KR101371609B1 - Organic small molecular solar cells with a double interfacial layer - Google Patents

Abstract

According to an aspect of the present invention, An anode layer on the substrate; A double interface layer comprising a metal oxide layer on the anode layer and an alignment layer on the metal oxide layer; A photoactive layer on the dual interface layer; And it discloses an organic solar cell comprising a cathode layer on the photoactive layer.

Description

Organic small molecular solar cells with a double interfacial layer

The present invention relates to an organic solar cell, and more particularly, to a low molecular planar heterojunction organic solar cell.

Metal-phthalocyanines (MPc) and fullerenes (C ₆₀ ) are widely used as donor and acceptor molecules for planar heterojunction organic solar cells, respectively. However, MPc / C ₆₀ based low molecular heterojunction organic solar cells have low power conversion efficiencies (η _p ) and short lifetimes of 1-2%. Recently, co-deposition of donor and acceptor materials has been used to improve the power conversion efficiency (η _p ) by making bulk heterojunctions (BHJs) of low molecular weight. However, low molecular co-deposited layers are not as successful as polymers in forming BHJ structures because of the high mixing entropy to reduce their effects on phase separation. The power conversion efficiency (η _p ) of the device using the low molecular co-deposited layer represents about 2 to 3%.

Meanwhile, the MPc / C ₆₀ planar heterojunction solar cell exhibits photo-degradation characteristics even under a short period of light irradiation in a nitrogen atmosphere. Several mechanisms have been proposed to account for this photodegradation. Formation of a gap state at the interface between the donor and acceptor by the photo-reaction of C ₆₀ with oxygen, and the diffusion of oxygen-induced photons from the ITO (indium-tin-oxide) to the donor layer photo-assisted diffusion) and reduction of the work function of ITO by UV light. On the other hand, KR publication 2010-0121928 discloses a hole injection interface layer. However, the mechanism of photodegradation has not been elucidated in detail.

One aspect of the present invention is to provide an organic solar cell having high power conversion efficiency and excellent light stability.

According to an aspect of the present invention, a double interface layer including a first electrode, a metal oxide layer on the first electrode, and an alignment layer on the metal oxide layer, a photoactive layer on the double interface layer, and an agent on the photoactive layer An organic solar cell including two electrodes is disclosed.

The metal oxide layer may include, for example, a molybdenum oxide layer, a tungsten oxide layer, or a rhenium oxide layer.

The alignment layer may be a metal halide layer. The alignment layer is, for example, copper iodide (CuI), copper bromide (CuBr), copper chloride (CuCl), copper sulfide (CuS), copper disulfide (CuS ₂ ), silver bromide (AgBr) or silver iodide (AgI) Can be made.

The photoactive layer may have a stacked structure including a donor layer made of a donor material on the metal oxide layer and an acceptor layer made of an acceptor material on the donor layer. Alternatively, the photoactive layer may be made of a bulk heterojunction of a donor material and an acceptor material.

The donor material may be a π-conjugated compound. The donor material may be, for example, CuPc (Copper Phthalocyanine: copper phthalocyanine), ZnPc (Zinc Phthalocyanine: zinc phthalocyanine), PbPc (lead phthalocyanine: lead phthalocyanine), ClAlPc (chloroaluminum phthalocyanine: aluminum phthalocyanine chloride, Subphthalocyanine chloride, Subphthalocyanine chloride) : Boron chloride subphthalocyanine), TiOPc (Oxytitanium phthalocyanine), pentacene (pentacene), diindenoperylene (diindenoperylene), or oligothiophene (oligothiophene) derivatives.

Or the donor material is for example poly (p-phenylenevinylene) and its derivatives, cyano-containing poly (p-phenylenevinylene), cyano and thiophene-containing poly (p-phenylenevinylene), Acetylene-containing poly (p-phenylenevinylene); Fluorene-based conjugated polymers; Poly (2,7-carbazole) polymers, indole [3,2-b] carbazole polymers; Poly (3-alkylthiophene) and derivatives thereof, poly (3-hexylselenophene), isotianaphthene-based polymer, cyclopenta [2,1-b: 3,4 -b '] dithiophene-based polymer, silafluorene- and dithieno [3,2-b: 2', 3'-d] silol (dithieno [3,2-b: 2 ', 3') -d] silole) polymer, dithieno [3,2-b: 2 ', 3'-d] pyrrole polymer, benzo [1,2-b: 4,5-b '] dithiophene (benzo [1,2-b: 4,5-b'] dithiophene) polymer, thieno [3,4-b] thiophene [3,4-b] thiophene) polymer, thieno [3,2-b] thiophene polymer, poly (thienylvinylene) s (PTV); poly (arylene ethylene); triarylamine-based polymer; phenothiazine-based polymer; porphyrin-based polymer; or platinum metallopolyyne-based polymer .

The acceptor layer is C ₆₀ fullerene, C ₇₀ fullerene, PCBM ([6,6] -phenyl-C ₆₁ -butyric acid methyl ester: [6,6] -phenyl-C ₆₁ -butyl acid methyl ester), C ₇₁ -PCBM, perylene, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride: 3,4,9,10-perylenetetracarboxylic dianhydride) or PTCBI (3,4,9,10 -perylenetetracarboxylic bisbenzimidazole: 3,4,9,10-perylenetetracarboxylic bisbenzimidazole).

The electron transport layer on the acceptor layer may be further included.

The electron transport layer is BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine), Bphen (4,7-diphenyl-1,10-phenanthroline), B3PYMPM (bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine), 3TPYMB (Tris- [3- (3-pyridyl) mesityl] borane), BmPyPb ((1,3-bis (3,5-dipyrid-3 -yl-phenyl) benzene), TmPyPb ((1,3,5-tri (m-pyrid-3-yl-phenyl) benzene), OXD7 (1,3-bis (4-tert-butylphenyl-1,3, 4-oxadiazoyl) phenylene), OXD8 (1,3-bis (4- (dimethylamino) -phenyl-1,3,4-oxadiazoyl) phenylene), or TAZ (3- (biphenyl-4-yl) -4-phenyl -5- (4-tert-butylphenyl) -1,2,4-triazole)).

The substrate may be a transparent glass substrate or PET (Poly Ethylene Terephthlate), PES (Polyethersulphone: polyether sulfone), PC (Polycarbonate: polycarbonate), PI (Polyimide: polyimide), PEN (Polyethylene Naphthalate) Phthalate) or PAR (Polyarylate).

The first electrode includes tin oxide (SnO ₂ ), AZO (Al-doped Zinc Oxide: Al doped zinc oxide), ITO (Indium Tin Oxide: Indium Tin Oxide), FTO (Flourine-doped Tin Oxide: fluorine doped tin Oxide) or IZO (Indium Zinc Oxide).

The second electrode may include Al, Ca, Mg, K, Ti, Li, or an alloy thereof.

By using a double layer of a metal oxide layer and a halogenated metal layer between the electrode and the photoactive layer, a low molecular organic solar cell having high power conversion efficiency and light stability can be provided.

1 is a cross-sectional view schematically showing an organic solar cell according to one embodiment.
2 is a current density-voltage graph of the organic solar cell device of Example 1, Comparative Example 1, and Comparative Example 2. FIG.
3A to 3C are graphs of current density-voltage measured while irradiating light to the organic solar cells of Comparative Example 1, Comparative Example 2 and Example 1 for 60 minutes, respectively.
4A to 4C illustrate changes in short-circuit current density, open voltage, filling rate and power conversion efficiency measured while irradiating light to the organic solar cells of Comparative Examples 1, 2 and 1 for 60 minutes, respectively. It is a graph.
5A to 5C are current density-voltage graphs when the organic solar cells of Comparative Example 2 are irradiated with 325 nm, 442 nm, and 633 nm laser light, respectively.
6A-6C are TOF-SIMS depth profiles before and after aging of Samples 1 to 3, respectively.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

 1 is a cross-sectional view schematically showing an organic solar cell 100 according to one embodiment. Referring to FIG. 1, the organic solar cell 100 includes a double interface layer of a substrate 110, an anode layer 120, a metal oxide layer 131, and an alignment layer 132 that are sequentially stacked. 130, a photoactive layer 140, an electron transport layer 150, and a cathode layer 160.

The substrate 110 is for supporting an organic solar cell. For example, the substrate 110 may be a transparent glass substrate, PET (Polyethylene Terephthlate), PES (Polyethersulphone), PC (Polycarbonate) A transparent plastic substrate such as polyimide (polyimide), PEN (polyethylene naphthalate), or PAR (polyarylate) may be used.

The anode layer 120 can be made of a conductive transparent electrode of a metal oxide having a high work function. The anode layer 120 may include, for example, tin oxide (SnO ₂ ), AZO (Al-doped Zinc Oxide: Al doped zinc oxide), ITO (Indium Tin Oxide: Indium Tin Oxide), FTO (Flourine-doped Tin Oxide). : Fluorine-doped tin oxide) or IZO (Indium Zinc Oxide).

The double interfacial layer 130 may include a metal oxide layer 131 and an alignment layer 132 on the metal oxide layer 131.

The metal oxide layer 131 may be formed of, for example, a molybdenum oxide, a tungsten oxide layer, or a rhenium oxide layer including MoO ₃ . When light is irradiated, oxygen may be photo-induced release from the anode layer 120 made of a metal oxide, and the oxygen may diffuse into the alignment layer 132. Oxygen diffused from the anode layer 120 to the alignment layer 132 may react with the metal compound of the alignment layer 132 to release metal atoms. The metal atoms emitted from the alignment layer 132 may diffuse to the photoactive layer 140 to form an electrical path, which may deteriorate the solar cell device by losing the diode characteristics of the solar cell. . The metal oxide layer 131 prevents oxygen induced by light-induced emission from the anode layer 120 from diffusing into the alignment layer 132 by irradiation with light to react with the released oxygen of the metal compound of the alignment layer 132. It is possible to prevent the emission of atoms. By preventing diffusion of metal atoms from the alignment layer 132 into the photoactive layer 140, deterioration of the solar cell device may be prevented.

The alignment layer 132 is a layer for improving the alignment of molecules constituting the photoactive layer 140. For example, when the photoactive layer 140 is composed of a donor layer and an acceptor layer on the donor layer, the energetic layer 132 may improve the alignment of molecules of the donor layer. The alignment layer 132 may be made of a metal halide layer. The metal halide layer is, for example, copper iodide (CuI), copper bromide (CuBr), copper chloride (CuCl), copper sulfide (CuS), copper disulfide (CuS ₂ ), silver bromide (AgBr), silver iodide (AgI), or the like. It may include a metal compound of, preferably copper iodide (CuI). The alignment layer 132 is a planar stack of molecules of the compound of the photoactive layer 140 in contact with the alignment layer 132 is a planar π-conjugated compound, the plane of the molecules of the compound parallel to the substrate Can help. Planar π-conjugated compounds, when stacked in a plane, can facilitate charge transport due to overlap of π orbitals between neighboring molecules up and down. When the metal compound of the alignment layer 132 does not react with oxygen and maintains a stable state, deterioration of the solar cell device may be prevented.

The photoactive layer 140 may include a donor layer made of a donor material and an acceptor layer made of an acceptor material, and a donor material and an acceptor material may form a bulk heterojunction, but the photoactive layer 140 may be The structure is not limited to these.

The donor material may be a p-type semiconductor as a material whose main charge carriers are holes. The donor material may be a planar π-conjugated compound as described above, for example CuPc (Copper Phthalocyanine (copper phthalocyanine), ZnPc (Zinc Phthalocyanine (zinc phthalocyanine)), PbPc (lead phthalocyanine) Phthalocyanine-based materials such as ClAlPc (chloroaluminum phthalocyanine), SubPc (boron subphthalocyanine chloride) or TiOPc (Oxytitanium phthalocyanine: titanium phthalocyanine). The donor material may also include penylene, perylene derivatives such as diindenoperylene (diindenoperylene), or oligothiophene derivatives.

The donor material may also consist of π conjugated polymer. π conjugated polymers include, for example, poly (p-phenylenevinylene) and derivatives thereof, cyano-containing poly (p-phenylenevinylene), cyano and thiophene-containing poly (p-phenylenevinylene) Poly (p-phenylenevinylene) -based conjugated polymers such as acetylene-containing poly (p-phenylenevinylene); Fluorene-based copolymers containing electron-rich moieties, fluorene-based copolymers containing electron-deficient moieties, fluorenes containing phosphorescent complexes Fluorene-based conjugated polymers such as system conjugated polymers; Carbazole conjugated polymers such as poly (2,7-carbazole) polymers or indole [3,2-b] carbazole polymers; Poly (3-alkylthiophene) and derivatives thereof, poly (3-hexylselenophene), polythiophene with conjugated side chain, isothiaphenane polymer, cyclopenta [ 2,1-b: 3,4-b '] dithiophene-based polymer, silafluorene- and dithieno [3,2-b: 2', 3'-d] silol (dithieno [3, 2-b: 2 ′, 3′-d] silole) polymer, dithieno [3,2-b: 2 ′, 3′-d] pyrrole (dithieno [3,2-b: 2 ′, 3 ′) -d] pyrrole polymer, benzo [1,2-b: 4,5-b '] dithiophene (benzo [1,2-b: 4,5-b'] dithiophene polymer, thieno [3 , 4-b] thiophene (thieno [3,4-b] thiophene) polymer, thieno [3,2-b] thiophene polymer, other fused ( fused) thiophene conjugated polymer, thiophene conjugated polymer such as poly (thienylvinylenes) (PTV); poly (aryleneethylene); triarylamine- and phenothiazine ( phenothiazine-based polymers, porphyrin-based polymers, or platinum It may include the phthaloyl poly (metallopolyyne platinum) based polymers.

The acceptor material may be an n-type semiconductor as the main charge carrier is an electron. For example, C ₆₀ or C ₇₀ fullerenes, such as, PCBM ([6,6] -phenyl- C 61 -butyric acid methyl ester) or a C ₆₀ or C ₇₀ fullerene derivatives such as C ₇₁ -PCBM, perylene (perylene ), PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride: 3,4,9,10-perylenetetracarboxylic dianhydride) or PTCBI (3,4,9,10-perylenetetracarboxylic bisbenzimidazole: 3,4 Perylene derivatives, such as (9,10-perylenetetracarboxylic bisbenzimidazole).

When the conductive metal is diffused into the photoactive layer 140, a new path for the charges separated from the exciton is generated, thereby reducing the shunt resistance of the device, thereby deteriorating the diode characteristics of the device. Therefore, the conductive metal should not diffuse from the other layer to the photoactive layer 140. The dual interfacial layer 130 including the metal oxide layer 131 can prevent diffusion of photoinduced emission oxygen from the anode layer 120 and thus diffusion of metal atoms from the alignment layer 132 as described above. Can be.

The electron transport layer 150 may receive electrons from the photoactive layer 140 to facilitate transport to the cathode layer 160 or prevent diffusion of excitons from the photoactive layer 140 to the cathode layer 160. Electron transport layer 150 is, for example, BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine), Bphen (4,7-diphenyl-1,10-phenanthroline), B3PYMPM (bis -4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine), 3TPYMB (Tris- [3- (3-pyridyl) mesityl] borane), BmPyPb ((1,3-bis (3, 5-dipyrid-3-yl-phenyl) benzene), TmPyPb ((1,3,5-tri (m-pyrid-3-yl-phenyl) benzene), OXD7 (1,3-bis (4-tert-butylphenyl -1,3,4-oxadiazoyl) phenylene), OXD8 (1,3-bis (4- (dimethylamino) -phenyl-1,3,4-oxadiazoyl) phenylene), or TAZ (3- (biphenyl-4-yl ) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole)) can be used.

The cathode layer 170 may be made of a metal having a low work function. The cathode layer 170 may be made of, for example, Al, Ca, Mg, K, Ti, Li, or an alloy thereof.

Hereinafter, a method of manufacturing the organic solar cell 100 according to another embodiment.

Referring back to FIG. 1, the double interface layer 130, the photoactive layer 140, and the electron transport layer of the anode layer 120, the metal oxide layer 131, and the alignment layer 132 on the substrate 110. 150 and the cathode layer 170 are sequentially formed.

The substrate 110 may be formed of a transparent glass substrate as described above or a transparent plastic substrate such as PET, PES, PC, PI, PEN, or PAR, but is not limited thereto.

The anode layer 120 may be formed of a conductive transparent electrode of a metal oxide having a high work function. The conductive transparent electrode of the metal oxide having a high work function may include, for example, a tin oxide (SnO ₂ ), AZO, ITO, FTO, or IZO. The conductive transparent electrode of the metal oxide may be formed by thermal evaporation or sputtering.

The dual interface layer 130 may be formed of the metal oxide layer 131 and the alignment layer 132 thereon. The metal oxide layer 131 may be formed of molybdenum oxide, tungsten oxide, or rhenium oxide including MoO ₃ , and may be formed by thermal deposition or sputtering. The alignment layer 132 may be formed of a metal halide layer. For example, the alignment layer 132 may be copper iodide (CuI), copper bromide (CuBr), copper chloride (CuCl), copper sulfide (CuS), copper disulfide (CuS ₂ ), silver bromide (AgBr) or silver iodide ( AgI) or the like, and for example, can be formed by a method of thermal evaporation.

The photoactive layer 140 may be formed in a stacked structure. In this case, the donor layer may be formed of a phthalocyanine-based material such as CuPc, ZnPc, PbPc, ClAlPc, SubPc, or TiOPc, a perylene derivative such as pentacene or DIP, or an oligothiophene derivative. It can be formed as. The donor layer may also be prepared by the π conjugated polymer as described above, for example, poly (p-phenylenevinylene) and its derivatives, cyano-containing poly (p-phenylenevinylene), cyano and thiophene-containing poly poly (p-phenylenevinylene) -based conjugated polymers such as (p-phenylenevinylene) and acetylene-containing poly (p-phenylenevinylene); Fluorene-based copolymers containing electron-rich moieties, fluorene-based copolymers containing electron-deficient moieties, fluorenes containing phosphorescent complexes Fluorene-based conjugated polymers such as system conjugated polymers; Carbazole conjugated polymers such as poly (2,7-carbazole) polymers or indole [3,2-b] carbazole polymers; Poly (3-alkylthiophene) and derivatives thereof, poly (3-hexylselenophene), polythiophene with conjugated side chain, isothiaphenane polymer, cyclopenta [ 2,1-b: 3,4-b '] dithiophene-based polymer, silafluorene- and dithieno [3,2-b: 2', 3'-d] silol (dithieno [3, 2-b: 2 ′, 3′-d] silole) polymer, dithieno [3,2-b: 2 ′, 3′-d] pyrrole (dithieno [3,2-b: 2 ′, 3 ′) -d] pyrrole polymer, benzo [1,2-b: 4,5-b '] dithiophene (benzo [1,2-b: 4,5-b'] dithiophene polymer, thieno [3 , 4-b] thiophene (thieno [3,4-b] thiophene) polymer, thieno [3,2-b] thiophene polymer, other fused ( fused) thiophene conjugated polymer, thiophene conjugated polymer such as poly (thienylvinylenes) (PTV); poly (aryleneethylene); triarylamine- and phenothiazine ( phenothiazine-based polymers, porphyrin-based polymers, or platinum The layer of the polymer may be formed by a spin coating method, a dip coating method, a blade coating method, an inkjet printing method, a nozzle printing method, or a gravure method or an offset printing method. It can be formed using a two-roll method.

The acceptor layer may be formed by, for example C ₆₀ or C ₇₀ and fullerene, PCBM, C ₆₀ or perylene derivatives, such as derivatives, perylene, or PTCDA PTCBI of C ₇₀ fullerenes such as C ₇₁ -PCBM like, For example, it can form by a thermal evaporation method.

When the photoactive layer 140 is formed in a bulk heterojunction structure, for example, a mixed solution of a donor material and an acceptor material is used, and spin coating, dip coating, blade coating, inkjet printing, and nozzle printing are used. The photoactive layer 140 may be formed using a roll-to-roll method such as a gravure method or an offset printing method.

The electron transport layer 150 may be formed of, for example, BCP, BPhen, B3PYMPM, 3TPYMB, BmPyPb, TmPyPb, OXD7, OXD8, or TAZ, and may be formed by, for example, thermal deposition.

The cathode layer 170 may be formed of a metal having a low work function. Metals having a low work function can be, for example, Al, Ca, Mg, K, Ti, Li or alloys thereof. The negative electrode layer 170 may be formed by, for example, thermal deposition or sputtering.

Example  One

Layer structure of glass substrate / ITO (150nm) / MoO ₃ (3nm) / CuI (3nm) / ZnPc (25nm) / C ₆₀ (40nm) / BCP (8nm) / Al (100nm) An organic solar cell having was prepared. A 150 nm thick ITO coated glass substrate was washed successively with acetone and isopropyl alcohol and then exposed to UV / ozone for 10 minutes. A 3 nm thick MoO ₃ and 3 nm thick CuI layer was deposited on an ITO coated glass substrate at a deposition rate of 0.2 μs / s. Then the BCP of C ₆₀ and 8㎚ thickness of ZnPc, 40㎚ thickness of the CuI layer thickness on 25㎚ ^10-7 The films were thermally deposited in order at a deposition rate of 1 kW / s under a pressure of Torr. A 100 nm thick Al cathode layer was then deposited over the BCP layer using a shadow mask. All layers were deposited while maintaining a vacuum continuously. The active area of the device was 4 mm 2. The insulating layer on the ITO electrode and the anode layer on top defined the cell region. The device was then sealed with a glass can using an epoxy resin in a nitrogen atmosphere.

Comparative Example  One

An organic solar cell was manufactured in the same manner as in Example 1, except that the MoO ₃ and CuI layers were not formed. That is, an organic solar cell having a layer structure of a glass substrate / ITO (150 nm) / ZnPc (25 nm) / C ₆₀ (40 nm) / BCP (8 nm) / Al (100 nm) was prepared.

Comparative Example  2

An organic solar cell was manufactured in the same manner as in Example 1, except that the MoO ₃ layer was not formed. That is, an organic solar cell having a layer structure of a glass substrate / ITO (150 nm) / Cu (3 nm) / ZnPc (25 nm) / C ₆₀ (40 nm) / BCP (8 nm) / Al (100 nm) Prepared.

Current-voltage characteristic

The current density vs. voltage characteristics of the organic solar cell elements of Examples 1, Comparative Examples 1 and 2 were measured using an AM 1.5G 100 mW / cm ² solar simulator (300 W Oriel 69911A). (Keithley 237). Before each measurement, the measurement setup was calibrated using a reference Si solar cell accredited by the National Renewable Energy Laboratory covered with a KG-5 filter.

2 is a current density-voltage graph of the organic solar cell device of Example 1, Comparative Example 1, and Comparative Example 2. FIG. Current density while varying the voltage between the ITO electrode and the Al electrode of the organic solar cell elements of Example 1, Comparative Example 1 and Comparative Example 2 while irradiating 100 mW / cm ² of AM 1.5G from -0.3V to 0.8V Was measured.

Referring to FIG. 2, the organic solar cell of Comparative Example 1 showed a short circuit current density (J _SC ) −4.83 mA / cm ² , an open voltage (V _OC ) 0.46V, and a fill factor (FF) of 0.57. On the other hand, the power conversion efficiency (η _p ) of the organic solar cell of Comparative Example 1 was 1.27%. These values were almost in agreement with those conventionally known for the structure of Comparative Example 1.

The organic solar cell of Comparative Example 2 exhibited a short circuit current density (J _SC ) -8.63 mA / cm ² , an open voltage (V _OC ) 0.61V, and a fill factor (FF) 0.62. On the other hand, the power conversion efficiency (η _p ) of the organic solar cell of Comparative Example 2 was 3.30%. From this, it can be seen that the performance of the organic solar cell of Comparative Example 2 was significantly improved compared to that of the organic solar cell of Comparative Example 1.

The organic solar cell of Example 1 exhibited a short circuit current density (J _SC ) -8.19 mA / cm ² , an open voltage (V _OC ) 0.56V, and a fill factor (FF) 0.63. On the other hand, the power conversion efficiency (η _p ) of the organic solar cell of Example 1 was 2.89%. The performance of the organic solar cell of Example 1 was slightly lower than that of Comparative Example 2 containing only a CuI layer as an interfacial layer, but was more than two times greater than that of Comparative Example 1 containing no interfacial layer.

Table 1 summarizes the short-circuit current densities, open voltages, fill rates, and power conversion efficiencies of Example 1, Comparative Example 1, and Comparative Example 2.

Short circuit current density
(mA / cm ² ) Open-circuit voltage
(V) Fill factor Power conversion efficiency
(%) Example 1 -8.19 0.56 0.63 2.89 Comparative Example 1 -4.83 0.46 0.57 1.27 Comparative Example 2 -8.63 0.61 0.62 3.30

Optical stability ( photo - stability ) Measure

3A to 3C are graphs of current density-voltage measured while irradiating light to the organic solar cells of Comparative Example 1, Comparative Example 2 and Example 1 for 60 minutes, respectively.

4A to 4C illustrate changes in short-circuit current density, open voltage, filling rate and power conversion efficiency measured while irradiating light to the organic solar cells of Comparative Examples 1, 2 and 1 for 60 minutes, respectively. It is a graph.

Referring to FIG. 3A, in the organic solar cell of Comparative Example 1, an S-shaped kink was developed in a current density-voltage curve according to light irradiation, indicating a deterioration in the performance of the organic solar cell. Meanwhile, referring to FIGS. 4A and 3A, the power conversion efficiency of the organic solar cell of Comparative Example 1 decreased below 70% of the initial value after 60 minutes of light irradiation, without a significant change in short-circuit current density and open voltage. It can be seen that mainly due to the decrease in the filling rate. This behavior is believed to be due to the reduction of the work function (absolute value) of ITO by UV light irradiation and the formation of a hole injection barrier layer at the interface between the ITO electrode and the ZnPc layer.

3B and 4B, the organic solar cell of Comparative Example 2 exhibits very different deterioration behavior from that of Comparative Example 1 under light irradiation. Under light irradiation, the shunt resistance of the organic solar cell of Comparative Example 2 was sharply reduced, which resulted in a decrease in the filling rate and the open voltage. This behavior indicates that the characteristics of the pn junction disappeared by forming a new charge transfer path by light irradiation in the organic solar cell of Comparative Example 2. Meanwhile, referring to FIG. 4B, the power conversion efficiency of the organic solar cell of Comparative Example 2 was reduced to about 30% of the initial value after 60 minutes of light irradiation.

Referring to FIGS. 3C and 4C, it can be seen that the organic solar cell of Example 1 has little change in current density-voltage characteristics, and almost no change in short-circuit current density, open voltage, fill factor, and power conversion efficiency. . This indicates that the organic solar cell of Example 1 has high light stability.

By wavelength  Light safety measurement

While the performance of the organic solar cell of Comparative Example 2 was excellent, the current density-voltage characteristic was measured while irradiating light sources of three different wavelengths for 30 minutes in order to elucidate the photodegradation mechanism from the result of greatly deteriorating light stability.

5A to 5C are respectively simulated sunlight of AM 1.5G 100 mW / cm ² in a nitrogen atmosphere in the organic solar cell of Comparative Example 2 as 325 nm HeCd laser light (a) of 3.9 mW / cm ² , 3.6 mW / cm ^It is a current density-voltage graph in the case of irradiating ² 442 nm HeCd laser beams (b) and 633 nm HeNe laser beams (c) of 4 mW / cm ² . Light of 633 nm is only absorbed by ZnPc, light of 442 nm is mainly absorbed by C ₆₀ , and 325 nm light is absorbed by ITO. Therefore, it is possible to infer whether the deterioration of the device is caused by the deterioration of which material by confirming which deterioration of the device occurs by light irradiation at which wavelength.

Referring to Fig. 5C, since the 633 nm laser light c absorbed by ZnPc does not deteriorate the device at all, the excitation of ZnPc does not deteriorate the device. 5B and 5C, in the case of light irradiation at 442 nm (b) no decrease in the fill rate and the open voltage was observed, whereas a decrease in the fill rate and open voltage was observed by (325) light irradiation at 325 nm. Observed. This indicates that the photodegradation of the device containing CuI is mainly due to the UV induced reaction of CuI at the interface between CuI and the ITO electrode.

Depth profile ( depth profile )

Depth profile of mass spectra before and after irradiation of sample devices using time-of-flight secondary ion mass spectrometry (TOF-SIMS) (IONTOF GmbH) to determine the cause of device degradation It was. In order to obtain the mass spectrum, 25 keV Bi ⁺ of 0.9 으로서 as primary ion Ions were used. Mass spectra were obtained in an area of 50 × 50 μm ² . 31 kPa of 0.5 keV Cs + ions were used for the depth profile. The sputtered area was 200 × 200 μm ² . Samples 1-3 for depth profile were each prepared on 0.1 × 0.1 cm ² ITO glass substrates. Light irradiation for aging used a UV light source of 15 mW / cm ² .

Sample 1

ITO glass (150 nm) / MoO ₃ (3 nm) / CuI (3 nm) / ZnPc in the same manner as in the device fabrication method of Example 1 except that BCP (8 nm) / Al (100 nm) was not formed A layer structure of (25 nm) / C ₆₀ (40 nm) was formed.

Sample 2

A layer of ITO glass (150 nm) / ZnPc (25 nm) / C ₆₀ (40 nm) in the same manner as in the device fabrication method of Comparative Example 1 except that BCP (8 nm) / Al (100 nm) was not formed The structure was formed.

Sample 3

ITO glass (150 nm) / CuI (3 nm) / ZnPc (25 nm) / C _{60 in the} same manner as in the device fabrication method of Comparative Example 2 except that BCP (8 nm) / Al (100 nm) was not formed A layer structure of (40 nm) was formed.

6A-6C are TOF-SIMS depth profiles before and after aging of Samples 1 to 3, respectively. Ions were chosen to define the interface between the layers. CuI ^- ions as markers for indicating the CuI layer, C ₂ N ₂ Cs ^- and ZnC ₂ N ₂ ^- ions as markers for indicating the ZnPc layer, C ^- as markers for indicating the C ₆₀ layer In ^- ions were selected as the marker for the ions representing the ITO layer.

Referring to FIG. 6A, no change in the mass spectral depth profile of the selected ions before and after aging of Sample 1 is observed.

Referring to FIG. 6B, no noticeable change was observed from the sample after aging compared to the sample before aging in the mass spectral depth profile of the selected ions of Sample 2.

6C, a significant difference in depth profile was observed before and after aging in the mass spectral depth profile of the selected ions of Sample 3. After irradiation of UV light, the strength of CuI ^- was reduced to almost zero, while the strength of Cu ^- was larger and wider. This shows that CuI decomposed | disassembled into Cu by light irradiation. Cu ^- were of the tail (tail) moves to the interface between the ZnPc layer and C layer _60, this indicates that the decomposition Cu atom or ion is diffused into ZnPc layer has reached the interface between the layer and the ZnPc C ₆₀ layer.

From this, it can be inferred that the diffusion of Cu induced by light forms a new migration path of charge separated from the p-n junction diode, reducing the device's short circuit resistance. Prolonged irradiation results in a loss of diode characteristics due to a decrease in short circuit resistance. These observations of the depth profile are consistent with the photodegradation characteristics of the organic solar cell device including the CuI layer, and it is determined that the organic solar cell device of Example 1 effectively blocks photodegradation caused by the CuI layer.

100: organic solar cell 110: substrate
120: anode layer 130: double interface layer
131: molybdenum oxide layer 132: alignment layer
140: photoactive layer 141: donor layer
142: acceptor layer 150: electron transport layer
160: cathode layer

Claims (17)

Board;
An anode layer on the substrate;
A double interface layer comprising a metal oxide layer on the anode layer and an alignment layer on the metal oxide layer;
A photoactive layer on the dual interface layer;
Including a cathode layer on the photoactive layer,
The metal oxide layer is composed of a molybdenum oxide layer, a tungsten oxide layer or rhenium oxide layer,
The alignment layer is an organic solar cell consisting of a metal halide layer. delete delete The organic solar cell of claim 1, wherein the metal halide layer includes copper iodide (CuI), copper bromide (CuBr), silver bromide (AgBr), or silver iodide (AgI). delete The organic solar cell of claim 1, wherein the photoactive layer comprises a donor layer made of a donor material on the metal oxide layer and an acceptor layer made of an acceptor material on the donor layer. The organic solar cell of claim 1, wherein the photoactive layer comprises a bulk heterojunction of a donor material and an acceptor material. The organic solar cell of claim 6 or 7, wherein the donor material is a π-conjugated compound. The method of claim 8, wherein the π conjugated compound is CuPc (Copper Phthalocyanine (copper phthalocyanine), ZnPc (Zinc Phthalocyanine (zinc phthalocyanine)), PbPc (lead phthalocyanine (lead phthalocyanine)), ClAlPc (chloroaluminum phthalocyanine) aluminum phthalocyanine) organic sun including boron subphthalocyanine chloride, boron subphthalocyanine, TiOPc (Oxytitamium phthalocyanine: titanium oxide phthalocyanine), pentacene, diindenoperylene (DIP), or oligothiophene derivatives battery. 9. The polyconjugated compound of claim 8, wherein the π conjugated compound is poly (p-phenylenevinylene) and its derivatives, cyano-containing poly (p-phenylenevinylene), cyano and thiophene-containing poly (p-phenylene Vinylene), acetylene-containing poly (p-phenylenevinylene); Fluorene-based conjugated polymers; Poly (2,7-carbazole) polymers, indole [3,2-b] carbazole polymers; Poly (3-alkylthiophene) and derivatives thereof, poly (3-hexylselenophene), isotianaphthene-based polymer, cyclopenta [2,1-b: 3,4 -b '] dithiophene-based polymer, silafluorene- and dithieno [3,2-b: 2', 3'-d] silol (dithieno [3,2-b: 2 ', 3') -d] silole) polymer, dithieno [3,2-b: 2 ', 3'-d] pyrrole polymer, benzo [1,2-b: 4,5-b '] dithiophene (benzo [1,2-b: 4,5-b'] dithiophene) polymer, thieno [3,4-b] thiophene [3,4-b] thiophene) polymer, thieno [3,2-b] thiophene polymer, poly (thienylvinylene) s (PTV); poly (arylene ethylene); triarylamine-based polymer; phenothiazine-based polymer; porphyrin-based polymer; or organic metal including platinum metallopolyyne-based polymer battery. delete The method of claim 6, wherein the acceptor layer is C ₆₀ fullerene, C ₇₀ fullerene, PCBM ([6,6] -phenyl-C ₆₁ -butyric acid methyl ester: [6,6] -phenyl-C ₆₁ -butyl acid Methyl ester), C ₇₁ -PCBM, perylene, PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride: 3,4,9,10-perylenetetracarboxylic dianhydride) or PTCBI (3 , 4,9,10-perylenetetracarboxylic bisbenzimidazole: an organic solar cell comprising 3,4,9,10-perylenetetracarboxylic bisbenzimidazole). The organic solar cell of claim 6, further comprising an electron transport layer on the acceptor layer. The method of claim 13, wherein the electron transport layer is BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline, bathucuproine), Bphen (4,7-diphenyl-1,10-phenanthroline), B3PYMPM ( bis-4,6- (3,5-di-3-pyridylphenyl) -2-methylpyrimidine), 3TPYMB (Tris- [3- (3-pyridyl) mesityl] borane), BmPyPb ((1,3-bis (3 , 5-dipyrid-3-yl-phenyl) benzene), TmPyPb ((1,3,5-tri (m-pyrid-3-yl-phenyl) benzene), OXD7 (1,3-bis (4-tert- butylphenyl-1,3,4-oxadiazoyl) phenylene), OXD8 (1,3-bis (4- (dimethylamino) -phenyl-1,3,4-oxadiazoyl) phenylene), or TAZ (3- (biphenyl-4- yl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole)). The method of claim 1, wherein the substrate is a transparent glass substrate or PET (Poly Ethylene Terephthlate), PES (Polyethersulphone: polyether sulfone), PC (Polycarbonate: polycarbonate), PI (Polyimide), PEN Organic solar cell comprising (Polyethylene Naphthalate: polyethylene naphthalate) or PAR (Polyarylate: polyarylate). The method of claim 1, wherein the anode layer is tin oxide (SnO ₂ ), AZO (Al-doped Zinc Oxide: Al doped zinc oxide), ITO (Indium Tin Oxide: Indium Tin Oxide), FTO (Flourine-doped Tin Oxide) : Organic solar cell comprising fluorine-doped tin oxide) or IZO (Indium Zinc Oxide). The organic solar cell of claim 1, wherein the cathode layer comprises Al, Ca, Mg, K, Ti, Li, or an alloy thereof.

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