CN114751921A

CN114751921A - Non-condensed ring receptor molecule based on chlorophenyl-central nucleus and application thereof

Info

Publication number: CN114751921A
Application number: CN202210344417.4A
Authority: CN
Inventors: 方慧雨; 陈凯; 马伟
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2022-03-31
Filing date: 2022-03-31
Publication date: 2022-07-15

Abstract

The invention discloses a non-condensed ring receptor molecule based on a chlorophenyl-central nucleus and application thereof, wherein the general formula of the non-condensed ring receptor molecule is as follows:

wherein: r represents a conjugated bridging unit; r₁Is selected from C₁～C₁₂One of (1); r₂Indicating that the acceptor terminal group is connected to R by a carbon-carbon double bond. The non-condensed ring receptor molecule has stronger light absorption capacity and higher photoelectric conversion efficiency.

Description

Non-condensed ring receptor molecule based on chlorophenyl-central nucleus and application thereof

Technical Field

The invention belongs to the technical field of electrochemical materials, and particularly relates to a non-condensed ring receptor molecule based on a chlorophenyl-central core and application thereof.

Background

With the rapid development of non-fullerene acceptor molecular materials, the energy conversion efficiency of the organic solar cell rapidly exceeds 18%, and the highest efficiency breaks through 19%. The development in this field has been leading to a threshold for industrialization, and cost factors are one of the key factors that have to be considered in order to achieve the goal of industrialization of organic solar cells, and therefore, research on low-cost receptor materials has become a hot spot in recent years. The continuous development of non-condensed ring type receptor material molecules with low cost and high efficiency is particularly important.

Disclosure of Invention

The invention aims to provide a non-condensed ring receptor molecule based on a chlorophenyl-central nucleus and application thereof, wherein the non-condensed ring receptor molecule has stronger light absorption capacity and higher photoelectric conversion efficiency.

The invention adopts the following technical scheme: non-fused ring acceptor molecules based on a chlorophenyl-central core, the non-fused ring acceptor molecules having the general formula:

wherein: r represents a conjugated bridging unit;

R₁is selected from C₁～C₁₂One of (1);

R₂indicating that the acceptor terminal group is connected to R by a carbon-carbon double bond.

Further, the conjugated bridging unit is selected from one of the following:

further, the R is₂The acceptor terminal group is selected from one of the following:

the invention also discloses the non-condensed ring acceptor molecule based on the chlorophenyl-central nucleus, which is used as an acceptor material of a solar cell.

The invention also discloses a solar cell, and the material based on the chlorophenyl-central core non-condensed ring acceptor is selected as an electron acceptor.

The invention also discloses a preparation method of the non-condensed ring receptor molecule based on the chlorophenyl-central nucleus, which comprises the following steps:

step one, preparation of 1, 4-dibromo-2-chloro-5-methoxybenzene from 4-dibromo-2-chloro-5-methoxyaniline, and representation of 1, 4-dibromo-2-chloro-5-methoxybenzene with a1, the following:

step two, compound A1 and compound B1 are subjected to Stille coupling reaction to obtain compound C1, wherein compounds B1 and C1 are shown as the following formulas:

step three, carrying out an aldehyde reaction on the compound C1 to obtain a compound D1, which has the following formula:

step four, compound D1 is condensed with a terminal group E1 to obtain an acceptor Cl-4F, which has the following formula:

the invention has the beneficial effects that: 1. the open-circuit voltage of the organic solar cell is increased based on the chlorophenyl-central non-condensed ring acceptor material as an electron acceptor material, and the organic solar cell has very high energy conversion efficiency. 2. The method for preparing Cl-4F has fewer synthesis steps, mild reaction conditions and easy purification. Compared to fused ring molecules, there is no need to go through low-yield, high-cost fusion reactions, whereas compared to developing more sophisticated fluorination strategies, chlorination strategies do not need to go through low-yield and harsh-conditions exchange reactions to obtain halogen-containing precursors. 3. The chlorophenyl-central core non-condensed ring-based acceptor material effectively reduces the HOMO energy level of the cell, and is suitable for being used as an electron acceptor material in an organic solar cell. 4. The material based on the chlorophenyl-central core non-condensed ring receptor has a wider absorption spectrum, can absorb the light absorption range of about 400-800nm, and is favorable for absorbing the energy in sunlight. 5. The material based on the chlorophenyl-central core non-condensed ring receptor can be dissolved in common organic solvents such as chlorobenzene, trichloromethane, tetrahydrofuran and the like, and is easy to process in solution.

Drawings

FIG. 1 is a diagram showing a UV-VIS absorption spectrum of Cl-4F prepared in the present invention in a chloroform solution.

FIG. 2 is a diagram showing the UV-VIS absorption spectrum of a film formed by spin coating Cl-4F prepared in example 1 of the present invention.

FIG. 3 is a GIWAXS graph of a film formed by spin-coating Cl-4F prepared in example 2 of the present invention.

FIG. 4 is a cyclic voltammogram measured on a dilute solution of Cl-4F prepared in example 3 of the present invention.

FIG. 5 is a graph of hydrogen spectrum data for Compound A1.

FIG. 6 is a graph of hydrogen spectrum data of compound Cl-4F.

FIG. 7 is a graph of mass spectral data for compound Cl-4F.

FIG. 8 is an External Quantum Efficiency (EQE) spectrum of a Cl-4F organic solar cell prepared in example 4 of the present invention.

FIG. 9 is a graph showing the photoelectric conversion efficiency of Cl-4F organic solar cell prepared in example 4 of the present invention.

Fig. 10 is a graph of photocurrent-effective bias voltage of the Cl-4F organic solar cell prepared in example 4 of the present invention.

FIG. 11 is a voltage variation curve of the Cl-4F organic solar cell prepared in example 4 of the invention under variable light intensity.

FIG. 12 is a current density variation curve of the Cl-4F organic solar cell prepared in example 4 of the present invention under a variable light intensity.

FIG. 13 is a GIWAXS experiment conducted on Cl-4F thin films prepared in example 5 of the present invention to investigate the molecular packing and crystallization patterns of the blended films.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The non-fused ring acceptor molecule based on the chlorophenyl-central core in each example is represented by the acceptor Cl-4F, and the synthetic route of the acceptor Cl-4F is as follows:

the method specifically comprises the following steps: 4-dibromo-2-chloro-5-methoxyaniline (2.35g, 10mmol) was weighed and dissolved in 10mL of anhydrous acetonitrile, and dropwise added to an acetonitrile solution (30mL) containing copper bromide (15mmol) and tert-butyl nitrite (24mmol) at 0 ℃ using a constant pressure dropping funnel. After the reaction was completed by stirring at room temperature for 2 hours, the mixture was poured into a 3M hydrochloric acid solution, extracted with dichloromethane, washed with water three times, the organic phase was collected, dried over anhydrous Mg2SO4, and most of the solvent was removed by rotary evaporation, and purified by silica gel column chromatography (PE/DCM 20/1, v/v), and the target compound was collected.

The objective compound was a white solid (1.9g), that is, the compound 1, 4-dibromo-2-chloro-5-methoxybenzene.

compound A1(1.75g, 5.9mmol) was weighed and compound A1 was subjected to hydrogen spectrum detection, as shown in FIG. 5, compound B1(13.4mol), Pd₂(PPh₃)₄(0.5mmol), 50mL of THF was added to a 100mL reaction tube under a nitrogen atmosphere, and the mixture was reacted overnight at 80 ℃. Cooling to room temperature after the reaction is finished, washing with saturated potassium fluoride solution for three times, extracting with dichloromethane, collecting an organic phase, and using anhydrous Na₂SO₄After drying and removing most of the organic liquid by rotary evaporation, the product was purified by silica gel column chromatography (PE/DCM 10/1, v/v) to collect the objective compound.

The target compound was 1.7g of yellow oil, which was compound C1.

to a 50mL three-necked reaction flask equipped with a stirrer (equipped with a condenser and nitrogen blanket purge) were added D1(199.6mg, 0.2mmol) and E1(230.0mg, 1 mmol). Reflux at 60 ℃ overnight. After cooling to room temperature, the reaction solution was added to 80mL of methanol, and the precipitate was filtered to give a crude product, which was purified by silica gel column (DCM/PE ═ 1/1) to give the product as a dark purple solid (180.6 mg). The compounds were confirmed by mass spectrometry and hydrogen spectrometry, as shown in FIGS. 6 and 7, giving the formula of Cl-4F.

The above method for preparing Cl-4F has less synthesis steps, mild reaction conditions and easy purification. Compared to fused ring molecules, there is no need to go through low-yield, high-cost fusion reactions, whereas compared to developing more sophisticated fluorination strategies, chlorination strategies do not need to go through low-yield and harsh-conditions exchange reactions to obtain halogen-containing precursors.

The receptor Cl-4F prepared above was used for the following validation:

example 1

Preparing a Cl-4F film:

the glass substrate bearing the film was first prepared, the glass substrate was scrubbed with a detergent, and then the glass substrate was sequentially sonicated with a detergent-water mixture, deionized water, acetone, and isopropanol, each step lasting 30 minutes. Prior to use, the glass substrates were treated with UV-ozone for 30 minutes and then the glass substrates were transferred into a nitrogen glove box. Dissolving Cl-4F in chloroformThe concentration of the solution is 20mg mL^-1And stirred overnight on a hot plate at 50 ℃. And (3) moving, throwing and rotating the Cl-4F solution to the surface of the glass substrate at 3500rpm for 30s to obtain the Cl-4F film, and measuring the thickness of the film by using a step profiler, wherein the thickness of the film is about 100nm and meets the requirement of the thickness of the film between 60 and 120 nm.

The ultraviolet-visible absorption spectrum of CL-4F is shown in FIG. 1, and the chloroform solution of Cl-4F shows stronger absorptivity in the region of 550-750nm, has wider absorption spectrum, and is beneficial to absorbing the energy in sunlight.

UV-VIS absorption spectrum of Cl-4F in the thin film state As shown in FIG. 2, the maximum absorption of Cl-4F shifted from 673nm in solution to 683nm in the thin film, indicating that the copolymer can form compact molecular groups in the thin film. In addition, the absorption spectrum in the thin film state shows a shoulder, which indicates that Cl-4F has some aggregation and intermolecular interaction in this state.

Example 2

Preparing a Cl-4F film:

a base wafer bearing a thin film is first prepared, the wafer is scrubbed with a detergent, and then sequentially sonicated with a detergent-water mixture, deionized water, acetone, and isopropyl alcohol (each step lasting 30 minutes). Before use, the silicon wafers were treated with UV-ozone for 30 minutes and then transferred to a nitrogen glove box. Cl-4F was dissolved in chloroform to a solution concentration of 20mg mL^-1And stirred overnight on a hot plate at 50 ℃. And (3) moving and throwing the Cl-4F solution to the surface of the silicon wafer at 3500rpm for 30s to obtain the silicon-based Cl-4F film, and measuring the thickness of the film by using a step profiler to ensure that the film thickness is 110nm (+ -10 nm). Silicon-based Cl-4F films were used for GIWAXS measurements, in-plane orientation, as shown in FIG. 3

Position with (100) peak, in the out-of-plane direction

There was a (010) peak at the position. This indicates that the Cl-4F film has a layered stack and a pi-pi stack, which is a formThe features facilitate charge transport.

Example 3

Preparation of a Cl-4F dilute solution:

0.8mg of Cl-4F was weighed out, and Cl-4F was dissolved in 400ul of chloroform at a concentration of 2mg mL-1 and stirred on a hot plate at 50 ℃ overnight. Thus obtaining the Cl-4F dilute solution. As shown in FIG. 4, the HOMO and LUMO levels of Cl-4F were calculated from the cyclic voltammogram to have a HOMO level of-5.55 eV and a LUMO level of-4.19 eV. The energy level of the organic solar cell and the energy level of the polymer donor PM6 can be well matched to form a built-in electric field, so that dissociation of excitons of the organic solar cell and transfer of charges are driven.

Example 4:

preparation of PM6 Cl-4F organic solar cell:

preparing a device: using ITO/ZnO/PM6: Cl-4F/MoO₃the/Al inverter configuration was used to fabricate solar cells. Indium Tin Oxide (ITO) glass substrates were first scrubbed with a detergent and then sequentially sonicated with a detergent-water mixture, deionized water, acetone and isopropanol (each step lasting 30 minutes). Before use, the glass substrate was treated with UV-ozone for 30 minutes. ZnO (Heraeus Clevios PVP AI 4083) was spin coated at 4500rpm on the ITO of the glass substrate for 30s, approximately 30nm thick, and baked in air at 200 ℃ for 30 minutes before transferring the glass into a nitrogen glove box. The donor: the receptor mixture (1: 1 by weight) was dissolved in chloroform to give a total concentration of 20mg mL of the mixture solution of all the mixtures^-1CN was selected as an additive at 0.5% by volume and stirred on a 50 ℃ hot plate overnight. The solution with donor and acceptor was spun to the ZnO surface at 4500rpm for 30s to give an active layer film with a thickness of about 120nm as measured by a surface profiler (Dektak XT, Bruker). The glass substrate bearing the active thin film was placed in a custom evaporation dish and annealed by CF solvent for about 15 seconds. Subsequently, the glass substrate bearing the active film was placed in a vacuum box and evacuated for 30min to remove excess additives, and the active film was annealed on a hot plate at 100 ℃ for 10 min. Finally, at 1 × 10^-4Vacuum steaming is carried out on the active film in sequence under the vacuum level of PaMoO with a plating thickness of 10nm₃And 100nm of metallic Al as an anode.

EQE data were collected using an integrated spectral response system (QE-R3018, enli technologies ltd) and light intensity was calibrated by standard single crystal silicon photovoltaic cells. The obtained External Quantum Efficiency (EQE) spectrum of the PM6: Cl-4F organic solar cell shows strong and wide photoresponse in the wavelength range of 350-800nm as shown in FIG. 8, and the short-circuit current density J based on the Cl-4F device calculated from the EQE curve_SCThe value was 19.66mA cm^-2This is substantially consistent with the short circuit current derived from the J-V curve,

PM6 is used as an electron donor material, and an inverse device structure ITO/ZnO/PM6: Cl-4F/MoO is adopted₃Al to prepare bulk heterojunction solar cells and select chloroform as the processing solvent, the current density-voltage (J-V) curves of all devices were measured using an AAA solar simulator (SS-F5-3A, enlite) in a glove box filled with nitrogen. As shown in FIG. 9, the radiation intensity (AM 1.5G spectrum, 100mW cm)^-2) Calibrated by standard silicon cells with KG5 filters (calibrated by Enli Tech Optoelectronic Calibration lab. and Keighley 2400 source instrumentation unit). The photoelectric conversion efficiency curve of the obtained Cl-4F organic solar cell is shown in FIG. 9, wherein the J-V curve is measured in the forward direction of-0.2 to 1.0V, the scanning step size is 20mV, and the retention time is 1 ms. The organic solar cell based on PM6: Cl-4F showed 11.71% photoelectric conversion efficiency, 0.95V open-circuit voltage and 19.73mA/cm short-circuit current²The fill factor was 62.78%. This approaches the highest photoelectric conversion efficiency of non-fused ring non-fullerene organic solar cells, and appropriate central nuclear chlorination strategies show great potential in achieving strong molecular packing and conformational adjustment.

The graph of photocurrent-effective bias voltage of the Cl-4F organic solar cell is shown in fig. 10, and the exciton dissociation and charge collection process of the molecule is explored by the dependence of photocurrent on effective bias voltage. The exciton dissociation efficiency of the device based on PM6: Cl-4F after chloronaphthalene addition and heat treatment was calculated to be 85.97% at maximum power. The higher exciton dissociation efficiency indicates that PM6: Cl-4F obtains efficient exciton dissociation and charge collection, which is consistent with its excellent device performance.

The voltage change curve of the Cl-4F organic solar cell under a variable light intensity is shown in fig. 11, wherein an S value indicates a defect state recombination degree, and when S is 1, bimolecular recombination is performed; when S is 2, the compound is monomolecular, which is a perfect defect state compound, and is not favorable for charge transport. The S value of the device based on PM6: Cl-4F is 1.008, which indicates that the defect state in the PM6: Cl-4F device is less recombination, and the charge transfer is facilitated.

The current density variation curve of the prepared Cl-4F organic solar cell under the variable light intensity is shown in FIG. 12, wherein the slope alpha represents the degree of bimolecular recombination. As α approaches 1, it indicates less bimolecular recombination of the device. If α is close to infinity being close to 1, it means that all charges are collected by the electrodes without recombination in the device. As shown in FIG. 12, the device α value based on PM6: Cl-4F is 0.872, which indicates that bimolecular recombination is less in the PM6: Cl-4F device, which is favorable for charge transport.

Example 5:

preparation of silicon-based PM6 Cl-4F film:

first, a base silicon wafer for supporting a thin film is prepared. The wafer was scrubbed with a detergent and then sequentially sonicated with a detergent-water mixture, deionized water, acetone and isopropyl alcohol (each step lasting 30 minutes). Before use, the silicon wafers were treated with UV-ozone for 30 minutes and then transferred to a nitrogen glove box. Donor PM6 and the acceptor Cl-4F blend prepared in example 2 (weight ratio 1: 1) were dissolved in chloroform at a total concentration of 20mg mL-1 and stirred on a hot plate at 50 ℃ overnight. The blend solution was spun at 4500rpm for 30s to obtain PM6: Cl-4F film, which was measured by a step profiler to a film thickness of 110nm (+ -10 nm). Silicon-based PM6: Cl-4F films were used for GIWAXS measurements, as shown in FIG. 13, for PM6: Cl-4F films in the out-of-plane direction

The (010) peak is stronger than the in-plane, indicating that the alignment of the molecules in the PM6: Cl-4F film is typically in a face-to-face (face-on) orientation that favors the chargeAnd (5) transmitting.

From the above, compared with the non-chlorophenyl-core non-condensed ring acceptor material, the chlorophenyl-core non-condensed ring acceptor material can effectively deepen the energy level of the organic solar cell, improve the crystallization performance of the material, and further adjust the open-circuit voltage and the filling factor of the organic solar cell, thereby improving the efficiency of the organic solar cell. And can also provide more choices of acceptor materials for the development of the active layer materials of the polymer solar cell. Promoting the forward development of organic solar cells.

The invention constructs a novel non-condensed ring receptor material based on the chlorophenyl as a central core unit, the polymer receptor material can absorb the light absorption range of about 400-800nm, and can effectively reduce the HOMO energy level of the cell, improve the crystallization performance of the polymer and further improve the energy conversion efficiency of the polymer when being applied to an organic solar cell.

Claims

1. Non-fused ring acceptor molecules based on a chlorophenyl-central core, characterized in that the non-fused ring acceptor molecules have the following general formula:

wherein: r represents a conjugated bridging unit;

R₁is selected from C₁～C₁₂One of (a) and (b);

2. The chlorophenyl-central core-based non-fused ring acceptor molecule according to claim 1, wherein the conjugated bridging unit is selected from one of the following:

3. the chlorophenyl-central core-based non-fused ring acceptor molecule according to claim 1 or 2, wherein R is₂The acceptor terminal group is selected from one of the following:

4. the non-fused ring acceptor molecule based on a chlorophenyl-central core according to claim 1, 2 or 3 for use as an acceptor material for solar cells.

5. A solar cell, characterized in that the chlorophenyl-center core-based non-condensed ring acceptor material according to claim 4 is used as an electron acceptor.

6. A process for the preparation of a non-fused ring acceptor molecule based on a chlorophenyl-central core according to any one of claims 1 to 3, characterized in that it is as follows: