PM6:Y6 (CA6OB) active layers in Embodiment 3 and Comparative Example 1 of the present invention. Figure 5The graph shows the device efficiency degradation curves of the solar cells prepared in Example 3 and Comparative Example 1 of this invention under nitrogen atmosphere and heating conditions of 85 °C. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Experimental materials description: The polymer donor PM6, non-fullerene acceptor Y6, and electron transport layer material PDINN were purchased from Jiaxing Hepu Optoelectronics Technology Co., Ltd.; the hole transport layer material PEDOT:PSS, solvent additive 1-CN, and methanol were purchased from Beijing Bailingwei Technology Co., Ltd.; and the liquid crystal small molecule CA6OB was purchased from Shanghai Haohong Biomedical Technology Co., Ltd.

[0022] General steps for solution preparation: Dissolve PDINN in methanol and stir at room temperature until clear and transparent to prepare a 1 mg / ml PDINN methanol solution for later use.

[0023] For the active layer solution, according to the proportions set in different embodiments, the donor PM6, acceptor Y6 and liquid crystal additive CA6OB are weighed respectively, chloroform solvent is added, and the solution is heated and stirred at 40°C for at least 2 hours to ensure that the materials are fully dissolved and mixed.

[0024] Example 1: This invention provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure, wherein the amount of CA6OB added in the active layer is 0.5%, specifically including the following steps: (1) Substrate cleaning: ITO glass slides were placed in beakers containing detergent, deionized water, acetone and isopropanol in sequence, and ultrasonically cleaned for 30 min each. After removal, they were dried with nitrogen gas and then placed in a plasma cleaner for 3 min to remove organic residues on the surface and improve the work function.

[0025] (2) Preparation of hole transport layer: PEDOT:PSS solution was spin-coated onto a cleaned ITO glass slide using a static spin-coating method. The spin-coating parameters were set to a rotation speed of 5000 rpm and a time of 35 s. After spin-coating, the sample was placed on a heating stage and annealed at 150°C for 20 min to form a dense hole transport layer. The sample was then transferred to a nitrogen-filled glove box.

[0026] (3) Preparation of the organic active layer: PM6, Y6, and CA6OB were mixed at a PM6:Y6 mass ratio of 1:1.2 and CA6OB mass of 0.5% of the total mass of PM6 and Y6, dissolved in chloroform, with the total concentration controlled at approximately 16 mg / mL. The mixture was heated and stirred at 50°C for 2 hours in a glove box. 30 min before spin coating, 0.5% (v / v) of 1-CN was added to the mixed solution. The active layer solution was dropped onto the PEDOT:PSS layer and spin-coated at 3500 rpm for 35 s to obtain a mixed film with a thickness of approximately 100 nm. The sample was then annealed on a heating stage at 100°C for 5 min. During this process, CA6OB underwent a polymerization reaction to generate a PCA6OB network.

[0027] (4) Preparation of electron transport layer: Take a pre-prepared 1 mg / mL PDINN methanol solution and form a film on the active layer using dynamic spin coating. The spin coating speed is set to 2500 rpm and held for 25 s.

[0028] (5) Electrode deposition: The sample is transferred to a vacuum deposition chamber, and a metal Ag electrode is deposited on the PDINN layer to complete the device fabrication. Its structure is shown in the figure. Figure 1 As shown.

[0029] Example 2: This invention provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure. The fabrication method in this embodiment is the same as in Embodiment 1, except for the active layer ratio. The mass ratio of PM6 to Y6 is 1:1.2, and the mass of CA6OB added is 1% of the total mass of PM6 and Y6. The parameters of the remaining steps remain unchanged.

[0030] Example 3: This invention provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure. The fabrication method in this embodiment is the same as in Embodiment 1, except for the active layer ratio. The mass ratio of PM6 to Y6 is 1:1.2, and the mass of CA6OB added is 2% of the total mass of PM6 and Y6. All other parameters remain unchanged. This ratio represents the optimal embodiment of this invention.

[0031] Example 4: This invention provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure. The fabrication method in this embodiment is the same as in Embodiment 1, except for the active layer ratio. The mass ratio of PM6 to Y6 is 1:1.2, and the mass of CA6OB added is 3% of the total mass of PM6 and Y6. The parameters of the remaining steps remain unchanged.

[0032] Example 5: This invention provides a method for fabricating an organic solar cell based on a high thermal conductivity network structure. The fabrication method in this embodiment is the same as in Embodiment 1, except for the active layer ratio. The mass ratio of PM6 to Y6 is 1:1.2, and the mass of CA6OB added is 3.5% of the total mass of PM6 and Y6. The parameters of the remaining steps remain unchanged.

[0033] Comparative Example 1: This invention provides a standard PM6:Y6 device without liquid crystal molecules as a comparative example. The preparation method is the same as in Example 1, except that CA6OB is not added to the active layer solution, i.e., the mass ratio of PM6 to Y6 is 1:1.2, and the CA6OB content is 0%. The parameters of the remaining steps remain unchanged.

[0034] Performance testing and results analysis: 1. Morphological characterization analysis The morphology of the thin film was characterized using atomic force microscopy, such as... Figure 2 As shown, the results indicate that after thermal annealing, the root mean square roughness of the film containing CA6OB is significantly reduced compared to before treatment, and the film surface exhibits a tightly packed and highly ordered morphology. This phenomenon confirms that the liquid crystal small molecule CA6OB underwent an in-situ polymerization reaction under thermal annealing conditions, and the resulting liquid crystal polymer PCA6OB constructed an ordered interpenetrating network structure in the active layer.

[0035] 2. Thermal conductivity analysis The thermal conductivity and thermal diffusivity of each component thin film were tested, such as... Figure 3 As shown, the results indicate that the film doped with CA6OB and polymerized exhibits a higher thermal conductivity compared to pure PM6 and Y6 films. This demonstrates that the high thermal conductivity network constructed by PCA6OB effectively enhances the heat transfer capability of the blend film, facilitating the rapid removal of heat from the device.

[0036] 3. Photovoltaic performance analysis At AM1.5G, 100mW / cm 2 Under standard simulated sunlight, the JV characteristics of the devices in Examples 1-5 and Comparative Example 1 were tested using a Keithley 2400 source meter. Figure 4 The JV curves of Comparative Example 1 and Example 3 are compared. Specific performance parameters are summarized in the table below, where PCE = V OC * J SC *FF / Pin (Pin is the incident light intensity):

[0037] Analysis of the data in the table above shows that as the content of CA6OB liquid crystal molecules increases, the device performance exhibits a trend of first increasing and then decreasing. The open-circuit voltage changes relatively little, but the fill factor and short-circuit current density are significantly affected by the amount added. When the amount of CA6OB added is 2% (Example 3), all device parameters reach their optimal levels, and the short-circuit current density increases to 28.32 mA cm⁻¹. -2 The fill factor is as high as 76.49%, and the power conversion efficiency reaches 18.35%, which is much higher than the 16.55% of Comparative Example 1. This indicates that the introduction of an appropriate amount of CA6OB not only optimizes the morphology, but also improves the photoelectric conversion capability of the device by balancing carrier transport.

[0038] 4. Thermal stability analysis The unencapsulated devices of Example 3 and Comparative Example 1 were placed in a nitrogen glove box and subjected to continuous thermal aging tests on an 85°C heating stage (e.g., Figure 5 (As shown). The device efficiency of Comparative Example 1 showed a significant decrease in the initial stage of heating, indicating that its morphology was unstable under heated conditions. In contrast, the device of Example 3 maintained a high level of initial efficiency (with minimal decrease) even after 1000 hours of continuous heating. This fully demonstrates that the high thermal conductivity network structure formed by PCA6OB effectively suppresses morphology degradation caused by heat accumulation and significantly enhances the thermal stability of the device.

[0039] In summary, this invention successfully constructed an organic solar cell device with both high efficiency and high thermal stability by introducing polymerizable liquid crystal molecules CA6OB into the PM6:Y6 system, which has significant application and promotion value.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An organic solar cell based on a high thermal conductivity network structure, characterized in that, The device structure of the organic solar cell, from bottom to top, includes: a transparent conductive substrate, a hole transport layer, an organic active layer, an electron transport layer, and a metal electrode. The organic active layer comprises a polymer donor PM6, a non-fullerene electron acceptor Y6, and a liquid crystal molecule CA6OB; wherein the chemical structural formulas of the polymer donor PM6, the non-fullerene electron acceptor Y6, and the liquid crystal molecule CA6OB are as follows: ； ； 。 2. An organic solar cell based on a high thermal conductivity network structure according to claim 1, characterized in that, The organic solar cell is a forward device structure, and its specific stacked structure from bottom to top consists of: an ITO glass substrate, a PEDOT:PSS hole transport layer, an organic active layer, a PDINN electron transport layer, and a metal Ag cathode.

3. The organic solar cell based on a high thermal conductivity network structure and its fabrication method according to claim 1, characterized in that, The organic active layer is a bulk heterojunction thin film containing polymer donor PM6, non-fullerene electron acceptor Y6, and liquid crystal molecule CA6OB.

4. The organic solar cell based on a high thermal conductivity network structure and its fabrication method according to claim 3, characterized in that, The proportions of each component in the organic active layer are as follows: the mass ratio of polymer donor PM6 to non-fullerene electron acceptor Y6 is 1:1.15-1.25; the added mass of liquid crystal molecule CA6OB is 1.5% to 2.5% of the total mass of polymer donor PM6 and non-fullerene electron acceptor Y6.

5. An organic solar cell based on a high thermal conductivity network structure and its fabrication method according to claim 4, characterized in that, The preferred mass ratio of polymer donor PM6 to non-fullerene electron acceptor Y6 in the organic active layer is 1:1.2, and the preferred mass of added liquid crystal molecule CA6OB is 2% of the total mass of polymer donor PM6 and non-fullerene electron acceptor Y6.

6. A method for fabricating an organic solar cell based on a high thermal conductivity network structure according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Substrate cleaning treatment The ITO glass sheet was ultrasonically cleaned in a series of solutions: detergent, deionized water, acetone, and isopropanol. After cleaning, the ITO glass sheet was surface treated using a plasma cleaner. Step 2: Prepare the hole transport layer PEDOT:PSS solution was coated onto the surface of a treated ITO glass sheet using a static spin coating process, followed by a heating and annealing process to form a PEDOT:PSS hole transport layer. Step 3: Preparation of the organic active layer The polymer donor PM6, the non-fullerene electron acceptor Y6, and the liquid crystal molecule CA6OB were dissolved together in chloroform solvent according to a set ratio. The mixed solution was transferred to a glove box under nitrogen atmosphere and heated and stirred. 30 minutes before the start of the spin coating process, 0.5% by volume of 1-CN additive was added to the mixed solution. Subsequently, the mixed solution was spin-coated onto the surface of the PEDOT:PSS hole transport layer and annealed to form a bulk heterojunction organic active layer. The mass ratio of PM6 to Y6 was 1:1.15-1.25, and the mass of CA6OB was 1.5% to 2.5% of the total mass of PM6 and Y6. Step 4: Fabrication of the electron transport layer PDINN material was dissolved in methanol solvent to prepare a precursor solution. The PDINN solution was then coated onto the surface of the organic active layer using a dynamic spin coating process to form an electron transport layer. Step 5: Electrode Deposition The device is fabricated by depositing a metallic Ag electrode onto the PDINN electron transport layer using a vapor deposition process.

7. The method for fabricating an organic solar cell based on a high thermal conductivity network structure according to claim 6, characterized in that, In step two, the rotation speed of the static spin coating is 4500-5500 rpm; the temperature of the heating annealing treatment is between 145-155℃, and the annealing time is maintained at 15-20 minutes.

8. An organic solar cell based on a high thermal conductivity network structure and its fabrication method according to claim 6, characterized in that, In step three, the total solute concentration in the mixed solution used to prepare the bulk heterojunction organic active layer is controlled between 15 mg / mL and 17 mg / mL.

9. The method for fabricating an organic solar cell based on a high thermal conductivity network structure according to claim 6, characterized in that, In step three, the spin coating speed is 3000-4000 rpm; the annealing temperature after spin coating is set to 90-120℃, and the annealing time is 5 minutes.

10. The method for fabricating an organic solar cell based on a high thermal conductivity network structure according to claim 6, characterized in that, In step four, the concentration range of the PDINN methanol solution is 0.5-1.5 mg / mL; the spin coating speed during the dynamic spin coating process is 2000-3000 rpm, and the spin coating time is 25 seconds.

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