KR101369627B1 - High conductive PEDOT:PSS thin film added acetone and organic solar cells using it - Google Patents

Abstract

The present invention relates to a method for manufacturing an organic solar cell using a PEDOT: PSS thin film to which acetone solvent is added as a hole transport layer in order to manufacture a high efficiency organic solar cell.
Conventional organic solar cells manufacture organic solar cells using a mixture of P3HT and PCBM as a photoactive layer and PEDOT: PSS as a hole transport layer. However, electrons and holes generated in the photoactive layer in the organic solar cell cause loss of light conversion efficiency due to low mobility in the thin film. Therefore, there is a need to solve this problem. The present invention reduces the resistivity by adding a solvent of acetone to the above-described PEDOT: PSS, thereby increasing the conductivity of the thin film to increase the mobility of the holes generated in the photoactive layer. Reduce Therefore, the light conversion efficiency of the organic solar cell can be increased.

Description

High conductivity PEDOT: PSS thin film added acetone and organic solar cells using it}

The present invention relates to an organic solar cell, and more particularly, to a technology for improving conductivity of a hole transport layer for transferring holes generated in a photoactive layer of an organic solar cell to an anode.

As we enter the 21st century, the demand for energy from emerging economies is increasing rapidly. In addition, with the rise of oil reserves, securing energy resources is becoming an important issue that will determine the future of each country. However, fossil fuels such as petroleum cause global pollution because they cause environmental pollution such as air pollution and greenhouse gases. Therefore, the development of new energy using pollution-free solar energy, which replaces fossil fuels, is competitive in each country. Among them, the organic solar cell has an advantage that the organic ink can be produced as if printing paper on a flexible substrate, and the manufacturing cost can be lowered. Therefore, it has been spotlighted as a key renewable energy source in the future because it has high growth potential in areas that inorganic solar cells cannot have.

The organic solar cell has a structure of an anode / photoactive layer / cathode. The anode and cathode use metals with different work functions to allow charges generated in the photoactive layer to be collected in the direction of the bulb-in-potential. Accordingly, the anode uses ITO, which has a high work function, is transparent and has good conductivity, and the cathode mainly uses a metal such as Al having a low work function. The photoactive layer consists of an electron donor (donor) poly (3-hexylthiophene) (P3HT) and an electron acceptor (acceptor) (6,6) phenyl-C61-butyric acid methyl ester (PCBM). When sunlight is exposed to the photoactive layer region, electrons and holes are generated as electrons in the highest occupied molecular orbital (HOMO) level of the electron donor material are excited to the lowest unoccupied molecular orbital (LUMO) level. At this time, an exciton, an electron-electron pair, is formed from the electron donor material. The electron-electron pair is separated at the interface, so that holes are separated into an anode and electrons are separated into a cathode to generate a current.

Poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT: PSS), which is used to increase the transport efficiency of holes generated in organic solar cells through the above mechanism, is transparent and has an appropriate energy level. Organic material mainly used as a hole transport layer. However, PEDOT: PSS has a lower hole conductivity than inorganic thin film. Therefore, in order to overcome this problem, PEDOT: PSS increases the conductivity of the thin film itself by lowering the resistivity of the thin film by adding various solvents to improve the efficiency of the organic solar cell. Attempts have been made, and research on the selection of inexpensive and readily available solvents for improving efficiency is still an open area.

Therefore, an object of the present invention is to add a PEDOT: PSS used as a hole transport layer to lower the resistivity, and to apply this as a hole transport layer of an organic solar cell to select a new organic solvent that can improve the light conversion efficiency to produce an organic solar cell It is intended to provide a way to.

Accordingly, the present invention provides an organic solar cell using the PEDOT: PSS thin film containing acetone as a hole transport layer.

That is, the present invention is a thin film used as a hole transport layer laminated between the anode and the photoactive layer in an electronic device composed of an anode / photoactive layer / cathode,

It is possible to provide a method for producing an organic thin film, characterized in that a thin film is formed by coating a mixture of acetone added to PEDOT: PSS on the anode.

In addition, the present invention can provide a method for producing an organic thin film, characterized in that the thin film formed of a mixture of acetone added to PEDOT: PSS is heat treated at 50 to 200 ℃.

In addition, the present invention can provide a method for producing an organic thin film, characterized in that the amount of acetone which is an organic solvent to PEDOT: PSS is 25 to 67 wt%.

In addition, the present invention, the method of producing an organic thin film, characterized in that for stirring for 2 to 10 hours at 100 to 1000 rpm to uniformly disperse the mixed solution of PEDOT: PSS and acetone. Can be provided.

In addition, the present invention, using the organic thin film produced by the above method as a hole transport layer,

The hole transport layer is laminated on the transparent electrode / glass substrate in a thin film,

P3HT: PCBM mixed chlorobenzene solution is coated on the hole transport layer and heat treated to form a photoactive layer,

An organic solar cell can be provided by depositing a cathode on the photoactive layer.

In addition, the present invention, in the organic solar cell, the cathode may provide an organic solar cell, characterized in that formed in a thin film in contact with LiF and Al.

The present invention reduces the resistivity of the hole transport layer through a simple method of mixing acetone solvent in PEDOT: PSS having low hole mobility, thereby greatly improving the conductivity of the hole transport layer. In particular, acetone is a readily available material, and can be an environmentally friendly process because it is not toxic.

In addition, it is possible to improve the efficiency of the P3HT and PCBM-based organic solar cell using the hole transport layer, in addition to this can be applied to various organic electronic devices such as OTFT, OLED, FOLED using the high-efficiency organic thin film.

1 illustrates a method of fabricating an organic solar cell using a PEDOT: PSS thin film to which acetone is added according to the present embodiment as a hole transport layer.
2 is a structure of an organic solar cell manufactured according to FIG. 1.
FIG. 3 shows a current density-voltage graph (JV) of an organic solar cell using the PEDOT: PSS thin film added with acetone according to the present embodiment as a hole transport layer.
4 is a short-circuit current density (J _sc ) _{, an} open circuit voltage (V _oc ) _{, a} fill factor (FF), and a light conversion efficiency of the organic solar cell manufactured according to FIG. 1. The table shows the values of power conversion efficiency (PCE).
Figure 5 is a schematic diagram to explain the process of improving the electrical conductivity by the acetone organic solvent according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, an organic solar cell as shown in FIG. 2 is manufactured by performing steps 1 to 6 below.

Stage 1

In order to fabricate an organic solar cell according to FIG. 1, the line width is 1 to 6 by wet etching for 1 hour in a solution in which hydrochloric acid: nitric acid: distilled water is mixed at an appropriate ratio through photolithography. A rectangular ITO patterning in mm is formed. The hydrochloric acid: nitric acid: distilled water is preferably 45 to 49: 1 to 5:50 by volume ratio, but this ratio is not limited.

Step 2

In order to prepare a solution for manufacturing a hole transport layer in an organic solar cell, acetone is mixed in a predetermined ratio as a solvent in PEDOT: PSS which is used as an existing hole transport layer. In this example, 25, 33, 50, 67 wt% of the ratio was mixed to find the optimum concentration. The mixed solution formed in this way is agitated, and in this embodiment, the solution is prepared by stirring at 100 to 1000 rpm, preferably 240 rpm for 2 to 10 hours, preferably 8 hours. Ready. At this time, PEDOT: PSS and acetone in the stirring process is expected to cause a chemical reaction to improve the conductivity, the mechanism thereof will be described later with reference to FIG.

Step 3

In order to form a hole transport layer on the patterned transparent electrode / glass substrate, the acetone-added PEDOT: PSS solution prepared in step 2 is applied, laminated, and heat-treated. In the present embodiment, the mixed solution is spin-coated at about 3000 rpm for about 30 seconds, and thin films are laminated. After lamination, 5 to 20 minutes at a temperature of 50 to 200 ° C., preferably 150 ° C., preferably, 10 Heat treatment was performed for a minute. In addition to spin coating, a thin film may be formed using various methods such as inkjet printing, roll-to-roll printing, dip coating, or spray coating.

Step 4

A photoactive layer is fabricated from P3HT, an electron donor, and PCBM organic, an electron acceptor. That is, in order to produce a photoactive layer, P3HT, which is an electron donor material, and PCBM, which is an electron acceptor material, are prepared in a glove box of a moisture-free, oxygen-free atmosphere. Prepare to a concentration of 12 mg / ml, and dissolve these two materials in chlorobenzene solvent and stir at 100 to 1000 rpm, preferably 240 rpm for 2 to 10 hours, preferably 8 hours.

Step 5

After moving the ITO substrate on which the acetone-added PEDOT: PSS thin film is deposited to a glove box in a moisture-free and oxygen-free atmosphere, the chlorobenzene solution mixed with P3HT: PCBM is preferably 1500 using a spin coating method. Laminating about 30 seconds at about rpm and heat treatment is performed at a temperature of 50 to 200 ℃, preferably 120 ℃ for 5 to 20 minutes, preferably 10 minutes and placed in a glove box for 15 minutes.

6 steps

The organic solar cell deposited up to the photoactive layer is transferred into a thermal evaporation apparatus to deposit LiF to aid ohmic contact and aluminum (Al) used as a cathode. At this time, the thickness of LiF is deposited within 1 to 10 nm, preferably within 5 nm and the thickness of aluminum (Al) is deposited within 90 to 200 nm, preferably within 120 nm. After electrode deposition is completed, heat treatment is performed again at 50 to 200 ° C., preferably at 120 ° C. for 5 to 20 minutes, preferably for 10 minutes in a glove box in a moisture-free, oxygen-free atmosphere.

The organic solar cell manufactured by the above process was investigated in IV characteristics and is shown in FIG. 3, and a short-circuit current density (J _sc ) _{, an} open circuit voltage (V _oc ) _{and a} fill factor (fill factor, FF) and power conversion efficiency (PCE) are shown in Table 4.

3 and 4, when the acetone organic solvent concentration is 50 wt% compared to the organic solar cell made of PEDOT: PSS only hole transport layer, it can be seen that the efficiency of the organic solar cell is significantly improved.

에 비교해

의 향상된 저항률을 가져 정공의 전달효율을 높이는 것으로 나타났고, 이에 따라 양극인 ITO 투명 전도막 까지 충분히 이동시켜 유기태양전지의 효율을 향상시켰다. 따라서 아세톤 첨가량은 50 wt%를 중심으로 약간의 범위를 갖는 정도가 바람직하다고 본다. That is, when 50 wt% of acetone solvent is added, existing PEDOT: PSS thin film has

Compared to

It has been shown to improve the hole transfer efficiency by improving the resistivity of, and thus the efficiency of the organic solar cell is improved by sufficiently moving to the ITO transparent conductive film as the anode. Therefore, it is considered that the amount of acetone added has a slight range around 50 wt%.

Thus, the mechanism by which the acetone solvent increases the hole transport rate of the hole transport layer may be described as shown in FIG. 5.

PEDOT is a conductive material, PSS is a non-conductive material, PEDOT can be seen to exist in the form surrounded by PSS. Therefore, the transport of holes in the pair of electron holes is weakened by the PSS, which is a non-conductive material on the outside, and it can be regarded as being trapped or recombined in the process.

Acetone, on the other hand, is a polar organic solvent with a large dipole moment (value over 2.0D). Therefore, when acetone is mixed with PEDOT: PSS, the polarized PEDOT is electrically activated and redistributed by the dipole moment of acetone, which is dispersed to the outside where PSS is distributed to activate the entire hole transport layer electrically. It is to increase the transportation rate.

As a result, it can be seen to increase the efficiency of the organic solar cell. Therefore, the amount of acetone should be sufficient to disperse the distribution of PEDOT, and it should be noted that an excess may adversely affect the energy level characteristics of the original PEDOT: PSS.

As described above, the hole transport rate is increased by increasing the conductivity of the hole transport layer while lowering the manufacturing cost, thereby lowering the rate at which holes generated in the photoactive layer disappear due to recombination in the hole transport layer, thereby manufacturing a high-efficiency solar cell at low cost.

In addition, in the present embodiment, only the solar cell device fabrication is mentioned, but the same hole transport layer may be equally applied to OTFT, OLED, FOLED, and the like.

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

No reference

Claims (6)

A thin film used as a hole transport layer laminated between the anode and the photoactive layer in an electronic device composed of an anode / photoactive layer / cathode,
PEDOT: Stirring a mixture of acetone added to the PSS for 6 to 10 hours to disperse the PEDOT to the outside of the PSS to coat the mixture of the hole transport layer electrically activated on the anode to form a thin film,
A method for producing an organic thin film, wherein the amount of acetone, which is an organic solvent, is 25 to 67 wt% in PEDOT: PSS. The method of claim 1, wherein the thin film formed of a mixture of acetone added to PEDOT: PSS is heat-treated at 50 to 200 ° C. delete delete Using the organic thin film produced by the method of any one of claims 1 or 2 as a hole transport layer,
The hole transport layer is laminated on the transparent electrode / glass substrate in a thin film,
P3HT: PCBM mixed chlorobenzene solution is coated on the hole transport layer and heat treated to form a photoactive layer,
An organic solar cell, characterized in that by fabricating a cathode on the photoactive layer. The organic solar cell of claim 5, wherein the cathode is formed of a thin film in contact with LiF and Al.

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