Application of thiophene type solid additive in organic solar cell

Abstract

The invention relates to application of a thiophene type solid additive in an organic solar cell, and belongs to the technical field of organic functional materials and photovoltaic cells. The invention discloses an application of thiophene type solid additives C6BT and C8BT in a binary organic solar cell. The C8BT solid additive is added into a PM6: Y6 binary organic solar cell as a solid additive, preferably, the organic solar cell treated by using C8BT as the solid additive has better intermolecular accumulation, the energy conversion efficiency (PCE) of a device is 17.0% and is improved by 10% compared with the PCE (15.4%) of a binary organic solar cell treated without adding C8BT, and the C8BT solid additive shows relatively strong morphology improvement capability. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of organic solar cell solid additive materials and organic solar cell devices: 1. A class of thiophene solid additives, 1,6-bis(2,5-dibromothiophen-3-yl)hexane (C6BT) and 1,8-bis(2,5-dibromothiophen-3-yl)octane (C8BT); 2. Using the materials as solid additives and binary organic solar cells as active layer materials, a bulk heterojunction organic photovoltaic cell device is prepared, achieving a power conversion efficiency (PCE) of 17.0% and a method for effectively improving the PCE of the device. Background Art

[0002] Organic solar cells (OSCs) are considered a promising new energy technology due to their outstanding advantages, including light weight, flexibility, and the ability to fabricate large-area devices. However, the photovoltaic performance of bulk heterojunction solar cells (OSCs) depends largely on the morphology of the active layer. As the primary method for optimizing the morphology of the active layer of organic solar cells, the addition of additives currently offers a direct and effective strategy to improve the morphology of the active layer. The first approach involves the introduction of solvent additives such as 1,8-diiodooctane (DIO), diphenyl ether (DPE), and 1-chloronaphthalene (CN). The high boiling point and selectivity of these solvent additives optimize the kinetics of film formation, increase the duration of self-organization, and reduce interference between donors and acceptors during the crystallization phase. This approach facilitates the formation of interconnected networks. While these strategies are effective in optimizing the morphology of the active layer and improving device performance, challenges remain in the commercialization of OSCs. For example, the high boiling point of the solvent additives often results in residues remaining in the active layer. This residual solvent additive can continuously erode the active layer, ultimately impairing its morphology and, consequently, the performance of the OSC. In recent years, solid additives have become a key tool for improving the morphology of the active layer in OSCs. Solid additives can be completely removed from the active layer through thermal annealing and the introduction of alcohol washing methods, alleviating the negative effects associated with solvent-based additives. The mechanism of action of solid additives can be divided into: 1. Since in the OSC active layer, the thermal annealing process is mainly used to remove solid additives, resulting in an increase in free volume within the donor and acceptor. This process creates additional space that acts as free volume, promoting nanoscale phase separation and enhanced molecular organization, which is important for improving the overall performance of OSCs by promoting better charge transport and light absorption properties. 2. The significant influence of the interaction between solid additives and donor or acceptor molecules, mainly through mechanisms such as hydrogen bonds, halogen bonds and π-π interactions. These intermolecular forces are important for increasing the aggregation of donor or acceptor molecules, promoting π-π stacking, improving the formation of bicontinuous interpenetrating networks, and vertical phase separation, all of which contribute to improved device performance and stability.

[0003] With the development of new solid additives used in various OSC blend systems, the efficiency of OSCs has gradually increased while enhancing the active layer morphology, device stability, and reproducibility for large-scale production. Therefore, the use of solid additives to control the morphology in OSCs has gained a lot of appeal.

[0004] A large number of studies have shown that solid additives can effectively increase the open circuit voltage (V oc ), short-circuit current (J sc ) and fill factor (FF). However, there is currently little research on improving device performance by forming stronger planar thiophene solid additives. Therefore, the study of using this thiophene solid additive material in the active layer of organic solar cells to improve device performance is meaningful and interesting. Summary of the Invention

[0005] In view of the current research status of organic solar cell additives, the purpose of the present invention is to use thiophene solid additives to improve device performance and prepare bulk heterojunction organic solar cell devices to obtain a new method for achieving high PCE.

[0006] The present invention provides a thiophene solid additive, the structure of which is shown below:

[0007]

[0008] The present invention provides application of C6BT and C8BT thiophene solid additives in organic solar cells.

[0009] We used two thiophene compounds, 1,6-bis(2,5-dibromothiophen-3-yl)hexane (C6BT) and 1,8-bis(2,5-dibromothiophen-3-yl)octane (C8BT), as active layer additives to dope into the active layer of organic solar cells to prepare binary non-fullerene organic solar cells.

[0010] The device structure is: ITO / PEDOT:PSS / PM6:Y6 / PDINN / Ag (100nm). The active layer is the classic PM6:Y6.

[0011] The active layer was prepared by dissolving PM6:Y6 in chloroform at a mass ratio of 1:1.2 in a nitrogen glove box, with the donor PM6 concentration at 7.5 mg / mL and the acceptor concentration at 9.0 mg / mL. Different concentrations of C6BT or C8BT were then added, followed by spin coating at 3000 rpm for 30 seconds, followed by annealing and subsequent cooling at room temperature for 20 minutes to form a uniform and smooth film.

[0012] The concentration of C6BT or C8BT dissolved in chloroform is 4 to 6 mg / mL, preferably 5 mg / mL.

[0013] The annealing conditions are: annealing at 90-110°C for 10 min, preferably annealing at 100°C for 10 min; (Table 4-6 and Figure 7-9 )

[0014] Compared to existing technologies, the present invention's beneficial effects are primarily reflected in the introduction of a solid thiophene additive, C8BT, to achieve high PCE organic solar cells. Compared to previously reported liquid thiophene additives, solid thiophene additives have been little studied in organic solar cells, making in-depth research on them highly valuable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a structural diagram of an organic solar cell device according to Example 1 of the present invention;

[0016] Figure 2 The structural formulas of the active layer donor material PM6 and the acceptor material Y6 are:

[0017] Figure 3 The structural formulas of additive materials C6BT and C8BT;

[0018] Figure 4 The current-voltage (JV) curves of the organic solar cell devices of Example 1 of the present invention and Comparative Example 1 are shown;

[0019] Figure 5 Current-voltage (JV) curves of PM6:Y6 system devices with different concentrations of C8BT;

[0020] Figure 6 Current-voltage (JV) curves of PM6:Y6 system devices with different concentrations of C6BT;

[0021] Figure 7 Current-voltage (JV) curves of PM6:Y6 system devices at different temperatures;

[0022] Figure 8 Current-voltage (JV) curves of PM6:Y6 system devices with the optimal ratio of C8BT added at different temperatures;

[0023] Figure 9 Current-voltage (JV) curves of PM6:Y6 system devices with the optimal ratio of C6BT added at different temperatures. Specific implementation plan

[0024] The following specific examples are intended to further illustrate the present invention, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0025] Example 1

[0026] The device structure of an organic solar cell based on the polymer donor material PM6 in Example 1 is: ITO / PEDOT:PSS / active layer / PDINN / Ag. The thickness of ITO is approximately 150 nm, the PEDOT:PSS is approximately 30 nm, the active layer is approximately 100 nm, the PDINN is approximately 5 nm, and the Ag is approximately 100 nm. The mass ratio of the active layer materials PM6:Y6 is 1:1.2. The concentration of the PM6 donor is 7.5 mg / mL, and the acceptor concentration is 9.0 mg / mL. The fabrication protocol is as follows:

[0027] Cleaning and pretreatment of ITO substrates

[0028] The ITO substrates were cleaned in an ultrasonic cleaner using a detergent solution (10 min), isopropyl alcohol (20 min), acetone (20 min), deionized water (10 min x 4), and isopropyl alcohol (20 min) in this order. The substrates were then dried in an oven overnight. Prior to use, the ITO surfaces were treated with UV-ozone for 15 min and allowed to cool to room temperature.

[0029] Spin coating of hole transport layer PEDOT:PSS

[0030] The PEDOT:PSS solution was spin-coated at a speed of 4500 r / min for 30 s in a room temperature air environment, then baked at 100°C for 15 min, and then cooled at room temperature for 15 min to prepare a uniform and smooth film.

[0031] Mixing and spin coating of active layer materials

[0032] In a nitrogen atmosphere glove box, PM6:Y6 was dissolved in chloroform at a mass ratio of 1:1.2 and a donor concentration of 7.5 mg / mL. 5 mg / mL of C6BT or C8BT additive was added and spin-coated at a speed of 3000 r / min for 30 seconds. The film was then annealed at 100°C for 10 minutes and then cooled at room temperature for 20 minutes to form a uniform and smooth film.

[0033] Spin coating of electron transport layer PDINN and evaporation of cathode Ag

[0034] In a nitrogen atmosphere glove box, PDINN with a concentration of 1 mg / mL was spin-coated at a speed of 3000 r / min for 30 s to prepare a uniform and smooth film. The spin-coated device was then placed in a vacuum evaporation chamber at 1×10 -5 A 100nm thick metal electrode Ag was evaporated on the active layer under Pa.

[0035] Device performance testing

[0036] Under standard test conditions (AM1.5, 100mW / cm 2 ), and the V oc =0.851V, J sc =26.4mA / cm 2 , FF = 75.5%, PCE = 17.0%, adding V of C6BT device oc =0.845V, J sc =26.2mA / cm 2 , FF=74.0%, PCE=16.4%.

[0037] Table 1. Performance parameters of PM6:Y6 devices with different concentrations of C8BT added

[0038]

[0039] Table 2. Performance parameters of PM6:Y6 devices with different concentrations of C6BT added

[0040]

[0041] Comparative Example 1

[0042] The PM6:Y6 binary bulk heterojunction solar cell, without any additives, has a device structure of ITO / PEDOT:PSS / PM6:Y6 / PDINN / Ag. The mass ratio of PM6:Y6 in the active layer is 1:1.2. The fabrication process is as follows:

[0043] Cleaning and pretreatment of ITO substrates

[0044] The ITO substrates were cleaned in an ultrasonic cleaner using a detergent solution (10 min), isopropyl alcohol (20 min), acetone (20 min), deionized water (10 min x 4), and isopropyl alcohol (20 min) in this order. The substrates were then dried in an oven overnight. Prior to use, the ITO surfaces were treated with UV-ozone for 15 min and allowed to cool to room temperature.

[0045] Spin coating of hole transport layer PEDOT:PSS

[0046] The PEDOT:PSS solution was spin-coated at a speed of 4500 r / min for 30 s in a room temperature air environment, then baked at 100°C for 15 min, and then cooled at room temperature for 15 min to prepare a uniform and smooth film.

[0047] Mixing and spin coating of active layer materials

[0048] In a nitrogen atmosphere glove box, PM6:Y6 was dissolved in chloroform at a mass ratio of 1:1.2 and a donor concentration of 7.5 mg / mL. The film was spin-coated at a speed of 3000 r / min for 30 seconds, then annealed at 100°C for 10 minutes and subsequently cooled at room temperature for 20 minutes to form a uniform and smooth film.

[0049] Spin coating of electron transport layer PDINN and evaporation of cathode Ag

[0050] In a nitrogen atmosphere glove box, PDINN with a concentration of 1 mg / mL was spin-coated at a speed of 3000 r / min for 30 s to prepare a uniform and smooth film. The spin-coated device was then placed in a vacuum evaporation chamber at 1×10 -5 A 100nm thick metal electrode Ag was evaporated on the active layer under Pa.

[0051] Device performance testing

[0052] Under standard test conditions (AM1.5, 100mW / cm 2 ), and the device's V oc =0.851V, J sc =24.7mA / cm 2 , FF=73.6%, PCE=15.5%.

[0053] Table 3. Performance parameters of PM6:Y6 devices based on different additive conditions

[0054]

[0055] Table 4. Device performance parameters of PM6:Y6 at different annealing temperatures without any additives

[0056]

[0057] Table 5. Device performance parameters of PM6:Y6 with C8BT added at different annealing temperatures

[0058]

[0059] Table 6. Device performance parameters of PM6:Y6 with C6BT added at different annealing temperatures

[0060]

[0061] Although the present invention has been described in conjunction with the preferred embodiments, the present invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should appreciate that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

Claims

1. A thiophene solid additive is used in an organic solar cell, characterized in that: The structure of thiophene solid additive is as follows:

2. The use of the thiophene solid additive according to claim 1 in an organic solar cell, characterized in that: The application of thiophene solid additives as active layer solid additives added to PM6:Y6 binary organic solar cells.

3. The use of the thiophene solid additive according to claim 1 in an organic solar cell, characterized in that: In a glove box with a nitrogen atmosphere, PM6:Y6 was dissolved in chloroform at a mass ratio of 1:1.2, and then a thiophene solid additive was added. After spin coating, the film was annealed and then cooled at room temperature to form a uniform and smooth film as the active layer.

4. The use of the thiophene solid additive in an organic solar cell according to claim 3, characterized in that: The concentration of the additive C6BT or C8BT in the PM6:Y6 chloroform solution system is 4-6 mg / mL.

5. The use of the thiophene solid additive in an organic solar cell according to claim 3, characterized in that: The concentration of the additive C6BT or C8BT in the PM6:Y6 chloroform solution system is 5 mg / mL.

6. Use of the thiophene solid additive according to claim 1 in an organic solar cell, characterized in that: The annealing condition is 90-110°C for 10 min.

7. The use of the thiophene solid additive in an organic solar cell according to claim 1, characterized in that: The annealing condition is 100°C for 10 min.

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