JP2020137161A - Photoelectric conversion device - Google Patents

Abstract

To provide a photoelectric conversion device using a perovskite solar cell capable of suppressing a decrease in power generation performance when shifting from a dark environment to a light intensity that can generate electricity.SOLUTION: The photoelectric conversion device includes: a perovskite solar cell 24; and a bias voltage applying mechanism 20, electrically connected to the solar cell, capable of applying a bias voltage to the solar cell. The bias voltage applying mechanism includes: voltage output means 21 for applying a voltage to a solar battery cell; and control means 22 for controlling to apply a bias voltage Vb to the solar cell after the solar cell is exposed to a condition of illuminance of 10 Lx or less and before the solar cell is again exposed to a situation where the illuminance exceeds 10 Lx.SELECTED DRAWING: Figure 4

Description

The present invention relates to a photoelectric conversion device having a perovskite type solar cell.

In recent years, perovskite-type solar cells have been attracting attention as materials that have the potential to replace silicon-based photovoltaic cells due to their high photoelectric conversion efficiency and ease of manufacture. Further, since it has a feature of showing excellent power generation efficiency even under low illuminance, it is considered to be an effective application such as being used as a source of sensor data of a sensor operating in a particularly small area or an IoT device.

For example, Patent Document 1 states that by incorporating a perovskite-type solar cell into an electronic device, a device having a high degree of freedom in decoration can be provided.
Further, Patent Document 2 discloses a technique of passing a current through a light absorption layer during non-power generation because the conversion efficiency of a perovskite solar cell also decreases with time if it is continuously irradiated with sunlight.

JP-A-2018-125359 International Publication Patent No. 2017-221535

When the present inventors examined the application of a perovskite-type solar cell, the perovskite-type solar cell was placed in a dark environment where it could not generate electricity, and then immediately after being placed under a light intensity capable of generating electricity. It turned out that the power generation capacity did not appear. According to the study by the present inventors, the perovskite type solar cell maintains a low power generation voltage for a while when it is placed under a light intensity capable of generating power after being placed in a dark environment where it cannot generate power. , It was found that it takes about 10 minutes to demonstrate the original power generation capacity.
An object of the present invention is to provide a photoelectric conversion device using a perovskite type solar cell, which can suppress a decrease in power generation voltage when shifting from a dark environment to a light intensity capable of generating power.

The present inventors have proceeded with research to solve the above problems, and after the environment in which the perovskite-type solar cell is placed becomes below a certain illuminance, the perovskite-type solar cell is subjected to an appropriate bias voltage having the same polarity as during power generation. We have found that by applying the power, the desired power generation capacity can be quickly developed without causing such a problem, and the present invention has been reached. The present invention includes the following.

(1) It has a perovskite type solar cell and a bias voltage applying mechanism that is electrically connected to the solar cell and can apply a bias voltage to the solar cell.
The bias voltage applying mechanism includes a voltage output means for applying a voltage to the solar cell and a situation in which the solar cell is exposed to a state where the illuminance exceeds 10 Lx again after the solar cell is exposed to a state where the illuminance is 10 Lx or less. A photoelectric conversion device having a control means capable of controlling the application of a bias voltage Vb to the solar cell before being performed.
(2) The photoelectric conversion device according to (1), wherein the bias voltage applying mechanism has a detecting means for detecting that the illuminance is 10 Lx or less.
(3) The photoelectric conversion device according to (1) or (2), wherein the applied bias voltage Vb is Vb / Voc = 0.05 to 1.2 (however, Voc is a perovskite type solar cell under the condition of LED light source 200Lx. The open circuit voltage of the cell).
(4) The photoelectric conversion device according to (3), wherein the applied bias voltage Vb is Vb / Voc = 0.1 to 1.0.
(5) The photoelectric conversion device according to any one of (1) to (4), wherein the perovskite type solar cell is a normal type perovskite type solar cell.
(6) The photoelectric conversion device according to any one of (1) to (5), which has a perovskite type solar cell module in which the perovskite type solar cell is serialized.
(7) A method of operating a perovskite-type solar cell and a photoelectric conversion device having a bias voltage applying mechanism that is electrically connected to the solar cell and can apply a bias voltage to the solar cell. ,
A method of operating a photoelectric conversion device including an application step of applying a bias voltage Vb to the solar cell in a state where the solar cell has an illuminance of 10 Lx or less.

It is sectional drawing which shows typically the photoelectric conversion element as one Embodiment. It is sectional drawing which shows typically the solar cell as one Embodiment. It is sectional drawing which shows typically the solar cell module as one Embodiment. It is a block diagram which shows typically the photoelectric conversion apparatus as one Embodiment.

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents. It can be implemented with various modifications within the scope of the abstract.

The photoelectric conversion device according to an embodiment of the present invention includes a perovskite type solar cell and a bias voltage applying mechanism capable of applying a bias voltage to the solar cell. A perovskite-type solar cell usually has a pair of electrodes and an active layer containing a halide-based organic-inorganic perovskite semiconductor compound located between them. Details will be described later.

The photoelectric conversion device according to the present embodiment has a bias voltage applying mechanism, and the bias voltage applying mechanism is exposed to a voltage output means for applying a voltage to the solar cell and a state in which the solar cell has an illuminance of 10 Lx or less. After that, the solar cell is provided with a control means that can control the application of the bias voltage Vb to the solar cell before it is exposed to the situation where the illuminance exceeds 10 Lx again. Further, it may have a detecting means for detecting that the environment of the solar cell has an illuminance of 10 Lx or less.

In the perovskite type solar cell of the present embodiment, when placed in a dark environment with an illuminance of 10 Lx or less, methylammonium ions and iodine ions existing at both electrodes of the upper electrode and the lower electrode diffuse into the active layer. .. After that, even if it is placed under the light intensity that can generate power, the power generation capacity becomes insufficient until the ions move to both electrodes of the upper electrode and the lower electrode, and the power generation voltage remains low for a while. It is based on the finding that it takes about 10 minutes to demonstrate the power generation capacity of. The photoelectric conversion device of the present embodiment has a bias voltage application mechanism, and the bias voltage application mechanism exposes the perovskite type solar cell to a state of illuminance of 10 Lx or less, and then the solar cell again has an illuminance of 10 Lx. By controlling the application of the bias voltage Vb to the solar cell before being exposed to the situation exceeding the above, the original power generation capacity is promptly developed. Hereinafter, description will be made based on FIG.

FIG. 4 shows a schematic view of the photoelectric conversion device 200 of the present embodiment.
The perovskite type solar cell 24 is a voltage output means 2 in the bias voltage application mechanism 20.
It is electrically connected to 1.
The voltage output means 21 is not particularly limited as long as a bias voltage can be applied to the perovskite type solar cell 24, and may be an external power source. However, in an environment where a solar cell is usually installed, there is no outlet for an external power source. Therefore, a battery, a capacitor, or the like may be used as the voltage output means.

The voltage output means 21 is controlled by the control means 22 to output a voltage. As an example, the control of the control means 22 is performed by obtaining a numerical value of the illuminance detected by the illuminance detection means 23 such as an illuminance sensor, and when the illuminance is 10 Lx or less, the voltage output means 21 is used to control the perovskite type sun. Controlled so as to apply a bias voltage to the battery cell 24 can be mentioned.

The photoelectric conversion device of the present embodiment may not have the illuminance detecting means 23. For example, in a factory or home, when the illuminance when the light is turned off is 10 Lx or less and the time for turning on the light is predetermined, the light is turned on by incorporating a timer in the control means 22. The bias voltage can be controlled to be applied to the perovskite type solar cell 24 before a certain period of time.

The timing at which the bias voltage is applied to the perovskite type solar cell 24 by the voltage output means 21 is not particularly limited, but as described above, the perobskite type solar cell 24 once exposed to the dark environment has the original power generation capacity. Since it takes about 10 minutes to exert the effect, the bias voltage may be applied 5 minutes before the illuminance exceeds 10 Lx again, the bias voltage may be applied 7 minutes before, and the bias voltage may be applied 10 minutes before. May be applied. On the other hand, if the bias voltage is applied well before the time when the illuminance exceeds 10 Lx again, energy is wasted. Therefore, the voltage may be applied within 30 minutes, and the voltage may be applied within 20 minutes. It may be applied, and the voltage may be applied within 15 minutes before.
On the other hand, when it is unclear at what timing the illuminance exceeds 10 Lx again, control may be performed so that the voltage is applied when the illuminance becomes 10 Lx or less.

The bias voltage (Vb) applied to the perovskite type solar cell 24 by the voltage output means 21 is not particularly limited, but as a value with respect to the open circuit voltage (Voc) of the perovskite type solar cell under the LED light source 200Lx, that is, Vb / Voc. It is usually 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, and usually 1.2 or less, preferably 1.0 or less, more preferably 0. It is 8 or less. By setting the above lower limit range, it is possible to return to the original power generation characteristics by sufficiently promoting the ion diffusion in the active layer in the perovskite type solar cell, while by setting the above upper limit range, the perovskite type It is possible to suppress deterioration of the power generation characteristics of the solar cell.

The perovskite type solar cell 24 may be a normal type perovskite type solar cell or an inverted type perovskite type solar cell, but is a normal type perovskite type with respect to the reverse type perovskite type solar cell. The solar cell has a feature that the dopant of the hole transport layer becomes unstable in a dark environment such as an illuminance of 10 Lx or less, so that the power generation characteristics are more significantly deteriorated.

Next, a perovskite type solar cell (hereinafter, also referred to as a photoelectric conversion element) will be described with reference to the drawings.
[1. Photoelectric conversion element according to one embodiment]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a photoelectric conversion element. The photoelectric conversion element shown in FIG. 1 has a structure of a photoelectric conversion element used in a general thin-film solar cell, but the photoelectric conversion element according to the present embodiment is not limited to the structure shown in FIG. Absent. In the photoelectric conversion element 100 shown in FIG. 1, the active layer 103 is located between the pair of electrodes composed of the lower electrode 101 and the upper electrode 105. Further, in the photoelectric conversion element 100, the electron transport layer 102 may be arranged between the lower electrode 101 and the active layer 103, and the hole transport layer 104 may be arranged between the upper electrode 105 and the active layer 103. May be placed. Further, as shown in FIG. 1, the photoelectric conversion element 100 may have other layers such as a base material 106, an insulator layer, and a work function tuning layer.

[1.1 Active layer]
The active layer 103 is a layer on which photoelectric conversion is performed. When the photoelectric conversion element 100 receives light, the light is absorbed by the active layer 103 to generate carriers, and the generated carriers are taken out from the lower electrode 101 and the upper electrode 105.

In the present embodiment, the active layer 103 contains an organic-inorganic hybrid semiconductor material. The organic-inorganic hybrid semiconductor material refers to a material in which an organic component and an inorganic component are combined at the molecular level or the nano level, and exhibits semiconductor characteristics.

In the present embodiment, the organic-inorganic hybrid semiconductor material is a compound having a perovskite structure (hereinafter, may be referred to as a perovskite semiconductor compound). The perovskite semiconductor compound refers to a semiconductor compound having a perovskite structure. The perovskite semiconductor compound is not particularly limited, but can be selected from, for example, those listed in Galasso et al. Structure and Properties of Inorganic Solids, Chapter 7 --Perovskite type and related structures. For example, the perovskite semiconductor compounds, of the general formula _A 2 MX ₄ type represented by those or the general formula _A 2 MX ₄ of AMX ₃ type represented by AMX ₃ and the like. Here, M refers to a divalent cation, A refers to a monovalent cation, and X refers to a monovalent anion.

The monovalent cation A is not particularly limited, but the one described in the above-mentioned Galasso's book can be used. More specific examples include cations containing Group 1 and Group 13 to Group 16 elements of the periodic table. Among these, cesium ion, rubidium ion, ammonium ion which may have a substituent or phosphonium ion which may have a substituent are preferable. Examples of ammonium ions that may have a substituent include primary ammonium ions or secondary ammonium ions. There are no particular restrictions on the substituents. Specific examples of ammonium ions that may have a substituent include alkylammonium ions or arylammonium ions. In particular, monoalkylammonium ions having a three-dimensional crystal structure are preferable in order to avoid steric hindrance, and from the viewpoint of improving stability, alkylammonium ions substituted with one or more fluorine groups are preferably used. Further, a combination of two or more kinds of cations can be used as the cation A.

Specific examples of the monovalent cation A include methylammonium ion, monofluoromethylammonium ion, difluoride methylammonium ion, trifluoride methylammonium ion, ethylammonium ion, isopropylammonium ion, n-propylammonium ion, and isobutylammonium ion. , N-butylammonium ion, t-butylammonium ion, dimethylammonium ion, diethylammonium ion, phenylammonium ion, benzylammonium ion, phenethylammonium ion, guanidium ion, formamidinium ion, acetoamidinium ion or imidazolium Ions and the like can be mentioned.

The divalent cation M is also not particularly limited, but is preferably a divalent metal cation or a metalloid cation. Specific examples include cations of Group 14 elements of the periodic table, and more specific examples include lead cations (Pb ²⁺ ), tin cations (Sn ²⁺ ), and germanium cations (Ge ²⁺ ). Further, a combination of two or more kinds of cations can be used as the cation M. From the viewpoint of obtaining a stable photoelectric conversion element, it is particularly preferable to use a lead cation or two or more kinds of cations containing a lead cation.

Examples of monovalent anion X include halide ion, acetate ion, nitrate ion, sulfate ion, borate ion, acetylacetonate ion, carbonate ion, citrate ion, sulfur ion, tellurium ion, thiocyanate ion, and titanoic acid. Examples thereof include an ion, a zirconate ion, a 2,4-pentandionato ion, a siliceous fluorine ion and the like. In order to adjust the bandgap, X may be one kind of anion or a combination of two or more kinds of anions. In one embodiment, X includes a halide ion or a combination of a halide ion and another anion. Examples of the halide ion X include chloride ion, bromide ion, iodide ion and the like. It is preferable to use iodide ions from the viewpoint of not widening the band gap of the semiconductor too much.

The active layer 103 contains at least a halide-based organic-inorganic perovskite semiconductor compound in which X is a halide ion or a combination of a halide ion and another anion, and may contain another perovskite semiconductor compound. For example, a perovskite semiconductor compound in which at least one of A, B, and X is different may be contained in the active layer 103. Further, the active layer 103 may have a laminated structure formed of a plurality of layers containing different materials or having different components.

Examples of halide organic-inorganic perovskite semiconductor _{compound, CH 3 NH 3 PbI 3,} CH 3 NH 3 PbBr 3, CH 3 NH 3 PbCl 3, CH 3 NH 3 SnI 3, CH 3 NH 3 SnBr 3, CH 3 NH ₃ SnCl ₃ , CH ₃ NH ₃ PbI _(3-x) Cl _x , CH ₃ NH ₃ PbI _(3-x) Br _x , CH ₃ NH ₃ PbBr _(3-x) Cl _x , CH ₃ NH ₃ Pb _{( 1-y)} Sn _y I ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Br ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y Cl ₃ , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Cl _x , CH ₃ NH ₃ Pb _(1-y) Sn _y I _(3-x) Br _x , and CH ₃ NH ₃ Pb _(1-y) Sn _y Br _(3-x) Cl _x , and those in which CFH ₂ NH ₃ , CF ₂ HNH ₃ , or CF ₃ NH ₃ is used instead of CH ₃ NH ₃ in the above compounds, and the like can be mentioned. Note that x indicates an arbitrary value of 0 or more and 3 or less, and y indicates an arbitrary value of 0 or more and 1 or less.

The amount of the perovskite semiconductor compound contained in the active layer 103 is preferably 50% by mass or more, more preferably 70% by mass or more, and more preferably 80% by mass or more so that good semiconductor properties can be obtained. is there. There is no particular upper limit. Further, the active layer 103 may contain an additive in addition to the perovskite semiconductor compound. Examples of additives include inorganic or organic compounds such as halides, oxides, or inorganic salts such as sulfides, sulfates, nitrates or ammonium salts.

There is no particular limitation on the thickness of the active layer 103. The thickness of the active layer 103 is 10 nm or more in one embodiment, 50 nm or more in another embodiment, 100 nm or more in yet another embodiment, and 120 nm or more in yet another embodiment in that more light can be absorbed. Is. On the other hand, the thickness of the active layer 103 is 1500 nm or less in one embodiment, 1000 nm or less in another embodiment, and 600 nm or less in another embodiment in terms of lowering the series resistance or increasing the charge extraction efficiency. Is.

The method for forming the active layer 103 is not particularly limited, and any method can be used. Specific examples include a coating method and a vapor deposition method (or a co-evaporation method). The coating method can be used in that the active layer 103 can be easily formed. For example, the active layer 103 is coated with a coating liquid containing a perovskite semiconductor compound or a precursor thereof, and if necessary, heat-dried.
There is a method of forming. Further, after applying such a coating solution, the perovskite semiconductor compound can be precipitated by further applying a solvent having low solubility of the perovskite semiconductor compound.

The precursor of a perovskite semiconductor compound refers to a material that can be converted into a perovskite semiconductor compound after the coating liquid is applied. As a specific example, a perovskite semiconductor compound precursor that can be converted into a perovskite semiconductor compound by heating can be used. For example, a coating liquid can be prepared by mixing a compound represented by the general formula AX, a compound represented by the general formula MX ₂ , and a solvent, and heating and stirring the mixture. By applying this coating liquid and performing heat drying, the active layer 103 containing the perovskite semiconductor compound represented by the general formula AMX ₃ can be produced. The solvent is not particularly limited as long as the perovskite semiconductor compound and the additive are dissolved, and examples thereof include organic solvents such as N, N-dimethylformamide.

Any method can be used as the coating method, and for example, a spin coating method, an inkjet method, a doctor blade method, a drop casting method, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, etc. Examples thereof include a spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation / coating method, and a curtain coating method.

[1.2 Electrode]
The electrode has a function of collecting holes and electrons generated by light absorption in the active layer 103. The photoelectric conversion element 100 according to one embodiment has a pair of electrodes, one of the pair of electrodes is referred to as an upper electrode, and the other is referred to as a lower electrode. When the photoelectric conversion element 100 has a base material or is provided on the base material, an electrode closer to the base material can be called a lower electrode, and an electrode farther from the base material can be called an upper electrode. Further, the transparent electrode may be referred to as a lower electrode, and the electrode having lower transparency than the lower electrode may be referred to as an upper electrode. The photoelectric conversion element 100 shown in FIG. 1 has a lower electrode 101 and an upper electrode 105.

As the pair of electrodes, an anode suitable for collecting holes and a cathode suitable for collecting electrons can be used. In this case, the photoelectric conversion element 100 may have a forward configuration in which the lower electrode 101 is the anode and the upper electrode 105 is the cathode, or the lower electrode 101 is the cathode and the upper electrode 105 is the anode. It may have a mold configuration.

One of the pair of electrodes may be translucent, and both may be translucent. Translucent means that sunlight is transmitted by 40% or more. Further, the solar light transmittance of the transparent electrode is preferably 70% or more because more light passes through the transparent electrode and reaches the active layer 103. The light transmittance can be measured with a spectrophotometer (for example, U-4100 manufactured by Hitachi High-Tech).

When the lower electrode and / or the upper electrode is a transparent electrode, the lower electrode and / or the upper electrode is formed of a single layer of a transparent conductive layer or a metal layer as long as it has the above-mentioned visible light transmittance. It may be formed by laminating a transparent conductive layer and a metal layer. However, when the transparent electrode is formed only by the transparent conductive layer, the resistance is high and the conversion efficiency may decrease because it tends not to exhibit good conductivity. Further, when the transparent electrode is formed only by a thin metal layer, the metal layer is easily corroded and the photoelectric conversion element tends to deteriorate over time. Therefore, the electrode to be the transparent electrode is made of a transparent conductive layer and a metal layer. It is preferably formed by laminating.

The material used for the transparent conductive layer is not particularly limited, but tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), and the like. Oxides of zinc and aluminum (AZO), indium oxide (In ₂ O ₃ ), and the like. Among these, non-tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), tungsten-doped indium oxide (IWO), zinc-tin composite oxide (ZTO), etc. It is preferable to use crystalline oxide.

Further, the transparent conductive layer preferably has a sheet resistance of 100 Ω / □ or less, more preferably 50 Ω / □ or less, and more preferably 0.1 Ω / □ or more.

The material of the metal layer is not particularly limited, and examples thereof include metals such as gold, platinum, silver, aluminum, nickel, titanium, magnesium, calcium, barium, sodium, chromium, copper, and cobalt, or alloys thereof. Among these, the material forming the metal layer is preferably silver or an alloy of silver which exhibits high electrical conductivity and high visible light transmittance in the thin film. As silver alloys, in order to be less susceptible to sulfide or chlorination and to improve stability as a thin film, silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper alloys, etc. Examples include alloys of palladium and alloys of silver and platinum.

The thickness of the metal layer is not particularly limited as long as it can maintain a visible light transmittance of 70% or more as a transparent electrode, but is preferably 1 nm or more in order to obtain good conductivity, and is preferably 5 nm or more. On the other hand, in order to prevent the light transmittance from decreasing and the amount of light incident on the active layer from decreasing, it is preferably 15 nm or less, and more preferably 10 nm or less.

As described above, as long as one electrode is a transparent electrode, the other electrode does not necessarily have to be a transparent electrode, and may be a non-transparent electrode. When a non-transparent electrode is used, there is no particular limitation, but for example, the non-transparent electrode can be formed by forming a thick metal layer as described above. When both the lower electrode and the upper electrode are transparent electrodes, it is preferable that both the lower electrode and the upper electrode have a laminated structure of a metal layer and a transparent conductive layer.

The total thickness of the lower electrode and the upper electrode is not particularly limited and may be arbitrarily selected in consideration of optical characteristics and electrical characteristics. Among them, in order to suppress the sheet resistance, the film thickness of each of the lower electrode and the upper electrode is preferably 10 nm or more, more preferably 20 nm or more, further preferably 50 nm or more, while it is more preferable. In order to maintain a high transmittance, it is preferably 10 μm or less, more preferably 1 μm or less, and further preferably 500 nm or less.

The method for forming the lower electrode and the upper electrode is not particularly limited, and the lower electrode and the upper electrode can be formed by a known method according to the material to be used. Examples of the film forming step in coating include a vacuum method such as a vapor deposition method and a sputtering method, or a wet method in which an ink containing nanoparticles or a precursor is applied. The electrical characteristics, wettability, and the like may be improved by surface-treating the lower electrode and the upper electrode.

[1.3 Electron or hole transport layer]
The electron transport layer 102 and the hole transport layer 104 are layers located between the active layer 103 and at least one of the pair of electrodes 101 and 105. The electron transport layer 102 and the hole transport layer 104 can be used, for example, to improve the carrier transfer efficiency from the active layer 103 to the lower electrode 101 or the upper electrode 105.

There are no particular restrictions on the constituent members of the electron transport layer 102 and the hole transport layer 104 and the manufacturing method thereof, and well-known techniques can be used. For example, International Publication No. 2013/171517
No., International Publication No. 2013/180230 or Japanese Patent Application Laid-Open No. 2012-191194, and other known documents can be used.

[1.4 Base material]
The photoelectric conversion element 100 usually has a base material 106 as a support. The material of the base material 106 is not particularly limited as long as the effect of the present invention is not significantly impaired, and for example, known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230 or JP2012-191194A. The materials described in 1 can be used.

[1.5 Other layers]
The photoelectric conversion element 100 may have other layers. For example, the photoelectric conversion element 100 has a work function tuning layer that adjusts the work function of the electrode between the lower electrode 101 and the electron transport layer 102, or between the upper electrode 105 and the hole transport layer 104. You may. Further, the photoelectric conversion element 100 has a thin insulator layer between the lower electrode 101 and the active layer 103, or between the upper electrode 105 and the active layer 103, which prevents moisture or the like from reaching the active layer 103. You may have. Further, in order to improve durability, the photoelectric conversion element 100 may be further sealed. For example, the photoelectric conversion element 100 can be sealed by further laminating a sealing plate on the upper electrode 105 and fixing the base material 106 and the sealing plate with an adhesive.

[2. Manufacturing method of photoelectric conversion element]
The photoelectric conversion element 100 can be manufactured by forming each layer constituting the photoelectric conversion element 100 according to the above method. There are no particular restrictions on the method of forming each layer constituting the photoelectric conversion element 100, and the layers can be formed by a sheet-to-sheet (single-leaf) method or a roll-to-roll method.

The roll-to-roll method is a method in which a flexible base material wound in a roll shape is unwound and processed intermittently or continuously while being wound by a winding roll. is there. According to the roll-to-roll method, it is possible to collectively process long substrates on the order of km, so that the roll-to-roll method is more suitable for mass production than the sheet-to-sheet method. On the other hand, when each layer is to be formed by the roll-to-roll method, the film may be damaged or partially peeled off due to the contact between the film-forming surface and the roll due to its structure.

The size of the roll that can be used in the roll-to-roll method is not particularly limited as long as it can be handled by the roll-to-roll method manufacturing apparatus, but the upper limit of the outer diameter is preferably 5 m or less, more preferably 3 m or less, and more preferably. It is 1 m or less. On the other hand, the lower limit is preferably 10 cm or more, more preferably 20 cm or more, and more preferably 30 cm or more. The upper limit of the outer diameter of the roll core is preferably 4 m or less, more preferably 3 m or less, and more preferably 0.5 m or less. On the other hand, the lower limit is preferably 1 cm or more, more preferably 3 cm or more, more preferably 5 cm or more, still more preferably 10 cm or more, and particularly preferably 20 cm or more. It is preferable that these diameters are not more than the above upper limit because the roll is easy to handle, and more than the lower limit is preferable because the layer formed in each step is less likely to be broken by bending stress. .. The lower limit of the width of the roll is preferably 5 cm or more, more preferably 10 cm or more, and more preferably 20 cm or more. On the other hand, the upper limit is preferably 5 m or less, more preferably 3 m or less, and more preferably 2 m or less. It is preferable that the width is not more than the upper limit from the viewpoint of high roll handleability, and it is preferable that the width is not more than the lower limit because the degree of freedom in the size of the photoelectric conversion element 100 increases.

Further, after stacking the upper electrodes 105, the photoelectric conversion element 100 is heated to 50 ° C. or higher in one embodiment and 80 ° C. or higher in another embodiment, while 300 ° C. or lower in one embodiment and 280 ° C. or lower in another embodiment. In yet another embodiment, heating can be performed in a temperature range of 250 ° C. or lower (this step may be referred to as an annealing process). When the annealing treatment step is performed at a temperature of 50 ° C. or higher, the adhesion between the layers of the photoelectric conversion element 100, for example, the adhesion between the electron transport layer 102 and the lower electrode 101, the electron transport layer 102 and the active layer 103, etc. The effect of improvement can be obtained. By improving the adhesion between the layers, the thermal stability and durability of the photoelectric conversion element can be improved. When the temperature of the annealing treatment step is set to 300 ° C. or lower, the possibility that the organic compound contained in the photoelectric conversion element 100 is thermally decomposed is reduced. In the annealing treatment step, stepwise heating using different temperatures within the above temperature range may be performed.

The heating time is 1 minute or more in one embodiment and 3 minutes or more in another embodiment, while 180 minutes or less in one embodiment, in order to improve adhesion while suppressing thermal decomposition, in another embodiment. It is less than 60 minutes. The annealing process can be completed when the open circuit voltage, short circuit current and fill factor, which are the parameters of the solar cell performance, reach constant values. Further, the annealing treatment step can be carried out under normal pressure and in an inert gas atmosphere in order to prevent thermal oxidation of the constituent materials. As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be placed in a heating atmosphere such as an oven. Further, the heating may be performed by a batch method or a continuous method.

[3. Photoelectric conversion characteristics]
The photoelectric conversion characteristics of the photoelectric conversion element 100 can be obtained for each light source used as follows. The photoelectric conversion element 100 is irradiated with light, and the current-voltage characteristics are measured. From the obtained current-voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open circuit voltage (Voc), fill factor (FF), series resistance, and shunt resistance can be obtained.

As the light source used for obtaining the photoelectric conversion characteristics, sunlight and an artificial light source can be used. Examples of the artificial light source include halogen lamps, xenon lamps, metal halide lamps, fluorescent lamps, white LED lamps, bulb-colored LED lamps, mercury lamps, sodium lamps, and combinations of these lamps.

Generally, a xenon lamp or a metal halide lamp is used as a light source for pseudo-sunlight, and light under conditions similar to the spectrum of AM1.5G is used as a measurement light source for obtaining photoelectric conversion characteristics at an irradiation intensity of 100 mW / cm ^2. To do. The low illuminance light source is not particularly limited, but a white LED lamp is used and is used as a measurement light source for obtaining photoelectric conversion characteristics at an illuminance of 1 to 5000 Lx.

The photoelectric conversion efficiency of the photoelectric conversion element 100 is not particularly limited, but is 3% or more in one embodiment, 5% or more in another embodiment, and 8% or more in another embodiment. On the other hand, there is no particular upper limit, and the higher the limit, the better. The fill factor of the photoelectric conversion element 100 is not particularly limited, but is 0.6 or more in one embodiment, 0.7 or more in another embodiment, and 0.8 or more in another embodiment. On the other hand, there is no particular upper limit, and the higher the limit, the better.

The photoelectric conversion element according to the present embodiment has a maximum output (Pmax) maintenance rate of 60% or more and 80% or more in one embodiment after being left in a test environment at a temperature of 85 ° C. for one day. 90% or more in another embodiment and 95% or more in yet another embodiment. For example, the Pmax maintenance rate can be obtained based on the initial Pmax immediately after the photoelectric conversion element is manufactured and the Pmax after the photoelectric conversion element is placed in the test environment. Further, the Pmax retention rate can be measured after sealing the photoelectric conversion element as described above. Here, the Pmax maintenance rate can be calculated as follows based on Pmax before and after being placed in the test environment.
Pmax maintenance rate (%) = ((Pmax after being placed in the test environment) / (Pmax before being placed in the test environment)) × 100

Further, the Pmax maintenance rate after being left in the test environment at a temperature of 85 ° C. for a long time (for example, 60 hours or more) is 40% or more, 60% or more in one embodiment, and 80 in another embodiment. % Or more, 90% or more in yet another embodiment, and 95% or more in yet another embodiment.

[4. Solar cell]
In one embodiment, the photoelectric conversion element 100 is used as a solar cell element of a solar cell, particularly a thin film solar cell. FIG. 2 is a cross-sectional view schematically showing the configuration of the solar cell according to the embodiment, and FIG. 2 shows the thin film solar cell which is the solar cell according to the embodiment. As shown in FIG. 2, the thin-film solar cell 14 includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter film 4, a sealing material 5, a solar cell element 6, and a seal. A stop material 7, a getter film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. The thin-film solar cell 14 according to the present embodiment has the photoelectric conversion element described above as the solar cell element 6. Then, light is irradiated from the side where the weather resistant protective film 1 is formed (lower part in FIG. 2), and the solar cell element 6 generates electricity. The thin-film solar cell 14 does not have to have all of these constituent members, and the necessary constituent members can be arbitrarily selected.

There are no particular restrictions on these constituent members constituting the thin-film solar cell and the manufacturing method thereof, and well-known techniques can be used. For example, the techniques described in known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and JP2012-191194A can be used.

The use of the solar cell according to the present embodiment, particularly the thin-film solar cell 14 described above, is not limited, and can be used for any purpose. For example, the solar cells according to the embodiment include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, solar cells for airplanes, solar cells for spacecraft, and solar cells for home appliances. It can be used as a battery, a solar cell for a mobile phone, or a solar cell for a toy.

The solar cell according to the present embodiment, particularly the thin-film solar cell 14 described above, may be used as it is, or may be used as a component of the solar cell module. For example, as shown in FIG. 3, a solar cell module 13 having the solar cell according to the present embodiment, particularly the above-mentioned thin-film solar cell 14 on the base material 12, is manufactured, and the solar cell module 13 is installed at a place of use. Can be used. A well-known technique can be used as the base material 12, and for example, as the material of the base material 12, the materials described in International Publication No. 2013/171517, International Publication No. 2013/180230, JP-A-2012-191194, etc. Can be used. For example, when a plate material for building materials is used as the base material 12, by providing the thin film solar cell 14 on the surface of the plate material, the solar cell panel for the outer wall of the building can be manufactured as the solar cell module 13.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to the specific examples of the following Examples.

[Preparation of coating liquid]
(Preparation of coating liquid for electron transport layer)
A 7.5% tin oxide aqueous dispersion was prepared by adding ultrapure water to a tin (IV) oxide 15% aqueous dispersion (manufactured by Alfa Aesar).

(Preparation of coating liquid for active layer)
Lead (II) iodide was weighed into a vial and introduced into the glove box. N, N-dimethylformamide was added as a solvent so that the concentration of lead (II) iodide was 1.3 mol / L, and then the coating liquid 1 for the active layer was prepared by heating and stirring at 100 ° C. for 1 hour. ..

Next, in another vial, formamidine hydroiodide (FAI), methylamine hydrobromide (MABr), and methylamine hydrochloride (MACl) in a mass ratio of 10: 1: 1. Weighed so that it became, and introduced it into the glove box. By adding isopropyl alcohol as a solvent there, a coating liquid 2 for an active layer having a total concentration of FAI, MAbr, and MACl of 0.49 mol / L was prepared.

(Preparation of coating liquid for hole transport layer)
64 mg of poly [bis (4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA, manufactured by Sigma Aldrich) and 7.2 mg of 4-isopropyl-4'-methyldiphenyliodonium tetrakis (pentafluoro). Phenyl) borate (TPFB, manufactured by TCI) was weighed into a vial and introduced into a glove box. 1.6 mL of ortodichlorobenzene was added thereto as a solvent. Next, the obtained mixed solution was heated and stirred at 150 ° C. for 1 hour to prepare a coating solution for a hole transport layer.

A glass substrate (manufactured by Geomatec) provided with a patterned indium tin oxide (ITO) transparent conductive film was subjected to ultrasonic cleaning using ultrapure water, drying by nitrogen blowing, and UV-ozone treatment.

Next, the coating liquid for the electron transporting layer prepared as described above was spin-coated on the above-mentioned substrate at room temperature at a speed of 2000 rpm to form an electron transporting layer having a thickness of about 35 nm. Then, the substrate was heated on a hot plate at 150 ° C. for 10 minutes.

Next, the substrate was introduced into the glove box, 150 μL of the coating liquid 1 for the active layer heated to 100 ° C. was dropped onto the electron transport layer, and spin coating was performed at a speed of 2000 rpm. Next, the lead iodide layer was formed by heating and annealing the substrate on a hot plate at 100 ° C. for 10 minutes. Next, after the substrate has returned to room temperature, the active layer coating solution 2 (120 μL) is spin-coated on the lead iodide layer at a speed of 2000 rpm and heated at 150 ° C. for 20 minutes to obtain an active layer of organic-inorganic perovskite. (Thickness 650 nm) was formed.

Next, after returning the substrate to room temperature, the hole transport layer coating solution (200 μL) was spin-coated on the active layer at a speed of 1500 rpm, and further heated on a hot plate at 90 ° C. for 5 minutes to obtain holes. A transport layer (170 nm) was formed.

Next, silver having a thickness of about 100 nm was vapor-deposited on the hole transport layer by a resistance heating type vacuum vapor deposition method to form a metal layer, which was used as an upper electrode. As described above, the photoelectric conversion element was manufactured.

Next, an ultraviolet curable epoxy resin (TB3124) manufactured by ThreeBond Co., Ltd. was prepared as a sealing resin. Under a light source in which ultraviolet rays are cut in the glove box, the above-mentioned sealing resin is applied to the peripheral edges of the four sides of the lower substrate, specifically, about 3 mm from the edge of the substrate, and the sealing glass (Technoprint Co., Ltd.) (Made, thickness 0.7 mm, 40 mm square) were overlapped. Subsequently, the active layer portion was masked, and the entire surface of the substrate was irradiated with xenon light for about 2 minutes using a spot light source (LIGHTNINGCURE LC8 manufactured by Hamamatsu Photonics Co., Ltd.). After that, the thickness 5 was sufficiently photo-cured.
A μm sealing layer and a perovskite-type solar cell were obtained.

<Measurement method of power generation characteristics of perovskite type solar cell>
After applying the above-mentioned applied bias load, the obtained current-voltage curve was measured from the lower substrate side of the perovskite type solar cell using a low illuminance measuring device (BLD-100 manufactured by Spectrometer Co., Ltd.). For the measurement, a source meter (2400 manufactured by Keithley) was used at a temperature of 23 ° C., and the maximum output voltage (Pmax) was calculated from the measurement results.

<Example 1>
The perovskite type solar cell produced as described above is allowed to stand for 15 minutes under irradiation at a temperature of 23 ° C. and an illuminance of 200 Lx, and then IV measurement is performed using an LED light source having an illuminance of 200 Lx to obtain Pmax. (Pmax0). Then, after applying a bias voltage of 0.2 V having the same polarity as that of the solar cell at the time of power generation for 15 minutes in a dark environment where the illuminance is substantially 0 Lx, IV measurement is performed using an LED light source having an illuminance of 200 Lx to obtain Pmax. (Pmax1). The Pmax maintenance rate was calculated by the following formula. The results obtained are shown in Table 1.
Pmax maintenance rate = Pmax1 / Pmax0 × 100

<Example 2>
The Pmax maintenance rate was determined by the same method as in Example 1 except that the bias voltage was 0.5 V. The results obtained are shown in Table 1.

<Example 3>
The Pmax maintenance rate was determined by the same method as in Example 1 except that the bias voltage was set to 0.8 V. The results obtained are shown in Table 1.

<Example 4>
Immediately after standing for 15 minutes under irradiation with an illuminance of 200 Lx, the Pmax maintenance rate was determined by the same method as in Example 1 except that a step of standing for 30 minutes in an environment of 10 Lx or less was added. The results obtained are shown in Table 1.

<Example 5>
The Pmax maintenance rate was determined by the same method as in Example 1 except that the bias voltage was set to 0.05 V. The results obtained are shown in Table 1.

<Example 6>
The Pmax maintenance rate was determined by the same method as in Example 4 except that the time for applying the bias voltage was set to 3 minutes. The results obtained are shown in Table 1.

<Comparative example 1>
The Pmax maintenance rate was determined by the same method as in Example 1 except that the bias voltage was not applied in a dark environment where the illuminance was substantially 0 Lx. The results obtained are shown in Table 1.

<Comparative example 2>
The Pmax maintenance rate was determined by the same method as in Example 1 except that the bias voltage was not applied in an environment with an illuminance of 3 Lx. The results obtained are shown in Table 1.

The perovskite-type solar cells of Examples 1, 2 and 3 had a high Pmax retention rate, whereas those of Comparative Examples 1 and 2 had a low Pmax retention rate. It is probable that the characteristics of the perovskite solar cell placed in the dark place did not deteriorate due to the application of the bias voltage because the ions existing in the active layer in the dark place moved to both electrodes. Therefore, as in Examples 1 and 2, it is considered that the original power generation performance could be obtained immediately by applying a voltage having the same polarity as the power generation from the external power source even without light irradiation. In addition, the perovskite-type solar cell of Example 5 had a higher Pmax retention rate than Comparative Example 1 in which no bias voltage was applied. Furthermore, it was found that the effect of applying the bias voltage is exhibited even if the step of standing in a dark place is included as in Examples 4 and 6. This suggests that it can also be applied to perovskite-type solar cells stored in the dark for a long time.

1 Weather-resistant protective film 2 Ultraviolet cut film 3, 9 Gas barrier film 4, 8 Getter film 5, 7 Encapsulant 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin-film solar cell 100 Photoelectric conversion element 101 Lower part Electrode 102 Electrode transport layer 103 Active layer 104 Hole transport layer 105 Upper electrode 106 Base material 200 Photoelectric conversion device 20 Bias voltage application mechanism 21 Voltage application means 22 Control means 23 Illumination detection means 24 Perobskite type solar cell

Claims (7)

It has a perovskite type solar cell and a bias voltage applying mechanism that is electrically connected to the solar cell and can apply a bias voltage to the solar cell.
The bias voltage applying mechanism includes a voltage output means for applying a voltage to the solar cell and a situation in which the solar cell is exposed to a state where the illuminance exceeds 10 Lx again after the solar cell is exposed to a state where the illuminance is 10 Lx or less. A photoelectric conversion device having a control means capable of controlling the application of a bias voltage Vb to the solar cell before being performed. The photoelectric conversion device according to claim 1, wherein the bias voltage applying mechanism has a detecting means for detecting that the illuminance is 10 Lx or less. The photoelectric conversion device according to claim 1 or 2, wherein the applied bias voltage Vb is Vb / Voc = 0.05 to 1.2 (however, Voc is the open circuit voltage of a perovskite type solar cell under the condition of LED light source 200Lx. Is). The photoelectric conversion device according to claim 3, wherein the applied bias voltage Vb is Vb / Voc = 0.1 to 1.0. The photoelectric conversion device according to any one of claims 1 to 4, wherein the perovskite type solar cell is a normal type perovskite type solar cell. The photoelectric conversion device according to any one of claims 1 to 5, further comprising a perovskite type solar cell module in which the perovskite type solar cell is serialized. A method of operating a photoelectric conversion device having a perovskite type solar cell and a bias voltage applying mechanism that is electrically connected to the solar cell and can apply a bias voltage to the solar cell.
A method of operating a photoelectric conversion device including an application step of applying a bias voltage Vb to the solar cell in a state where the solar cell has an illuminance of 10 Lx or less.

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