Modulation method for phase separation and charge transfer of organic photovoltaic film by using acid ester

Abstract

The invention discloses a modulation method for phase separation and charge transfer of an organic photovoltaic film by using acid ester, and belongs to the field of organic solar cells. The preparation method mainly comprises the following steps: adding fatty acid ester PM6 or Y6 with different concentrations and different chain lengths and dissolving the fatty acid ester PM6 or Y6 and an organic polymer into an organic solvent chloroform to obtain a ternary blended solution, and spin-coating to obtain an organic polymer film, so that the distribution of organic polymer molecules on the surface of the film is modulated, and the phase separation of the mixed film is further changed; therefore, polymer molecule charge transfer is regulated and controlled. The invention has the advantages of low cost, easy realization, simple process, good repeatability and the like, and can realize the modulation of charge transfer in the organic solar cell device on the premise of ensuring the broadband absorption of the solar spectrum.

Description

Technical Field

[0001] The present invention belongs to the field of organic solar cells, and particularly relates to a method for modulating the microstructure characteristics and charge transfer characteristics of the donor-acceptor of the active layer material of an organic solar cell device by using methyl fatty acid ester and methyl dodecanoate as additives. Specifically, by adding methyl fatty acid ester and methyl dodecanoate into an organic polymer hybrid film, and utilizing the effect of their long alkyl chains to further expel Y6 from the eutectic region, the formation of the eutectic is modulated, and a method for expanding the phase morphology range available to the polymer and the charge transfer characteristics at its phase separation interface is provided. Background Art

[0002] As a low-cost, lightweight, and flexible photovoltaic device, the bulk heterojunction organic solar cell has made rapid progress in recent years. The photoactivity of this device is usually an interpenetrating network structure formed by mixing a polymer electron donor and a non-fullerene and its derivative electron acceptor, which is called the microstructure of the bulk heterojunction. It is reported that there is a close connection between the change in the microstructure of the bulk heterojunction and the transfer of charges. Therefore, regulating the microstructure of the bulk heterojunction is the key to improving the efficiency of organic thin-film solar cell devices. To improve the performance of organic solar cell devices, it is necessary to further explore the relationship between the change in microstructure and the charge generation mechanism. Currently, there are many empirical strategies to improve device performance by regulating the microstructure of the thin film during or after solution treatment. For example: casting solvent optimization, the use of additives, thermal annealing, solvent annealing, etc. These methods essentially modulate the charge generation by changing the phase separation characteristics of the hybrid film. The present invention will introduce a method for regulating the phase morphology range and charge transfer characteristics of the donor-acceptor hybrid film of the active layer material of an organic solar cell device by using methyl fatty acid ester and methyl dodecanoate as additives. Summary of the Invention

[0003] The object of the present invention is to propose a method for modulating the phase morphology range of the polymer hybrid film of an organic solar cell device by adding methyl fatty acid ester and methyl dodecanoate additives, so as to realize the modulation of the charge (including electrons or / and holes) generation characteristics of the device by using the expanded polymer phase morphology range generated by the long alkyl chains of methyl fatty acid ester and methyl dodecanoate.

[0004] The modulation of the charge generation characteristics of the polymer hybrid film of the organic solar cell device in the present invention is achieved based on the change in the phase morphology range of the hybrid film by the long alkyl chains of methyl fatty acid ester and methyl dodecanoate. Preparing a certain proportion of methyl fatty acid ester and methyl dodecanoate into the organic semiconductor hybrid film, specifically including the following steps:

[0005] 1) Substrate treatment: Select a substrate, wash the substrate with a glass cleaner, and then ultrasonically treat it in deionized water, acetone, and absolute ethanol solvents for 15 minutes in sequence. After ultrasonic treatment, dry it with a nitrogen gun and bombard the surface with an oxygen plasma machine at a bombardment power of 18 W for 30 s to improve the solution wettability of the substrate.

[0006] 2) Solution preparation: Prepare a blend solution, which includes PM6, Y6, and an additive. The additive is methyl fatty acid ester Me7 or methyl dodecanoate Me12. The mass ratio of PM6:Y6 is 1:1.2, the molar ratio of PM6:Me7 is 1:10 - 1:14, preferably 1:10 and 1:14, the molar ratio of PM6:Me12 is 1:10, the total concentration of the blend solution is 15 mg / mL, and the solvent is chloroform. After the blend solutions are prepared respectively, stir them for 2 h at a stirring temperature of 55 °C to dissolve them fully.

[0007] 3) Film preparation: Spin - coat the blend solution obtained in step 2) onto the substrate at a speed of 2000 rpm for 40 s to prepare donor, acceptor intrinsic films and blend films.

[0008] The substrate in step 1) is flexible or non - flexible, such as a quartz substrate.

[0009] As an organic photovoltaic film, under the excitation condition of visible light at 400 - 800 nm, it realizes the modulation of the enhanced charge (including electrons or / and holes) characteristics of the device, compared with the enhanced charge (including electrons or / and holes) characteristics modulation of PM6 and Y6.

[0010] The present invention has the following advantages:

[0011] 1) The present invention does not need to use expensive equipment and has low cost;

[0012] 2) The process required by the present invention is simple and the preparation cycle is short;

[0013] 3) The controllable factors in the present invention are relatively obvious. The phase - separation region of the prepared blend film can be modulated by changing the proportion of Me7 and Me12;

[0014] 4) The present invention can realize the preparation of large - size blend films;

[0015] 5) The present invention realizes different polymer blend films by selecting different organic polymer materials and different additive materials;

[0016] 6) If a flexible material is selected as the substrate to prepare the blend film in the present invention, a flexible organic solar cell device can be realized;

[0017] 8) The present invention is easy to implement and has good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Surface morphology of each blend film. It can be seen from the figure that after adding additives Me7 and Me12, the molecular phase separation increases.

[0019] Figure 2 This is the steady-state absorption spectra of PM6 and Y6 intrinsic films. The absorption of PM6 intrinsic film is mainly in the spectral range of 400-700nm, and the absorption of acceptor Y6 intrinsic film is mainly in the spectral range of 600-900nm. It can be seen that the absorption range of PM6 intrinsic film and the absorption range of Y6 intrinsic film can complement each other in the visible light and near-infrared regions. We can achieve coverage of visible light and near-infrared solar radiation spectra through blended films.

[0020] Figure 3 Figure 2 is the steady-state absorption spectrum of each mixed film. After adding Me7 and Me12 to the PM6:Y6 blend film, the absorption spectrum red-shifts, and with the increase of Me7 proportion and the addition of Me12, the spectrum red-shift phenomenon becomes more obvious, indicating that the intermolecular force increases and the phase separation of PM6 and Y6 molecules increases. The absorption peak near 800nm ​​is closer to the absorption peak of the Y6 intrinsic film.

[0021] Figure 4 The transient absorption spectra of PM6 intrinsic film and each blend film under 400nm excitation. Under 400nm excitation, PM6 was selectively excited, and Y6 was not excited; while each blend film observed a strong GSB signal from Y6, indicating that a significant electron transfer process occurred in the blend film, and the ESA signals of the intrinsic excited (LE) state (near 700nm) and the interface (CT) state charge (near 900nm, which is not found in PM6 and Y6 and is a new signal) were also observed. The signal intensity of the CT state charge of the ternary blend film with the addition of the additive Me7 was enhanced compared with that of the binary blend film with only PM6 and Y6, proving the enhancement of electron transfer; the signal intensity of the CT state charge of the ternary blend film with the addition of the additive Me12 was weakened compared with that of the binary blend film with only PM6 and Y6, proving the electron transfer, but the electron transfer was relatively weak relative to the binary film.

[0022] Figure 5Transient absorption spectra of the Y6 intrinsic film and various blend films under 800 nm excitation. Under 800 nm excitation, Y6 was selectively excited and PM6 was not excited; strong GSB signals from PM6 were observed in all blend films, indicating a significant hole transfer process in the blend films; small grooves in the GSB signal near 900 nm, i.e., the interfacial (CT) state charge absorption signal, were observed, but the signal intensities of the CT state charges in the blend films were different, indicating that the CT state excitons in the blend films would be affected by the alkyl chain length of the additive; the signal intensity of the CT state charge in the ternary blend film with 1:10 Me7 (i.e., PM6:Me7 molar ratio of 1:10) added was enhanced compared to the binary blend film with only PM6 and Y6, demonstrating enhanced hole transfer; the signal intensities of the CT state charges in the two ternary blend films with 1:14 Me7 (i.e., PM6:Me7 molar ratio of 1:14) and 1:10 Me12 (i.e., PM6:Me12 molar ratio of 1:10) added were weakened compared to the binary blend film with only PM6 and Y6, demonstrating hole transfer, but the hole transfer was relatively weak compared to the binary film. Detailed implementation manners

[0023] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to this embodiment.

[0024] Embodiment: A modulation method for the phase separation and charge transfer characteristics of PM6:Y6 mixed thin films based on the longer alkyl chains of fatty acid methyl esters and methyl dodecanoate.

[0025] 1) Dissolve PM6 or Y6 in chloroform solution respectively to make the donor and acceptor intrinsic solutions with a concentration of 15 mg / mL; spin-coat on a quartz substrate at a speed of 2000 rpm to obtain an intrinsic film with a certain thickness.

[0026] 2) According to the mass ratio of PM6:Y6 of 1:1.2, dissolve it in chloroform solution to prepare a binary blend solution with a concentration of 15 mg / mL; spin-coat the above binary blend solution on a quartz substrate at a speed of 2000 rpm to obtain a binary blend film with a certain thickness, and its atomic force microscope (AFM) image is as shown in Figure 1 a in the appendix;

[0027] 3) Dissolve them in chloroform solutions respectively according to the mass ratio of PM6:Y6 being 1:1.2 and the molar ratios of PM6:Me7 being 1:10 and 1:14 respectively to prepare two ternary blend solutions with a total concentration of 15 mg / mL; dissolve them in chloroform solutions according to the mass ratio of PM6:Y6 being 1:1.2 and the molar ratio of PM6:Me12 being 1:10 to prepare a third ternary blend solution with a total concentration of 15 mg / mL; spin-coat the ternary blend solutions on quartz substrates at a speed of 2000 rpm to obtain ternary blend films with a certain thickness. The atomic force microscope (AFM) images are as shown in Figure 1 b, c, and d in the appendix;

[0028] 4) Perform steady-state absorption spectroscopy tests on the intrinsic films and blend films obtained in the above steps respectively, and compare the steady-state absorption spectra of the PM6:Y6 binary blend film and the blend film doped with fatty acid methyl ester and dodecanoic acid methyl ester to obtain the modulation of the intermolecular forces of the blend film by fatty acid methyl ester and dodecanoic acid methyl ester. The measured steady-state absorption spectra are as shown in Figure 2 and Figure 3 shown.

[0029] 5) Excite the PM6 intrinsic film and each blend film obtained in the above steps with 400 nm femtosecond light to selectively excite the donor PM6 and perform transient absorption spectroscopy (TA) tests. Compare the transient absorption spectra of the PM6:Y6 blend film and the blend film doped with fatty acid methyl ester and dodecanoic acid methyl ester to obtain the modulation of the intramolecular charge transfer of the blend film when the main excited donor is PM6. The measured TA spectra are as shown in Figure 4 shown.

[0030] 6) Excite the Y6 intrinsic film and each blend film obtained in the above steps with 800 nm femtosecond light to selectively excite the acceptor Y6 and perform transient absorption spectroscopy (TA) tests. Compare the transient absorption spectra of the PM6:Y6 blend film and the blend film doped with fatty acid methyl ester and dodecanoic acid methyl ester to obtain the modulation of the intramolecular charge transfer of the blend film when the main excited acceptor is Y6. The measured TA spectra are as shown in Figure 5 shown.

Claims

1. A method for modulating phase separation and charge transfer of organic photovoltaic thin films using acid esters, characterized in that: The following steps are involved: 1) Substrate treatment: Select the substrate, wash the substrate with glass cleaning agent, and then ultrasonically treat it in deionized water, acetone, and anhydrous ethanol solvents for 15 minutes in sequence. After ultrasonic treatment, use a nitrogen gun to dry it, and use an oxygen plasma machine to bombard the surface with a bombardment power of 18W for 30s to improve the solution wettability of the substrate; 2) Solution preparation: preparing a blended solution, the blended solution comprising PM6, Y6 and an additive, wherein the additive is fatty acid methyl ester Me7 or methyl dodecanoate Me12, wherein the mass ratio of PM6:Y6 is 1:1.2, the molar ratio of PM6:Me7 is 1:10-1:14, preferably the molar ratio of PM6:Me7 is 1:10 and 1:14, and the molar ratio of PM6:Me12 is 1:10, the total concentration of the blended solution is 15 mg / mL, and the solvent is chloroform; after the blended solutions are prepared, stirring is performed for 2 hours at a stirring temperature of 55° C. to fully dissolve them; 3) Thin film preparation: The blended solution obtained in step 2) is spin-coated onto the substrate at a rotation speed of 2000 rpm for 40 seconds to prepare donor and acceptor intrinsic thin films and blended thin films.

2. The method according to claim 1, characterized in that Step 1) The substrate is flexible or non-flexible, such as a quartz substrate.

3. An organic photovoltaic film prepared according to the method of claim 1 or 2.

4. Application of the organic photovoltaic film prepared by the method according to claim 1 or 2, as an organic photovoltaic film, to achieve enhanced charge (including electrons and / or holes) characteristic modulation of the device under the condition of visible light 400-800nm ​​excitation, relative to the enhanced charge (including electrons and / or holes) characteristic modulation of PM6 and Y6.

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