An organic solar cell based on a polymer donor-star non-fullerene acceptor and a preparation method thereof

Abstract

The application relates to an organic solar cell based on a polymer donor-star non-fullerene acceptor and a preparation method thereof. The organic active layer of the application comprises a polymer donor P(BTT-DPP) and a star non-fullerene acceptor small molecule BDP-3PDI or BDP-4PDI. The star non-fullerene small molecule acceptor material provided by the application can form good absorption complementation and energy level matching with the narrow-bandgap polymer donor material, so that the open-circuit voltage and short-circuit current of the device are improved. In addition, the rigid skeleton structure of the star acceptor molecule has large steric hindrance, can effectively inhibit the excessive aggregation of the molecule in the film forming process, and thus improves the active layer morphology, finally improves the energy conversion efficiency of the organic solar cell based on the polymer donor-star non-fullerene acceptor, and good effects are obtained, and the photoelectric conversion efficiency reaches 10.97% and 13.94% respectively, and the application has a good application prospect in the field of organic solar cells.

Description

Technical Field

[0001] This invention belongs to the field of organic solar cells and their device fabrication, specifically relating to an organic solar cell with a polymer donor-star fullerene acceptor and its fabrication method. Background Technology

[0002] Faced with the increasingly severe energy crisis and environmental problems, the development of clean and renewable energy sources such as solar and wind power is receiving increasing attention. Solar cells are a photovoltaic technology that directly converts solar energy into electrical energy. Utilizing the photovoltaic principle of organic semiconductor materials, photon energy from the sun can be converted into electrical energy. Organic solar cells (OSCs) based on bulk heterojunction (BHJ) active layers, as an important component of solar cells, are a promising photovoltaic technology with many unique advantages, such as tunable color, light weight, wide availability of materials, low manufacturing cost, and large-area fabrication on flexible substrates, thus attracting widespread attention from researchers. In the early stages of developing OSC-based BHJ active layers, these active layers were composed of a mixture of polymer or small molecule donors and fullerene acceptors, serving as light-absorbing active layers with energy conversion efficiencies exceeding 10%. However, some inherent drawbacks of fullerene acceptor materials limit further improvements in the performance of organic solar cells, including weak light absorption and insufficient utilization of the visible light region, difficulties in preparation and purification, high synthesis costs, and poor energy level tuning. Therefore, developing new electron acceptor materials to replace fullerene derivatives has become a new hot topic in the field of organic solar cell research. In this regard, non-fullerene small molecule acceptors (NFSMAs) exhibit significant advantages over fullerene-based acceptor materials due to their lower synthesis cost, strong absorption in the visible light region, higher stability, easily tunable energy levels, and higher open-circuit voltage. However, most current organic non-fullerene small molecule acceptors typically involve multiple and complex synthesis steps, resulting in low overall yields and high synthesis costs, which are detrimental to future large-scale commercial applications. Therefore, developing novel NFSMAs that are easy to synthesize and possess high photovoltaic performance is of significant scientific importance.

[0003] Among various NFSMAs, PDI is one of the most promising non-fullerene small molecule acceptors (SMAs) due to its strong light absorption, high electron mobility, suitable and tunable electronic energy levels, ease of synthesis, and good photochemical and environmental stability. To date, many PDI-based non-fullerene acceptors have been successfully developed. However, many PDI-based small molecule acceptors with large coplanar configurations tend to form excessively strong aggregates and high crystalline domains, resulting in unfavorable micron-scale phase separation in bulk heterojunctions. This hinders exciton diffusion and separation, leading to poor OSC performance. To address this issue, significant efforts have been made to develop acceptors based on nonplanar PDIs.

[0004] Fluoroborodipyrrolemethyl fluoropolymers (BODIPY) are a class of multifunctional fluorophores possessing many excellent properties, such as high fluorescence quantum yield, large molar extinction coefficient, good photostability and thermal stability, low optical band gap, and excellent redox properties. Furthermore, their photophysical and electrochemical properties can be well tuned by introducing appropriate electron donors and acceptors at different sites on the BODIPY. In addition, BODIPY dyes typically possess deep HOMO levels, resulting in high open-circuit voltages (Voc). The superior photophysical and electrochemical properties of BODIPY make it a promising candidate for applications in organic solar cells.

[0005] In addition, current organic solar cells also suffer from problems such as the absorption spectrum of the active layer not being perfectly matched with the solar spectrum, poor matching of electronic energy levels between donor and acceptor, and low charge carrier mobility.

[0006] This invention relates to an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor and its fabrication method. The invention utilizes polymer electron donors (P(BTT-DPP)) and star-shaped non-fullerene electron acceptors (BDP-3PDI or BDP-4PDI) as active layer materials in organic solar cells, achieving excellent results with photoelectric conversion efficiencies of 10.97% and 13.94%, respectively, demonstrating promising application prospects in the field of organic solar cells. Summary of the Invention

[0007] Purpose of the invention: To address the shortcomings of existing technologies, the purpose of this invention is to provide an organic solar cell based on a polymer donor-star nonfullerene acceptor and its preparation method, so as to construct a high-efficiency organic solar cell based on a polymer donor (P(BTT-DPP)):star nonfullerene acceptor (BDP-3PDI or BDP-4PDI) system.

[0008] This invention selects a polymer (P(BTT-DPP)) as the donor material and a star-shaped non-fullerene molecule (BDP-3PDI or BDP-4PDI) as the acceptor material. The polymer donor (P(BTT-DPP)) and the star-shaped non-fullerene acceptor (BDP-3PDI or BDP-4PDI) can form good energy level matching and complementary absorption spectra, broadening the light absorption range of the entire system and thus improving the open-circuit voltage (V) of the device. oc ) and short-circuit current (J sc This ultimately improves device efficiency. Furthermore, the star-shaped structure of BDP-3PDI or BDP-4PDI can effectively suppress excessive aggregation of molecular chains during film formation, thereby optimizing the morphology of the active layer and effectively improving the photoelectric conversion performance of the device.

[0009] Technical solution: To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0010] The present invention discloses an organic solar cell with polymer donor-star non-fullerene acceptor, comprising, from bottom to top, a transparent conductive substrate, a hole transport layer, an organic active layer, an electron transport layer, and a metal electrode A1. The organic active layer includes polymer donor P (BTT-DPP) and star non-fullerene acceptor small molecules BDP-3PDI or BDP-4PDI.

[0011] The molecular structures of the polymer donor P (BTT-DPP), the star-shaped non-fullerene acceptor small molecule BDP-3PDI, or BDP-4PDI in the organic active layer of this invention are shown below:

[0012]

[0013]

[0014] The organic active layer is a bulk heterojunction (BHJ)P(BTT-DPP): BDP-3PDI or BDP-4PDI;

[0015] The mass ratio of P(BTT-DPP):BDP-3PDI or BDP-4PDI in the active layer is 1:05 to 1:4, preferably 1:1.3;

[0016] The organic solar cell forward device has the following structural layers from bottom to top: ITO glass, poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonic acid) (PSS) hole transport layer, organic active layer, polyfluorene derivative (PFN) electron transport layer, and metal Al electrode.

[0017] The present invention discloses a method for preparing a polymer donor-star-shaped non-fullerene acceptor organic solar cell, comprising the following steps:

[0018] (1) ITO glass is first ultrasonically cleaned with detergent, deionized water, acetone and isopropanol, and then vacuum dried.

[0019] (2) PEDOT:PSS was spin-coated onto ITO glass to prepare a hole transport layer with a thickness of 35-40 nm.

[0020] (3) Dissolve the electron donor and electron acceptor materials together in chloroform solvent according to the mass ratio of P(BTT-DPP):BDP-3PDI or BDP-4PDI of 1:05 to 1:4, and spin-coat them on the hole PEDOT:PSS transport layer at room temperature and in a nitrogen atmosphere to form a bulk heterojunction; then anneal in tetrahydrofuran vapor for 40s.

[0021] (4) Dissolve PFN in methanol solvent and spin-coat it onto the active layer to form an electron transport layer;

[0022] (5) Under vacuum conditions, metal Al electrodes are deposited onto the PFN electron transport layer.

[0023] In step (2), the spin coating speed is 3000 rpm / min;

[0024] In step (3), the spin coating speed is 2500 rpm / min, the spin coating time is 1 min, and the concentration of the active layer is 16 mg / mL;

[0025] In step (4), the spin coating speed is 3000 rpm / min and the spin coating time is 1 min;

[0026] In step (5), the vacuum level is below 10. -5 Torr.

[0027] Beneficial effects of the present invention

[0028] Compared with the prior art, the organic solar cell based on polymer donor-star nonfullerene acceptor and its preparation method of the present invention have the following advantages: (1) The absorption spectrum of P(BTT-DPP) is complementary to the absorption spectrum of BDP-3PDI or BDP-4PDI, which can broaden the light absorption range of the entire system, thereby helping to improve the short-circuit current (J) of the device. sc (2) The donor and acceptor have good compatibility and can form good energy level matching and effective charge transfer; (3) The three-dimensional rigid structure of the acceptor small molecule star not only improves the crystallinity of the active layer, but also effectively inhibits the excessive aggregation of the active layer in the film, thereby forming a more suitable phase separation, optimizing the morphology of the active layer, making the system have better stability and better photoelectric conversion performance, and has a good application prospect in the field of solar energy. Attached Figure Description

[0029] Figure 1 This is a normalized ultraviolet-visible absorption spectrum of the thin films of BDP-3PDI, BDP-4PDI and P(BTT-DPP) in the solar cell of the present invention; where the horizontal axis is wavelength (nm) and the vertical axis is absorbance (Abs).

[0030] Figure 2 This is an energy level diagram of the organic solar cells based on BDP-3PDI, BDP-4PDI and P(BTT-DPP) in this invention. The vertical axis represents the energy level, and the unit is eV.

[0031] Figure 3 The device current (J) in solar cells based on P(BTT-DPP):BDP-3PDI and P(BTT-DPP):BDP-4PDI in Comparative Examples 2, 1, and 2 of this invention is shown. sc - Voltage (V) oc )picture. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings, but the embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0033] The instruments used for testing were: a Shimadzu UV-3100 UV-Vis spectrophotometer (scanning range 300–900 nm, optical path slit 2 nm) for electronic absorption spectroscopy; and a Keithley 2400 source meter (AM1.5G, 100 mW / cm²) for device photoelectric conversion efficiency. 2 )test.

[0034] Dissolve PFN in methanol and stir at room temperature until clear and transparent to prepare a PFN methanol solution with a concentration of 2 mg / mL for later use.

[0035] According to the mass ratio of P(BTT-DPP):BDP-3PDI of 1:0.4, 1:0.8, 1:1.1, 1:1.3, and 1:1.5, the donor P(BTT-DPP) and the astrological acceptor BDP-3PDI were weighed respectively, and then dissolved in chloroform to prepare an active layer solution with a concentration of 16 mg / mL for use in the fabrication of bulk heterojunction devices.

[0036] According to the mass ratio of P(BTT-DPP):BDP-4PDI of 1:0.4, 1:0.8, 1:1.1, 1:1.3, and 1:1.5, the donor P(BTT-DPP) and the astrological acceptor BDP-4PDI were weighed respectively, and then dissolved in chloroform to prepare an active layer solution with a concentration of 16 mg / mL for use in the preparation of bulk heterojunction devices.

[0037] Example 1

[0038] The ITO glass slide was sequentially cleaned with detergent, deionized water, acetone, and isopropanol, each ultrasonically for 30 min, and then vacuum dried. A PEDOT:PSS layer with a thickness of 35–40 nm was spin-coated onto the cleaned ITO glass at a rotation speed of 3000 rpm / min, and then transferred to a glove box under a nitrogen atmosphere. A chloroform solution for the active layer, prepared according to the above-mentioned P(BTT-DPP):BDP-3PDI mass ratio of 1:0.4, was spin-coated onto the hole transport layer at a spin speed of 2500 rpm / min for 1 min, forming a bulk heterojunction film. The device was then annealed by exposing it to tetrahydrofuran vapor for 40 s. The above-mentioned PFN methanol solution was then spin-coated onto the bulk heterojunction active layer to obtain a PFN electron transport layer film at a spin speed of 3000 rpm / min for 1 min. Finally, an Al metal electrode was deposited onto the PFN electron transport layer under vacuum conditions.

[0039] Example 2

[0040] The ITO glass slide was sequentially cleaned with detergent, deionized water, acetone, and isopropanol, each ultrasonically for 30 min, and then vacuum dried. A PEDOT:PSS layer with a thickness of 35–40 nm was spin-coated onto the cleaned ITO glass at a rotation speed of 3000 rpm / min, and then transferred to a glove box under a nitrogen atmosphere. A chloroform solution for the active layer, prepared according to the above-mentioned P(BTT-DPP):BDP-4PDI mass ratio of 1:0.4, was spin-coated onto the hole transport layer at a spin speed of 2500 rpm / min for 1 min, forming a bulk heterojunction film. The device was then annealed by exposing it to tetrahydrofuran vapor for 40 s. The above-mentioned PFN methanol solution was then spin-coated onto the bulk heterojunction active layer to obtain a PFN electron transport layer film at a spin speed of 3000 rpm / min for 1 min. Finally, an Al metal electrode was deposited onto the PFN electron transport layer under vacuum conditions.

[0041] Example 3

[0042] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-3PDI in the bulk heterojunction device was 1:0.8.

[0043] Example 4

[0044] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-3PDI in the bulk heterojunction device was 1:1.1.

[0045] Example 5

[0046] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-3PDI in the bulk heterojunction device was 1:1.3.

[0047] Example 6

[0048] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-3PDI in the bulk heterojunction device was 1:1.5.

[0049] Example 7

[0050] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-4PDI in the bulk heterojunction device was 1:0.8.

[0051] Example 8

[0052] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-4PDI in the bulk heterojunction device was 1:1.1.

[0053] Example 9

[0054] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-4PDI in the bulk heterojunction device was 1:1.3.

[0055] Example 10

[0056] The control device was prepared according to the method of Example 1, except that the mass ratio of the active layer P (BTT-DPP):BDP-4PDI in the bulk heterojunction device was 1:1.5.

[0057] Figure 1 The images show the thin-film absorption spectra of the astral small molecule acceptors BDP-3PDI, BDP-4PDI, and P(BTT-DPP). The acceptor molecules BDP-3PDI and BDP-4PDI have strong absorption in the ranges of 300–700 nm and 300–800 nm, respectively, which are complementary to the absorption spectrum of the polymer donor P(BTT-DPP).

[0058] Photovoltaic performance testing of devices

[0059] The light source is AM 1.5G, and the sunlight intensity is 100mW / cm². 2 The simulated sunlight was tested and calibrated using a standard silicon cell, and the testing instrument was a Keithley 2400 source meter.

[0060] The device current (J) based on the solar cells in Examples 5 and 9 was obtained through testing. sc - Voltage (V) oc ) curve, such as Figure 3 As shown.

[0061] The performance of the devices prepared in Examples 1-10, obtained through testing, is shown in the table below: including open-circuit voltage (V). oc ), short-circuit current (J) sc ), fill factor (FF) and power conversion efficiency (PCE), where: PCE = (V oc *J sc *FF) / Pin (Pin is the light intensity of the incident light).

[0062]

Claims

1. An organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor, characterized in that, From bottom to top, the structure consists of a transparent conductive substrate, a hole transport layer, an organic active layer, an electron transport layer, and a metal electrode Al. The organic active layer includes a polymer donor P (BTT-DPP) and a star-shaped non-fullerene acceptor small molecule BDP-3PDI or BDP-4PDI. The molecular structures of the polymer donor P (BTT-DPP), the astral small molecule non-fullerene acceptor BDP-3PDI, or the organic active layer are as follows:

2. The organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 1, characterized in that, The organic active layer is a bulk heterostructure type P(BTT-DPP):BDP-3PDI or P(BTT-DPP):BDP-4PDI.

3. An organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 1 or 2, characterized in that, The mass ratio of P(BTT-DPP):BDP-3PDI in the organic active layer is 1:1.

3.

4. An organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 1 or 2, characterized in that, The mass ratio of P(BTT-DPP):BDP-4PDI in the organic active layer is 1:1.

3.

5. A method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor as described in claim 1, characterized in that, Includes the following steps: (1) The ITO glass was ultrasonically cleaned with detergent, deionized water, acetone and isopropanol in succession, and then vacuum dried. (2) PEDOT:PSS was spin-coated onto ITO glass and then heated and annealed to form a hole transport layer of 35-40 nm. (3) Dissolve the electron donor and electron acceptor materials together in chloroform solvent according to the mass ratio of P(BTT-DPP):BDP-3PDI or BDP-4PDI of 1:1.3, spin-coat them on the hole PEDOT:PSS transport layer at room temperature and nitrogen atmosphere to form a bulk heterojunction; then expose them in tetrahydrofuran vapor for 40s and anneal them with solvent vapor. (4) Dissolve PFN in methanol solvent and spin-coat it onto the active layer to form an electron transport layer; (5) Under vacuum conditions, metal Al electrodes are deposited onto the PFN electron transport layer.

6. The method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 5, characterized in that, The spin coating speed in step (2) is 3000 rpm.

7. The method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 5, characterized in that, In step (3), the spin coating speed is 2500 rpm; the concentration of the active layer is 16 mg / mL; and the donor to acceptor mass ratio is 1:1.

3.

8. The method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 5, characterized in that, In step (4), the methanol solution concentration is 2 mg / ml, the spin coating speed is 3000 rpm, and the spin coating time is 1 min.

9. The method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 5, characterized in that, In step (5), the vacuum level is below 10. -5 Torr.

10. The method for preparing an organic solar cell based on a polymer donor-star-shaped non-fullerene acceptor according to claim 5, characterized in that, Using P(BTT-DPP) as the organic active layer donor material and non-fullerene solar cell acceptors BDP-3PDI or BDP-4PDI as the organic active layer acceptor materials, respectively, in organic solar cells, the photoelectric conversion efficiency can reach 10.97% and 13.94%, respectively.

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