CN111584718A - A kind of high-efficiency organic solar cell and preparation method thereof - Google Patents

Abstract

The invention discloses a high-efficiency organic solar cell and a preparation method thereof, wherein the organic solar cell is of an inverted structure and sequentially comprises the following components from bottom to top: the device comprises a substrate layer, a transparent conductive cathode, a cathode buffer layer, an optical activity layer, an anode buffer layer and a metal anode; wherein the photoactive layer consists of a polymer electron donor, an electron acceptor and an amphiphilic small molecule additive. The invention adopts a novel amphiphilic micromolecule additive which is added into an active layer of an organic solar cell according to a certain weight ratio to assist in improving the photoelectric conversion performance of the organic solar cell. The amphiphilic micromolecule additive is used for regulating and controlling the micro morphology of the active layer, so that the active layer is orderly crystallized, pi-pi stacking of the donor and acceptor is promoted, a network interpenetrating microstructure is formed, exciton separation and charge transmission are facilitated, and meanwhile, the stability of the device is effectively improved. The photoelectric conversion efficiency of the organic solar cell prepared by the method is improved by about 7-22%.

Description

A kind of high-efficiency organic solar cell and preparation method thereof

technical field

The invention relates to an organic solar cell and a preparation method thereof, in particular to a method for applying an amphiphilic small molecule additive to a photoactive layer, belonging to the technical field of photovoltaics.

Background technique

Bulk heterojunction (BHJ) polymer solar cells (PSCs), as a promising green renewable energy technology, have gradually become one of the most promising technologies due to their advantages of light weight, low cost, simple fabrication, and large-area fabrication of flexible solar cells. hotspots of research. At present, the highest photovoltaic power conversion efficiency (PCE) of single-junction cells has exceeded 17%. However, compared with inorganic solar cells, the disadvantages of low energy conversion efficiency, short lifespan and poor stability have become the main factors restricting their commercialization. Among them, the morphology of the active layer plays an important role in BHJ organic solar cells. How to precisely control the heterojunction phase separation, the microscopic film crystal size, and the orientation of the acceptor molecules have become important factors limiting the device efficiency and stability.

In order to overcome these problems and realize high-efficiency organic solar cells, an effective method is to introduce additives into the active layer to effectively control the film morphology. Usually, including solvent additives, solid additives are used to control the microscopic morphology of the active layer to improve the battery performance. Solvent additives can improve device efficiency, but have poor repeatability and stability; solid additives only have a positive effect on some active layer materials and are not universal. Therefore, how to choose efficient additives is the key to improve the photoelectric conversion efficiency of organic solar cells.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a high-efficiency organic solar cell and a preparation method thereof, so as to solve the problems of poor stability and low efficiency of the organic solar cell.

To achieve the above object, the technical scheme adopted in the present invention is:

A high-efficiency organic solar cell, the organic solar cell has an inversion structure, and the order from bottom to top is: a substrate layer, a transparent conductive cathode, a cathode buffer layer, a photoactive layer, an anode buffer layer and a metal anode; wherein the photoactive layer is composed of Polymer electron donor, electron acceptor and amphiphilic small molecule additives.

Preferably, the amphiphilic small molecule additive is a nonionic surfactant, preferably dodecyl glyceryl acetate DGI.

Preferably, the weight ratio of the polymer electron donor, the electron acceptor and the amphiphilic small molecule additive in the photoactive layer is 1:1:(0-0.2).

Preferably, the electron donor material is a narrow-band polymer electron donor, preferably a polythiophene derivative.

Preferably, the electron acceptor material is a fullerene derivative or a small molecule acceptor.

Preferably, the material of the anode buffer layer is an organic compound or metal oxide with hole transport ability or electron blocking ability, preferably one of molybdenum oxide MoO ₃ , aluminum-doped zinc oxide AZO, zinc oxide ZnO and titanium dioxide TiO ₂ one or more; the thickness of the anode buffer layer is 1-200 nm.

Preferably, the cathode buffer layer material is an organic compound or metal oxide with electron transport ability or hole blocking ability, such as zinc oxide ZnO, and the cathode buffer layer has a thickness of 1-200 nm.

Preferably, the substrate layer material is glass or transparent polymer, and the transparent polymer material is polyethylene, polymethyl methacrylate, polycarbonate, polyurethane, polyphthalimide, vinyl acetate or One or more of polyacrylic acid.

Preferably, the transparent conductive cathode is a transparent or semi-transparent conductive material in the visible light region, and the light transmittance is greater than 50%.

Preferably, the metal anode material is one of gold, silver, platinum, copper, and aluminum.

A method for preparing a high-efficiency organic solar cell, comprising the following steps: cleaning a substrate composed of a substrate layer and a transparent conductive cathode with a surface roughness of less than 1 nm, and drying with nitrogen after cleaning; spin coating on the surface of the transparent conductive cathode A cathode buffer layer is formed, and thermal annealing is performed; a photoactive layer is prepared by spin coating on the cathode buffer layer; an anode buffer layer is evaporated on the surface of the photoactive layer; and a metal anode is evaporated on the anode buffer layer.

Beneficial effects: the present invention is used to adjust the microscopic thin film morphology of the active layer by adding amphiphilic small molecule additives into the active layer to improve device performance. The device prepared by the invention has good active layer morphology, and can realize the preparation of high-efficiency photovoltaic devices.

Compared with the prior art, a stable and high-efficiency organic solar cell provided by the present invention has the following advantages:

1) The self-assembled network layered structure of amphiphilic small molecule additives induces the crystallization of small molecule receptors, which enhances the π-π stacking between the receptor molecules and induces the receptor molecules to be inclined to face-to-face orientation. Molecular mobility increases, reduces intermolecular and intramolecular carrier recombination, significantly increases short-circuit current, and improves device efficiency;

2) The self-assembly time of the amphiphilic small molecule additive is short, so the phase separation of the acceptor is restricted and plasticized in a short time, thereby improving the morphology stability of the active layer and improving the stability of the device;

3) Amphiphilic small molecule additives are universal. The network layered self-assembly structure not only significantly regulates non-fullerene receptors, but also has a good regulatory effect on fullerene receptors.

Description of drawings

1a to 1f are the polymer electron donor materials PBDB-TF, PBDB-T selected for the active layer in Examples 2-7; electron acceptor materials IT-4F, PC ₇₁ BM, ITIC; Molecular structure of molecular additive DGI;

2 is a schematic structural diagram of the high-efficiency organic solar cell device of Example 1;

FIG. 3 is a graph of current density-voltage characteristics of the devices described in Examples 2-7 under AM 1.5 (intensity of 100 mW/cm ² ) irradiation.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention can be better understood from the following examples. However, those skilled in the art can easily understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims. .

Example 1

A high-efficiency organic solar cell, as shown in Figure 2, the cell adopts an inversion structure, from bottom to top: a substrate layer, a transparent conductive cathode, a cathode buffer layer, a photoactive layer, an anode buffer layer, and a metal anode; wherein An amphiphilic small molecule additive is introduced into the photoactive layer, and the weight percentage of the photoactive layer is composed of: 40.5-50% of polymer electron donor, 40.5-50% of electron acceptor, and 0-15.5% of amphiphilic small-molecule additive.

The amphiphilic small molecule additive is DGI, and the structure is shown in Figure 1f. The polymer electron donor materials in the photoactive layer are PBDB-TF and PBDB-T, and the structures are shown in Figures 1a to 1b. The electron acceptor materials in the photoactive layer are IT-4F, _PC71BM , ITIC, and the structures are shown in Figures 1c to 1e.

The material of the anode buffer layer is molybdenum oxide (MoO ₃ ), and the thickness of the anode buffer layer is 8 nm. The material of the cathode buffer layer is zinc oxide (ZnO), and the thickness of the cathode buffer layer is 35 nm. The material of the substrate layer is a glass substrate, and the material of the transparent electrode is indium tin oxide (ITO). The metal anode is silver (Ag).

Example 2

This example served as a control group.

The substrate composed of a transparent substrate layer and a transparent conductive cathode ITO with a surface roughness of less than 1nm was cleaned, and dried with nitrogen after cleaning; ZnO (4500rpm, 40s, 25nm) was spin-coated on the surface of the transparent conductive cathode ITO to prepare a cathode buffer layer, and thermally annealed the formed film (200°C, 60min); spin coating on the cathode buffer layer to prepare a photoactive layer (2500rpm, 60s, 95nm), in the photoactive layer, PBDB-TF:IT-4F The mass ratio was 1:1; MoO ₃ (8nm) was evaporated on the surface of the photoactive layer; metal anode Ag (80nm) was evaporated on the anode buffer layer. Under standard test conditions (AM 1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.86V, the short circuit current (J _SC )=20.60mA/cm ² , the fill factor (FF)=0.74 of the device were measured, Photoelectric conversion efficiency (PCE)=13.10%.

Example 3

This example is basically the same as Example 2, except that in the photoactive layer, the mass ratio of PBDB-TF:IT-4F:DGI is 1:1:0.15. Under standard test conditions (AM 1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.84V, the short circuit current (J _SC )=22.80mA/cm ² , the fill factor (FF)=0.75 of the device were measured, Photoelectric conversion efficiency (PCE)=14.50%. Compared with the control group, the short-circuit current of the device was significantly improved, and the photoelectric conversion efficiency was increased by 10.7%.

Example 4

This example served as a control group.

This example is basically the same as Example 2, except that the photoactive layer is prepared by spin coating (2300rpm, 60s, 95nm), and the mass ratio of PBDB-T:ITIC in the photoactive layer is 1:1. Under standard test conditions (AM 1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.88V, the short circuit current (J _SC )=16.30mA/cm ² , the fill factor (FF)=0.64 of the device were measured, Photoelectric conversion efficiency (PCE)=9.25%.

Example 5

This example is basically the same as Example 2, except that the photoactive layer is prepared by spin coating (2300rpm, 60s, 95nm), and the mass ratio of PBDB-T:ITIC:DGI in the photoactive layer is 1:1:0.15. Under standard test conditions (AM 1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.90V, the short circuit current (J _SC )=18.20mA/cm ² , the fill factor (FF)=0.69 of the device were measured, Photoelectric conversion efficiency (PCE)=11.30%. Compared with the control group, the short-circuit current and fill factor of the device were significantly improved, and the photoelectric conversion efficiency was increased by 22.1%.

Example 6

This example served as a control group.

This example is basically the same as Example 2, except that the photoactive layer is prepared by spin coating (2000rpm, 60s, 95nm). In the photoactive layer, the mass ratio of PBDB-T: _PC71BM is 1:1.5. Under standard test conditions (AM 1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.82V, the short circuit current (J _SC )=14.91mA/cm ² , the fill factor (FF)=0.71 of the device were measured, Photoelectric conversion efficiency (PCE)=8.70%.

Example 7

This example is basically the same as Example 2, except that the photoactive layer is prepared by spin coating (2000rpm, 60s, 95nm). In the photoactive layer, the mass ratio of PBDB-T: _PC71BM :DGI is 1:1.5:0.15. Under standard test conditions (AM1.5, 100mW/cm ² ), the open circuit voltage (V _OC )=0.83V, the short circuit current (J _SC )=15.40mA/cm ² , the fill factor (FF)=0.72 of the device were measured , photoelectric conversion efficiency (PCE)=9.30%. Compared with the control group, the short-circuit current of the device is significantly improved, and the photoelectric conversion efficiency is increased by 6.9%.

Figure 3 is a graph of the current density-voltage characteristics of the devices described in Examples 2-7 under AM 1.5 (intensity of 100 mW/cm ² ) irradiation, illustrating that between polymer donors: small molecule acceptors and polymer donors Body: In the fullerene acceptor system, the amphiphilic small molecule additive DGI can effectively improve the short-circuit current and fill factor, and ultimately improve the device efficiency. The photoelectric conversion efficiency is improved by about 7-22%.

A high-efficiency organic solar cell device provided by the present invention and its preparation method are introduced in detail above. By adding amphiphilic small molecules as additives to the photoactive layer, the microscopic morphology of the film can be optimized, phase separation can be improved, and molecules can be adjusted. Orientation and crystal size can inhibit bimolecular charge recombination, leading to more efficient charge generation and transport, increasing the short-circuit current density of the device, and ultimately improving the photoelectric conversion performance of the device.

The above is only the preferred embodiment of the present invention, it should be pointed out that: for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of the present invention.

Claims (10)

1. A high efficiency organic solar cell, characterized by: this organic solar cell is the inversion structure, and from the bottom up is in proper order: the device comprises a substrate layer, a transparent conductive cathode, a cathode buffer layer, an optical activity layer, an anode buffer layer and a metal anode; wherein the photoactive layer consists of a polymer electron donor, an electron acceptor and an amphiphilic small molecule additive.

2. A high efficiency organic solar cell as claimed in claim 1, wherein: the amphiphilic small molecule additive is a nonionic surfactant.

3. A high efficiency organic solar cell as claimed in claim 1, wherein: in the photoactive layer, the weight ratio of the polymer electron donor to the electron acceptor to the amphiphilic micromolecule additive is 1:1: (0-0.2).

4. A high efficiency organic solar cell as claimed in claim 1, wherein: the material of the polymer electron donor is a narrow-band polymer electron donor; the electron acceptor material is a fullerene derivative or a small molecule acceptor.

5. A high efficiency organic solar cell as claimed in claim 1, wherein: the anode buffer layer is made of organic compounds or metal oxides with hole transmission capacity or electron blocking capacity, and the thickness of the anode buffer layer is 1-200 nm.

6. A high efficiency organic solar cell as claimed in claim 1, wherein: the cathode buffer layer is made of organic compounds or metal oxides with electron transmission capacity or hole blocking capacity, and the thickness of the cathode buffer layer is 1-200 nm.

7. A high efficiency organic solar cell as claimed in claim 1, wherein: the substrate layer is made of glass or transparent polymer, and the transparent polymer material is one or more of polyethylene, polymethyl methacrylate, polycarbonate, polyurethane, polyphthalamide, vinyl chloride-vinyl acetate copolymer or polyacrylic acid.

8. A high efficiency organic solar cell as claimed in claim 1, wherein: the transparent conductive cathode is made of a transparent or semitransparent conductive material in a visible light area, and the light transmittance is greater than 50%.

9. A high efficiency organic solar cell as claimed in claim 1, wherein: the metal anode material is one of gold, silver, platinum, copper and aluminum.

10. A method of fabricating a high efficiency organic solar cell as claimed in claim 1, wherein: the method comprises the following steps: cleaning a substrate with the surface roughness less than 1nm and consisting of a substrate layer and a transparent conductive cathode, and drying by using nitrogen after cleaning; rotationally coating a cathode buffer layer on the surface of the transparent conductive cathode, and carrying out thermal annealing; preparing an optical active layer on the cathode buffer layer by adopting spin coating; evaporating an anode buffer layer on the surface of the optical active layer; and evaporating a metal anode on the anode buffer layer.

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