CN102024906B - An organic solar cell structure based on oxide-doped organic materials - Google Patents

Abstract

The invention relates to the technical field of organic photoelectric devices, and discloses an organic solar cell structure based on oxide-doped organic materials. The structure includes from bottom to top: a transparent substrate; an anode deposited on the substrate; a buffer layer on the anode; an organic electron donor layer deposited on the buffer layer; an organic electron acceptor layer deposited on the organic electron donor layer; and a cathode deposited on the organic electron acceptor layer. Among them, the anode is made of ITO or FTO, the buffer layer is made of oxide-doped organic materials, the oxides are low-temperature materials such as MoO ₃ and ReO ₃ , the organic electron donor layer is made of CuPc or ZnPc, and the organic electron acceptor layer is made of C60 or PTCDA or For PTCBI, the cathode is made of aluminum or magnesium-silver alloy. Each layer except the anode and the cathode can be prepared by vacuum evaporation, spraying, printing and other methods of depositing organic thin films. The present invention can improve the stability of organic solar cells.

Description

An organic solar cell structure based on oxide-doped organic materials

technical field

The invention relates to the technical field of organic photoelectric devices, in particular to an organic solar cell structure based on oxide-doped organic materials, which uses metal oxide-doped organic materials as a buffer layer without reducing the energy conversion efficiency of organic solar cells Under the premise of improving the stability of the battery.

Background technique

At present, solar cell products on the market are mainly based on inorganic materials, mainly based on semiconductor materials such as silicon wafers, cadmium telluride, and III-V compounds. This type of battery has stable performance and long service life, but its production cost is high, the process is complicated, the material requirements are harsh, and it may cause follow-up pollution, which makes this type of solar cell unable to be popularized in a large area. Organic solar cells use a wide range of materials, low prices, simple preparation processes, and easy access to large areas, making it possible to reduce battery costs, and can use flexible substrates, which are easy to carry.

The reason for the low energy conversion efficiency of organic solar cells lies in the working principle of the cells and the basic properties of organic semiconductor materials. When light irradiates an organic solar cell, the photons are absorbed by the organic semiconductor layer, which excites electrons to transition from the valence band to the conduction band, forming electron-hole pairs (excitons). These excitons can only be separated into free carriers by diffusing to the pn junction composed of p-type material and n-type material. The exciton diffusion length of organic materials is only about 10nm, so it is only 20nm around the donor-acceptor interface Excitons can be separated. In addition, the carrier mobility of organic materials is very low, generally between 10 ^-8 and 10 ^-2 cm ² /V·s, and the carriers are easy to recombine or be trapped by traps during transport.

In the past few decades, scientific researchers have carried out a lot of work, and the research on double-layer heterojunction devices, bulk heterojunction devices, mixed evaporation small molecule devices and organic/inorganic hybrid devices has made great progress. Progress. At present, the efficiency of organic dye-sensitized nanocrystalline cells has exceeded 10%, and the efficiency of organic small molecule solar cells has reached 5% in the laboratory. According to simulation predictions, when the energy level structure of the device, the band system of the material, and the mobility are all optimized, the efficiency of the bulk heterojunction polymer/fullerene solar cell can reach 11%, and the efficiency of the cascaded device can reach 11%. up to 16%.

In addition to battery efficiency, another important indicator to measure the performance of solar cells is the life of the battery, that is, the stability. It is generally believed that when the conversion efficiency of solar cells exceeds 10%, and the service life reaches 10,000 hours, the technology will be adopted at a faster rate. From the perspective of conversion efficiency and service life, even the organic solar cells with the best performance have a service life of only a few thousand hours. The instability of organic solar cells is mainly due to the influence of the external environment, the poor stability of electrode materials and organic materials, and the interaction between electrodes and organic thin films at the interface. For the impact of the external environment, packaging technology is usually used to prevent oxygen and water molecules in the air from entering the device and reacting with the film. It is worth noting that the interface between the electrode and the organic film has a great influence on the device lifetime. For example, ITO glass is often used as an anode in organic semiconductor devices, and In in ITO film penetrates into the organic film to change its material properties, which is an important reason for reducing the stability of the device.

Contents of the invention

(1) Technical problems to be solved

In view of this, the main purpose of the present invention is to provide an organic solar cell structure based on oxide-doped organic materials, so as to improve the stability of unpackaged organic solar cells without reducing the energy conversion efficiency of organic solar cells. sex.

(2) Technical solution

In order to achieve the above object, the present invention provides an organic solar cell structure based on oxide-doped organic materials, which comprises from bottom to top:

transparent substrate;

an anode deposited on the substrate;

a buffer layer deposited on the anode;

an organic electron donor layer deposited on the buffer layer;

an organic electron acceptor layer deposited on the organic electron donor layer; and

A cathode deposited on the organic electron acceptor layer.

In the above solution, the anode is ITO or FTO.

In the above scheme, the structure also includes a modification material for modifying the anode to improve carrier transport between the anode and the buffer layer, and the modification material is nickel Ni or gold Au.

In the above solution, the buffer layer is made of oxide-doped organic material.

In the above solution, the oxide in the buffer layer is MoO ₃ , ReO ₃ or WO ₃ .

In the above solution, CuPc or ZnPc is used as the organic material in the buffer layer.

In the above scheme, when the oxide and the organic material in the buffer layer are doped, the growth rate ratio is between 1:10 and 1:1.

In the above solution, the organic electron donor layer adopts CuPc or ZnPc.

In the above solution, the organic electron acceptor layer adopts C60 and its derivatives, PTCDA or PTCBI.

In the above scheme, the cathode adopts aluminum Al or magnesium-silver alloy.

(3) Beneficial effects

As can be seen from the foregoing technical solutions, the present invention has the following beneficial effects:

The organic solar cell structure based on oxide-doped organic materials provided by the present invention will improve the interface morphology between the organic donor layer and the anode by introducing a doped buffer layer, and at the same time reduce the ITO anode from In to organic materials. penetration, which in turn can improve the stability of organic solar cells.

Description of drawings

Fig. 1 is a schematic diagram of an organic solar cell structure based on an oxide-doped organic material provided by the present invention;

Fig. 2 is the IV curve of the organic solar cell structure based on the oxide-doped organic material provided by the present invention; Wherein the standard device refers to the ITO/CuPc/C60/Al device, and the structural device of the present invention is ITO/MoO ₃ : CuPc/CuPc/ C60/Al device, the light source is 100mW/cm ² AM1.5 simulated light;

Fig. 3 is a time-varying curve of the efficiency of a standard device and a device with a structure of the present invention, the test is carried out in an atmospheric environment, and the device is not packaged.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Please refer to Fig. 1, Fig. 1 is a schematic diagram of an organic solar cell structure based on oxide-doped organic materials provided by the present invention, the structure includes from bottom to top:

A transparent substrate 10, glass or flexible polymer with good light transmission can be used;

An anode 20, the anode 20 is deposited on the substrate 10, the anode can be any of the following materials: ITO, FTO, or ITO or FTO modified with high work function metals such as gold or nickel;

A buffer layer 30, the buffer layer 30 is deposited on the anode 20, and is composed of an oxide-doped organic material; the oxide can be selected from any of the following materials: MoO ₃ , ReO ₃ , WO ₃ ; the organic material can be selected from any of the following materials : CuPc, ZnPc; the growth rate ratio of oxide and organic material in the buffer layer 30 is between 1:10 and 1:1 when doped;

An organic electron donor layer 40, the organic electron donor layer 40 is deposited on the buffer layer 30, any of the following materials can be selected: CuPc, ZnPc;

An organic electron acceptor layer 50, the organic electron acceptor layer 50 is deposited on the organic electron donor layer 40, any of the following materials can be selected: C60 and its derivatives, PTCDA, PTCBI; and

A cathode 60, the cathode 60 is deposited on the organic electron acceptor layer 50, and any of the following materials can be selected: aluminum Al, magnesium-silver alloy.

The present invention provides an organic solar cell structure that can improve the stability of an organic solar cell, and what it relates to is an organic solar cell structure that uses a metal oxide-doped organic material as an anode buffer layer, as shown in Figure 1. The structure is sequentially composed of a transparent substrate 10 , an anode 20 , a buffer layer 30 , an electron donor layer 40 , an electron acceptor layer 50 and a cathode 60 from bottom to top.

In the present invention, the transparent substrate 10 can be made of glass or a flexible polymer with good light transmission, and light enters the device from the substrate 10 .

In the present invention, the anode 20 is deposited on the substrate 10, and the anode can be any of the following materials: ITO, FTO, or ITO or FTO modified with high work function metals such as gold or nickel.

In the present invention, the buffer layer 30 refers to an organic-inorganic composite material capable of smoothing, wetting the anode surface, and matching energy levels so that holes can be transported well. The inorganic material can be a low-temperature metal oxide, and the following can be selected: Any material: MoO ₃ , ReO ₃ , WO ₃ , organic material can choose CuPc or ZnPc. The growth rate ratio of oxide and organic material in the buffer layer 30 during doping is between 1:10 and 1:1.

In the present invention, the organic electron donor layer 40 and the organic electron acceptor layer 50 are light absorbing layers, the excitons are separated at the interface to form free carriers, and the LUMO and HOMO energy levels of the donor must be higher than those of the acceptor. The LUMO and HOMO energy levels of the donor, and the difference between the LUMO and HOMO energy levels of the donor and acceptor must be greater than 0.4eV. In addition, the organic electron donor layer 40 should match the HOMO energy level of the doped buffer layer, CuPc or ZnPc can be used; the organic electron acceptor layer 50 can choose any of the following materials: C60 and its derivatives, PTCDA, PTCBI.

In the present invention, the cathode 60 can be made of aluminum or magnesium-silver alloy.

In the present invention, except for the anode and the cathode, the other layers can be prepared by various methods of depositing organic films such as vacuum evaporation, spin coating, and printing. The buffer layer (such as MoO ₃ doped CuPc) can be realized by co-evaporation technology or co-dissolving oxide and organic materials in the same solvent and then spin-coating or printing.

By introducing a doped buffer layer, the interface morphology between the organic donor layer and the anode will be improved, and at the same time, the infiltration of In in the ITO anode into the organic material will be reduced, which can improve the stability of the organic solar cell.

In the structure of the organic solar cell proposed by the invention, the filling factor of the cell is increased, and the energy conversion efficiency is slightly improved. Table 1 is the performance comparison between the standard device and the device of the present invention. The stability of the device is improved compared to the standard device structure (see Figure 3).

Table 1

The present invention is specifically described below in conjunction with the examples, but the present invention is not limited to the examples listed.

金属Al生长速率约

电池的有效面积约0.5mm²。氙灯为太阳能模拟光源，光强为100mW/cm²，I-V曲线用Keithley2400进行测量，所有测试都是在大气环境下进行。Solar cells are grown on cleaned ITO glass substrates, the thickness of ITO is about 150nm, and the sheet resistance is about 20Ω/□. The organic film and the cathode are grown by organic molecular beam deposition equipment (OMBD), and the vacuum is about 4×10 ^-7 Torr during growth. The organic film growth rate is about

The metal Al growth rate is about

The active area of the battery is about 0.5 mm ² . The xenon lamp is a simulated solar light source with a light intensity of 100mW/cm ² . The IV curve is measured with Keithley2400, and all tests are carried out in an atmospheric environment.

The device structure is: standard device ITO/CuPc 40nm/C6050nm/Al, and the inventive structure device ITO/MoO ₃ : CuPc (1:10) 10nm/CuPc 30nm/C6050nm/Al.

The I-V curve of the device under light conditions is shown in Figure 2, and the change of device efficiency with time is shown in Figure 3. After being placed in the air for 30 minutes, the efficiency of the standard device is reduced to 63% of the initial value, while the efficiency of the device of the present invention is 80% of the initial value, and the stability of the device is improved.

The meanings of the abbreviated names in this article are as follows:

ITO: indium tin oxide

MoO ₃ : molybdenum oxide

ReO ₃ : rhenium oxide

WO ₃ : Tungsten Oxide

CuPc: copper phthalocyanine (Copper phthalocyanine)

ZnPc: Zinc phthalocyanine

C60: fullerene (fulleren)

PTCDA: perylene tetracarboxylic dianhydride (3,4,9,10-perylene tetracarboxylic)

PTCBI: Dibenzimidazole-3,4,9,10-tetracarboxyperylene (3,4,9,10-perylenetetracarboxylic bis-benzimidazole)

HOMO: Highest Molecular Occupied Orbital

LUMO: lowest molecular unoccupied orbital

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. the organic solar energy cell structure based on oxide-doped organic material is characterized in that, this structure comprises from the bottom to top successively:

Transparent substrates;

Be deposited on the anode on this substrate;

Be deposited on the resilient coating on this anode;

Be deposited on the organic electronic donor layer on this resilient coating;

Be deposited on the organic electronic receptive layers on this organic electronic donor layer; And

Be deposited on the negative electrode on this organic electronic receptive layers;

Wherein, said resilient coating is made up of oxide-doped organic material, and said oxide adopts MoO ₃, ReO ₃Or WO ₃, said organic material adopts CuPc or ZnPc, and oxide and organic material are when mixing in the said resilient coating, and the growth rate ratio is between 1: 10 to 1: 1.

2. the organic solar energy cell structure based on oxide-doped organic material according to claim 1 is characterized in that, said anode is ITO or FTO.

3. the organic solar energy cell structure based on oxide-doped organic material according to claim 1; It is characterized in that; This structure also comprises modifies to improve the decorative material of the carrier transport between anode and the resilient coating said anode, and this decorative material adopts nickel or golden Au.

4. the organic solar energy cell structure based on oxide-doped organic material according to claim 1 is characterized in that, said organic electronic donor layer adopts CuPc or ZnPc.

5. the organic solar energy cell structure based on oxide-doped organic material according to claim 1 is characterized in that, said organic electronic receptive layers adopts C60 and derivative, PTCDA or PTCBI.

6. the organic solar energy cell structure based on oxide-doped organic material according to claim 1 is characterized in that, said negative electrode adopts aluminium Al or magnesium silver alloy.

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