Method for preparing solar cell by using green solvent and green additive

Abstract

The invention discloses a method for preparing a solar cell by using a green solvent and a green additive. The method comprises the following steps: preparing materials: preparing a hole transport layer, an active layer solution and an electron transport layer; pretreating the substrate, spin-coating the hole transport layer on the substrate, and then drying the hole transport layer; spin-coating an active layer solution, and transferring the spin-coated glass sheet to a heating table for annealing at 100 DEG C for 5 minutes; spin-coating an electron transport layer, and putting the spin-coated glass sheet into a mask plate for electrode evaporation; the preparation process of the active layer solution specifically comprises the following steps: weighing donor molecules and acceptor molecules according to a mass ratio of 1: 1, adding apigenin which accounts for 5% of the mass of an acceptor as a solid additive, putting the apigenin into a small bottle, adding a tetrahydrofuran support mixed solution into the small bottle, and stirring the mixed solution. According to the invention, the harm to the environment and the human body is greatly reduced, the accumulation structure of molecules is effectively regulated and controlled by virtue of the hydrogen bond interaction of apigenin, the crystallinity of the molecules is improved, and the efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of organic solar cell preparation, in particular to a method for preparing solar cells using green solvents and green additives. Background Art

[0002] Organic solar cells (OSCs) exhibit great application potential in the fields of wearable devices and building-integrated photovoltaics due to their unique advantages such as semi-transparency, color tunability, light weight, and flexibility. However, currently, highly efficient organic solar cells prepared in the laboratory generally rely on harmful halogen-containing solvents such as chloroform (CF) and chlorobenzene (CB), which severely restricts the large-scale production of organic photovoltaic technology. When preparing organic solar cells using halogen-free solvents, the solubility of organic photovoltaic materials is the primary consideration. Compared with other material types, small molecule materials exhibit better solubility in halogen-free solvents due to their lower molecular weight. This characteristic provides significant advantages for preparing all-small molecule organic solar cells (ASMOSCs) using halogen-free solvents, thus promoting the development of efficient and environmentally friendly production processes. However, the absence of halogen atoms in the halogen-free solvent system weakens the molecular interaction between the donor / acceptor materials and the solvent, resulting in poor control of the blend film morphology (especially phase separation and crystallinity control), ultimately affecting device performance. Therefore, the inherent limitations of the halogen-free solvent system have become the key obstacle to achieving controllable regulation of the nano-scale phase separation structure of ASMOSCs.

[0003] In ASMOSCs processed with halogen-free solvents, precise control of the bulk heterojunction morphology is crucial for improving device efficiency because it directly affects the exciton dissociation, charge transport, and collection processes. To control the blend film morphology of ASMOSCs, strategies such as solvent vapor annealing (SVA) and solvent additives have been widely adopted. However, solvent vapor annealing requires precise control of the solvent evaporation process, which limits its industrial application. Moreover, the residue of high-boiling solvent additives may reduce device stability. Therefore, developing efficient and simple strategies to regulate molecular arrangement and aggregation while achieving ideal nano-scale phase separation is crucial for improving device efficiency and accelerating the commercialization process of organic solar cells.

[0004] In the existing organic solar cell regulation methods, the solid additive strategy is often used for morphology optimization. The solid additive strategy can achieve precise regulation of molecular packing and aggregation by adding trace solid molecules to the active layer. These solid additives interact with donor or acceptor materials through fine intermolecular forces such as hydrogen bonds, π-π interactions, or van der Waals forces. In addition, the solid additive strategy has the advantages of simple operation, good reproducibility, and high stability, and is very suitable for the large-scale application of organic solar cells. Although such additives have the ability to optimize morphology, the presence of halogens in their structures still poses a potential threat to the environment and restricts the commercialization process of all-small-molecule organic solar cells. To conform to the concept of environmental friendliness and sustainable development, it is particularly important and urgent to develop green halogen-free solid additives to optimize the morphology of ASMOSCs blend films. Summary of the Invention

[0005] In order to overcome the above problems existing in the prior art, the present invention proposes a method for preparing a solar cell using a green solvent and a green additive.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a method for preparing a solar cell using a green solvent and a green additive, comprising the following steps: Step 1, preparation of materials: prepare a hole transport layer, an active layer solution, and an electron transport layer; Step 2, pre-treat the substrate, spin-coat the hole transport layer on the substrate and then dry it; Step 3, spin-coat the active layer solution, and transfer the spin-coated glass sheet to a heating stage for annealing at 100 °C for 5 minutes; Step 4, spin-coat the electron transport layer, and place the spin-coated glass sheet into a mask for electrode evaporation; The specific process for preparing the active layer solution in Step 1 is as follows: weigh the donor molecule and the acceptor molecule according to a mass ratio of 1:1, add apigenin as a solid additive at 5% of the acceptor mass into a vial, add a tetrahydrofuran support mixture to the vial, and stir the mixture.

[0007] In the above method for preparing a solar cell using a green solvent and a green additive, the hole transport layer used in Step 1 is PEDOT:PSS; the electron transport layer is an ethanol solution of PDINO.

[0008] The above method for preparing a solar cell using a green solvent and a green additive, the pretreatment process of the substrate in step 2 is specifically as follows: Put the ITO glass substrate into a polytetrafluoroethylene bracket and scrub it clean with detergent, then rinse it with deionized water; Put the bracket with the ITO glass into a glass beaker, pour deionized water into the glass beaker until it covers the ITO glass substrate, ultrasonically treat for 15 minutes, and pour out the deionized water; Replace it with acetone solvent to cover the ITO glass and ultrasonically clean for 15 minutes; Replace it with isopropanol and ultrasonically clean for 15 minutes, and dry the glass with nitrogen; Place the ITO side of the ITO glass substrate facing up in a glass dish and transfer it to a UV-O3 surface cleaner for surface wettability modification treatment for 10 minutes.

[0009] The above method for preparing a solar cell using a green solvent and a green additive, when preparing the active layer solution in step 1, the amount of tetrahydrofuran is determined according to the concentration requirement of the donor at 8 mg / mL.

[0010] The above method for preparing a solar cell using a green solvent and a green additive, the donor molecule in the active layer solution is DAPor-DPP, and the acceptor molecule is 6TIC.

[0011] The above method for preparing a solar cell using a green solvent and a green additive, step 3 is specifically as follows: Keep the water content of the glove box at 0.05 ppm and the oxygen content below 0.50 ppm, and transfer the dried ITO / PEDOT:PSS glass sheet to the glove box; Fix the glass substrate with a spin coater, set the rotation speed to 1600 rpm, and set the spin coating time to 25 s; Use a pipette to extract 20 μL of the active layer solution and drop it on the glass substrate, and immediately start spin coating to spread the active layer material evenly by centrifugal force; Transfer the glass sheet with the spin-coated active layer to a heating table for annealing at 100 °C for 5 minutes.

[0012] The above method for preparing a solar cell using a green solvent and a green additive, the spin coating of the electron transport layer in step 4 specifically includes: Place the annealed material on the spin coater again and fix it, set the rotation speed to 3000 rpm, and set the spin coating time to 25 s. Use a pipette to extract 75 μL of PDINO solution and drop it on the glass sheet, and immediately start spin coating to spread the active layer material evenly by centrifugal force.

[0013] The above method for preparing a solar cell using a green solvent and a green additive, the electrode evaporation process in step 4 specifically includes: Put the spin-coated glass sheet into a mask plate for silver electrode evaporation, and define the effective area of the device as 4 mm²; Evacuate the vacuum chamber with the substrate, and when the air pressure reaches 10 -4When the pressure is below Pa, the silver particles for thermal evaporation are heated. After heating, the silver particles escape from the material to form a vapor stream, which is evaporated and deposited on the surface of the substrate to form a solid thin film. By controlling the evaporation time and rate, the thickness of the evaporated thin film is controlled to be 100 nm.

[0014] The beneficial effects of the present invention are as follows: (1) Green environmental protection characteristics: Tetrahydrofuran (THF) is used to replace traditional toxic solvents (such as chloroform, dichlorobenzene, etc.), which conforms to the concept of green chemistry, significantly reduces the environmental pollution risk during the production process, and protects the health of operators. The additive apigenin is an extract of natural products with excellent biocompatibility, avoiding the synthesis complexity and toxicity problems of traditional additives.

[0015] (2) Efficient improvement of optoelectronic performance: Through the synergistic effect of apigenin, the morphology of the active layer is optimized, the intermolecular ordered arrangement is promoted, the charge recombination is inhibited, the exciton dissociation efficiency is improved, the charge transport ability is enhanced, and the photoelectric conversion efficiency (PCE) of the device is increased to 14.51%, achieving a relatively high energy conversion efficiency.

[0016] (3) Reduction of material cost: Apigenin is widely sourced (such as celery, citrus plants), and the extraction process is mature, which can be applied to the preparation of large-scale devices. Description of the Drawings

[0017] Figure 1 It is the device structure diagram of the embodiment of the present invention; Figure 2 It is the J-V curve of the solar device described in the embodiment of the present invention; Figure 3 It is the EQE spectrum of the solar device described in the embodiment of the present invention. Detailed Embodiments

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0019] This embodiment discloses a method for preparing an all-small molecule solar cell by a fully green process that synergistically uses a green solvent and a green additive. The structure of the prepared solar cell device from bottom to top is successively: ITO electrode, hole transport layer, active layer, electron transport layer, silver electrode, as Figure 1 shown, and the specific preparation method is as follows.

[0020] Control the laboratory temperature at 25 ± 2 °C and the relative humidity at 30% - 50% to ensure the stability of the experimental environment.

[0021] Step 1, preparation of materials: a Preparation of the hole transport layer: Put on clean nitrile gloves and goggles. Take out the appropriate pipette tip from the tip box and tightly install it on the pipette (eppendord).

[0022] Adjust the pipette range to 1 mL. Vertically insert the pipette into the PEDOT:PSS (Clevios PAI 4083) solution, slowly press the button to the first gear, aspirate the solution, and ensure that there are no air bubbles in the tip. Extrude the excess solution and aspirate again. Transfer the aspirated PEDOT:PSS to a 4 mL vial using the pipette.

[0023] Replace with a new pipette tip and adjust the pipette range to 1 mL. Insert the pipette into deionized water and aspirate 1 mL of deionized water in the same way as aspirating the solution above. Add the deionized water to the vial. At this time, the total volume of the solution in the vial is about 2 mL.

[0024] Cover the cap of the vial to ensure a good seal. Shake the vial on a shaker (SCI-FS) for 3 min.

[0025] b Preparation of the active layer solution: Place the electronic balance (SHIMADINAU W120D) on a horizontal and stable workbench for calibration.

[0026] Prepare a clean magnetic stir bar. After rinsing it with deionized water, soak it in anhydrous ethanol for ultrasonic treatment for 15 minutes. Take it out and dry it with nitrogen to ensure that there are no impurities on the surface of the magnetic stir bar.

[0027] Check the operating status of the nitrogen glove box (VICOR) to ensure that the water content in the glove box remains at 0.05 ppm and the oxygen content remains below 0.50 ppm. Turn on the glove box circulation system in advance and purify it.

[0028] Take out the donor molecule DAPor-DPP, acceptor molecule 6TIC (Solarmer), and apigenin (AP) from the storage environment. Check the appearance and purity of the reagents to ensure that the reagents are not deteriorated and free of impurities.

[0029] Put on clean nitrile gloves and goggles. Open the wind shield of the electronic balance, place a clean weighing paper on the balance tray, and press the zero key to make the balance display zero. Carefully use a clean spatula to take the donor molecule DAPor-DPP from the reagent bottle and slowly add it to the weighing paper until the mass displayed on the balance reaches the required value. Record the mass m1 of the weighed donor molecule. Replace the weighing paper and repeat the above operation to weigh the acceptor molecule 6TIC (Solarmer) according to a mass ratio of 1:1, and record the mass m2 of the weighed acceptor molecule. Carefully transfer the weighed donor molecule and acceptor molecule to the prepared 2 mL vial, avoiding material spillage.

[0030] According to the mass m2 of the receptor molecules weighed, calculate the mass m3 of apigenin (AP) to be added: m3 = m2 × 5%. Use an electronic balance to accurately weigh apigenin (AP) with a mass of m3, and add it to the 2 mL vial containing the donor molecules and receptor molecules.

[0031] Put a clean magnetic stir bar into the vial containing the materials. Quickly place the vial into the nitrogen glove box, close the transfer hatch of the glove box, and perform vacuum pumping and nitrogen filling operations on the transfer hatch according to the operating procedures of the glove box to ensure that the environment inside the transfer hatch is the same as that inside the glove box.

[0032] Inside the nitrogen glove box, according to the mass m1 of the donor molecules and the concentration requirement of 8 mg / mL, calculate the volume V of tetrahydrofuran to be pipetted. Select a pipette with an appropriate measuring range, install the pipette tip, and accurately pipette a volume of V of tetrahydrofuran from the reagent bottle containing tetrahydrofuran into the vial containing the active layer materials. During the pipetting process, operate slowly to avoid generating bubbles. Seal the vial with tape to ensure good sealing and prevent the solution from volatilizing and external air from entering.

[0033] Place the vial containing the mixture on a magnetic stirrer to ensure that the magnetic stir bar can rotate freely. Turn on the magnetic stirrer (ZNCL - BS140*140), set the rotation speed to 400 rpm, and start stirring. Set the stirring time to overnight (about 12 - 16 hours) to ensure that the materials are fully dissolved and mixed evenly.

[0034] Preparation of the electron transport layer: Weigh PDINO using an electronic balance and put it into a 4 mL vial. After adding a magnetic stir bar, use a pipette to transfer anhydrous ethanol to prepare a 1 mg / mL PDINO solution. Seal it with tape and transfer it to the glove box for stirring overnight, with the rotation speed set to 400 rpm.

[0035] Step 2, device preparation: a Substrate treatment: Put the ITO glass (preferred by Liaoning Science and Technology) substrate into a polytetrafluoroethylene bracket, scrub it clean with detergent, and rinse it twice with deionized water. Then place the bracket with the ITO glass into a glass beaker, pour deionized water into the beaker to submerge the ITO glass, and use an ultrasonic cleaner (SB - 5200D) for ultrasonic treatment for 15 min. Then pour out the deionized water. Replace it with acetone solvent to submerge the ITO glass and perform ultrasonic cleaning for 15 min. Finally, replace it with isopropanol for ultrasonic cleaning for 15 min, and then dry the glass with nitrogen. Place the ITO glass with the ITO side facing up in a glass dish and transfer it to a UV - O3 surface cleaner (MondelUV - O3Cleaner) for surface wettability modification treatment for 10 min. Then transfer the ITO glass to a clean bench. The temperature of the clean bench is maintained at 27 °C, and the humidity should be less than 35%.

[0036] b Hole transport layer spin coating: Use a syringe to draw diluted PEDOT:PSS, then add a 0.5 μm filter tip for filtration and uniformly coat it on ITO. Set the rotation speed to 3000 rpm and the spin coating time to 20 s. Transfer the spin-coated ITO glass to an oven (JVD-6020) and bake it at 150 °C for 15 min.

[0037] c Active layer spin coating: Keep the water content in the glove box at 0.05 ppm and the oxygen content below 0.50 ppm. Transfer the dried ITO / PEDOT:PSS glass sheet to the glove box through a transfer chamber. First, use a mixer to shake the vial for 5 min until the sample in the vial is mixed evenly. Fix the glass sheet on a spin coater, set the rotation speed to 1600 rpm, and set the spin coating time to 25 s. Use a pipette to draw 20 μL of the active layer solution and drop it on the glass sheet, then immediately start the spin coater. With the help of centrifugal force, the active layer material is spread evenly. Transfer the glass sheet with the spin-coated active layer to a preheated hot plate and anneal it at 100 °C for 5 min. After the annealing is completed, turn off the hot plate and let the glass sheet cool naturally to room temperature in the glove box.

[0038] d Electron transport layer spin coating: Place the annealed material on a spin coater (KW-4A) again and fix it. Set the rotation speed to 3000 rpm and the spin coating time to 25 s. Use a pipette to draw 75 μL of PDINO solution and drop it on the glass sheet, then immediately start the spin coating. With the help of centrifugal force, the active layer material is spread evenly.

[0039] e Electrode preparation: Place the spin-coated glass sheet into a mask and thermally evaporate a 100 nm silver electrode. Define the effective area of the device as 4 mm². Vacuum evaporation is a commonly used efficient method for preparing top electrodes. Then turn on the ZD-400 single-chamber high-vacuum resistive evaporation equipment and evacuate the vacuum chamber containing the substrate. When the air pressure reaches below 10 -4 Pa, heat the evaporated silver particles. The silver particles escape from the material when heated, forming a vapor stream, which evaporates and deposits on the surface of the substrate to form a solid film. By controlling the evaporation time and rate, the thickness of the evaporated film can be controlled to 100 nm.

[0040] Perform performance tests on the obtained solar cells, including current density-voltage (Jsc-Voc) tests and external quantum (EQE) efficiency tests. The current density-voltage (Jsc-Voc) test is specifically as follows: After the device is fabricated, use standard simulated light (SS-XAM1.5G standard spectral sunlight simulator) with AM1.5G and 100 mW / cm2 as the light source to perform optoelectronic tests on the device in an N2 glove box, and obtain the J-V curve of the OSCs device. Preheat the machine for half an hour before the test, and then use a standard Si cell to calibrate the light source to the intensity of one sunlight. According to the obtained J-V curve, parameters such as PCE, Voc, Jsc, and FF of the device can be further obtained. The test results are as Figure 2 shown. The PCE of the device is 14.51%, the Voc is 0.844 V, and the Jsc is 23.05 mAcm -2 , and the FF is 74.6%.

[0041] The external quantum (EQE) efficiency test is specifically as follows: The ratio of the number of charge carriers generated by the device to the total number of photons collected by the irradiated battery device is the external quantum efficiency. Before the test, turn on the test equipment QE-R and preheat it for half an hour. Then, use a Si electrode for calibration, and clamp the sample with a probe after calibration. The test wavelength range is 300 - 1000 nm. Figure 3 The photovoltaic property characterization results shown indicate that the DAPor-DPP:6TIC-based device exhibits a broad spectral response in the 300 - 900 nm band, and the maximum value of its external quantum efficiency exceeds 80%. This performance data fully demonstrates that the device has efficient carrier transport and charge collection capabilities.

[0042] The above embodiments are only exemplary embodiments of the present invention and are not used to limit the present invention. Those skilled in the art can make various modifications or equivalent replacements within the essence and protection scope of the present invention, and such modifications or equivalent replacements should also be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a solar cell using a green solvent and a green additive, characterized in that, It includes the following steps: Step 1, preparation of materials: Prepare a hole transport layer, an active layer solution, and an electron transport layer; Step 2, pre-treat the substrate, spin-coat the hole transport layer on the substrate and then dry it; Step 3, spin-coat the active layer solution, and transfer the spin-coated glass slide to a heating stage for annealing at 100 °C for 5 minutes; Step 4, spin-coat the electron transport layer, and place the spin-coated glass slide into a mask for electrode evaporation; The specific process for preparing the active layer solution in Step 1 is as follows: Weigh the donor molecule and the acceptor molecule according to a mass ratio of 1:1, and add apigenin as a solid additive at 5% of the acceptor mass into a vial. Add a tetrahydrofuran support mixture to the vial and stir the mixture.

2. The method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, In Step 1, the hole transport layer used is PEDOT:PSS; the electron transport layer is an ethanol solution of PDINO.

3. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, The specific process for pre-treating the substrate in Step 2 is as follows: Put the ITO glass substrate into a polytetrafluoroethylene bracket, scrub it clean with detergent, and then rinse it with deionized water; Put the bracket with the ITO glass into a glass beaker, pour deionized water into the glass beaker until it covers the ITO glass substrate, and perform ultrasonic treatment for 15 min, then pour out the deionized water; Replace it with acetone solvent and add it until it covers the ITO glass and perform ultrasonic cleaning for 15 min; Replace it with isopropanol and perform ultrasonic cleaning for 15 min, and dry the glass with nitrogen; Place the ITO glass substrate with the ITO side facing up in a glass dish and transfer it to a UV-O3 surface cleaner for surface wettability modification treatment for 10 min.

4. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, When preparing the active layer solution in Step 1, determine the amount of tetrahydrofuran according to the concentration requirement of 8 mg / mL of the donor.

5. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, The donor molecule in the active layer solution is DAPor-DPP, and the acceptor molecule is 6TIC.

6. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, Step 3 is specifically as follows: Keep the water content of the glove box at 0.05 ppm and the oxygen content below 0.50 ppm. Transfer the dried ITO / PEDOT:PSS glass slide to the glove box; Fix the glass substrate with a spin coater, set the rotation speed to 1600 rpm, and set the spin-coating time to 25 s; Use a pipette to extract 20 μL of the active layer solution and drop it on the glass substrate, and immediately start spin-coating to spread the active layer material evenly by centrifugal force; Transfer the glass slide with the spin-coated active layer to a heating stage for annealing at 100 °C for 5 min.

7. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, wherein, The spin-coating of the electron transport layer in Step 4 specifically includes: Place the annealed material on the spin coater again for fixation, set the rotation speed to 3000 rpm, and set the spin-coating time to 25 s. Use a pipette to extract 75 μL of the PDINO solution and drop it on the glass slide, and immediately start spin-coating to spread the active layer material evenly by centrifugal force.

8. A method for preparing a solar cell using a green solvent and a green additive according to claim 1, characterized in that, The specific process of the electrode evaporation in Step 4 includes: putting the spin-coated glass slide into a mask plate for silver electrode evaporation, and defining the effective area of the device as 4 mm²; evacuating the vacuum chamber containing the substrate, and when the air pressure reaches below 10 -4 Pa, heating the evaporated silver particles. After being heated, the silver particles escape from the material to form a vapor flow, which evaporates and deposits on the surface of the substrate to form a solid film; controlling the thickness of the evaporated film to be 100 nm by controlling the evaporation time and rate.

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