KR20180105985A - Organic photovoltaics and method for manufacturing the same - Google Patents

Abstract

The present invention improves performance of an organic photovoltaic cell by improving ohmic contact properties between a hole transport layer and an upper electrode by having a surface-treated hole transport layer. A substrate, a lower electrode, an electron transport layer, a photoactive layer, a hole transport layer, and an upper electrode are sequentially stacked.

Description

≪ Desc / Clms Page number 1 > ORGANIC PHOTOVOLTAICS AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to an organic solar cell and a method of manufacturing the same.

 Organic solar cell is a multilayer thin film structure in which a photoactive layer, a hole transporting layer and an electron transporting layer are introduced between both electrodes. Since the shape, structure and lamination state of each thin film are directly related to the performance of the organic solar cell, It is one.

Conventional organic solar cells having a multilayer thin film structure can be manufactured by various coating methods such as slot die coating, spin coating and gravure coating.

Korean Patent Laid-Open Publication No. 2010-0062742 discloses a method in which one material is first coated, and then another material is coated, thereby coating a heterogeneous material into a multilayer coating. However, in the case of the above method, the spreadability and the wettability are poor due to the mutual properties of the materials, so that the coating process can not proceed smoothly.

In order to manufacture large-area organic solar cells for mass production, a roll-to-roll slot die coating method is mainly used.

However, in the case of forming a thin film layer by a roll-to-roll method using a slot die, spreadability and wettability are not good due to the surface energy of the thin film formed first and the surface tension of the coating solution to be coated later. As a result, Is difficult to obtain. In addition, if the roll-to-roll process is repeated several times, the possibility of contamination on the web surface is high, and the generated contamination causes a surface tension imbalance of the coating solution, thereby causing defects on the surface of the thin film. As a result, there is a problem in that mass production of organic solar cells conforming to a desired design value can not be achieved.

Particularly, since the photoactive layer has hydrophobicity and the hole transport layer has hydrophilicity, due to the difference in surface energy between the two, the hole transport layer is shrunk in the direction of TD (Transverse Direction, width direction) Resulting in non-uniformity.

On the other hand, a metal layer, that is, an Ag electrode is formed as an upper electrode on the upper part of the hole transporting layer. In this case, during the operation of the organic solar cell, Ag ions penetrate (or migrate) into the hole transporting layer, And the like. Penetration of such metal ions occurs more severely when the upper electrode is patterned in the form of a grid or mesh in the conventional full-printing type.

Korean Utility Model Publication No. 2012-0065483 (2012.06.21), Organic solar cell module using metal-based multilayer thin film type transparent electrode and manufacturing method thereof Korean Patent Laid-Open Publication No. 2014-0115515 (Apr. 10, 2014), multilayer transparent electrodes and organic solar cells using the same

Accordingly, the present inventors have conducted various studies to solve the above problems. As a result, they have found that by controlling the surface morphology through the surface treatment of the hole transport layer, the electric conductivity of the hole transport layer is increased and the shrinkage of the film in the TD direction is suppressed, It is possible to perform the function of a barrier layer which not only blocks metal ions flowing in from the outside but blocks impurities flowing from the outside.

Furthermore, the organic solar cell and the surface treatment thereof can be continuously processed through a roll-to-roll process, and it is possible to manufacture a large-area organic solar cell through mass production.

Accordingly, an object of the present invention is to provide an organic solar cell having a hole transport layer whose surface morphology is controlled.

It is another object of the present invention to provide a method of manufacturing the organic solar cell.

In order to achieve the above object, the present invention provides a semiconductor device comprising: a substrate; A lower electrode; An electron transport layer; A photoactive layer; A hole transport layer; And an upper electrode are sequentially stacked, and the hole transport layer provides a surface-treated organic solar cell.

At this time, the surface layer of the surface-treated hole transport layer has a dense thin film structure.

The surface treatment may be carried out in the presence of an organic solvent such as ethylene glycol, dimethylsulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, 4-methoxyphenol, acetonitrile, tetrahydrofuran, methanol, Is carried out with at least one organic solvent selected from the group consisting of propyl alcohol, butanol, acetone, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol and methyl ether ketone.

In addition, the surface treatment is performed with at least one acid selected from the group consisting of formic acid, sulfuric acid, 4-toluenesulfonic acid, 1-naphthalenesulfonic acid and dodecylsulfonic acid.

In addition, the present invention provides a semiconductor device comprising a substrate; A lower electrode; An electron transport layer; A photoactive layer; A hole transport layer; And an upper electrode sequentially stacked on a substrate, wherein the surface treatment is performed using the surface treatment agent after the hole transport layer is formed.

In this case, the surface treatment is performed by a roll-to-roll process.

The organic solar cell according to the present invention improves the cell performance by improving the electrical conductivity through the surface treatment of the hole transporting layer and has the surface layer of dense thin film structure so that the metal ion introduced from the upper electrode or the impurity introduced from the outside Thereby increasing the reliability of the battery.

In addition, since the surface treatment can be applied to a roll-to-roll process, it is possible not only to produce an organic solar cell through a continuous process but also to manufacture an organic solar cell having a large area as well as a small- .

1 is a cross-sectional view of a structure of an organic solar cell according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can readily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like reference numerals in the drawings denote like elements, and the sizes and thicknesses of the respective elements may be exaggerated for convenience of explanation.

When a member is referred to herein as being " on " another member, it includes not only a member in contact with another member but also another member between the two members.

Whenever a component is referred to as " comprising ", it is to be understood that the component may include other components as well, without departing from the scope of the present invention.

1 is a cross-sectional view showing an organic solar cell 100 according to the present invention.

Referring to FIG. 1, an organic solar cell 100 includes a substrate 10; A lower electrode 20; An electron transport layer 30; A photoactive layer (40); A hole transport layer 50; And the upper electrode 60 are sequentially stacked.

At this time, the surface of the hole transport layer 50 according to the present invention is surface-treated with organic solvent or acid to adjust the surface morphology so as to form a surface layer having a dense thin film structure than the lower layer of the hole transport layer 50.

The hole transport layer 50 may be formed of at least one selected from the group consisting of poly (3,4-ethylenedioxythiophene; PEDOT), poly (styrene sulfonate) (PSS), polyaniline, phthalocyanine, (T-butyl) diphenylacetylene, poly (trifluoromethyl) diphenylacetylene, copper phthalocyanine (Cu-PC) poly (bistrifluoromethyl) acetylene, polybis (T-butyldiphenyl) acetylene, poly (trimethylsilyl) diphenylacetylene, poly (carbazole) diphenylacetylene, polydiacetylene, polyphenylacetylene, polypyridine acetylene, polymethoxyphenylacetylene, polymethylphenylacetylene, Butyl) phenylacetylene, polynitrophenylacetylene, poly (trifluoromethyl) phenylacetylene, and poly (trimethylsilyl) phenylacetylene. Preferably, the hole transport Layer 50 may comprise a mixture of poly (3,4-ethylenedioxythiophene) and poly (styrenesulfonate) (hereinafter referred to as 'PEDOT: PSS').

The thickness of the hole transporting layer 50 according to the present invention may be 0.5 to 10 탆, preferably 1 to 5 탆. When the thickness of the hole transporting layer 50 is less than the above range, improvement of the hole transporting property and protective effect of the photoactive layer 40 can not be obtained. On the contrary, when the thickness exceeds the above range, permeability may be lowered, have.

The above-described hole transport layer 50 has hydrophilicity and the lower photoactive layer 40 has hydrophobicity and shrinkage in the TD direction after the hole transport layer 50 is formed. In addition, the upper electrode 60 (e.g., Ag) is formed on the upper portion of the hole transporting layer 50, and the Ag ions penetrate (or migrate) into the hole transporting layer 50 during the driving of the battery, Which is formed in the hole transporting layer 50, causing a short circuit in driving the cell. Particularly, ion migration occurs in Ag, Sn, Cu, Au and the like, and among these, Ag is most easily generated.

Therefore, the present invention solves the above-mentioned problem by surface treatment of the hole transporting layer (50).

Conventional surface treatment includes a dry method such as a corona treatment and a plasma treatment, or a wet method such as a coating solvent. In the present invention, in order to solve the above-mentioned problems and to solve the above- Method.

That is, the surface treatment referred to in the present specification means applying a solution of another surface treatment agent (that is, organic solvent and acid) to the surface of the hole transport layer 50 after forming the hole transport layer 50.

Through such surface treatment, the surface morphology is changed so that a surface layer having a dense thin film structure can be formed on the surface of the hole transport layer 50 (the side in contact with the upper electrode 60). At this time, the hole transport layer (50) is present as an integrated film without a separate interface between the surface layer having a dense thin film structure and the surface untreated layer at the bottom.

The surface morphology control through the surface treatment of the hole transport layer 50 is described in detail using PEDOT: PSS.

PEDOT: PSS is a complex composed of PEDOT with a positive charge (+) and PSS with a negative charge (-). The PEDOT chains are bonded to the PSS chain and are dispersed in the aqueous phase in the form of entangled gels. PEDOT: PSS has high chemical stability and wet coating process such as roll-to-roll can be applied, so that a uniform thin film can be mass-produced economically.

In the case of PEDOT: PSS, the hydrophobic PEDOT is located on the lower side and the hydrophilic PSS is located on the upper side when forming the hole transporting layer 50, and the PSS-rich region is formed on the upper side of the film after the hole transporting layer 50 is formed. When the surface of the hole transport layer 50 is surface-treated with the surface treatment agent, the PSS is volatilized in the drying process after the surface treatment, and the PEDOT-rich film is formed in the surface-treated region. Film is formed. In this case, the PEDOT crystal in the PEDOT-rich region can increase the crystallinity and the grain size of the polymer chain as compared with the PEDOT region in the lower region, thereby facilitating the movement of electrons, thereby greatly improving the electrical characteristics.

In order to observe the microstructure, the surface of the PEDOT: PSS hole transport layer (50) was cut in the cross-section direction to use OM, Scanning Electron Microscope and Scanning Electron Microscope (EEMS) and Electron Backscatter Diffraction (EBSD) / RTI > The center portion of the hole transport layer 50 is referred to as a center and the upper portion of the hole transport layer 50 is referred to as a surface. In the interface portion, a portion which is in contact with the photoactive layer 40 is referred to as a hydrophobic PEDOT-rich region, which is mainly composed of PEDOT: PSS in the center portion, and PEDOT-rich region, which has a crystal grain size larger than that of the interface and the center portion and has a dense thin film structure. It can be seen that it has a larger grain size.

These structural changes can provide the following effects.

That is, since the PEDOT-rich region mainly present at the interface of the hole transport layer 50 is hydrophobic, the interface property with the hydrophobic photoactive layer 40 existing at the bottom is improved, Suppress or prevent shrinkage.

The electrical conductivity increases due to the PEDOT-rich property in the surface layer of the dense thin film structure on the surface of the hole transport layer 50 to improve the ohmic contact between the hole transport layer 50 and the upper electrode 60 It is possible to prevent the penetration of the metal ions which migrate from the upper electrode 60 to the hole transport layer 50 due to the densified structure.

(Such as air or water) introduced from the upper part of the hole transport layer 50, that is, from the outside, due to the PEDOT-rich characteristic of the surface, in other words, the PSS having a high hygroscopicity, have.

Though the surface layer of such a dense thin film structure varies depending on the thickness of the hole transport layer 50, the kind of the surface treatment agent, the time, and the like, when the thickness of the hole transport layer 50 is 1 占 퐉, the thickness is 200 nm or less, preferably 10 nm to 200 nm . If it is differently surfaced, it can be formed with a thickness ratio of 1: 0.01 to 1: 0.2. If the thickness is less than the above range, it is difficult to secure the above-mentioned effect. If the thickness is too thick, the hole transport ability may be lowered.

As the surface treatment agent for obtaining the above effect, an organic solvent and an acid can be used.

Examples of usable organic solvents include organic solvents such as ethylene glycol, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, 4-methoxyphenol, acetonitrile, tetrahydrofuran, methanol, It is possible to use at least one organic solvent selected from the group consisting of alcohol, butanol, acetone, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol and methyletherketone. Preferred are dimethylsulfoxide, ethylene glycol, isopropyl alcohol and the like, more preferably dimethylsulfoxide.

The acid as the surface treatment agent can be at least one selected from the group consisting of formic acid, sulfuric acid, 4-toluenesulfonic acid, 1-naphthalenesulfonic acid and dodecylsulfonic acid, preferably 4-toluenesulfonic acid.

The surface treatment using such a surface treatment agent may be performed by various methods and may be performed by a method such as slot-die coating, spraying, spin coating, dipping, printing, doctor blading or the like on the surface of the hole transporting layer 50 . ≪ / RTI >

The surface treatment of the surface of the hole transport layer 50 with an organic solvent may be performed for 5 seconds to 5 minutes, preferably 30 seconds to 3 minutes. In the step of surface-treating the surface of the substrate with an organic solvent, the surface modification may not be performed and the effect thereof may be insufficient. The surface treatment time is preferably as long as it is sufficiently long. On the contrary, if the surface treatment time is longer than the above-mentioned range, the surface treatment effect may not be obtained any more, and the process time may be wasted.

After the surface treatment, the drying process is carried out. The dopant such as PSS in the hole transport layer 60 is removed through the drying process, and the crystal grain of the PEDOT is adjusted through the removal of the dopant. Thus, the temperature and the time are appropriately controlled.

The drying depends on the kind of the surface treatment agent to be used, and is specifically carried out at 60 to 200 ° C for 5 minutes to 1 hour. If the temperature and the time are less than the above range, it is difficult to remove the dopant and relocate the crystal grains and the like to achieve a desired effect. On the contrary, if the temperature and the time are out of the above ranges, deterioration may occur, have.

Drying can be carried out by means of a device used in a roll-to-roll process, NIR drying, or UV drying.

The surface treatment may be performed at least once, and if necessary, the surface treatment may be carried out in two steps or may be carried out with different kinds of surface treatment agents. For example, in the case of using DMSO, a second surface treatment may be performed by first performing surface treatment for 30 seconds to 1 minute and then further treating with DMSO, wherein the treatment temperature and the drying temperature are different Can be performed. In addition, the surface treatment may be performed with a solvent in the first stage, and the surface treatment may be performed with an acid in the second stage. Selection and modification of such a process are not particularly limited in the present invention, and can be appropriately selected by a person skilled in the art.

Meanwhile, the hole transport layer 50 according to the present invention may further include various additives in order to increase electrical conductivity, if necessary.

For example, a small amount of 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM TCB) may be added to an aqueous solution of PEDOT: PSS (Clevios ™ PH 1000) as an ionic liquid have.

In addition, as the above-mentioned additive, there may be used, for example, sodium dodecyl sulfonate (SDS), sodium p-toluenesulfonate (TsONa), dodecylbenzenesulfonic acid sodium salt Anionic surfactants may be added.

In order to improve spreadability and wettability, a fluorine-based polymer may be further included. The fluorine-based additive is a fluorine-based polymer exhibiting water solubility by a functional group substituted on at least one terminal of both ends of the polymer. The fluorine-based additive is not sensitive to the dispersing power, And a fluorine moiety having a high electronegativity also serves to lower the polarizability at the interface of the composition for forming a positive hole transport layer.

The fluorine-based polymer specifically includes a perfluoropolyether (PFPE), polyvinylidene fluoride, polyvinyl fluoride, polychlorotrifluoroethylene, polytetrafluoroethylene or poly-1,2-difluoroethylene And is preferably a perfluoropolyether.

Meanwhile, other components of the organic solar cell 100 according to the present invention including the above-described hole transport layer 50 are not particularly limited in the present invention, but are well known in the art.

The substrate 10 is not particularly limited as long as it has transparency so that light can be transmitted therethrough. For example, the substrate 10 may be a transparent inorganic substrate 10 such as quartz or glass, or a transparent inorganic substrate 10 such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polystyrene (PS) (PP), polyimide (PI), polyethylene sulfonate (PES), polyoxymethylene (POM), polyetheretherketone (PEEK), polyether sulfone (PES) and polyetherimide A transparent plastic substrate 10 may be used. Of these, it is preferable to use a transparent plastic substrate 10 in the form of a film which is flexible and has high chemical stability, mechanical strength and transparency.

In addition, the substrate 10 preferably has a transmittance of at least 70% or more, preferably 80% or more in a visible light wavelength range of about 400 to 750 nm.

The thickness of the substrate 10 is not particularly limited and may be suitably determined according to the intended use, for example, 1 to 500 탆.

The upper electrode 60 and the lower electrode 20 may be an anode or a cathode, and the role thereof may be different in a general structure and an inverted structure. For example, when the upper electrode 60 is an anode, the lower electrode 20 may be a cathode, and when the upper electrode 60 is a cathode, the lower electrode 20 may be an anode.

The material of the electrode may be indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO) Doped tin oxide (AZO), indium tin oxide (ITO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide oxide; FTO), zinc tin (tin oxide zinc oxide; ZTO), gallium indium oxide (indium gallium oxide; IGO), ZnO-Ga 2 O 3, ZnOAl 2 O 3, SnO 2 -Sb 2 O 3 , and combinations thereof A metal oxide transparent electrode selected from the group consisting of: An organic transparent electrode such as a conductive polymer, a graphene thin film, a graphene oxide thin film, or a carbon nanotube thin film; Or an organic-inorganic bonding transparent electrode such as a carbon nanotube thin film to which a metal is bonded.

The thickness of the cathode 20 may be 10 nm to 3 탆.

The anode 50 includes a common metal having a low work function and is made of a metal such as Ag, Cu, Au, Pt, Ti, Al, Metal particles such as nickel (Ni), zirconium (Zr), iron (Fe), and manganese (Mn); Or, for the precursor, for containing the metal elements of silver nitrate _{(AgNO 3), Cu (HAFC} ) 2 (Cu (hexafluoroacetylacetonate) 2), Cu (HAFC) (1,5-Cyclooctanediene), Cu (HAFC) (1, 5-Dimethylcyclooctanediene), Cu (HAFC ) (4-Methyl-1-pentene), Cu (HAFC) (Vinylcyclohexane), Cu (HAFC) (DMB), Cu (TMHD) 2 (Cu (tetramethylheptanedionate) 2), DMAH ( dimethylaluminum hydride, TMEDA (tetramethylethylenediamine), DMEAA (dimethylethylamine alane, NMe2Et.AlH3), TMA (trimethylaluminum), TEA (triethylaluminum), TBA (triisobutylaluminum), TDMAT ), But is not limited thereto.

The thickness of the anode 50 may be 10 to 5000 nm.

Preferably, in the present invention, the lower electrode 20 is a cathode and the upper electrode 60 is a cathode.

At this time, the anode can be manufactured as a front-printed or patterned electrode such as a grid or a mesh. In addition, the shape of the pattern may be at least one selected from the group consisting of dot, rhombus, circle, polygon, stripe, grid, wave and zigzag, but is not limited thereto.

The electron transport layer 30 is positioned on the cathode 20 and enhances the efficiency of the organic solar battery 100 by increasing the electron transport capability. In addition, it is possible to prevent oxygen and moisture introduced from the outside from affecting the photoactive layer 40.

The electron transport layer 30 may be formed of a metal oxide and an organic material, and the metal oxide may be at least one selected from the group consisting of Ti, Zn, Si, Mn, Sr, (B), potassium (K), niobium (Nb), iron (Fe), tantalum (Ta), tungsten (W), bismuth (Bi), nickel (Ni), copper (Cu), molybdenum , At least one metal oxide selected from the group consisting of cerium (Ce), platinum (Pt), silver (Ag) and rhodium (Rh). Specifically, the metal oxide thin film layer may be made of zinc oxide (ZnO) having a wide band gap and a semiconductor property, and the organic material may be polyethyleneimine (PEI), ethoxylated polyethyleneimine (PEIE), or the like.

The average particle diameter of the metal oxide contained in the electron transport layer 30 is 10 nm or less, specifically 1 to 8 nm, and more specifically, 3 to 7 nm.

The electron transport layer 30 may be formed through a coating process, and the coating process may be performed by a method such as a slot die coating, a spin coating method, a spray coating method, a screen printing method, a bar coating method, a doctor blade coating method, However, the method can be used without limitation as long as it can coat the metal oxide. In particular, it may be advantageous for the electron transport layer 30 to use a slot die coating.

The electron transporting layer 30 may have a thickness of 1 to 100 nm, and when the thickness is outside the range of the thickness defined above, the electron transporting ability may be deteriorated.

The photoactive layer 40 is located on the above-described electron transport layer 30 and has a bulk heterojunction structure in which a hole receptor and an electron acceptor are mixed.

The hole acceptor includes an organic semiconductor such as an electrically conductive polymer or an organic low-molecular semiconductor material. The electrically conductive polymer may be at least one member selected from the group consisting of polythiophene, polyphenylenevinylene, polyfulorene, polypyrrole, and copolymers thereof. The organic low-molecular semiconductor material may include one or more selected from the group consisting of pentacene, anthracene, tetracene, perylene, oligothiophene, and derivatives thereof. can do.

Specifically, the hole acceptor may be a poly-3-hexylthiophene (P3HT), a poly-3-octylthiophene (P3OT), a poly- polyvinylidene fluoride (PPV), poly (9,9'-dioctylfluorene), poly (2-methoxy-5- (2-ethyl-hexyloxy) , 2-methoxy-5- (2-ethyl-hexyloxy) -1,4-phenylenevinylene (MEH-PPV) -Dimethyloctyloxy)) - 1,4-phenylene vinylene (MDMOPPV), which is a compound selected from the group consisting of poly (2-methyl-5- And may include one or more species.

The electron acceptor may include at least one selected from the group consisting of fullerene (C60), fullerene derivatives such as C70, C76, C78, C80, C82 and C84, CdS, CdSe, CdTe and ZnSe.

Specifically, the electron acceptor is (6,6) -phenyl-C61-butyric acid methyl ester ((6,6) -phenyl-C61-butyric acid methyl ester; PCBM) Butyric acid methyl ester ((6,6) -thienyl (C7-PCBM), (6,6) -thienyl-C61- -C6-butyric acid methyl ester (ThCBM), and carbon nanotubes.

More preferably, the photoactive layer 40 comprises a mixture of P3HT and PCBM as a hole acceptor, wherein the mixing weight ratio of P3HT and PCBM may be 1: 0.1 to 1: 2.

The thickness of the photoactive layer 40 may be 10 to 1000 nm, specifically 100 to 500 nm. When the thickness of the photoactive layer 40 is less than the above range, it is impossible to sufficiently absorb the sunlight, and the photocurrent is lowered and the efficiency is expected to decrease. Conversely, when the thickness exceeds the above range, excited electrons and holes can not move to the electrode, Problems can arise.

The above-described organic solar cell 100 can be manufactured according to a known method.

The method of manufacturing the organic solar cell 100 of the present invention includes a step of forming a thin film layer by coating the substrate 10 with a coating solution while transferring the substrate 10 by a roll-to-roll method. At this time, the thin film layer may be at least one selected from the group consisting of a photoactive layer 40, an electron transport layer 30, a hole transport layer 50, and upper and lower electrodes 20 and 60, A composition for forming a thin film layer and a solvent. Hereinafter, the lower electrode 20 is a cathode and the upper electrode 60 is an anode, and the order thereof may be different if necessary.

First, a substrate 10 is prepared and a cathode is formed on the substrate 10 with the lower electrode 20.

The cathode on the prepared substrate 10 can be formed according to a conventional method. Specifically, the cathode may be formed on one surface of the substrate 10 by a thermal vapor deposition, electron beam deposition, RF or magnetron sputtering, chemical vapor deposition or the like.

At least one method selected from the group consisting of O ₂ plasma treatment, UV / ozone cleaning, surface cleaning using an acid or an alkali solution, nitrogen plasma treatment, and corona discharge cleaning may be selectively performed on the substrate prior to formation of the cathode The surface of the substrate may be pretreated.

And then coating the coating solution while transferring the negative electrode-formed base material in a roll-to-roll manner to form a thin film layer. At this time, the thin film layer is the electron transport layer 30, the photoactive layer 40, the hole transport layer 50, and the upper electrode 60.

The coating solution includes a substance and a solvent contained in each thin film layer.

Specifically, the coating solution may be a composition for forming the electron transport layer 30, a composition for forming the photoactive layer 40, a composition for forming the hole transport layer 50, and a cathode composition.

Next, the electron transport layer 30 may be formed on the lower electrode 20 using a composition for forming the electron transport layer 30. [

The composition for forming the electron transport layer (30) is prepared by dissolving the metal oxide in a solvent and applying the composition to form a coating film.

The solvent is not particularly limited as long as it is capable of dissolving or dispersing the metal oxide. Examples of the solvent include water, 2-ethylhexanol, 2-butoxyhexanol, n-propyl alcohol, At least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol and dipropylene glycol can be used.

The solvent may be contained in an amount of the remainder in the composition for forming the electron transport layer 30. Specifically, the solvent may be included in an amount of 1 to 95% by weight based on the total weight of the composition for forming the electron transport layer 30. [ When the content of the solvent exceeds 95 wt%, it is difficult to obtain the function of the desired coating layer. When the content of the solvent is less than 1 wt%, it is difficult to form a thin film having a uniform thickness.

The application may be carried out by conventional coating methods such as slot die coating, spin coating, gravure coating, bar coating, Meyer bar coating, spraying, dip coating, comma coating, curtain coating, doctor blading, And specifically, slot die coating or spin coating may be performed.

After the coating layer is formed with the composition for forming the electron transport layer 30, a post-treatment process of drying or heat-treating the coated substrate 10 may be selectively performed. The drying may be performed by hot air drying, NIR drying, or UV drying at 50 to 400 ° C, specifically, at 70 to 200 ° C for 1 to 30 minutes.

Next, the photoactive layer 40 can be formed on the electron transport layer 30 using a composition for forming the photoactive layer 40. [

The composition for forming the photoactive layer 40 is prepared by dissolving the hole receptor and the electron acceptor described above in a solvent, and applying the composition to form a coating film.

The solvent can be used without particular limitation as long as it can dissolve or disperse the electron acceptor and the hole acceptor. In one example, the solvent is water; Alcohols such as ethanol, methanol, propanol, isopropyl alcohol and butanol; Or an organic solvent such as acetone, pentane, toluene, benzene, diethyl ether, methyl butyl ether, N-methylpyrrolidone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, carbon tetrachloride, dichloromethane, Organic solvents such as trichlorethylene, chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol and methyletherketone, or mixtures thereof, It is preferable to appropriately select and use the compound in the above-described solvent depending on the kind of the target material when preparing the composition for forming the electron transport layer (30).

The application may be carried out by conventional coating methods such as slot die coating, spin coating, gravure coating, bar coating, Meyer bar coating, spraying, dip coating, comma coating, curtain coating, doctor blading, And specifically, slot die coating or spin coating may be performed.

After the coating layer is formed with the composition for forming the photoactive layer 40, a post-treatment process of drying or heat-treating the coated substrate 10 may be selectively performed. The drying may be performed by hot air drying, NIR drying, or UV drying at 50 to 400 ° C, specifically, at 70 to 200 ° C for 1 to 30 minutes.

For example, in the case of the photoactive layer 40, post-treatment may be performed after drying and heat treatment at 25 to 150 ° C for 5 to 145 minutes after the coating process. By appropriately controlling the drying step and the heat treatment step, appropriate phase separation can be induced between the electron acceptor and the hole acceptor, and the orientation of the electron acceptor can be induced. If the temperature is less than 25 ° C, the mobility of the electron acceptor and the hole acceptor may be low and the heat treatment effect may be insignificant. If the annealing temperature exceeds 150 ° C, Can be degraded. If the heat treatment time is less than 5 minutes, the mobility of the electron acceptor and the hole acceptor may be low and the heat treatment effect may be insufficient. If the heat treatment time exceeds 145 minutes, the performance deteriorates due to deterioration of the electron acceptor .

Next, a hole transport layer 50 is formed on the photoactive layer 40 using a composition for forming the hole transport layer 50.

The composition for forming the hole transport layer 50 is a paste containing the hole transport material and the solvent described above and is patterned on the substrate 10 by a printing method.

The solvent contained in the composition for forming the hole transport layer (50) is not particularly limited as long as it is used for uniformly mixing the hole transport material and controlling the viscosity, and is generally used in the art.

Preferably, the solvent may be an alcohol-based solvent, for example, 2-ethylhexanol, 2-butoxyhexanol, n-propyl alcohol, isopropyl alcohol, ethylene glycol, diethylene glycol, triethylene Glycol, tetraethylene glycol, propylene glycol, and dipropylene glycol may be used.

The composition for forming the hole transport layer 50 is preferably optimized for a printing process. Specifically, the composition for forming the hole transport layer 50 may have a viscosity ranging from 300 to 10,000 cps. If the viscosity of the composition for forming the hole transport layer 50 is less than the above range, spreading of the pattern may occur. On the contrary, if the viscosity exceeds the above range, uniform distribution of the hole transport material may be difficult and printing property may be deteriorated have.

In the present invention, a variety of commonly used printing processes can be applied to the printing method. For example, the printing may be any one of ink jet printing, aerosol jet printing, EHD jet printing, gravure printing, gravure offset printing, imprinting, flexographic printing, or screen printing, preferably screen printing.

After the printing process is performed, it may be fired according to a drying and firing method commonly used in the art, preferably a nitrogen, oxygen, or argon hot air alone, a Middle Infra Red (MIR) lamp, Can be used simultaneously and dried and fired.

Next, a surface treatment using the above-mentioned surface treatment agent is performed on the hole transport layer 50.

The surface treatment is carried out over the entire surface of the hole transport layer 50, and drying is performed through the above-described drying method after application of the surface treatment agent.

Next, a positive electrode is formed on the surface-treated positive hole transport layer 50. The cathode may be formed by a method such as screen printing, gravure printing, gravure-offset printing, thermal vapor deposition, electron beam deposition, RF or magnetron sputtering, or chemical vapor deposition, .

In addition, the organic solar cell 100 of the present invention includes a metal oxide thin film layer (not shown) between the transparent electrode 120 and the photoactive layer 40. The metal oxide thin film layer acts as a negative electrode to increase the speed of electrons to enable the operation of the organic solar cell 100 and blocks oxygen and moisture penetrating from the outside to prevent the polymer contained in the photoactive layer 40 from being dissolved in oxygen And moisture of the organic solar battery 100, thereby improving the lifetime of the organic solar battery 100

The metal oxide thin film layer may have a thickness of 10 to 500 nm, preferably 20 to 300 nm, more preferably 20 to 200 nm. When the thickness of the metal oxide thin film layer is within the above range, it is possible to effectively prevent the oxygen and moisture from penetrating from the outside and affecting the photoactive layer 40 and the hole transport layer 50 while enhancing the electron transporting speed.

The metal oxide included in the metal oxide thin film layer may have an average particle diameter of 10 nm or less, preferably 1 to 8 nm, and more preferably 3 to 7 nm.

The metal oxide may be selected from the group consisting of Ti, Zn, Si, Mn, Sr, In, Ba, K, Nb, Fe, Ta, W, Sa, Bi, Ni, Cu, Mo, Ce, Pt, Ag, Rh, And may be an oxide of any one of metals selected from the group consisting of ZnO, and preferably ZnO. The ZnO has a wide bandgap and a semiconducting property, so that when used together with the transparent electrode 120, the movement of electrons can be further improved.

In the present invention, at the time of forming each layer on the substrate 10, the speed at which the substrate 10 is transported by the roll-to-roll method may be 0.01 m / min to 20 m / min, preferably 0.1 m / min to 5 m / min. The conveying speed can be optimally used according to the coating and drying speed of the individual layers using the roll-to-roll equipment.

The semitransparent organic solar cell 100 according to the present invention includes the hole transport layer 50 surface-treated on the photoactive layer 40 to realize the organic solar cell 100 having improved reliability and improved battery characteristics. In addition, the photoactive layer 40 can be protected from various impurities or metal ions from the anode, thereby improving the reliability of the organic solar cell 100.

Accordingly, since the organic solar cell has the same level of efficiency as that of the conventional organic solar cell, but has excellent transparency and reliability and can be continuously produced, it can be applied to various fields requiring electric power.

EXAMPLES, COMPARATIVE EXAMPLES AND EXPERIMENTAL EXAMPLES will be described below to help understand the effects of the present invention. It should be noted, however, that the following description is only an example of the contents and effects of the present invention, and the scope and effect of the present invention are not limited thereto.

[Example]

Example  One

(Prepared by mixing 247 mg of ZnO-containing coating solution (Zn (OAC) ₂ .2H ₂ O, 126 mg of KOH and 1 ml of 1-butanol) onto the ITO layer while transferring the base film on which the ITO layer was formed, Was coated on a slot die in stripe form and then dried at 140 ° C to form a metal oxide thin film layer of ZnO. The slot die coating was performed at a line speed of 5 mm / sec, a slot die height of 100 m, and a coating liquid flow rate of 0.15 ml / min.

(Prepared by mixing 15 mg of lisico® SP001 (manufactured by Merck), 12 mg of lisicon® A-600 (manufactured by Merck) and 1 ml of dichlorobenzene) on the ZnO metal oxide thin film layer, Slot-die coating, and dried at 80 캜 to prepare a photoactive layer (40). The slot die coating was performed at a line speed of 5 mm / sec, a slot die height of 100 m, and a coating liquid flow rate of 0.5 ml / min.

A coating solution containing PEDOT: PSS (manufactured by Orgacon EL-P 5010, agfa), isopropyl alcohol, and a fluorine-based additive (Zonyl FS300 manufactured by DuPont) in a weight ratio of 2: 1: 0.1 Was coated on a slot die, and dried at 120 캜 to form a hole transport layer. The slot die coating was performed at a line speed of 5 mm / sec, a slot die height of 800 m, and a coating fluid flow rate of 3.0 ml / min.

Next, DMSO (dimethylsulfoxide) was slot-die-coated on the hole transport layer 50 for 10 seconds and then dried at 150 DEG C for 2 minutes and 30 seconds.

Then, an Ag electrode was printed on the hole transport layer using a screen printer to produce an organic solar cell.

Example  2

An organic solar cell was fabricated in the same manner as in Example 1 except that ethylene glycol was used as the surface treatment.

Example  3

An organic solar cell was fabricated in the same manner as in Example 1 except that 4-toluenesulfonic acid was used as the surface treatment.

Comparative Example  One

Except that the step of performing the surface treatment with DMSO was carried out in the same manner as in Example 1, and an organic solar cell was fabricated.

Experimental Example  One

In order to confirm whether or not the film was shrunk in the TD direction, the film of the hole transporting layer was cast on the photoactive layer by the methods of the above Examples and Comparative Examples, and then the shrinkage ratio was measured.

The shrinkage measurements were made on 10 specimens, each of which was cut at 10 different points with a width of 50 mm (MD) and a length of 50 mm (MD). Each of the specimens was allowed to stand in an oven at 150 ° C. for 2 minutes and 30 seconds, and the degree of shrinkage of each specimen in the TD direction was measured to calculate an average heat shrinkage rate.

As a result, it was confirmed that in the case of the hole-transporting layer surface-treated as in Examples 1 to 3, there was almost no shrinkage in the TD direction as compared with the surface-untreated hole-transporting layer of Comparative Example 1. [

Further, comparing Examples 1 to 3, the treatment with DMSO of Example 1 and 4-toluenesulfonic acid of Example 3 showed better results than the surface treatment with isopropyl alcohol of Example 2.

Experimental Example  2

(1) Confirm thin film profile

Sectional SEM (scanning electron microscope) was performed to confirm the characteristics of the thin film of the hole transporting layer of the organic solar cell produced in the above Examples and Comparative Examples.

As a result of the cross-sectional SEM image inspection, it was confirmed that the thin film structure of PEDOT grains denser than the lower region was formed on the upper surface (150-200 nm thick) of the hole transport layer (total thickness 1 μm) surface-treated as in Examples 1 to 3.

On the other hand, in the case of the hole transport layer of Comparative Example 1, it was confirmed that the PEDOT crystal grains were distributed almost evenly throughout the film, while the crystal grains were more distributed in the lower region.

(2) Measurement of electrical conductivity change

In order to confirm the film characteristics of the hole transporting layer of the organic solar cell manufactured in the Examples and Comparative Examples, the resistance and electrical conductivity of the film of the hole transporting layer 50 were measured using a Hall-Effect measuring apparatus.

As a result, it was found that the surface-treated positive hole transport layer as in Examples 1 to 3 exhibited a lower electric field than the positive hole transport layer of Comparative Example 1, and thus it was confirmed that the electric conductivity of the hole transport layer can be improved through surface treatment .

In addition, the improvement of the electrical conductivity of Examples 1 to 3 was superior to the isopropyl alcohol surface treatment of Example 2 when DMSO of Example 1 and 4-toluenesulfonic acid of Example 3 were treated.

(3) Metal ion penetration  Prevention

In order to confirm the migration of Ag ions in the hole transport layer of the organic solar cell prepared in the above Examples and Comparative Examples, a test method using constant temperature and humidity proposed in IPC-TM 650, Method 2.6.14 (Resistance to electrochemical migration Polymer solder mask).

As a result, in the case of the hole transport layer surface-treated as in Examples 1 to 3, there was almost no migration of Ag ions, and in comparison with this, it was confirmed that Ag ions were precipitated in the hole transport layer of Comparative Example 1.

Experimental Example  3: Evaluation of organic solar cell performance

The performance of the organic solar cell fabricated in the above Examples and Comparative Examples was evaluated.

Voc: open-circuit voltage, open-circuit voltage

Isc: short-circuit photocurrent density, short-circuit current density

FF: fill factor, fill factor

Eff .: Efficiency, Efficiency

It was confirmed that the organic solar cells of Examples 1 to 3 having the surface-treated hole transporting layer according to the present invention can secure an improved effect on the Isc and FF surfaces as compared with the organic solar cell of Comparative Example 1. [

The organic solar cell according to the present invention can be suitably applied as a next generation power supply device.

100: Organic solar cell
10: substrate
20: Lower electrode
30: electron transport layer
40: photoactive layer
50: Surface treatment Hole transport layer
60: upper electrode

Claims (8)

Board; A lower electrode; An electron transport layer; A photoactive layer; A hole transport layer; And an upper electrode are sequentially stacked,
Wherein the hole transport layer is surface-treated. The method according to claim 1,
Wherein the hole transport layer has a thickness ratio of 1: 0.01 to 1: 0.2 in terms of the surface-treated layer with respect to the total thickness of the hole transport layer. The method according to claim 1,
Wherein the surface treatment is performed as a surface treatment agent of any one of an organic solvent and an acid. The method of claim 3,
The organic solvent may be at least one selected from the group consisting of ethylene glycol, dimethylsulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, 4-methoxyphenol, acetonitrile, tetrahydrofuran, methanol, , Butanol, acetone, cyclohexane, cyclopentanone, cyclohexanone, dioxane, terpineol and methyl ether ketone. The method of claim 3,
Wherein the acid is at least one selected from the group consisting of formic acid, sulfuric acid, 4-toluenesulfonic acid, 1-naphthalenesulfonic acid and dodecylsulfonic acid. The method according to claim 1,
Wherein the hole transport layer further comprises one selected from the group consisting of an ionic liquid, a surfactant, and a fluorinated polymer. Board; A lower electrode; An electron transport layer; A photoactive layer; A hole transport layer; And an upper electrode are stacked in this order,
The method of manufacturing an organic solar battery according to any one of claims 1 to 6, wherein a surface treatment process is performed after the hole transport layer is formed. 8. The method of claim 7,
Wherein the surface treatment is performed by applying a surface treatment agent followed by a drying step.

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