WO2015064862A1

WO2015064862A1 - Stacked organic solar cell including interconnection unit

Info

Publication number: WO2015064862A1
Application number: PCT/KR2014/003284
Authority: WO
Inventors: 김장주; 심현섭
Original assignee: 서울대학교 산학협력단
Priority date: 2013-11-01
Filing date: 2014-04-16
Publication date: 2015-05-07

Abstract

Provided is a stacked organic solar cell comprising: a substrate; an anode on the substrate; a lower battery on the anode; an upper battery positioned on the lower battery to absorb light of a wavelength that is different from an absorption wavelength of the lower battery; an interconnection unit which is between the lower battery and the upper battery to connect the lower battery and the upper battery in series; and a cathode on the upper battery. Here, the interconnection unit comprises: an electron transport layer being in contact with the lower battery and including an electron transport material; a hole transport layer which comes into contact with the upper battery and includes a hole transport material doped with a p-type dopant; and a metal layer which is between the electron transport layer and the hole transport layer.

Description

Stacked organic solar cell including connection unit

The present invention relates to an organic solar cell and a method for manufacturing the same, and more particularly, to a stacked organic solar cell including a connection unit.

Organic solar cells have attracted attention as sustainable energy sources, but have a problem in that the light absorption intensity is weak and the range of the light absorption wavelength of the active layer is limited. In order to overcome this, a stacked solar cell has been proposed. The series connection of two solar cells with minimal absorption wavelength overlap creates a large open voltage (Voc) and allows absorption of light over a wide wavelength range.

In a stacked solar cell, an interconnection unit is used in series connection of two sub solar cells. The charge carriers of the two lower solar cells in the connection unit must be recombinable and the connection unit should be transparent to reduce optical loss. In addition, to prevent the loss of the open voltage, the energy level alignment between the lower solar cells should be matched, and the current between the lower cells in order to prevent the accumulation of charge in one of the lower cells to deteriorate efficiency. Current matching must be made.

The connection units proposed so far can be broadly divided into p-n junction connection units and metal thin film connection units.

The pn junction connection unit consists of a p-doped layer and an n-doped layer, which is advantageous for aligning the energy levels between the lower cells (reducing the energy barrier), but the n-dopant diffuses into the pre-stacked layer, resulting in current loss. And the work function is small, which causes unstable oxygen. In addition, absorption loss occurs in the connection unit since the acceptor material is used as a host for n-doping for efficient electron transport from the acceptor to the recombination contact.

In the metal thin film connection unit, a metal thin film is combined with an organic or metal oxide layer. In the thin film connection unit, the absorption of light in the metal layer is negligible due to the thickness of the very thin metal film, and the absorption loss can be minimized because the metal oxide such as rhenium oxide or molybdenum oxide is transparent in the active window of the organic solar cell. have. Furthermore, charge carrier recombination can occur efficiently in the metal layer, thus reducing the open voltage (Voc) loss. However, in the metal thin film connection unit, as the thickness of the metal oxide layer is increased, the electrical conductivity decreases, so that the fill factor may be reduced because it does not play an appropriate role as an optical control layer of the microcavity structure.

Provided is a stacked organic solar cell including a connection unit that is optically transparent, has a low voltage loss, and serves as an optical spacer.

According to one aspect, a substrate; An anode on the substrate; A lower cell above the anode;

An upper cell positioned on the lower cell and absorbing light having a wavelength different from that of the lower cell; A connection unit connecting the lower battery and the upper battery in series between the lower battery and the upper battery; And a cathode on the top cell; It provides a stacked organic solar cell comprising a. In this case, the connection unit may include an electron transporting layer in contact with the lower cell and made of an electron transporting material, a hole transporting layer in contact with the upper cell and doped with a p-type dopant, and a metal layer between the electron transporting layer and the hole transporting layer. It includes.

The stacked organic solar cell may have a microcavity structure, and the connection unit may serve as an optical control layer satisfying a resonance condition.

The lower battery may include a first photoactive layer including a first donor layer and a first acceptor layer, and the upper battery may include a second photoactive layer including a second donor layer and a second acceptor layer. have.

Multi-layered organic solar cells are connected to each other by using an electron transporting layer, a metal layer, and a p-doped hole transporting layer, thereby providing a low luminous efficiency and low voltage loss. An organic solar cell can be provided.

1 is a schematic cross-sectional view of a structure of a stacked organic solar cell according to one embodiment.

Figure 2 is a graph measuring the light absorption of the film of Experimental Example 1 to Experimental Example 3 and the light transmittance of the film of Experimental Example 4 and Experimental Example 5.

3 is a graph measuring the current density versus the voltage characteristics of the organic solar cells of Comparative Example 1, Comparative Example 2 and Example 1.

4 is a graph measuring current density vs. voltage characteristics of organic solar cells of Comparative Examples 3, 1, 5, and 6;

FIG. 5 compares current density values experimentally obtained in organic solar cells of Comparative Examples 3 and 6 with changes in the thickness of the hole transport layer in the organic solar cell of Example 1. It is a graph.

6 is a graph showing the opening voltage and the filling rate according to the thickness of the hole transport layer of the organic solar cells of Comparative Example 3 and Examples 1 to 6.

Hereinafter, with reference to the embodiments of the present invention shown in the accompanying drawings will be described in detail the configuration and operation of the present invention.

1 is a cross-sectional view schematically illustrating a structure of a stacked organic solar cell 100 according to an embodiment.

The stacked organic solar cell 100 according to the embodiment includes a substrate 101, an anode 111, a lower cell 120, a connection unit 130, an upper cell 140, and a cathode 150 sequentially stacked. Include. The lower cell 120 includes a first interfacial layer 121 in contact with the anode 111 and a first photoactive layer 123 over the first interfacial layer 121, and the upper cell 140 includes a connection unit 130. ) And a second photoactive layer 143 on the second interface layer 141. The first photoactive layer 123 includes a first donor layer 123a and a first acceptor layer 123b, and the second photoactive layer 143 includes a second donor layer 143a and a second acceptor layer ( 143b). The connection unit 130 includes an electron transport layer 131, a metal layer 133, and a hole transport layer 135.

The substrate 110 is for supporting an organic solar cell, for example, a transparent glass substrate or PET (Poly Ethylene Terephthlate (polyethylene terephthalate), PES (Polyethersulphone: polyether sulfone), PC (Polycarbonate), It may be made of a transparent plastic substrate such as polyimide (PI), polyethylene naphthalate (PEN) or polyarylate (PAR).

The anode 111 collects holes separated from excitons generated by photoexcitation and may be made of a transparent conductive metal oxide having a high work function. The anode 111 may be formed of, for example, indium tin oxide (ITO), tin oxide (TO), fluorine-doped tin oxide (FTO), or indium zinc oxide (IZO). Indium zinc oxide), AZO (Al-doped Zinc Oxide), ZO (zinc oxide), ZITO (zinc indium tin oxide), GITO (gallium indium tin oxide, gallium) Indium tin oxide) and the like. The anode 111 may have a thickness in the range of 70-150 nm, for example.

The first interfacial layer 121 may be formed of a hole transporting p-type semiconductor material. Such hole transporting p-type semiconductor material may be a transition metal oxide. The transition metal oxide that may be used for the first interfacial layer 121 may include, for example, molybdenum oxide, vanadium oxide, nickel oxide, tungsten oxide, rhenium oxide, or silver oxide. These transition metal oxides have a large bandgap and are optically transparent in the visible and near infrared regions, and have a small difference (potential barrier) between the Fermi level and the HOMO energy level of the donor material, thereby enabling efficient hole extraction and transfer. Furthermore, the lowest energy level of the conduction band is located much higher than the LUMO energy levels of most donor and acceptor materials, allowing good electron blocking. The first interfacial layer 121 may have a thickness in the range of 0.1-20 nm, for example.

The first donor layer 123a absorbs light to generate excitons, and transports holes separated from the excitons to the anode 111 at the interface with the first acceptor layer 123b. The first donor layer 123a may have a thickness in the range of, for example, 5-40 nm in consideration of the diffusion distance of excitons.

The first donor layer 123a may be made of a donor material that is a p-type semiconductor. Donor materials are for example planar π-conjugated compounds, such as CuPc (Copper Phthalocyanine (copper phthalocyanine), ZnPc (Zinc Phthalocyanine (zinc phthalocyanine)), PbPc (lead phthalocyanine (PbPc), ClAlPc) phthalocyanine-based materials such as chloroaluminum phthalocyanine (aluminum phthalocyanine), SubPc (boron subphthalocyanine chloride) or TiOPc (Oxytitanium phthalocyanine: titanium phthalocyanine). Donor materials also include pentacene, diindenoperylene (DIP), rubrene, DCV3T (α, α'-bis- (2,2-dicyanovinyl) -terthiophene, α, α'- Bis- (2,2-dicyanovinyl) -teriophene), DCV5T or DBP (tetraphenyl-dibenzoperiflanthene, tetraphenyl-dibenzoperiflanthene).

The first acceptor layer 123b receives electrons from excitons at the interface with the first donor layer 123a and transports the electrons in the direction of the cathode 151. The first acceptor layer 123b may be made of an acceptor material which is an n-type semiconductor having high electron affinity. The first acceptor layer 123b may have a thickness in the range of 10-50 nm, for example.

The acceptor material can be, for example, fullerenes such as C ₆₀ or C ₇₀ , PC ₆₀ BM ([6,6] -phenyl-C61-butyric acid methyl ester), CP ₇₀ BM, CP ₈₄ BM, indene C ₆₀ , indene Derivatives of fullerenes such as C ₇₀ or endohedral fullerenes, perylenes, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic) Dianhydride) or perylene derivatives such as PTCBI (3,4,9,10-perylenetetracarboxylic bisbenzimidazole, 3,4,9,10-perylenetetracarboxylic bisbenzimidazole).

The electron transport layer 131 of the connection unit 130 collects electrons from the lower battery 120 and transfers the electrons to the metal layer 133, and may be made of an electron transport material. The electron transport material of the electron transport layer 131 is, for example, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10- Phenanthroline), Bphen (4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline), B3PYMPM (bis-4,6- (3,5-di- 3-pyridylphenyl) -2-methylpyrimidine, bis-4,6- (3,5-di-3-finidylphenyl) -2-methylpyrimidine), 3TPYMB (tris- [3- (3-pyridyl) mesityl] borane, tris- [3- (3-pyridyl) mesityl] borane), BmPyPb ((1,3-bis (3,5-dipyrid-3-yl-phenyl) benzene, 1,3-bis (3) , 5-dipyrid-3-yl-phenyl) benzene), TmPyPb (1,3,5-tri (m-pyrid-3-yl-phenyl) benzene, 1,3,5-tri (m-pyrid- 3-yl-phenyl) benzene), OXD7 (1,3-bis (5- (4-tert-butylphenyl) -1,3,4-oxadiazol-2-yl) benzene, 1,3-bis (5- ( 4-tert-butylphenyl) -1,3,4-oxadiazol-2-yl) benzene), OXD8 (1,3-bis (N, N-dimethylaminophenyl) -1,3,4-oxidazole, 1, 3-bis (N, N-dimethylaminophenyl) -1,3,4-oxadiazole) or TAZ (3- (biphenyl-4-yl) -4-phenyl-5- (4-tert-butylphenyl)- 1,2,4-triazole), 3- (biphenyl-4 -Yl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole)) can be used. The electron transport layer 131 may have a thickness in the range of 1-10 nm, for example.

The metal layer 133 of the connection unit 130 prevents electrons collected from the lower cell 120 and holes collected from the upper cell 140 to recombine to accumulate charge in the connection unit 130. The metal layer 133 may use silver (Ag), gold (Au), or aluminum (Al), for example. The metal layer 133 may have a thickness in the range of 0.1-1 nm, for example.

The hole transport layer 135 of the connection unit 130 collects holes from the upper cell 140 and transfers the holes to the metal layer 133, and may be made of a hole transport material doped with a p-type dopant. The p-type dopant may play a role of increasing the electrical conductivity of the hole transport layer.

Hole transporting materials include, for example, TAPC (1,1'-bis (di-4-tolylaminophenyl) cyclohexane, 1,1'-bis (di-4-tolylaminophenyl) cyclohexane), m-MTDATA (4, 4 ', 4' '-tris (N-3-methylphenyl-N-phenylamino) triphenylamine, 4,4,4 "-tris (N-3-methylphenyl-N-phenylamino) triphenylamine), 1-TNATA ( 4,4 ', 4 "-tris- (N- (naphthylen-1-yl) -N-phenylamine) triphenylamine, 4,4', 4" -tris- (N- (naphthylene-1-yl) -N -Phenylamine) triphenylamine), 2-TNATA (4,4 ', 4 "-tris- (N- (naphthylen-2-yl) -N-phenylamine) triphenylamine, 4,4', 4" -tris- (N- (naphthylene-2-yl) -N-phenylamine) triphenylamine), TCTA (4,4 ', 4 "-tris (carbazol-9-yl) triphenylamine, 4,4', 4"- Tris (carbazol-9-yl) triphenylamine), NPB (N, N'-di (naphthalen-1-yl) -N-N'-diphenyl-benzidine, N, N'-di (naphthalene-1- Yl) -N-N'-diphenyl-benzidine) or 4,4'-bis- (N, N-diphenylamino) -quaterphenyl (4,4'-bis- (N, N-diphenylamino) -quaterphenyl ) Can be used.

p-type dopants include rhenium oxide (ReO _x , x is 2-3, or Re ₂ O ₇ ), molybdenum oxide (MoO _x , x is 2-3), tungsten oxide (WO ₃ ), F4-TCNQ (tetrafluoro-tetracyano -quinodimethane, tetrafluorotetracyanoquinodimethane), vanadium oxide (V ₂ O ₅ ), antimony chloride (SbCl ₅ ), ferric chloride (FeCl ₃ ) or copper iodide (CuI).

Since the electrical conductivity of the hole transport layer 135 is high, the voltage drop and the current loss hardly occur due to the increase in thickness. Therefore, by adjusting the thickness of the hole transport layer 135 in the connection unit, the connection unit can sufficiently perform the role of an optical spacer for controlling the effective redistribution of the optical field.

The connection unit 130 including the electron transport layer 131, the metal layer 130, and the hole transport layer 135 as described above is optically transparent and has HOMO, LUMO energy levels, and Fermi energy with adjacent layers to facilitate charge transfer. By level alignment, the potential barrier can be reduced to reduce voltage losses and act as an optical control layer.

The second interface layer 141 may increase the crystallinity of the second donor layer 143a to maximize light absorption. For example, copper iodide (I) (CuI) and copper bromide ( I) (CuBr), copper chloride (I) (CuCl), copper sulfide (II) (CuS), silver bromide (I) (AgBr) or silver iodide (I) (AgI). The second interfacial layer 141 may have a thickness in the range of, for example, 0.1-3 nm.

Like the first donor layer 123a, the second donor layer 143a of the upper battery 140 may be made of a donor material that is a p-type semiconductor. The donor material of the second donor layer 143a may be, for example, CuPc, ZnPc, PbPc, ClAlPc, SubPc, TiOPc, pentacene, DIP, rublin, DCV3T, DCV5T, or the donor material of the first donor layer 123a. May include a DBP. Meanwhile, since the light absorption wavelengths of the upper cell 120 and the lower cell 140 must be different, the donor material of the second donor layer 143a should use a material different from the donor material of the first donor layer 123a. The second donor layer 143a may have a thickness, for example, in the range of 5-30 nm.

Like the first acceptor layer 123b, the second acceptor layer 143b of the upper cell 140 may be formed of an acceptor material which is an n-type semiconductor having high electron affinity. The acceptor material of the second acceptor layer 143b is the same as the acceptor material of the first acceptor layer 123b, for example, C ₆₀ , C ₇₀ , PC ₆₀ BM, CP ₇₀ BM, CP ₈₄ BM, Inden C ₆₀ , indene C ₇₀ , endohydral fullerenes, perylenes, PTCDA or PTCBI. As the acceptor material of the second acceptor layer 143b, the same material as the acceptor material of the first acceptor layer 123b or another material may be used. The second donor layer 143a may have a thickness in the range of 10-50 nm, for example.

The third interface layer 147 serves to transfer electrons from the second acceptor layer 143b to the cathode 151, and like the electron transport layer 131 of the connection unit 130, for example, BCP, Bphen, B3PYMPM, 3TPYMB, BmPyPb, TmPyPb, OXD7, OXD8 or TAZ can be used. The third interfacial layer 147 may have a thickness in the range of 1-10 nm, for example.

The cathode 151 may be made of a metal having a low work function as an electrode for collecting electrons from the third interfacial layer 147. Metals having a low work function can be, for example, Al, Ca, Mg, K, Ti, Li or alloys thereof. The cathode 151 may have a thickness in the range of 70-100 nm, for example.

Meanwhile, a fourth interface layer (not shown) made of the same material as the hole transport material of the hole transport layer 135 may be further included between the hole transport layer 135 and the second interface layer 141. The fourth interfacial layer (not shown) may serve to prevent quenching of excitons, and may have a thickness in the range of 0.1-20 nm, for example.

The organic solar cell 100 may obtain a high optical efficiency by the connection unit 130 satisfies the role of the optical control layer without loss of voltage.

Hereinafter, the organic solar cell according to the exemplary embodiment will be described in more detail with reference to non-limiting examples. However, the present invention is not limited to the following examples.

광흡수율 및 광투과도의 측정Measurement of light absorption and light transmittance

The UV-VIS absorption spectrum of the film was measured using a Cary 5000 UV-Vis-NIR spectrometer (Varian). Current density-voltage (J-V) characteristics were measured using an AM 1.5G solar simulator (Newport, 91160A) and a power supply (Keithley 237). Light intensity was adjusted using standard silicon solar cells from the National Renewable Energy Research Center (NREL) in the United States.

Experimental Example 1

C ₆₀ was thermally deposited to a thickness of 50 nm on a glass substrate to form a C ₆₀ film.

Experimental Example 2

SubPc was thermally deposited to a thickness of 50 nm on a glass substrate to form a SubPc film.

Experimental Example 3

CuI was thermally deposited to a thickness of 0.5 nm on the glass substrate, and PbPc was thermally deposited to a thickness of 20 nm to form a PbPc film.

Experimental Example 4

TAPC: ReO ₃ (75:25) (molar ratio) was co-deposited to a thickness of 5 nm on a glass substrate to form a TAPC: ReO ₃ film.

Experimental Example 5

TAPC: ReO ₃ (75:25) (molar ratio) was co-deposited on a glass substrate to a thickness of 100 nm to form a TAPC: ReO ₃ film.

FIG. 2 is a graph measuring the light absorption coefficient of the films of Experimental Examples 1 to 3 and the light transmittance of the films of Experimental Examples 4 and 5. FIG. Referring to FIG. 2, the overlap of light absorption of SubPc and PbPc is relatively small. From this, in the embodiment of the present invention using SubPc as the light absorbing material of the lower cell and PbPc as the light absorbing material of the upper cell, the solar photon flux has a minimum energy loss and the upper cell and the lower cell. It can be seen that it will be absorbed independently. On the other hand, the absorption of PbPc extends to the near-infrared region than is known, which is believed to be due to the improvement of the crystallinity of PbPc having the preferred orientation resulting from the presence of the underlying CuI layer.

Referring back to FIG. 2, the optical transmittance of the TAPC: ReO ₃ 5 nm film of Experimental Example 4 was found to be 95% or more, and from this, when TAPC: ReO ₃ was used at a thickness of 5 nm, it satisfies the optical transmittance requirement of the connection unit. Able to know. In the TAPC: ReO ₃ 100 nm film of Experimental Example 5, a new absorption peak appears at about 690 nm, because the TAPC molecule and the ReO ₃ molecule form a charge transfer complex. Formation of charge transfer complexes of TAPC molecules and ReO ₃ molecules indicates that holes will be formed by ReO ₃ doping to improve electrical conductivity. In addition, although the TAPC: ReO ₃ layer has a thickness of 100 nm, the transmittance in the active wavelength range is 85% or more, which is higher than that of MoO ₃ and ITO. This indicates that the p-doped hole transport layer has a minimum optical loss and can be used as an optical control layer.

Example 1

A laminated organic solar cell having a layer structure as follows was prepared:

ITO (150nm) / MoO ₃₃ (3nm) / SubPc (10nm) / C ₆₀₆₀ (15nm) / BCP (3nm) / Ag (0.3nm) / TAPC: ReO ₃₃ (75:25) (5nm) / TAPC (3nm) / CuI (1nm) / PbPc (15nm) / C ₆₀₆₀ (10nm) / BCP (8nm) / Al (100nm)

In this layer structure, ITO (150nm) is the anode, MoO ₃ (3nm) / SubPc (10nm) / C ₆₀ (15nm) is the bottom cell, BCP (3nm) / Ag (0.3nm) / TAPC: ReO ₃ (75: 25) (5nm) is the connection unit TAPC (3nm) / CuI (1nm) / PbPc (15nm) / C ₆₀ (10nm) / BCP (8nm) / Al (100nm) is the top cell, Al (100nm) is the cathode Configure

The ITO glass substrate on which the 150 nm-thick ITO film was sputter-deposited on the glass substrate was washed with acetone and isopropyl alcohol, and treated with UV-O ₃ to form an anode on the substrate. 3 nm thick MoO ₃ as an anode interface layer, 10 nm thick SubPc as a first donor layer, 15 nm thick C ₆₀ as a first acceptor layer, and 3 nm thick as an electron transport layer of a connection unit on the ITO glass substrate. BCP, a 0.3 nm thick as a metal layer of the connecting unit Ag, as a p-doped hole transport layer of the connecting unit TAPC of 5 nm thickness: ReO _3, as a second interface layer 3 interface layer of 3 nm thickness TAPC, a 1 nm thick CuI, 15 nm thick PbPc as the second donor layer, 10 nm thick C ₆₀ as the second acceptor layer, 8 nm thick BCP as the fourth interface layer, and 100 nm Al as the cathode were sequentially formed. . All layers on the ITO glass substrates were thermal evaporated at a base pressure of <10 ⁻⁷ Torr without breaking the vacuum. At this time, the deposition rate of the MoO ₃ layer is 0.1 Å / s, the deposition rate of ReO ₃ is 0.125 Å / s, the deposition rate of Ag in the connection unit is 0.2 Å / s, the deposition rate of Al of the cathode is 4 Å / s s was. The remaining layers were deposited at a deposition rate of 0.1 dl / s. Meanwhile, TAPC: ReO ₃ , a p-doped hole transport layer of the connection unit, formed a TAPC layer doped with 25 mol (mol) ReO ₃ by co-deposition.

4 mm ² each of the above layered structure Four or more devices having an active region of were formed simultaneously. Thereafter, the device was encapsulated using a glass can and epoxy resin in an N ₂ atmosphere.

Comparative Example 1

A single cell organic solar cell having a layer structure as follows was prepared.

ITO (150nm) / MoO ₃₃ (3nm) / SubPc (8nm) / C ₆₀₆₀ (35nm) / BCP (8nm) / Al (100nm)

An organic solar cell was manufactured in the same manner as in Example 1, except that the anode, the lower cell, and the cathode were formed in the layer structure and the thickness of the layer structure of Example 1.

Comparative Example 2

ITO (150nm) / CuI (1nm) / PbPc (20nm) / C ₆₀₆₀ (40nm) / BCP (8nm) / Al (100nm)

An organic solar cell was manufactured in the same manner as in Example 1, except that the anode, the upper cell, and the cathode were formed in the layer structure and the thickness of the layer structure of Example 1.

Comparative Example 3

An organic solar cell was manufactured in the same manner as in Example 1, except that the TAPC: ReO ₃ (75:25) layer was not used in Example 1.

Example 2

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC: ReO ₃ (75:25) was formed in a thickness of 10 nm instead of 5 nm in Example 1.

Example 3

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC: ReO ₃ (75:25) was formed in a thickness of 20 nm instead of 5 nm in Example 1.

Example 4

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC: ReO ₃ (75:25) was formed in a thickness of 50 nm instead of 5 nm in Example 1.

Example 5

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC: ReO ₃ (75:25) was formed in a thickness of 100 nm instead of 5 nm in Example 1.

Example 6

An organic solar cell was manufactured in the same manner as in Example 1, except that TAPC: ReO ₃ (75:25) was formed in a thickness of 130 nm instead of 5 nm in Example 1.

전류 밀도 대 전압의 측정Measurement of Current Density vs. Voltage

3 is a graph measuring the current density versus the voltage characteristics of the organic solar cells of Comparative Example 1, Comparative Example 2 and Example 1, Figure 4 is a Comparative Example 3, Example 1, Example 5 and Example 6 of It is a graph measuring the current density vs. voltage characteristics of an organic solar cell. Table 1 shows the performance of the organic solar cells of Comparative Example 1, Comparative Example 2, Example 1, Example 5 and Example 6.

3 and Table 1, the open circuit voltage (V _oc ) of the stacked organic solar cell of Example 1 is 1.47V, and the sum of the open circuit voltages (V _oc ) of the single organic solar cells of Comparative Examples 1 and 2 is 0.46. It appears to have a voltage loss of about 3% at V + 1.06V = 1.52V. This indicates that the energy barriers to holes and electrons to the recombination contact (metal layer) of the connection unit are negligible. In addition, the power conversion efficiency (PCE) of the stacked organic solar cell of Example 1 is 3.19%, which is higher than the power conversion efficiency (PCE) of 2.01% and 2.87% of the single organic solar cells of Comparative Examples 1 and 2.

Referring to FIG. 4 and Table 1, the stacked organic solar cell of Comparative Example 3, in which the hole transport layer is not used in the connection unit, has a S-type current density versus voltage graph. This indicates that there is an energy barrier between the top cell and the connection unit such that there is a resistance to transfer holes from the donor layer of the top cell to the metal layer of the connection unit. In the stacked organic solar cell of Example 1 in which the hole transport layer was introduced, the S-shape of the current density vs. voltage graph was removed, and the filling rate (FF) and the open voltage (V _oc ) were increased in comparison with those of Comparative Example 1. In addition, it can be seen from the graph of FIG. 4 that the value of the short-circuit current density J _sc significantly changes as the thickness of the hole transport layer changes.

FIG. 5 is a simulation result of current densities of a lower cell and an upper cell while varying the thickness of the TAPC: ReO ₃ hole transport layer in the stacked organic solar cell having the same layer structure as Example 1, and Comparative Examples 3 and 1 to Examples This is a graph comparing the current density values experimentally obtained in the organic solar cell of 6. For simulation of current density, see K. Vasseur, BP Rand, D. Cheyns, L. Froyen, P. Heremans, Chem. Mater., 23,886 (2011) and J. Lee, S.-Y. Kim, C. Kim, J.-J. Kim, Appl. Phys. Lett., 97, 083306 (2010), cited the complex refractive index values of the materials used. The exciton diffusion lengths (L _D ) for SubPc, PbPc, and C60 used for the simulation of current density were 9.94 nm, 8.8 nm and 14.4 nm, respectively. Shim, HJ Kim, JW Kim, S.-Y. Kim, W.-I. Jeong, T.-M. Kim, J.-J. Kim, J. Mater. Chem., 22, 9077 (2012) and Appl. Phys. Lett., 97, 083306 (2010).

Referring to FIG. 5, the change in current density of the upper cell is small according to the thickness of the hole transport layer, but the current density of the lower cell shows a simulation result in which the sinusoidal pattern varies considerably. This relates to the fact that the position of the photoactive layer of the top cell from the metal cathode is independent of the thickness of the p doped hole transport layer of the connection unit, but the position of the photoactive layer of the bottom cell varies with the thickness of the p doped hole transport layer of the connection unit. do. The current density of the stacked organic solar cell experimentally obtained in the graph of FIG. 5 coincides with the current density of the lower cell, indicating that the current density of the entire organic solar cell follows the current density of the lower cell having the lowest current density. Can be. Also from this the p-doped hole transport layer can act as an optical control layer with negligible optical loss and current density loss, thus optimizing current matching between the lower and upper cells by adjusting the thickness of the p-doped hole transport layer. It can be seen that.

FIG. 6 is a graph showing the opening voltage (V _OC ) and the filling rate (FF) according to the thickness of the TAPC: ReO ₃ hole transport layer of the organic solar cells of Comparative Example 3 and Examples 1 to 6. FIG. The graph of FIG. 6 shows that the filling rate is improved when the p-doped hole transport layer is used in the connection unit, and the filling rate does not worsen even when the thickness of the p-doped hole transport layer is increased. This indicates that little potential drop occurs when electrons and holes reach the recombination layer in the connection unit. The graph of FIG. 6 shows that the open voltage V _OC also increases with the introduction of the p-doped hole transport layer into the connection unit and slightly decreases with increasing thickness of the p-doped hole transport layer.

As the thickness of the p-doped hole transport layer increases from Examples 1 to 6, there is almost no change in the filling rate and very little loss of the open voltage (V _OC ), and a short circuit current according to the thickness of the p-doped hole transport layer. It can be seen that the change in density J _SC and open voltage V _OC is consistent with the simulation without considering electrical losses. This shows that the stacked organic solar cell including the connection unit of the present invention can use the microcavity structure to optimize the performance of the cell without electrical loss.

Table 1

	PCE (%)	J _SC (mA / cm ² )	V _OC (V)	FF	n	The J _S ¹ ¹ dark JV curve was obtained by fitting the Shockley diode equation. (nA / cm ² )	The calculated V _OC (V) ¹ ¹ Voc = nkT / q · ln (J _sc / J _s ) was obtained from the equation.
Comparative Example 3	2.03 ± 0.01	7.25 ± 0.01	0.46 ± 0.01	0.61	1.54	47.3	0.47
Example 1	2.87 ± 0.01	4.11 ± 0.01	1.06 ± 0.01	0.66	2.08	2.91 x 10 ^-3	1.12
Example 2	3.19 ± 0.03	3.62 ± 0.05	1.47 ± 0.01	0.60	3.96	1.14	1.52
Example 3	0.96 ± 0.01	1.16 ± 0.01	1.35 ± 0.01	0.61	4.00	1.82	1.37
Example 4	1.68 ± 0.01	2.03 ± 0.01	1.37 ± 0.02	0.59	4.01	2.08	1.42

Claims

Board;

An anode on the substrate;

A lower cell above the anode;

An upper cell positioned on the lower cell and absorbing light having a wavelength different from that of the lower cell;

An interconnection unit connecting the lower cell and the upper cell in series between the lower cell and the upper cell; And

A cathode on the top cell; Including,

The connection unit includes an electron transport layer in contact with the lower cell and made of an electron transporting material, a hole transport layer in contact with the upper cell and doped with a p-type dopant, and a metal layer between the electron transport layer and the hole transport layer. Laminated organic solar cell comprising.
According to claim 1,

The stacked organic solar cell of claim 1, wherein the connection unit serves as an optical spacer.
According to claim 1,

The electron transporting material of the electron transporting layer of the connection unit is BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenantrol Lin), Bphen (4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline), B3PYMPM (bis-4,6- (3,5-di-3- pyridylphenyl) -2-methylpyrimidine, bis-4,6- (3,5-di-3-finidylphenyl) -2-methylpyrimidine), 3TPYMB (tris- [3- (3-pyridyl) mesityl] borane, Tris- [3- (3-pyridyl) methyl] borane), BmPyPb ((1,3-bis (3,5-dipyrid-3-yl-phenyl) benzene, 1,3-bis (3,5) -Dipyrid-3-yl-phenyl) benzene), TmPyPb (1,3,5-tri (m-pyrid-3-yl-phenyl) benzene, 1,3,5-tri (m-pyrid-3- Mono-phenyl) benzene), OXD7 (1,3-bis (5- (4-tert-butylphenyl) -1,3,4-oxadiazol-2-yl) benzene, 1,3-bis (5- (4- Tert-butylphenyl) -1,3,4-oxadiazol-2-yl) benzene), OXD8 (1,3-bis (N, N-dimethylaminophenyl) -1,3,4-oxidazole, 1,3- Bis (N, N-dimethylaminophenyl) -1,3,4-oxadiazole) or TAZ (3- (biphenyl-4-yl) -4-phenyl-5- (4-tert-butylphenyl) -1, 2,4-triazole), 3- (non Carbonyl-4-yl) -4-phenyl-5- (4-tert-butylphenyl), an organic solar cell comprising a 1,2,4-triazole)).
According to claim 1,

The hole transporting material of the hole transporting layer of the linking unit is TAPC (1,1'-bis (di-4-tolylaminophenyl) cyclohexane, 1,1'-bis (di-4-tolylaminophenyl) cyclohexane), m- MTDATA (4,4 ', 4' '-tris (N-3-methylphenyl-N-phenylamino) triphenylamine, 4,4,4 "-tris (N-3-methylphenyl-N-phenylamino) triphenylamine), 1-TNATA (4,4 ', 4 "-tris- (N- (naphthylen-1-yl) -N-phenylamine) triphenylamine, 4,4', 4" -tris- (N- (naphthylene-1- Yl) -N-phenylamine) triphenylamine), 2-TNATA (4,4 ', 4 "-tris- (N- (naphthylen-2-yl) -N-phenylamine) triphenylamine, 4,4', 4 "-Tris- (N- (naphthylene-2-yl) -N-phenylamine) triphenylamine), TCTA (4,4 ', 4" -tris (carbazol-9-yl) triphenylamine, 4,4' , 4 "-tris (carbazol-9-yl) triphenylamine), NPB (N, N'-di (naphthalen-1-yl) -N-N'-diphenyl-benzidine, N, N'-di ( Naphthalen-1-yl) -N-N'-diphenyl-benzidine) or 4,4'-bis- (N, N-diphenylamino) -quaterphenyl (4,4'-bis- (N, N- Stacked organic solar cell comprising diphenylamino) -quaterphenyl).
According to claim 1,

The p-type dopant is rhenium oxide (ReO x , x is 2 to 3, or Re 2 O 7 ), molybdenum oxide (MoO x , x is 2 to 3), tungsten oxide (WO 3 ), F4-TCNQ (tetrafluoro- Stacked organics comprising tetracyano-quinodimethane, tetrafluorotetracyanoquinomethane, vanadium oxide (V 2 O 5 ), antimony chloride (SbCl 5 ), ferric chloride (FeCl 3 ) or copper iodide (CuI) Solar cells.
According to claim 1,

The metal layer is a stacked organic solar cell containing silver (Ag), gold (Au) or aluminum (Al).
According to claim 1,

The lower battery includes a first photoactive layer including a first donor layer and a first acceptor layer, and the upper battery includes a second photoactive layer including a second donor layer and a second acceptor layer. Organic solar cell.
The method of claim 7, wherein

The first donor layer and the second donor layer are SubPc (boron subphthalocyanine, boron subphthalocyanine), ZnPc (zinc phthalocyanine, zinc phthalocyanine), FePc (iron phthalocyanine, phthalocyanine iron), TiPc (titanium phthalocyanine, phthalocyanine) Rubrene, poly (3-hexthiophene), DCV3T (α, α'-bis- (2,2-dicyanovinyl) -terthiophene, α, α'-bis- (2,2-dicyanovinyl) Terthiophene), DCV5T (α, α'-bis- (2,2-dicyanovinyl) -kenxyfen), DIP (diindenoperylene, diindenoferylene), DBP (tetraphenyl-dibenzoperiflanthene, tetraphenyl-dibenzo Periplanthene), merocyanine dye, squaraine dye, DTDCTP (2-{[2- (5-N, N-di (p-tolyl) aminothiophen-2-yl) -pyrimidin-5-yl] methylene} -malononitrile) or DTS (PTTh 2 ) 2 (5,5'-bis {(4- (7-hexylthiophen-2-yl) thiophene-2-yl)-[1,2 , 5] -thiadiazolo [3,4, -c] pyridine} -3,3-di-2-ethylhexylsilylene-2,2'-bithiophene), and the first donor layer. The stacked organic solar cell of the second donor layer is different material.
The method of claim 7, wherein

The first acceptor layer and the second acceptor layer are each C 60 , C 70 , PC 60 BM ([6,6] -phenyl-C61-butyric acid methyl ester, [6,6] -phenyl-C61- Butyric acid methyl ester), PC 70 BM, PC 84 BM, indene C 60 , indene C 70 or endohedral fullerene (endohedral fullerene).
The method of claim 7, wherein

The lower battery further includes a first interfacial layer between the anode and the first donor layer,

The first interface layer is a laminated organic solar cell comprising molybdenum oxide, nickel oxide, vanadium oxide, tungsten oxide or silver oxide.
The method of claim 7, wherein

The upper battery further includes a second interface layer between the connection unit and the second donor layer,

The second interfacial layer is a multilayer organic solar cell including copper iodide (CuI), copper bromide (CuBr), silver bromide (AgBr) or silver iodide (AgI).
The method of claim 7, wherein

The upper cell further includes a third interfacial layer between the second acceptor layer and the cathode,

The third interface layer is a stacked organic solar cell comprising BCP, Bphen, B3PYMPM, 3TPYMB, BmPyPb, TmPyPb, OXD7, OXD8 or TAZ.
The method of claim 7, wherein

The upper cell further includes a fourth interface layer between the connection unit and the second donor layer,

The fourth interfacial layer is a stacked organic solar cell made of the same material as the hole transporting material.