KR20140095449A - Solar cell - Google Patents

Abstract

Disclosed is a solar cell. The solar cell comprises a transparent conductive layer formed on the upper part of a substrate; fine structures vertically or slantly protruding from the surface of the transparent conductive layer and made of the same material as the transparent conductive layer; an electron transport layer covering the fine structures while filling in at least one part of a space between the fine structures and formed of an electron transport metal oxide; a light absorber attached to inner pores or the surface of the electron transport layer; a hole transport layer filling in the pores of the electron transport layer, covering the surface of the electron transport layer and formed of a hole transporting material; and an electrode formed on the upper part of the hole transport layer.

Description

Solar cell {SOLAR CELL}

The present invention relates to a solar cell, and more particularly, to a dye-sensitized solar cell.

Today, due to high oil prices and environmental pollution, development of clean alternative energy is urgent. Among various alternative energies, the use of solar energy is recognized as the most economical way, and there is a growing interest in solar cells that convert optical energy directly into electrical energy.

Currently, solar cells can be classified into silicon solar cells, compound solar cells, CIGS solar cells, dye-sensitized solar cells, and organic solar cells depending on the structure and operation method. Among them, the dye-sensitized solar cell was first developed by Professor Michael Gratel at the Lausanne University in Switzerland in 1991. In the case of a dye-sensitized solar cell, a transparent or translucent solar cell can be realized through a low-cost process, various colors can be realized according to organic dyes, and high energy conversion efficiency is achieved.

However, a liquid electrolyte based dye-sensitized solar cell based on a thick thick film is not only low in light transmittance but also poses a problem of stability due to the use of a liquid electrolyte. This problem has been recognized as a serious problem in the commercialization of a liquid electrolyte based dye-sensitized solar cell.

In order to solve the problems of liquid electrolyte type dye-sensitized solar cell, in 1998, Prof. Michael Grachel of Lausanne Institute of Technology [Nature Vol 395, P 583] used organic-based solid electrolyte instead of liquid electrolyte system, And many studies have been conducted on dye-sensitized solar cells using solid electrolytes thereafter.

However, compared to conventional liquid electrolyte systems and other solar cells, solid electrolyte solar cells have a very low energy conversion efficiency. In the case where 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamine) -9-9'-spirobi-fluorene [Spiro-OMeTAD], which is a hole transporting organic material, is used as a solid electrolyte, The efficiency of about 5% is exhibited at the thickness of the light absorbing layer of 2 mu m. This is because, when the thickness of the light absorbing layer is as small as 2 占 퐉, the light can not be efficiently used, and many recombinations occur between the electrons of the inorganic semiconductor used as the light absorbing layer and the holes of the organic semiconductor.

In order to overcome this problem, studies have been made to increase the hole mobility of organic materials used as hole conductors, but the efficiency is still only 2 to 4%. Recently, TiO2 nanotubes have been used [J. Mater. Chem., 2009, Vol 19, P 5325] The thickness of the light absorbing layer has been tried to be improved, but the thickness of the light absorbing layer is still about 2 μm.

An object of the present invention is to provide a solar cell having a high current density and photoelectric conversion efficiency by maximizing the thickness of the light absorbing layer.

A solar cell according to an embodiment of the present invention includes: a transparent conductive layer formed on a substrate; Microstructures protruding vertically or obliquely from the surface of the transparent conductive layer and formed of the same material as the transparent conductive layer; An electron transport layer formed of an electron transporting metal oxide covering the microstructures while filling at least part of the space between the microstructures; A light absorber adhered to the inner pores and the surface of the electron transport layer; A hole transporting layer covering the surface of the electron transporting layer to which the light absorber is attached while filling the pores of the electron transporting layer, the hole transporting layer being formed of a hole transporting material; And an electrode formed on the hole transport layer.

In one embodiment, the microstructures may comprise nanowires. For example, the nanowire may include at least one selected from the group consisting of a nano-rod, a nano-wire, and a nano-needle.

In one embodiment, the transparent conductive layer and the microstructures may be doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, At least one selected from the group consisting of strontium titanate and cadmium sulfide and (La _0.5 Sr _0.5 ) CoO ₃ (LSCO), La _0.7 Sr _0.3 MnO ₃ (LSMO) and SrRuO ₃ (SRO) . For example, the doped indium oxide may include at least one selected from the group consisting of Sn-doped indium oxide (ITO), IGZO, IGO, and IZO, and the doped tin oxide may be at least one selected from the group consisting of F- a _{(SnO 2 Fluorine Tin oxide::} FTO, F) a and wherein the doped zinc oxide is Ga- doped zinc oxide (GZO) and Al- least one selected from the group consisting of doped zinc oxide (AZO) oxide And the doped strontium titanate includes Nb: SrTiO ₂ , and the doped titanium oxide may include Nb: TiO ₂ .

In one embodiment, the electron transport layer may be formed of at least one material selected from the group consisting of TiO ₂ , ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Zn ₂ SnO ₃ , BaTiO ₃ and BaSnO ₃ have.

In one embodiment, the electron transporting layer comprises an electron transporting thin film covering the surfaces of the microstructures and the transparent conductive layer; And an electron transporting nanoparticle layer formed on the electron transporting thin film and being porous than the electron transporting thin film. In this case, the electron transport nanoparticle layer may include electron transporting metal oxide nanoparticles coated on the electron transport thin film. The light absorber may include pores inside the electron-transporting nanoparticle layer and organic or inorganic dyes attached to the surface of the electron-transporting nanoparticle layer.

In one embodiment, the organic dye of the inorganic dye include a ruthenium-based organic dyes include CdS, CdSe, CdTe, PbS, PbSe, PbTe, InP, InGaP, InAs, InCuS _2, InCuSe _2, CuFeS _2, InN _{, In 2 S 3, InSb,} PbS, PbSe, Bi 2 S 3, Bi 2 Se 3, Sb 2 S 3, Sb 2 Se 3, SnTe, SnSx, NiS, CoS, FeS, In 2 S 3, ZnSe, ZnTe _{, MoS, MoSe, Cu 2 S} , Ge, Si, CsPbI 3, CsPbBr 3, CsSnI 3, CsSnBr 3, CH 3 NH 3 PbBr 3, CH 3 NH 3 SnBr 3, CH 3 NH 3 PbI 3, CH 3 NH 3 SnI < ₃ > and an alloy thereof.

In one embodiment, the hole transport layer may be formed to cover the surface of the electron transport nanoparticle layer while filling pores in the electron transport nanoparticle layer. In this case, the hole transport layer may be formed of an organic photoelectric material.

In one embodiment, the organic photoelectric material may include at least one selected from the group consisting of Spiro-OMeTAD, P3HT, P3AT, P3OT and PEDOT: PSS.

According to the present invention, the thickness of the light absorbing layer can be maximized based on the excellent physical property characteristics of the conductive metal oxide material, and thus a solar cell having high current density and photoelectric conversion efficiency can be manufactured.

The nano- or microstructures of conductive metal oxides are characterized by lowering the recombination rate between hole-transporting organic materials and semiconductor nanoparticles and higher charge collection efficiency characteristics compared to conventional solid-phase thin film solar cells based on conventional nanoparticles. This can increase the electron diffusion length of the light absorption layer, and the thickness of the light absorption layer in the present invention can be remarkably increased.

According to the present invention, by increasing the thickness of the low light absorption layer of all the solid-state thin film solar cells required at present, it is possible to provide a nano- Or a microstructure can be used.

1 is a view for explaining a dye-sensitized solar cell according to an embodiment of the present invention.
2A to 2G are views for explaining a method for manufacturing a solar cell according to an embodiment of the present invention.
3 is a scanning electron microscope (SEM) image for explaining an ITO nanowire grown on an ITO thin film according to an embodiment.
4 is a scanning electron microscope (SEM) image for explaining a TiO2 thin film formed by depositing TiO2 on ITO nanowire to a thickness of 10 nm according to an embodiment.
FIG. 5 is a scanning electron microscope (SEM) image for explaining a porous electron transport layer formed by applying a TiO 2 nanoparticle precursor on a TiO 2 thin film by a screen printing method.
FIG. 6 is a graph illustrating voltage and current relationships between a solar cell manufactured according to an embodiment and a solar cell manufactured according to a comparative example.
FIG. 7 is a graph showing a measurement result of a 'transient Voc' showing a decrease in Voc under an open-circuit voltage condition for a solar cell manufactured according to the embodiment and a solar cell manufactured according to a comparative example.
8 is a graph showing the results of measuring photocurrent density according to the thickness of a light absorbing layer for a solar cell manufactured according to the embodiment and a solar cell manufactured according to a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises ", or" having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, or combinations thereof, , Steps, operations, elements, or combinations thereof, as a matter of principle, without departing from the spirit and scope of the invention.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

<Dye-sensitized solar cell>

1 is a view for explaining a dye-sensitized solar cell according to an embodiment of the present invention.

1, a dye-sensitized solar cell 100 according to an embodiment of the present invention includes a transparent substrate 110, a transparent conductive layer 120, microstructures 130, an electron transport layer 140, A light emitting layer 150, a hole transporting layer 160, and an electrode layer 170.

As the transparent substrate 110, an ordinary semiconductor substrate, a quartz substrate, or the like can be used. For example, a substrate, such as a silicon (Si) substrate, a silicon oxide (SiO ₂ ) substrate, an aluminum oxide (Al ₂ O ₃ ) substrate or an STO (SrTiO ₃ ) substrate can be used.

The transparent conductive layer 120 may be located on the transparent substrate 110. The transparent conductive layer 120 may be made of a conductive metal oxide. For example, the transparent conductive layer 120 may be formed of a material selected from the group consisting of doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, strontium titanate, Cadmium sulfide, La _0.5 Sr _0.5 , CoO ₃ , La _0.7 Sr _0.3 MnO ₃ , and SrRuO ₃ (SRO). The doped indium oxide may be any one selected from Sn-doped indium oxide (ITO), IGZO, IGO, and IZO, and the doped tin oxide may be selected from the group consisting of F-doped tin oxide (FTO, F: SnO2), and the doped zinc oxide may be any one selected from Ga-doped zinc oxide (GZO) and Al-doped zinc oxide (AZO). And the doped strontium titanate may be Nb: SrTiO ₂ , and the doped titanium oxide may be Nb: TiO ₂ .

The microstructures 130 may include nano- or microscale structures formed vertically or obliquely from the transparent conductive layer 120 surface. In one example, the microstructures 130 may include nanowires. In this case, the nanowire is used to mean a nano-rod, a nano-wire, and a nano-needle. The microstructures 130 may be formed of the same material as the transparent conductive layer 120. For example, the microstructures 130 may be doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, strontium titanate, cadmium sulphide, (La _0.5 Sr _0.5) may be formed of one material selected from _{CoO 3 (LSCO), La 0.7} Sr 0.3 MnO 3 (LSMO), SrRuO 3 (SRO). The doped indium oxide may be Sn-doped indium oxide (ITO), IGZO, IGO, IZO, and the like. The doped tin oxide may be F-doped tin oxide (FTO) And the doped zinc oxide may be Ga-doped zinc oxide (GZO) or Al-doped zinc oxide (AZO). And the doped strontium titanate may be Nb: SrTiO ₂ , and the doped titanium oxide may be Nb: TiO ₂ . In one embodiment, the transparent conductive layer 120 and the microstructures 130 may be formed of ITO. ITO has excellent physical properties in electrical conductivity and optical transmittance.

The electron transport layer 140 may be formed to cover the upper portion of the microstructure 130 while filling the space between the microstructures 130. The electron transport layer 140 may be formed of a metal oxide capable of transporting electrons. For example, the electron transport layer 140 may be formed of TiO ₂ , ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Zn ₂ SnO ₃ , BaTiO ₃ , BaSnO _3, or the like. The electron transport layer 140 is preferably formed of TiO ₂ in terms of high electron mobility and electron decay prevention.

In one embodiment, the electron transporting layer 140 may include an electron transporting thin film 141 having a relatively low porosity and an electron transporting nanoparticle layer 143 having a relatively high porosity, that is, porous.

The electron transporting thin film 141 may be formed to cover the surfaces of the microstructures 130 and the transparent conductive layer 120. The electrons generated in the light absorber 150 by being formed so as to cover the surfaces of the microstructures 130 and the transparent conductive layer 120 have a relatively low porosity or a dense electron transporting film 141, It is possible to prevent the microstructure 130 and the transparent conductive layer 120 from being in direct contact with the hole transporting layer 160. In addition, The electron transporting thin film 141 may have a thickness of about 1 to 200 nm. When the thickness of the electron transporting thin film 141 is 1 nm or less, there is a problem that electrons and holes generated when the solar cell is driven are recombined very rapidly at the interface of the microstructure 130. When the thickness of the electron transporting thin film is 200 nm or more The generated electrons can not be easily collected into the microstructure 130, resulting in rapid recombination. In one embodiment, the electron transporting thin film 141 may have a thickness of about 10 to 50 nm so as to smoothly separate electrons and holes.

The electron transporting nanoparticle layer 143 may include electron transporting metal oxide nanoparticles coated on the electron transporting thin film 141. The electron transporting metal oxide nanoparticles may be located above the microstructures 130 covered by the space between the microstructures 130 covered by the electron transporting thin film 141 and the electron transporting thin film 141. When the electron-transporting metal oxide nanoparticles are arranged as described above, the thickness of the light-absorbing layer can be increased to increase the electron diffusion length in the light-absorbing layer, and as a result, high charge collection efficiency can be exhibited. The electron transfer nanoparticle layer 143 is formed to be porous so as to widen the contact area with the light absorber 150 to be subsequently bonded.

The light absorber 150 may be bonded to the surface of the electron transporting layer 140 and the pores of the electron transporting layer 140. For example, it may be bonded to the surface of the electron transporting metal oxide nanoparticles. In the present invention, as described above, since the electron transporting metal oxide nanoparticles are disposed in the space between the microstructures 130, the thickness of the light absorption layer can be drastically increased. The light absorber 150 may be in surface contact with the electron transporting metal oxide nanoparticles forming the electron transporting layer 140 to form an interface. As the light absorber 150, an organic dye or an inorganic dye can be used. As organic dyes, ruthenium-based organic dyes such as N719 or N3 may be used. And is an inorganic dye CdS, CdSe, CdTe, PbS, PbSe, PbTe, InP, InGaP, InAs, InCuS 2, InCuSe 2, CuFeS 2, InN, In 2 S 3, InSb, PbS, PbSe, Bi 2 S 3, Bi ₂ Se ₃ , Sb ₂ S ₃ , Sb ₂ Se ₃ , SnTe, SnS _x , NiS. _{CoS, FeS, In 2 S 3} , ZnSe, ZnTe, MoS, MoSe, Cu 2 S, Ge, Si, CsPbI 3, CsPbBr 3, CsSnI 3, CsSnBr 3, CH 3 NH 3 PbBr 3, CH 3 NH 3 SnBr 3 , CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ SnI _3, and alloys thereof.

The hole transport layer 160 may be formed on the electron transport layer 140 to which the light absorber 150 is coupled. The hole transport layer 160 may be formed to cover the surface of the electron transport layer 140 while filling the pores of the electron transport layer 140. The hole transport layer 160 may be formed of an organic photoelectric material. As the organic photoelectric material, a conjugated high molecular material having an energy difference of about 3.5 eV between a HOMO (Highest Occupied Molecular Orbital) level and a LUMO (Highest Unoccupied Molecular Orbital) level can be used. For example, the organic photoelectric material may be at least one selected from Spiro-OMeTAD, P3HT, P3AT, P3OT, and PEDOT: PSS.

The electrode layer 170 may be formed on the hole transport layer 160. The electrode layer 170 may be formed of a conductive metal or a composite thereof. For example, the electrode layer 170 may be formed of one or more materials selected from gold, silver, platinum, palladium, copper, aluminum, vanadium, molybdenum,

&Lt; Method for producing dye-sensitized solar cell &

FIG. 1 is a view for explaining a solar cell according to an embodiment of the present invention, and FIGS. 2A to 2G are views for explaining a method for manufacturing a solar cell according to an embodiment of the present invention.

Referring to FIGS. 1 and 2A to 2E, a method of manufacturing a solar cell according to an embodiment of the present invention includes forming a transparent conductive layer 120 on a substrate 110; Forming the microstructures 130 on the transparent conductive layer 120; Forming an electron transport layer 140 between and above the microstructures 130; Forming a hole transport layer (160) on the upper and inner pores of the electron transport layer (140); And forming an electrode 170 on the hole transport layer 160. [0033] FIG.

Referring to FIGS. 1 and 2A, a transparent conductive layer 120 may be formed on a substrate 110 to manufacture a solar cell according to an embodiment of the present invention.

As the substrate 110, an ordinary semiconductor substrate, a quartz substrate, or the like can be used. For example, a substrate, such as a silicon (Si) substrate, a silicon oxide (SiO ₂ ) substrate, an aluminum oxide (Al ₂ O ₃ ) substrate or an STO (SrTiO ₃ ) substrate can be used.

The transparent conductive layer 120 may be formed by depositing a transparent conductive metal oxide. For example, the metal oxide forming the transparent conductive layer 120 may be doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, strontium Titanate and cadmium sulfide, (La _0.5 Sr _0.5 ) CoO ₃ (LSCO), La _0.7 Sr _0.3 MnO ₃ (LSMO) and SrRuO ₃ (SRO). The doped indium oxide may be any one selected from Sn-doped indium oxide (ITO), IGZO, IGO, and IZO, and the doped tin oxide may be selected from the group consisting of F-doped tin oxide (FTO, F: SnO2), and the doped zinc oxide may be any one selected from Ga-doped zinc oxide (GZO) and Al-doped zinc oxide (AZO). And the doped strontium titanate may be Nb: SrTiO ₂ , and the doped titanium oxide may be Nb: TiO ₂ .

1 and 2B, the microstructures 130 made of a metal oxide or a semiconductor material may be formed on the transparent conductive layer 120. Referring to FIG. In this specification, the term 'microstructure' refers to a nano- or microscale structure grown vertically or obliquely on the transparent conductive layer 120. In one example, the microstructures 130 may comprise a conductive metal oxide nanowire formed on the transparent conductive layer 120. In this case, the nanowire is used to mean a nano-rod, a nano-wire, and a nano-needle.

The microstructures 130 may be formed of the same material as the transparent conductive layer 120. For example, the microstructures 130 may be doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, strontium titanate, cadmium sulphide, (La _0.5 Sr _0.5) may be formed of one material selected from _{CoO 3 (LSCO), La 0.7} Sr 0.3 MnO 3 (LSMO), SrRuO 3 (SRO). The doped indium oxide may be Sn-doped indium oxide (ITO), IGZO, IGO, IZO, and the like. The doped tin oxide may be F-doped tin oxide (FTO) And the doped zinc oxide may be Ga-doped zinc oxide (GZO) or Al-doped zinc oxide (AZO). And the doped strontium titanate may be Nb: SrTiO ₂ , and the doped titanium oxide may be Nb: TiO ₂ .

The microstructures 130 may be formed by a VLS process, a CVD (Chemical Vapor Deposition) process, an MOCVD process, a PLD (Pulsed Laser Deposition) process, a sol-gel process, a hydrothermal process, A wet chemical process, a paste thick process, or the like, or a vapor deposition process.

In one embodiment of the present invention, the microstructures 130 may be formed through a VLS process. For example, any one of SnO ₂ , CdO, ZnO, ITO, FTO, AZO, IZO, GZO, Nb: SrTiO ₂ , Nb: TiO ₂ , LSCO, LSMO and SRO is deposited on the substrate 110, The metal oxide nanowire 130 may be formed of the same material as the transparent conductive layer 120 through the VLS process on the transparent conductive layer 120. [

Specifically, in order to form the metal oxide nanowire 130 on the transparent conductive layer 120, a seed layer may first be formed on the transparent conductive layer 120. The seed layer may be formed by uniformly applying a noble metal such as gold (Au), platinum (Pt), or silver (Ag) nanoparticles stable at high temperatures and having a relatively low melting point on the transparent conductive layer 120 have. As an example, the seed layer may be formed to a thickness of about 10 to 50 nm through a sputtering process. Thereafter, the same metal oxide or precursor thereof as the material forming the transparent conductive layer 120 may be vaporized at a high temperature and then supplied to the seed layer in a solution state to grow a metal oxide nanowire. As the metal oxide or its precursor vapor melts into the noble metal solution droplet, it is supersaturated and the metal oxide nanowire grows.

Referring to FIGS. 1 and 2C, after the microstructures 130 are formed, an electron transport layer 140 may be formed in contact with the microstructures 130. The electron transport layer 140 may be formed of a metal oxide capable of transporting electrons. As the electron transporting metal oxide, TiO ₂ , ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Zn ₂ SnO ₃ , BaTiO ₃ , BaSnO ₃ and the like can be used.

In one embodiment, in order to form the electron transporting layer 140, the electron transporting thin film 141 made of an electron transporting metal oxide and having a relatively low porosity and the nanoparticles of the same material as the electron transporting thin film 141 And the electron transport nanoparticle layer 143 having a relatively high porosity, i.e., porous, can be sequentially formed.

The electron transport thin film 141 is formed to cover the surfaces of the microstructures 130 and the transparent conductive layer 120. It is possible to prevent direct contact with the hole transporting layer 160 to be formed after the microstructures 130 by the electron transporting thin film 141. The electron transporting thin film 141 may be formed by one or more methods selected from chemical vapor deposition (CBD), atomic layer deposition (ALD), layer-by-layer (LBL) deposition and spin coating. The electron transporting thin film 141 may be formed to a thickness of about 1 to 200 nm. When the thickness of the electron transporting thin film 141 is 1 nm or less, there is a problem that electrons and holes generated at the time of driving the solar cell are recombined very quickly at the interface of the microstructure 130. In addition, when the thickness of the electron transporting film 141 is 200 nm or more, generated electrons can not be easily collected into the microstructure 130, resulting in rapid recombination. In one embodiment, the electron transporting thin film 141 may be formed to a thickness of about 10 to 50 nm so as to smoothly separate electrons and holes.

The electron transporting nanoparticle layer 143 may be formed on the electron transporting thin film 141 using the same material as the electron transporting thin film 141, that is, the electron transporting metal oxide nanoparticles. For example, the electron transfer nanoparticle layer 143 may be formed by applying precursor nanoparticles and then heat-treating the precursor nanoparticles. The electron transporting metal oxide nanoparticles may be located above the microstructures 130 covered by the space between the microstructures 130 covered by the electron transporting thin film 141 and the electron transporting thin film 141. When the electron-transporting metal oxide nanoparticles are arranged as described above, the thickness of the light-absorbing layer can be increased to increase the electron diffusion length in the light-absorbing layer, and as a result, high charge collection efficiency can be exhibited. The electron transfer nanoparticle layer 143 may be formed to be porous in order to widen the contact area with the light absorber 150 to be bonded thereafter. The electron transfer nanoparticle layer 143 may be formed through a screen printing method, a spin coating method, a doctor blade method, or the like.

1 and 2D, after the electron transport layer 140 is formed, the light absorption body 150 may be bonded to the surface of the electron transport layer 140 and the pores of the electron transport layer 140. For example, it may be bonded to the surface of the electron transporting metal oxide nanoparticles. In the present invention, as described above, since the electron transporting metal oxide nanoparticles are disposed in the space between the microstructures 130, the thickness of the light absorption layer can be drastically increased. The light absorber 150 may be in surface contact with the metal oxide particles forming the electron transport layer 140 to form an interface. The light absorber 150 may comprise an organic dye or an inorganic dye. As organic dyes, ruthenium based organic dyes such as N719 or N3 may be used. And is an inorganic dye CdS, CdSe, CdTe, PbS, PbSe, PbTe, InP, InGaP, InAs, InCuS 2, InCuSe 2, CuFeS 2, InN, In 2 S 3, InSb, PbS, PbSe, Bi 2 S 3, Bi ₂ Se ₃ , Sb ₂ S ₃ , Sb ₂ Se ₃ , SnTe, SnS _x , NiS. _{CoS, FeS, In 2 S 3} , ZnSe, ZnTe, MoS, MoSe, Cu 2 S, Ge, Si, CsPbI 3, CsPbBr 3, CsSnI 3, CsSnBr 3, CH 3 NH 3 PbBr 3, CH 3 NH 3 SnBr 3 , CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ SnI _3, and alloys thereof.

Referring to FIGS. 1 and 2E, a hole transport layer 160 may be formed on the electron transport layer 140 to which the light absorber 150 is coupled. The hole transport layer 160 may be formed to cover the surface of the electron transport layer 140 while filling the pores of the electron transport layer 140. The hole transport layer 160 may be formed of an organic photoelectric material. As the organic photoelectric material, a conjugated high molecular material having an energy difference of about 3.5 eV between a HOMO (Highest Occupied Molecular Orbital) level and a LUMO (Highest Unoccupied Molecular Orbital) level can be used. For example, the organic photoelectric material may be at least one selected from Spiro-OMeTAD, P3HT, P3AT, P3OT, and PEDOT: PSS.

Referring to FIG. 1, an electrode layer 170 may be formed on the hole transport layer 160. The electrode layer 170 may be formed by depositing at least one material selected from the group consisting of gold, silver, platinum, palladium, copper, aluminum, vanadium, molybdenum and combinations thereof on the hole transporting layer 160.

[Example]

An ITO transparent conductive layer was formed on one side of a glass substrate having a size of 10 mm x 20 mm.

Then, gold (Au) was deposited on the transparent conductive layer to a thickness of about 10 to 50 nm by a sputtering method to form a seed layer. Then, the ITO nanowire was grown through a VLS method in a high temperature tube furnace. At this time, the precursor material for ITO nanowire synthesis was placed in the boat crucible, then placed in the center of the tube electric furnace, and the substrate on which the seed layer was formed was positioned at a certain distance from the center of the tube electric furnace. The carrier gas was flowed from one end of the tube and the amount of carrier gas was adjusted to a range of 10 to 500 sccm using a flow rate controller. The temperature of the tube furnace was controlled in the range of 500 ° C to 900 ° C in consideration of the vapor pressure of the nanowire precursor and the decomposition temperature of the precursor material.

In order to prevent the direct bonding between the grown ITO nanowire and the hole transport layer, a 10 nm thick TiO 2 thin film was formed through an ALD deposition method and then annealed at about 450 ° C. for about 1 hour. The TiO2 nanoparticle precursor was coated on the TiO2 thin film by screen printing method and then the precursor was heat-treated at a temperature of about 450 &lt; 0 &gt; C. Subsequently, the heat-treated substrate was carried on a 0.05 M titanium tetrachloride (TiCl4) diluent for about 2 hours. The temperature of the diluent was maintained at about 30 캜. Thereafter, the substrate was again subjected to heat treatment at about 450 DEG C for about 1 hour to form a porous electron transport layer.

Subsequently, Z907 ruthenium organic dye was dissolved at a concentration of 3 mM in a solution of about 1: 1 wt% (wt%) of tert-butanol and acetonitrile, and then immersed in a photo electrode The dye was adsorbed at room temperature for about 1 to 24 hours, after which the dye layer physically adsorbed on acetonitrile was removed and then dried.

Then, the hole transporting material was spin-coated at about 2000 rpm for about 45 seconds to form a hole transporting layer 160 so that the inner pores of the porous electron transporting layer were filled with spiro-OMeTAD, which is a hole- . The hole transport material was prepared by dissolving spiro-OMeTAD, which is a hole conductive material, in chlorobenzene at a concentration of about 180 mg / mL at about 70 to 100 ° C for about 30 minutes to 1 hour, adding 0.08 mL of tert-butyl pyridine The solution was prepared by adding about 0.16 mL of a solution of bis (trifluormethane) sulfonimide lithium salt dissolved in acetonitrile to a concentration of about 170 mg / mL.

Subsequently, gold (Au) was deposited on the hole transporting layer to a thickness of about 200 nm by a high-vacuum thermal evaporator to form an electrode layer.

[Comparative Example]

A glass substrate having a size of 10 mm x 20 mm was coated with fluorine-doped tin oxide (F-doped SnO 2, FTO) to form a transparent conductive layer.

Next, the TiO 2 nanoparticle precursor was coated on the transparent conductive layer by a doctor blade method, and then heat-treated at a temperature of about 450 ° C. The heat-treated photoelectrode was supported on a 0.05 M titanium tetrachloride (TiCl4) diluted solution for about 2 hours. The temperature of the diluent was maintained at about 30 degrees. Thereafter, the substrate was again subjected to heat treatment at a temperature of 450 DEG C for about 1 hour to form a porous electron transport layer.

Subsequently, the light absorber 150, the hole transport layer 160, and the electrode were formed using the same materials and process conditions as those of the embodiment.

[Experimental Example (Characteristic Evaluation)]

FIG. 3 is a scanning electron microscope (SEM) image for explaining the ITO nanowire grown on the ITO thin film according to the embodiment. FIG. 4 is a graph showing the SEM image of the TiO 2 thin film formed by depositing TiO 2 5 is a scanning electron microscope (SEM) image for illustrating a porous electron transport layer formed by applying a TiO2 nanoparticle precursor on a TiO2 thin film by a screen printing method. admit.

Referring to FIG. 3, nanowires, which are fine structures, can be formed on the transparent conductive layer according to the method described in the embodiment. The length of ITO nanowires can be controlled by controlling the process temperature and time.

Referring to FIGS. 4 and 5, according to the method described in the embodiment, an electron transporting thin film may be formed so as to cover the surface of the nanowires, and an electron transporting nanoparticle layer may be stably formed on the electron transporting thin film .

FIG. 6 is a graph illustrating voltage and current relationships between a solar cell manufactured according to an embodiment and a solar cell manufactured according to a comparative example. Table 1 shows measurement results of 'Jsc', 'Voc', 'Fill factor (FF)' and 'Efficiency' for the solar cell manufactured according to the embodiment and the solar cell manufactured according to the comparative example.

thickness
(탆) Jsc
(mA / cm ² ) Voc
(V) FF
(%) efficiency
(%) Comparative Example 2 4.04 0.863 80.11 2.79 Example 4.8 6.29 0.774 61.30 2.98

Referring to FIG. 6 and Table 1, in the solar cell manufactured according to the embodiment, the thickness of the electron transport layer is about 4.8 μm and the current density is about 6.29 mA / cm 2. On the other hand, The thickness of the electron transporting layer was about 2 mu m and the current density was about 4.04 mA / cm &lt; 2 &gt;. In other words, it can be seen that the photovoltaic cell manufactured according to the example exhibits a photocurrent density of 1.5 times higher than that of the solar cell manufactured according to the comparative example, without decreasing the current density even though the thickness of the light absorbing layer is twice or more thick have.

FIG. 7 is a graph showing the results of measurement of 'transient Voc', which indicates Voc reduction under an open-circuit voltage condition, for a solar cell manufactured according to the embodiment and a solar cell manufactured according to a comparative example.

Referring to FIG. 7, it can be seen that the solar cell manufactured according to the embodiment has an electron decay time about 10 times higher than that of the solar cell manufactured according to the comparative example. That is, it can be seen that the solar cell manufactured according to the embodiment has a charge collecting ability when the device is driven more efficiently than the solar cell manufactured according to the comparative example.

8 is a graph showing the results of measuring photocurrent density according to the thickness of a light absorbing layer for a solar cell manufactured according to the embodiment and a solar cell manufactured according to a comparative example.

Referring to FIG. 8, the solar cell manufactured according to the embodiment generates the highest current density at the light absorbing layer thickness of 4.8 mu m, and the solar cell manufactured according to the comparative example has the highest current density at the light absorbing layer thickness of 2 mu m Respectively.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

100: dye-sensitized solar cell 110: transparent substrate
120: transparent conductive layer 130: microstructures
140: electron transport layer 150: light absorber
160: hole transport layer 170: electrode layer

Claims (13)

A transparent conductive layer formed on the substrate;
Microstructures protruding vertically or obliquely from the surface of the transparent conductive layer and formed of the same material as the transparent conductive layer;
An electron transport layer formed of an electron transporting metal oxide covering the microstructures while filling at least part of the space between the microstructures;
A light absorber adhered to the inner pores and the surface of the electron transport layer;
A hole transporting layer covering the surface of the electron transporting layer to which the light absorber is attached while filling the pores of the electron transporting layer, the hole transporting layer being formed of a hole transporting material; And
And an electrode formed on the hole transport layer. The method according to claim 1,
Wherein the microstructures include nanowires. 3. The method of claim 2,
Wherein the nanowire includes at least one selected from the group consisting of a nano-rod, a nano-wire, and a nano-needle. 3. The method of claim 2,
The transparent conductive layer and the microstructures may be doped or undoped indium oxide, tin oxide, zinc oxide, titanium oxide, tungsten oxide, cadmium oxide, antimony oxide, niobium oxide, barium titanate, strontium titanate, sulfide and _{(La 0.5 Sr 0.5) CoO 3} (LSCO), La 0.7 Sr 0.3 MnO 3 (LSMO) , and SrRuO _3, characterized in that the solar cell is at least one selected from the group consisting of (SRO) formed of a material. 5. The method of claim 4,
The doped indium oxide includes at least one selected from the group consisting of Sn-doped indium tin oxide (ITO), IGZO, IGO and IZO,
The doped tin oxide includes F-doped tin oxide (FTO, F: SnO ₂ )
Wherein the doped zinc oxide comprises at least one selected from the group consisting of Ga-doped zinc oxide (GZO) and Al-doped zinc oxide (AZO)
Wherein the doped strontium titanate comprises Nb: SrTiO ₂ ,
The doped titanium oxide is Nb: the solar cell comprising the TiO _2. The method according to claim 1,
Wherein the electron transport layer is formed of at least one material selected from the group consisting of TiO ₂ , ZnO, SnO ₂ , WO ₃ , Fe ₂ O ₃ , Zn ₂ SnO ₃ , BaTiO ₃ and BaSnO ₃ . 7. The organic electroluminescent device according to claim 6,
An electron transporting thin film covering the surfaces of the microstructures and the transparent conductive layer; And
And an electron-transporting nanoparticle layer formed on the electron-transporting thin film and being more porous than the electron-transporting thin film. 8. The method of claim 7,
Wherein the electron transport nanoparticle layer comprises electron transporting metal oxide nanoparticles coated on the electron transport thin film. 8. The method of claim 7,
Wherein the light absorber comprises pores inside the electron-transporting nanoparticle layer and organic or inorganic dyes attached to the surface of the electron-transporting nanoparticle layer. 10. The method of claim 9,
Wherein the organic dye comprises a ruthenium-based organic dye,
The inorganic dyes include CdS, CdSe, CdTe, PbS, PbSe, PbTe, InP, InGaP, InAs, InCuS 2, InCuSe 2, CuFeS 2, InN, In 2 S 3, InSb, PbS, PbSe, Bi 2 S 3, Bi _{2 Se 3, Sb 2 S 3} , Sb 2 Se 3, SnTe, SnSx, NiS, CoS, FeS, In 2 S 3, ZnSe, ZnTe, MoS, MoSe, Cu 2 S, Ge, Si, CsPbI 3, CsPbBr 3 , At least one selected from the group consisting of CsSnI ₃ , CsSnBr ₃ , CH ₃ NH ₃ PbBr ₃ , CH ₃ NH ₃ SnBr ₃ , CH ₃ NH ₃ PbI ₃ , CH ₃ NH ₃ SnI ₃ and alloys thereof Solar cells featured. 8. The method of claim 7,
Wherein the hole transport layer is formed so as to cover the surface of the electron transport nanoparticle layer while filling pores inside the electron transport nanoparticle layer. 12. The method of claim 11,
Wherein the hole transport layer is formed of an organic photoelectric material. 13. The method of claim 12,
Wherein the organic photoelectric material comprises at least one selected from the group consisting of Spiro-OMeTAD, P3HT, P3AT, P3OT, and PEDOT: PSS.

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