KR101445024B1 - Organic solar cells having water removing membrane formed active layer and preparation method thereof - Google Patents

Abstract

The present invention relates to an organic solar cell having moisture regulating activity and surface roughness increasing activity inside and outside the photoactive layer and a method for producing the same, and more particularly, to a method for preparing an organic solar cell, which comprises applying isopropanol on the photoactive layer after 4 to 20 minutes of photoactive layer coating ; And a step of depositing an electrode layer (negative electrode) after the isopropanol coated on the photoactive layer is removed. The present invention also relates to a method of manufacturing the same. Accordingly, it is possible to prevent the dissolution of the photoactive layer, which may be caused by isopropanol, and to suppress moisture penetration into the photoactive layer generated at the time of forming the electrode layer, thereby controlling the moisture inside and outside the photoactive layer, It is possible to increase the light conversion efficiency retention rate (lifetime).
Further, by increasing the surface roughness of the photoactive layer, it is possible to increase the surface roughness of the electrode layer (negative electrode) deposited on the photoactive layer to cause scattering of incident light to induce reabsorption, and to increase the contact area between the electrode layer and the photoactive layer, And the conversion efficiency is improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic solar cell having a photoactive layer on which a water-removing film is formed,

The present invention relates to an organic solar cell having moisture regulating activity and surface roughness increasing activity inside and outside the photoactive layer and a method for producing the same, and more particularly, to a method for preparing an organic solar cell, which comprises applying isopropanol on the photoactive layer after 4 to 20 minutes of photoactive layer coating ; And a step of depositing an electrode layer after the isopropanol coated on the photoactive layer is removed. The present invention also relates to a method of manufacturing the same.

Solar cells are being reevaluated from the viewpoint of conservation of the global environment because of the advantage of no pollution, and research is being actively carried out as a next generation clean energy source.

The solar cells known so far include solar cells using single crystal or polycrystalline bulk silicon, thin film solar cells using amorphous, microcrystalline or polycrystalline silicon, compound semiconductor solar cells (CIS, CIGS), dye- Dye-sensitized solar cells (DSSCs) and organic solar cells (OSCs). Among them, silicon-based solar cells are generally used, but commercialized single-crystal bulk silicon solar cells have suffered from the problem of unstable supply and demand of wafers in recent years, And the recession is occurring throughout the photovoltaic industry. In addition, the company is not able to immediately respond to customer and market needs such as high light conversion efficiency, various design and portability. Accordingly, compound semiconductor solar cells, dye-sensitized solar cells, and organic solar cells have attracted attention.

Organic solar cell technology is a technology to convert solar energy into electric energy by using polymer or low molecular organic semiconductor. It is based on the low cost and easiness of manufacturing process, which is the biggest advantage of organic material, It is a next-generation technology that has all the features of ultra-low cost and versatile mass production such as a flexible device by a roll-to-roll method.

Generally, an organic solar cell has a junction structure of an electron donor and an electron acceptor material. When light enters the photoelectric conversion layer (photoactive layer), electrons and holes are generated in the electron donor As the electrons move to the electron acceptor, separation of electrons and holes occurs. Therefore, the carriers generated by the light are separated by the electron-hole, and the electric power is generated as the carrier moves to the external circuit.

However, the above-described organic solar cell has a limitation of being vulnerable to moisture (humidity), ultraviolet rays and oxygen due to the nature of the organic material used in the photoactive layer, and this limit has an adverse effect on the light conversion efficiency and the photo- . Therefore, in order to commercialize the organic solar cell, it is necessary to study the effect of removing moisture introduced into the surface and inside of the photoactive layer of the organic solar cell, and contributing to the photo conversion efficiency without adversely affecting the photoactive layer.

Meanwhile, 'isopropyl alcohol (IPA, isopropyl alcohol)' is mainly used for cleaning glass and removing foreign matter on the surface of LCD panel during LCD panel manufacturing process. It removes the surface of wafer and removes water marks ) It is a widely used substance for removal purpose.

Under the above background, the inventors of the present invention have been studying an organic solar cell manufacturing method capable of increasing the photo-conversion efficiency by controlling moisture inside and outside the photoactive layer of the organic solar cell and controlling the surface roughness, The photoactive layer was coated with isopropanol over the photoactive layer for 4 to 20 minutes, and then the electrode layer was deposited to form an organic solar cell. Then, an infrared spectrophotometer, a confocal laser scanning microscope, and an X-ray diffractometer As a result, the present inventors have completed the present invention by confirming that the moisture reduction phenomenon is exhibited inside the photoactive layer and the photo conversion efficiency and the photo-conversion efficiency retention ratio are improved.

It is an object of the present invention to provide a photovoltaic device having an organic solar cell having a photoactive layer for preventing water penetration and a surface moisture removing activity to improve a photoelectric conversion efficiency retention rate and an organic solar cell And a method for producing the same.

Another object of the present invention is to provide an organic solar cell manufactured by the above-described method.

According to an aspect of the present invention, there is provided a method of manufacturing an organic solar cell including a substrate, a hole transport layer, a photoactive layer, and an electrode layer, the method comprising: coating a photoactive layer on the hole transport layer; Applying the isopropanol on the photoactive layer after 4 to 20 minutes of the photoactive layer coating (step 2); And depositing an electrode layer after removing the isopropanol coated on the photoactive layer (Step 3).

Step 1 is a step of depositing a photoactive solution on the hole transport layer to form a photoactive layer on one surface of the hole transport layer. The photoactive solution is prepared by adding poly (3-hexylthiophene) and [6,6] -phenyl C ₇₁ butyric acid methyl ester to a dichlorobenzene solvent and adding poly (3-hexylthiophene) and [6,6] C ₇₁ butyric acid methyl ester is preferably added in a weight ratio of 3: 7 to 7: 3. More preferably 1: 1 by weight.

The present invention may further include a step of depositing a hole transporting layer on one surface of the substrate before the step 1.

The term "substrate " used in the present invention means that indium tin oxide (ITO) used as an anode is patterned on one surface of a glass substrate.

The term "hole transporting layer " used in the present invention means a layer which performs a buffering action between the anode and the photoactive layer of the organic solar cell to smooth the charge transfer between the respective interfaces. The hole transport layer is preferably poly (3,4-ethylenedioxythiophene) -poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT: PSS) It is preferable to deposit at a thickness of 20 nm to 100 nm. More preferably a thickness of 50 nm. The deposition may be performed by spin coating or spray deposition, but is not limited thereto.

Step 2 is a step of applying isopropanol (IPA) to the upper part of the photoactive layer to have moisture control activity and crystallinity improving activity in the photoactive layer. The application of isopropanol is preferably carried out after 4 to 20 minutes from the formation of the photoactive layer, followed by deposition. If isopropanol is applied 4 minutes before the formation of the photoactive layer, there is a problem that the photoactive layer is dissolved by isopropanol. In addition, if the coating is applied for more than 20 minutes, the crystallinity of the poly (3-hexylthiophene) (P3HT) can not be improved and the time for exposure to the external environment increases, .

In addition, the coating is isopropanol isopropanol 0.03 ㎖ / cm ² to 0.08 ㎖ / cm ² It is preferable to treat it in an appropriate amount. If, when the application amount is less than the isopropanol 0.03 ㎖ / cm ² does not contribute to the moisture removal of the photoactive layer and the enhancement effect of poly (3-hexylthiophene) (P3HT) crystalline, isopropanol application amount is more than 0.08 ㎖ / cm ² photoactive The drying time of the layer thin film is increased. The application of the isopropanol may be performed by a spin coating method, a spraying method, or a screen printing method, but is not limited thereto.

Step 3 is a step of depositing an aluminum electrode layer (cathode) on the photoactive layer to form an electrode layer on the photoactive layer to obtain an organic solar cell. The electrode layer is preferably deposited after the isopropanol coated on the photoactive layer is removed. The removal of isopropanol may be performed by isopropanol reacting with the inner and outer portions of the photoactive layer to absorb or evaporate into the photoactive layer and may be removed by a coating method or may be removed by natural evaporation according to the isopropanol application method.

The removal by the coating method is applied when isopropanol is applied through a spin coating method, and isopropanol is applied by a spin coating method, and isopropanol remaining in the inner and outer portions of the photoactive layer is removed by a high-speed spin. In addition, the natural evaporation at the atmospheric pressure or the low pressure is applied when isopropanol is applied through the spraying method and the screen printing method, and it may be changed according to the temperature of the applied isopropanol and the atmospheric pressure. However, Isopropanol application occurs after 13 to 40 minutes elapse.

The present invention also provides an organic solar cell produced by the above-described method.

According to an embodiment of the present invention, it has been confirmed that an organic solar cell produced by applying isopropanol to an upper part of a photoactive layer and then depositing an electrode layer has excellent photo-conversion efficiency. In particular, it has a step of coating isopropanol at 85 ° C, The photovoltaic conversion efficiency of the organic solar cell was improved by 15.95%. Also, it was confirmed that an organic solar cell including the step of coating isopropanol has a moisture control effect in the photoactive layer.

The method of manufacturing an organic solar cell according to the present invention is effective in preventing the dissolution of a photoactive layer generated by isopropanol by applying isopropanol over the photoactive layer after 4 to 20 minutes of photoactive layer coating, It is possible to increase the light conversion efficiency retention rate (lifetime) by controlling moisture in the inside and outside of the photoactive layer by reducing moisture penetration into the inside of the photoactive layer generated at the time of formation, thereby decreasing resistance increase due to moisture.

In addition, by increasing the surface roughness of the photoactive layer, the surface roughness of the electrode layer (negative electrode) deposited on the photoactive layer is increased to cause scattering of incident light to induce reabsorption, and the electrode layer There is an effect of increasing the light conversion efficiency by increasing the contact area between the photoactive layers.

Accordingly, the organic solar cell of the present invention and the method for producing the same can be easily used in the solar cell industry.

1 is a graph showing the results of a comparison between a photoactive layer coating (a) and a photoactive layer coating according to one embodiment of the present invention after one minute, (b) two minutes, (c) three minutes, (E) is a photograph showing a photoactive layer thin film (left) prepared without isopropanol coating and a photoactive layer thin film (right) prepared by applying isopropanol after 4 minutes of photoactive layer coating. FIG.
FIG. 2 is a schematic view illustrating the structure of an organic solar cell including an isopropanol applying step according to an embodiment of the present invention. However, the isopropanol coating layer 120 shows that it is used in the manufacturing process of an organic solar cell and does not mean that it exists in the finally produced organic solar cell.
FIG. 3 shows the results of an X-ray diffraction analysis (XRD) of an organic solar cell according to an embodiment of the present invention.
FIG. 4 shows a result of a comparative analysis of a confocal laser scanning microscope (CLSM) of an organic solar cell according to an embodiment of the present invention.
FIG. 5 shows a result of an infrared spectrophotometer (FT-IR) comparative analysis of an organic solar cell according to an embodiment of the present invention.
6 is a graph showing a change in light conversion efficiency of an organic solar battery according to an embodiment of the present invention.
FIG. 7 is a graph showing the difference in the light conversion efficiency maintenance (life) of an organic solar cell according to an embodiment of the present invention.

The present invention will be described in more detail with reference to the following examples and experimental examples. However, the following Examples and Experimental Examples are for illustrating the present invention, and the scope of the present invention is not limited by these Examples and Experimental Examples.

Example  One: Photoactive layer  Thin film formation

Isopropanol can dissolve the photoactive layer and can cause a problem in preventing film formation. Therefore, after the photoactive layer was coated, isopropanol was applied to the upper part of the photoactive layer to confirm the proper timing of the application of the isopropanol, and the degree of thin film formation was confirmed after 1 minute, 2 minutes, 3 minutes or 4 minutes of the photoactive layer coating.

First, an indium tin oxide (ITO) anode patterned glass substrate having a thickness of 150 nm and a sheet resistance of 10 Ω / square was washed with acetone, methanol and deionized water and dried on a hot plate at 150 ° C. for 10 minutes. Thereafter, poly (3,4-ethylene helixothiophene) -poly (styrene sulfonate) (PEDOT: PSS, Cleviois PH500., HC Starck) was coated on the indium tin oxide (ITO) Lt; RTI ID = 0.0 > 150 C < / RTI > for 10 minutes. Thereafter, poly (3-hexylthiophene) and [6,6] -phenyl C ₇₁ butyric acid methyl ester were added to dichlorobenzene (1 ml) at a weight ratio of 1: 1 (0.015 g each) After the photoactive layer was formed, isopropanol was applied to the top of the photoactive layer after 1 minute, 2 minutes, 3 minutes, or 4 minutes, and the degree of thin film formation was confirmed. The confirmation result is shown in Fig.

As shown in FIG. 1, when isopropanol was applied after 1 minute of the photoactive layer coating, the photoactive layer was dissolved by isopropanol and the thin film could not be formed. Even if isopropanol was applied after 2 minutes and 3 minutes, Was not formed. However, it was confirmed that thin film formation was easy when isopropanol was applied after 4 minutes or more.

Example  2 and 3: Isopropanol film formed The photoactive layer  Organic solar cell production

P3HT (rr-P3HT, Sigma-Aldrich) was used as the donor material for the photoactive layer and phenylmethyl-C7-butyric-methyl ester (PCBM) was used for the receptor material. The whole process of organic solar cell was carried out by spin coating technique.

First, an indium tin oxide (ITO) anode patterned glass substrate having a thickness of 150 nm and a sheet resistance of 10 Ω / square was washed with acetone, methanol and deionized water and dried on a hot plate at 150 ° C. for 10 minutes. Thereafter, poly (3,4-ethylenedioxythiophene) -poly (styrene sulfonate) (PEDOT: PSS, Cleviois PH500., HC Starck) was coated on the indium tin oxide (ITO) Lt; RTI ID = 0.0 > 150 C < / RTI > for 10 minutes. The photoactive solution obtained by adding poly (3-hexylthiophene) and [6,6] -phenyl C ₇₁ butyric acid methyl ester at a weight ratio of 1: 1 (0.015 g each) to dichlorobenzene (1 ml) Ethylenedioxythiophene) -poly (styrenesulfonate) (PEDOT: PSS) layer to form a photoactive layer. After 4 to 20 minutes, isopropanol was applied. At this time, in order to analyze the characteristic change according to the temperature change, isopropanol was adjusted by adjusting to 25 ° C (Example 2) and 85 ° C (Example 3). After the isopropanol was removed, an aluminum cathode of 150 nm thickness was then deposited on the photoactive layer and annealed in a hot plate at 150 캜 for 10 minutes. The schematic diagram of the organic solar cell fabricated in FIG. 2 is shown. The active area of the fabricated organic solar cell was 9 mm ² .

Comparative Example : Organic solar cell production

An organic solar cell was prepared in the same manner as in Examples 2 and 3 except that isopropanol was applied to the top of the photoactive layer.

First, an indium tin oxide (ITO) anode patterned glass substrate having a thickness of 150 nm and a sheet resistance of 10 Ω / square was washed with acetone, methanol and deionized water and dried on a hot plate at 150 ° C. for 10 minutes. Thereafter, poly (3,4-ethylenedioxythiophene) -poly (styrene sulfonate) (PEDOT: PSS, Cleviois PH500., HC Starck) was coated on the indium tin oxide (ITO) Lt; RTI ID = 0.0 > 150 C < / RTI > for 10 minutes. The photoactive solution obtained by adding poly (3-hexylthiophene) and [6,6] -phenyl C ₇₁ butyric acid methyl ester at a weight ratio of 1: 1 (0.015 g each) to dichlorobenzene (1 ml) Ethylenedioxythiophene) -poly (styrenesulfonate) (PEDOT: PSS) layer to form a photoactive layer. An aluminum cathode of 150 nm thickness was then deposited on the photoactive layer and annealed in a hot plate at 150 캜 for 10 minutes.

Experimental Example  1: Organic solar cell crystallinity analysis

For comparison of the crystallinity of the organic solar cell having the isopropanol layer prepared in Examples 2 and 3 and the organic solar cell prepared in the comparative example, an X-ray diffraction analyzer (kerMax-2500, manufactured by Rigaku Corp.) 3 ° to 80 ° in 0.02 ° increments. The results of the analysis are shown in Fig.

As shown in FIG. 3, the peak was increased by forming the isopropanol layer, and the amorphous P3HT polymer in the photoactive layer was rearranged due to the decrease of 2 Theta as well as the number of nano-domains per unit volume of P3HT in the photoactive layer, In the case of the present invention.

Experimental Example  2: Organic solar cell The photoactive layer  Surface roughness analysis

For comparative analysis of the surface roughness of the photoactive layer of the organic solar cell prepared by applying the isopropanol prepared in Examples 2 and 3 above the photoactive layer and the organic solar cell prepared in the comparative example, Surface conditions and surface roughness were measured using a scanning microscope (LSM700, Carl Zeiss Corp.). The measurement results are shown in Fig.

As shown in FIG. 4, the surface roughness of the photoactive layer of the organic solar cell of Example 3 (coated with 85 ° C isopropanol) was significantly higher than that of the photoactive layer of the organic solar cell of Comparative Example. As a result, The surface roughness of the deposited cathode layer is increased to cause scattering of incident light, thereby inducing reabsorption, thereby reducing loss of incident light. It also shows that the photoelectric conversion efficiency can be increased by increasing the contact area between the negative electrode and the photoactive layer.

Experimental Example  3: Analysis of moisture content in organic solar cell

For comparative analysis of moisture residues in the photoactive layer of the organic solar cell prepared by applying the isopropanol prepared in Examples 2 and 3 above the photoactive layer and the organic solar cell of the comparative example, an infrared spectrophotometer (Spectrum GX using & Autoimage, Perkin Elmer Corp.) was measured compared to the interval 1 cm ^-1 in 4000 cm ^-1 to 400 cm ^-1. The measurement results are shown in Fig.

As shown in Fig. 5, it was confirmed that the peak value decreased at 3500 cm < ^-1 > in the region of water (water), indicating that the moisture content in the photoactive layer coated with isopropanol was reduced.

Experimental Example  4: Organic solar cell Photoconversion  Efficiency and Photoconversion  Evaluation of Efficiency Retention Rate (Life)

In order to measure the electro-optical characteristics of the organic solar cell manufactured by applying the isopropanol prepared in Examples 2 and 3 above the photoactive layer and the organic solar cell of the comparative example, a source meter (2400 series, Keithley Inc ) And a solar simulator (XES-301S, San-ei Electric Corp.) under the standard condition AM 1.5G 100 mW / cm ² . The results are shown in Fig.

The optical open-circuit voltage (Voc), optical short-circuit current density (Jsc), fill factor (FF) and light conversion efficiency of the organic solar cells of Examples 2 and 3 and Comparative Examples are shown in Table 1 below. At this time, the fill factor (FF) was calculated as [voltage value at maximum power point (Vmax) × current density (Jmax)] / [open circuit voltage (Voc) × short circuit current density (Jsc) The efficiency was calculated as [Fill Factor (FF) x (Open Voltage (Voc) x Short Circuit Current Density (Jsc))] / Pin (Pin = 100 mW / cm ² ).

division Voc (V) Jsc (mA / cm ² ) FF Photoconversion efficiency (%) Comparative Example (Pristine) 0.64466 8.96049 0.52543 3.03516 Example 2 (25 < 0 > C IPA) 0.64917 9.30004 0.53425 3.22542 Example 3 (85 < 0 > C IPA) 0.65174 10.20993 0.52890 3.51941

As shown in FIG. 6, the photoconversion efficiency was increased by 6.26% when isopropanol was applied at 25 ° C, and the photoconversion efficiency was increased by 15.95% when isopropanol was applied at 85 ° C.

In addition, the electro-optical characteristics of the organic solar cells of Example 2 and Comparative Example were measured for 24 hours, and the change of the light conversion efficiency maintenance rate (life time) was analyzed by the light conversion efficiency value. The analysis results are shown in Tables 2 and 7 Respectively. At this time, the ambient humidity of the organic solar cell of Example 2 and the comparative example was 45% RH, and the light conversion efficiency retention rate (%) was calculated as [(each measurement time photo-conversion efficiency) / .

division 0 hr 1 hr 2 hr 4 hr 5 hr 18 hr 19 hr 23 hr 24 hr Comparative Example 1 (Pristine) Photoconversion efficiency (%) 1.67864 1.56963 1.51537 1.36701 1.30491 0.75112 0.71596 0.57007 0.51207 Photoconversion efficiency retention (%) 100 93.50 90.27 81.43 77.73 44.74 42.65 33.95 30.50 Example 2 (25 < 0 > C IPA) Photoconversion efficiency (%) 2.39578 2.31746 2.24261 2.1544 2.07598 1.65146 1.57992 1.42474 1.31552 Photoconversion efficiency retention (%) 100 96.73 93.60 89.92 86.65 68.93 65.94 59.46 54.90

As shown in Fig. 7, it was confirmed that the light conversion efficiency retention ratio (lifetime) was found to be 24.4% difference as a result of 24 hours comparison evaluation. As a result, it has been confirmed that there is continuous stability and effectiveness.

100: Organic solar cell
110: aluminum cathode layer
120: Isopropanol application layer
130: photoactive layer
140: hole transport layer
150: tin oxide oxide anode layer
160: glass substrate

Claims (7)

1. A method of manufacturing an organic solar cell comprising a substrate, a hole transport layer, a photoactive layer, and an electrode layer,
Coating a photoactive layer on the hole transport layer;
Applying isopropanol on the photoactive layer after 4 to 20 minutes of the photoactive layer coating; And
Wherein the coated isopropanol is reacted with the photoactive layer to be absorbed into the photoactive layer or evaporated to remove the electrode layer,
A method for manufacturing an organic solar cell.
The method of claim 1, wherein the optically active layer is poly (3-hexylthiophene) and [6,6] -phenyl C ₇₁ butyric acid methyl ester to 3: characterized in that it comprises a weight ratio of 3: 7 to 7
A method for manufacturing an organic solar cell.
The method of claim 1 wherein the isopropanol is applied is characterized in that the treatment of isopropanol with 0.03 ㎖ / cm ² to 0.08 ㎖ / cm ² amounts,
A method for manufacturing an organic solar cell.
The organic electroluminescent device according to claim 1, wherein the hole transport layer is formed by depositing poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS)
A method for manufacturing an organic solar cell.
The method of claim 1, wherein the isopropanol is applied by a spin coating technique, a spray technique or a screen printing technique.
A method for manufacturing an organic solar cell.
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