JP6542019B2 - Solar charger - Google Patents

Description

  The present invention relates to a solar charger, and more particularly to a solar charger comprising a dye-sensitized solar cell module. In this specification, a unit structure of a solar cell is referred to as a cell, a unitary package of a plurality of cells is referred to as a module, and a unit of a plurality of modules connected is referred to as an array.

  Solar cells are roughly classified into three, silicon-based, compound-based and organic-based, depending on the material. Silicon systems have high conversion efficiency, and solar cells using polysilicon are most widely used for power generation using sunlight. There is one organic dye-sensitized solar cell (hereinafter sometimes abbreviated as "DSC"). Although DSC has a conversion efficiency lower than that of silicon, it has an advantage of lower manufacturing cost than the case of using inorganic semiconductors such as silicon and compounds, and has been attracting attention in recent years.

Heretofore, since it is important to obtain a high power generation amount with a limited installation area, development of solar cells has been focused on improvement of conversion efficiency. In addition, the power generation efficiency has been regarded as important also in the use form of the solar cell. The conversion efficiency of a solar cell is typically evaluated based on the power generated when irradiated with sunlight having an illuminance of 100 mW / cm ² at 25 ° C. This illuminance is a high value corresponding to the illuminance at the south middle of the summer solstice of Japan.

FIG. 14 shows the illuminance dependency of the output voltage (open circuit voltage) of the solar cell. The horizontal axis in FIG. 14 is a logarithmic axis, indicating the illuminance (mW / cm ² ), and the vertical axis indicates the open circuit voltage Voc (V). In the figure, a polysilicon solar cell and a dye-sensitized solar cell are taken as an example, and a standard state (AM 1.5, 100 mW / cm ² pseudo-sunlight, surface temperature 25 specified in JIS standard using a solar simulator) C., light incident direction is orthogonal to the cell). In addition, the measurement result of a polysilicon solar cell (p-Si) is plotted by "-", and the measurement result of a dye-sensitized solar cell (DSC) is plotted by "-". Thus, it can be seen that the solar cell has the characteristic that the open circuit voltage decreases as the illuminance decreases. Conventionally, a silicon-based solar cell is used under illumination conditions where sufficient conversion efficiency and open circuit voltage can be obtained.

  In recent years, as a charger for charging a mobile electronic device represented by a mobile phone, a smartphone, a tablet PC, and an electronic book terminal, one having a solar cell module (hereinafter, referred to as "solar charger") is put on the market. There is. These solar chargers also use silicon-based solar cells with excellent conversion efficiency.

  On the other hand, attempts have also been made to improve the conversion efficiency of DSC. For example, in Patent Document 1, a titanium (Ti) film is formed on a transparent electrode film in order to prevent a leak current caused by the electrolyte directly contacting the transparent electrode film, and this titanium film is anodized. Discloses a method of using a titanium oxide film obtained by It is described that the conversion efficiency of DSC can be improved 1.5 times by forming a titanium oxide film having a thickness of 20 nm. Patent Document 1 describes that even if a titanium film having a thickness of 5 nm or less remains, the influence of the decrease in the transmittance is small, so that it is acceptable.

In addition, Patent Document 2 discloses a solar cell capable of generating electric power with low illuminance in order to provide a wireless sensor operable even under low illuminance (for example, several μW / cm ² ). According to Patent Document 2, a curvilinear factor (FF) can be obtained by setting the concentration of I ₃ ⁻ in an electrolyte solution containing I ⁻ and I ₃ ⁻ as a mediator (a redox couple) to more than 0.0 M and 0.02 M or less. Short circuit current (Isc) and open circuit voltage (Voc) can be increased to improve conversion efficiency. I represents iodine and M represents mol / liter.

JP, 2005-340167, A JP, 2007-172407, A

  However, according to the study of the present inventor, when a titanium oxide film having a thickness of 20 nm is formed as described in Patent Document 1, there is a problem that the current value decreases.

Further, as described in Patent Document 2, I ₃ ^- Lowering the concentration of up to below 0.02 M, referred Under high illumination, due to the carrier is insufficient, not obtained sufficient output There's a problem.

  An object of the present invention is to provide a solar charger that is suitably used to charge mobile electronic devices over a wide range of low to high illuminance.

  A solar charger according to an embodiment of the present invention has a structure in which a dye-sensitized solar cell module comprising a plurality of dye-sensitized solar cells, and a direct electrical connection and integration with a mobile electronic device, A structure integrated with a mobile electronic device and exposing the light receiving surface of the dye-sensitized solar cell module in a state of using the mobile electronic device, the dye-sensitized solar cell module including a substrate, an electrolyte A medium, a transparent conductive layer provided on the electrolyte medium side of the substrate, a metal oxide layer formed on the electrolyte medium side of the transparent conductive layer, and a metal oxide layer on the electrolyte medium side of the metal oxide layer And the sensitizing dye supported on the porous semiconductor layer, wherein the electrical resistance of the metal oxide layer is smaller than the electrical resistance of the porous semiconductor layer, One, greater than the electrical resistance of the transparent conductive layer. The mobile electronic device is, for example, an electronic book reader, a mobile phone, a smartphone, and a tablet PC.

  In one embodiment, the metal oxide layer is a non-porous layer.

  In one embodiment, the thickness of the metal oxide layer does not exceed 10 nm.

  In one embodiment, the metal oxide layer is a thermal oxide film.

  In one embodiment, the metal oxide layer is a titanium oxide layer.

In one embodiment, the electrolyte medium contains I 2 ⁻ and I ₃ ^−, and the concentration of I ₃ ⁻ is more than 0.02 M and less than 0.05 M.

  In one embodiment, the solar charger further comprises a voltage stabilization circuit between the output of the dye-sensitized solar cell module and the mobile electronic device. The voltage stabilization circuit performs boosting or bucking.

  In one embodiment, the solar charger is configured to output the output of the dye-sensitized solar cell module directly to the mobile electronic device. That is, in one embodiment, the solar charger does not have a DC / DC converter (for example, used for pulse width modulation (PWM)) and / or a Maximum Power Point Tracking (MPPT) circuit. It may have only one of the DC / DC converter and the MPPT circuit.

  In one embodiment, the plurality of dye-sensitized solar cells include two or more dye-sensitized solar cells connected in series.

  In one embodiment, the plurality of dye-sensitized solar cells share the substrate.

  According to an embodiment of the present invention, a solar charger is provided that is suitably used for charging mobile electronic devices. A solar charger according to an embodiment of the present invention can effectively supply power to a mobile electronic device while using the mobile electronic device, for example, in a wide illumination range from high illumination to low illumination.

It is a sectional view showing typically the structure of DSC100 used for the solar charger by the embodiment of the present invention. It is a sectional view showing typically the structure of DSC module 200 used for the solar charger by the embodiment of the present invention. It is a figure which shows the state which mounted | wore the mobile device 300 with the solar charger 200A by Embodiment 1 of this invention (front side). It is a figure which shows the state which mounted | wore the mobile device 300 with the solar charger 200A by Embodiment 1 of this invention (back side). It is a figure which shows typically the structure of 200 A of solar chargers by Embodiment 1 of this invention. It is a figure which shows typically the structure of the solar charger 200B by Embodiment 2 of this invention. It is a figure which shows typically the structure of the solar charger 200C by Embodiment 3 of this invention. Metal oxide layer is a graph showing the wavelength dependence of the difference in transmittance due to the difference of the thickness of the (TiO ₂ layer). It is a graph which shows the wavelength dependency of the difference of the transmittance | permeability by the difference in the thickness of Ti layer. It is a graph showing the wavelength dependence of the graph and the dye quantum efficiency of a wavelength dependence of the difference in transmittance due to the presence of the metal oxide layer (TiO ₂ layer) (left) (right). It is a graph which shows the illumination intensity dependence of the output voltage (operating voltage) of the DSC module used for the solar charger by embodiment of this invention. It is sectional drawing which shows typically the structure of other DSC module 200W used for the solar charger by embodiment of this invention. It is sectional drawing which shows typically the structure of the further another DSC module 200Z used for the solar charger by embodiment of this invention. It is a graph which shows the illuminance dependency of the open circuit voltage (Voc) of the conventional polysilicon solar cell and DSC.

  Hereinafter, with reference to the drawings, a mobile electronic device provided with a solar charger and a solar charger according to an embodiment of the present invention will be described. The mobile electronic device is, for example, an electronic book reader, a mobile phone, a smartphone, and a tablet PC. A solar charger according to an embodiment of the present invention has a structure electrically connected directly to and integrated with a mobile electronic device, and using the mobile electronic device in an integrated state with the mobile electronic device it can. That is, as shown in FIG. 4, the solar charger according to the embodiment of the present invention has a structure that exposes the light receiving surface of the dye-sensitized solar cell module in a state where the mobile electronic device is used.

  The solar charger is easily removable from the mobile electronic device and can function as a charger even when removed. Also, the solar charger may be integrated with the mobile electronic device and may have a structure in which the solar charger can not be removed by the user in the normal use mode. At this time, the entire device including the solar charger may also be called a mobile electronic device. The embodiments illustrated below do not limit the embodiments of the present invention.

  FIG. 1 shows a schematic cross-sectional view of a DSC 100 used in a solar charger according to an embodiment of the present invention, and FIG. 2 shows a schematic cross-sectional structure of a DSC module 200 having a plurality of DSCs 100. Here, the structure of the DSC module 200 having a monolithic integrated structure and the structure of the DSC 100 corresponding to the unit structure thereof will be described, but embodiments of the present invention are not limited thereto, and will be described later with reference to, for example, FIGS. Other types of DSC modules can also be used.

As shown in FIG. 1, the DSC 100 includes a transparent substrate 12, a photoanode 15 formed on the transparent substrate 12, a porous insulating layer 22 formed on the photoanode 15, and a porous insulating layer 22. And a substrate 32, and an electrolyte medium 42 filled between the photoanode 15 and the substrate 32. The electrolyte medium 42 is typically an electrolytic solution (electrolyte solution). The electrolyte contains at least I ⁻ and I ₃ ⁻ as a mediator (a redox couple). The electrolyte medium 42 intrudes into the porous insulating layer 22 provided between the photoanode 15 and the counter electrode 34, and the electrolyte medium 42 held by the porous insulating layer 22 functions as a carrier transport layer. If the counter electrode 34 is formed on the substrate 32 and the photoanode 15 and the counter electrode 34 do not physically contact with each other in the use environment of DSC, the porous insulating layer 22 can be omitted.

  However, as shown in FIG. 1, when the structure from the photoanode 15 to the counter electrode 34 is formed on the transparent substrate 12 (ie, monolithic integrated structure), for example, a relatively thin inexpensive glass plate is used as the substrate 32. It can be used. Such a substrate 32 (thinner than the substrate 12) may be called a cover member. Adopting a monolithic integrated structure has the advantage that the cost of the DSC module can be reduced since only one relatively expensive FTO-layered glass substrate (as the transparent substrate 12 and the transparent conductive layer 14) is required.

  As the transparent substrate 12 and the substrate 32, a known transparent substrate such as a glass substrate or a plastic substrate can be used. At least the transparent substrate 12 is selected to sufficiently transmit light of a wavelength that excites the photosensitizer of the DSC 100. The substrate 32 may or may not be transparent. However, when used under an environment where light also enters from the substrate 32 side, it is preferable that the substrate 32 be also transparent in order to increase the amount of light reaching the photosensitizer.

  The photoanode 15 of the DSC 100 includes a transparent conductive layer 14 provided on the electrolyte medium 42 side of the substrate 12, a metal oxide layer 16 formed on the electrolyte medium 42 side of the transparent conductive layer 14, and a metal oxide layer 16. A porous semiconductor layer 18 provided on the electrolyte medium 42 side and a sensitizing dye (not shown) carried on the porous semiconductor layer 18 are included. The porous semiconductor layer carrying a sensitizing dye may be referred to as a photoelectric conversion layer 18. The transparent conductive layer 14 is formed of, for example, a transparent conductive oxide (TCO) such as FTO (fluorine-doped tin oxide).

  The counter electrode 34 is in contact with the catalyst layer 24 having a function of reducing holes in the carrier transport layer 42 to collect electrons, and the transparent conductive layer 14 electrically insulated from the extraction electrode (opposed photoelectric conversion layer 18 (Not shown) and / or connected to the transparent conductive layer 14 or the metal oxide layer 16 of the adjacent DSC cell. The material of the counter electrode 34 is generally used in solar cells, for example, metal oxides such as FTO, indium tin complex oxide (ITO), zinc oxide (ZnO), titanium, tungsten, gold, silver, copper, nickel Materials having conductivity, such as metal materials such as In the DSC module having a monolithic integrated structure such as the DCS module 200 illustrated in FIG. 2, titanium is preferably used from the viewpoint of the film strength of the counter electrode 34.

Here, the electric resistance of the metal oxide layer 16 is smaller than the electric resistance of the porous semiconductor layer 18 and larger than the electric resistance of the transparent conductive layer 14. Since the metal oxide layer 16 has such an electrical resistance, it suppresses the generation of a leakage current caused by the direct contact of the I ₃ ⁻ in the electrolyte medium 42 with the transparent conductive layer 14, and It is possible to suppress the output current from being reduced more than necessary. As a result, as an experimental example will be shown later, the DSC 100 can maintain a relatively high open circuit voltage even at low illuminance, and can output power in a relatively wide illuminance range. The metal oxide layer 16 is preferably a non-porous layer. The thickness of the metal oxide layer 16 does not exceed 10 nm, for example. The metal oxide layer 16 is, for example, a thermal oxide film. The metal oxide layer 16 is, for example, a titanium oxide layer, a zirconium oxide layer or an aluminum oxide layer. Among these, a titanium oxide layer is preferred. The titanium oxide layer formed by thermal oxidation does not have a pinhole and can effectively suppress the generation of a leak current. Further, the thermally oxidized layer can be formed at lower cost than the anodized layer described in Patent Document 1. Further, if the thickness of the metal oxide layer 16 does not exceed 10 nm, sufficient output power can be obtained. The thickness of the metal oxide layer 16 is preferably, for example, 1 nm or more.

  The metal oxide layer 16 is preferably formed, for example, by heating (baking) a titanium layer formed on the transparent conductive layer 14 by a thin film deposition method such as vapor deposition or sputtering under an environment containing oxygen. For example, a titanium layer having a thickness of 2 nm is formed on the surface of a substrate having an FTO layer using a sputtering apparatus (CSS-2MT-1200R) manufactured by SYNCRON (for example, target power 1100 W, Ar flow rate 120 sccm, transfer speed 100 mm / s). Thereafter, the titanium layer is thermally oxidized in air, for example, at 500 ° C. for 1 h to obtain a titanium oxide layer having a thickness of 2 nm. The increase in thickness due to the oxidation of the titanium layer is only a few percent.

Alternatively, the metal oxide layer 16 may be obtained by subjecting the surface of the transparent conductive layer 14 to a surface treatment with an aqueous solution of titanium tetrachloride (TiCl ₄ ), a gas containing titanium tetrachloride, or the like, followed by firing. it can. For example, a 0.05 M aqueous solution of titanium tetrachloride is dropped onto the surface of the substrate having the FTO layer, and heat treated at 70 ° C. for about 20 minutes. After that, after washing with water and natural drying, the titanium layer is thermally oxidized in air, for example, at 500 ° C. for 1 h to obtain a titanium oxide layer with a thickness of 2 nm. In addition to the dropping method, the titanium tetrachloride aqueous solution can be applied to the surface of the substrate having the FTO layer by a known method such as a spin coating method or a dipping method.

Electrolyte medium 42, I ^- and I ₃ ^- and an electrolytic solution containing (aqueous), I ₃ ^- is preferably of concentration is less 0.02M ultra 0.05 M. By setting the concentration of I ₃ ^{− in} the above range, a drop in voltage can be suppressed, and efficient power generation can be performed from low illuminance to high illuminance. Examples of the solvent include carbonate solvents such as propylene carbonate, nitrile solvents such as acetonitrile, alcohol solvents such as ethanol, and the like. Among these, carbonate solvents and nitrile solvents are preferable, and these solvents can be used as a mixture of two or more. A nitrile solvent is particularly preferable from the viewpoint of power generation characteristics, and the solvent is comprehensively selected from the viewpoint of the solvent viscosity, the solubility of the electrolyte, and the like according to the temperature environment in which the DSC is installed.

  The configuration of the DSC 100 and the features thereof will be described later with reference to experimental examples.

  Next, with reference to FIG. 2, the structure of the DSC module 200 used for the solar charger according to the embodiment of the present invention will be described. The DSCs 100 are connected in series according to the required output voltage and used as a module. In FIG. 2, components having substantially the same functions as the components shown in FIG. 1 may be denoted by the same reference numerals, and the description thereof may be omitted.

  The DSC module 200 illustrated in FIG. 2 includes two or more DSCs 100 a electrically connected in series, and is integrally packaged. The plurality of DCSs 100 a share the transparent substrate 12. The electrolyte medium (carrier transport layer) 42 of each DSC 100 a is separated from each other by a sealing material 45 and sealed. The entire DSC module 200 is also sealed by a sealing material that adheres and fixes the transparent substrate 12 and the substrate 32 to each other.

  On the transparent substrate 12, the photoelectric conversion layer 18 including the transparent conductive layer 14, the metal oxide layer 16, and the porous semiconductor layer 18 a is formed in this order for each DSC 100 a. The photoelectric conversion layer 18 is covered with a porous insulating layer 22, and a counter electrode 34 is formed on the photoelectric conversion layer 18 with the catalyst layer 24 interposed therebetween. The counter electrode 34 is extended onto the metal oxide layer 16 of the adjacent DSC 100 a, and thereby electrically connected in series with the adjacent DSC 100 a. The metal oxide layer 16 may be formed so that the sealing material 45 is in direct contact with the transparent conductive layer 14.

  The number of DSCs 100 a connected in series in the DSC module 200 is appropriately set according to the required output voltage. For example, a DSC module, which will be described later in the experimental example, has seven DSC cells connected in series and has an output voltage of about 3.5V. The DSC module 200 can be manufactured by a known method except for the method of forming the metal oxide layer 16. For example, it can be produced by the method described in WO 2014/038570.

  The DSC included in the solar charger according to the embodiment of the present invention has a metal having an electrical resistance smaller than the electrical resistance of the porous semiconductor layer 18a and larger than the electrical resistance of the transparent conductive layer 14 as in the DSC 100 described above. An oxide layer 16 is provided. As a result, the DSC 100 can supply power to the mobile electronic device with a sufficiently high output voltage in a wide illumination range from high illumination to low illumination.

  The solar charger 200A according to embodiment 1 of the present invention is electrically connected directly to and integrated with the mobile electronic device 300, as shown, for example, in FIGS. The solar charger 200A is easily detachable from the mobile electronic device 300, and can function as a charger even in a detached state. In addition, the solar charger 200A may be integrated with the mobile electronic device 300, and may have a structure in which the user can not remove the solar charger 200A in a normal use mode. At this time, the entire device including the solar charger 200A may also be referred to as the mobile electronic device 400. The mobile electronic device 300 is, for example, an electronic book reader, a mobile phone, a smartphone, and a tablet PC. Here, the case of using an electronic book reader as the mobile electronic device 300 is illustrated.

  As shown in FIG. 3 and FIG. 4, when the solar charger 200A is attached to the electronic book terminal 300, the output of the solar charger 200A is connected to the input of the storage element of the electronic book terminal 300. The solar charger 200 </ b> A includes a housing 250 a that protects the back surface and the side surface of the electronic book terminal 300. Here, the storage element includes not only a so-called storage battery (secondary battery) but also a large capacity capacitor. When the solar charger 200A is used as the mobile electronic device 400 integrally with the mobile electronic device 300, the mobile electronic device 300 may not have a storage element.

  As shown in FIG. 3, in the state of using the electronic book terminal 300, the display unit 300D is directed to the user side. At this time, as shown in FIG. 4, the light receiving surface of the DSC module 200 a is exposed on the back surface side of the electronic book terminal 300. The DSC module 200a has, for example, the same structure as the DSC module 200 shown in FIG.

In the state where the electronic book reader 300 is used, the display unit 300D is disposed to directly receive sunlight or illumination light, and it is rare that sunlight or illumination light directly enters the light receiving surface of the DSC module 200a. Light reflected or scattered by an object around the user, in particular below the electronic book reader 300 is incident. Therefore, the light incident on the light receiving surface of the DSC module 200a exposed on the back surface of the electronic book terminal 300 is weak, and the illuminance on the light receiving surface of the DSC module 200a is low (for example, the illuminance of the display portion 80 μW / cm ² (about 300 Lux In the indoor environment), the light receiving surface of the module is less than 10 μW / cm ² (about 40 Lux)). Since the DSC module 200a can efficiently generate power from low illuminance to high illuminance, it can generate power by receiving reflected light / scattered light even in such a use state. When the electronic book terminal 300 is not used, the light receiving surface of the DSC module 200a may directly receive sunlight or illumination light with the display unit 300D facing the back.

  Many electronic book terminals 300 have displays with low power consumption, and once fully charged, they can be used continuously for several weeks. As described above, the operation of charging the e-book reader 300 which does not need to be charged over a long period of time is very troublesome for the user. For example, even finding a dedicated charger or charging cable can be annoying. Further, depending on the timing at which the electronic book reader 300 needs to be charged, there may be no dedicated charger or charging cable.

  The DSC module 200a can generate power even when the electronic book terminal 300 is in use. Therefore, if the solar charger 200A is attached, a small amount of power consumed in daily use of the electronic book reader 300 can be charged while being used. Since the electronic book reader 300 is usually used in a bright environment, as long as the light receiving surface of the DSC module 200a is exposed, for example, unless the light receiving surface of the DSC module 200a is placed on a desk, the solar charger 200A can charge the electronic book terminal 300. Since the power generation amount of the DSC module 200a is small, it takes a long time to fully charge the fully discharged electronic book terminal 300. However, if the solar charger 200A is attached to the electronic book terminal 300, the electronic book terminal Since it can be charged at the time of use of 300, it is sufficient to supplement the power consumed on a daily basis. As a storage element of the electronic book terminal 300, a lithium ion battery without a memory effect is preferable.

  Examples of solar chargers according to embodiments of the present invention will be described with reference to FIGS.

  FIG. 5 schematically shows the configuration of a solar charger 200A according to Embodiment 1 of the present invention. The solar charger 200A is configured to output the output of the DSC module 200a directly to the mobile electronic device 300. Since the DSC module 200a can generate power with sufficient output voltage stably from low illuminance to high illuminance, it is possible to use a voltage stabilization circuit, for example, a DC / DC converter that boosts or steps down as required, or an optimum. The MPPT circuit that performs control to follow the operating point can be omitted. Of course, if necessary, a voltage stabilization circuit may be provided.

  In FIG. 6, the structure of the solar charger 200B by Embodiment 2 of this invention is shown typically. The solar charger 200B has a DC / DC converter as a voltage stabilization circuit 220 between the output of the DSC module 200b and the mobile electronic device 300. Further, FIG. 7 schematically shows the configuration of a solar charger 200C according to Embodiment 3 of the present invention. The solar charger 200C has a DC / DC converter and an MPPT circuit as a voltage stabilization circuit 240 between the output of the DSC module 200c and the mobile electronic device 300. Of course, only the MPPT circuit may be provided as the voltage stabilization circuit 240.

  In general, a conventional solar cell is provided with a DC / DC converter, an MPPT circuit, etc. in order to stabilize the output voltage and maximize the output power. However, when the output voltage from the solar cell decreases, these circuits may stop driving or may not operate properly. The DSC modules 200b and 200c included in the solar chargers 200B and 200C according to the second and third embodiments of the present invention have the same configuration as the DSC module 200 described above, and are stable from low illuminance to high illuminance, sufficiently Power can be generated with various output voltages. Therefore, the problem that the voltage stabilizing circuits 220 and 240 of the solar chargers 200B and 200C do not operate properly does not occur.

  Below, an experimental example is shown and DSC100 suitably used for the solar charger by embodiment of this invention is demonstrated in detail. The above-described DSC modules 200a to 200c all have the same configuration as the DSC module 200 shown in FIG. 2, and have the same configuration as the DSC 100 shown in FIG. 1 as a unit cell. An example in which a DSC module in which seven DSC cells are continuously provided is manufactured will be described together.

For the experiment, a DSC having the following configuration was made on a trial basis.
Transparent substrate 12 and transparent conductive layer 14: Glass substrate with FTO layer made by Nippon Sheet Glass Co., Ltd. (TEC A9X), thickness 4 mm, size 20 mm × 70 mm (in DSC module, size 70 mm × 70 mm), electric resistance value 9 Ω / sq
Porous semiconductor layer 18: 7 mm × 50 mm × 24 μm thick rectangle (with a spacing of 1.2 mm in the DSC module, seven pieces) using porous titanium oxide, titanium oxide paste D / SP (manufactured by Solaronix) Continuous pattern), electric resistance value (general physical property value: 10 ⁻¹³ to 10 ⁻¹⁴ mho / cm), sensitizing dye A (trade name: Ruthenium 620-1H3TBA (manufactured by Solaronix), supported amount: about 7 × 10 ^{- 8} mol / cm ²
Porous insulating layer 22: A 7.2 mm × 50.2 mm × 13 μm rectangle (in the case of a DSC module, an interval of 1 mm is opened using a porous zirconium oxide or zirconium oxide paste Zr-Nanoxide Z / SP (manufactured by Solaronix) 7 consecutive patterns)
Counter electrode 34: As a catalyst layer, about 50 nm of Pt is deposited on the surface of the porous insulating layer 22 by sputtering, and a conductive layer is formed on the porous insulating layer 22, the transparent conductive layer 14 and the metal oxide layer 16. A layer of about 2 μm of a Ti layer was used. Here, the catalyst layer and the Ti layer are collectively referred to as the counter electrode, but may be referred to as the counter electrode 34 by referring only to the Ti layer. The electric resistance value of the counter electrode 34 was 0.6 Ω / sq (in the DSC module, the counter electrodes of adjacent DSC cells were formed by patterning so as to be electrically insulated by several hundred kiloΩ or more).
Substrate 32: Blue plate glass substrate (manufactured by Matsunami Glass Co., Ltd.), thickness 1 mm, size 10 mm × 70 mm (in DSC module, size 60 mm × 70 mm)
Sealed part (not shown): UV curable resin (model number: 31X-101 (manufactured by Three Bond)), seal width 1 mm
Electrolyte 42: I ₃ ^- concentration 0.05 M, solvent acetonitrile, a thickness of 50 [mu] m (gap)
The thickness of the metal oxide layer 16 produced DSC of 1 nm, 2 nm, 4 nm, 8 nm, 12 nm, and evaluated the reduction amount of the output voltage change amount and the short circuit current density Jsc by illumination difference. The illuminance at high illuminance conditions was 1.5 mW / cm ^2, and the illuminance at low illuminance conditions was 0.09 mW / cm ² . A titanium oxide layer was formed as the metal oxide layer 16. The titanium oxide layer was formed by the following method.

  A titanium layer having a thickness of about 2 nm was formed (target power 1100 W, Ar flow rate 120 sccm, transfer speed 100 mm / s) on a substrate surface having an FTO layer using a synchrotron sputtering apparatus (CSS-2MT-1200R). Thereafter, the titanium layer was thermally oxidized at 500 ° C. for 1 h in air to obtain a titanium oxide layer having a thickness of about 2 nm. In the case where the metal oxide layer is formed by a sputtering apparatus for passage film formation, the film thickness can be controlled by changing the transport speed. For example, a titanium oxide layer with a thickness of about 4 nm can be obtained by setting only the transport speed to 50 mm / s.

  The evaluation results are shown in Table 1 below. Note that “the decrease in Jsc from the decrease in transmittance” in Table 1 refers to the Jsc output from cells in which the metal oxide layer is formed at the same irradiation light amount from the Jsc output from cells in which the metal oxide layer is not formed. It is obtained by pulling.

  While a DSC that does not have the metal oxide layer 16 has a large amount of voltage change due to a difference in illuminance, providing the metal oxide layer 16 reduces the amount of voltage change due to a difference in illuminance even if the thickness is 1 nm. . In addition, when the thickness of the metal oxide layer 16 is 12 nm or more, the amount of voltage change due to the illuminance difference becomes large. Further, the decrease in Jsc from the decrease in transmittance is rapidly increased when the thickness of the metal oxide layer 16 is 12 nm.

  From the above, the thickness of the metal oxide layer 16 is preferably 1 nm or more and less than 12 nm, and more preferably 8 nm or less. By providing such a metal oxide layer 16, a change in output voltage (V) due to illuminance can be suppressed while keeping the output (W) of the DSC high.

In FIG. 8, the metal oxide layer (nonporous titanium oxide layer, sometimes referred to simply as "TiO ₂ layer") 16 has a thickness of 2 nm, 8 nm, 10 nm, 12 nm, 16 nm and 32 nm in the wavelength range Shows the wavelength dependence of the difference in transmittance for light of 300 nm to 1100 nm. The difference in transmittance is the transmittance based on the transmittance when the metal oxide layer 16 is not formed (the transmittance of only the substrate 12 and the transparent conductive layer 14).

As can be seen from FIG. 8, as the thickness of the metal oxide layer (TiO ₂ layer) 16 increases, the difference in transmittance increases. Therefore, as the thickness of the metal oxide layer (TiO ₂ layer) 16 increases, the amount of energy of light reaching the photoelectric conversion layer 18 is reduced by the difference in transmittance. In order to obtain sufficient output power, the thickness of the metal oxide layer 16 is preferably not more than 10 nm, and more preferably 4 nm or less.

  Although it is described in Patent Document 1 that the Ti layer may remain if the thickness is 5 nm or less, the thickness of the remaining Ti layer is preferably less than 4 nm. As can be seen from the graph showing the wavelength dependency of the difference in transmittance due to the difference in thickness of the Ti layer shown in FIG. 9, the transmittance of the Ti layer having a thickness of 4 nm is about 10% around 350 nm, 500 to It is reduced by about 6% in a wide range of 1100 nm. In order to suppress the decrease in transmittance due to the remaining Ti layer, the thickness is preferably less than 4 nm, more preferably 2 nm or less, and most preferably 1 nm or less.

  FIG. 10 is a graph showing the wavelength dependence of the difference in the transmittance (left axis) depending on the presence or absence of the metal oxide layer 16 and a graph showing the wavelength dependence of the quantum efficiency (right axis) of the dye A. The thickness of the metal oxide layer 16 is 4 nm. The normalized quantum efficiency shown in FIG. 10 was normalized by calculating the quantum efficiency of each wavelength, with the quantum efficiency at the wavelength taking the maximum value of the quantum efficiency spectrum of the dye being 1.

  The current output from the DSC is proportional to a value obtained by integrating [external quantum efficiency (value before normalization) at each wavelength × energy amount of light of each wavelength] over the entire wavelength range. Dye A shown in FIG. 10 has relatively high external quantum efficiency in the range of 300 nm to 800 nm. Therefore, as the thickness of the metal oxide layer (nonporous titanium oxide layer) 16 increases, the decrease in the transmittance (particularly on the short wavelength side (the transmittance of 300 to 500 nm)) increases, and as a result, the current decreases. It also increases proportionally.

  Next, Table 2 shows the results when dye B and dye C were used instead of dye A above. Dye B is a dye having less absorption of short wavelength than dye A, and dye C is a dye having more absorption of short wavelength than dye A. Table 2 also shows the results when dye A was used. The numerical value in () in the mass of the short circuit current density Jsc is the difference from the numerical value of the upper stage, and represents the change of the short circuit current density Jsc due to the thickness of the metal oxide layer 16.

  As apparent from the results of Table 2, when the thickness of the metal oxide layer 16 is 12 nm or more, the reduction amount of the short circuit current density Jsc increases rapidly although the degree varies depending on the type of the dye. Therefore, regardless of the type of dye, the thickness of the metal oxide layer 16 is preferably 1 nm or more and less than 12 nm, and more preferably 8 nm or less. Further, by providing such a metal oxide layer 16, it is possible to suppress a change in output voltage (V) due to illuminance while keeping the output (W) of the DSC high.

The electrolyte medium (carrier transport layer) of the DSC 100 preferably includes I 2 ⁻ and I ₃ ^−, and the concentration of I ₃ ⁻ is preferably more than 0.02 M and 0.05 M or less. By forming the metal oxide layer 16 and setting the I ₃ ^- concentration contained in the electrolyte medium to more than 0.02 M and 0.05 M or less, the voltage drop is suppressed, and efficiently from low illuminance to high illuminance. It becomes possible to generate electricity.

To prepare a DSC100 in the same manner as Experimental Example, I ₃ contained in the electrolytic solution ^- to adjust the concentration of. As the metal oxide layer 16, a titanium oxide layer having a thickness of 2 nm was formed. The conversion efficiency of each of the produced DSCs was determined as follows under low illumination conditions (0.09 mW / cm ² , LED illumination) and high illumination conditions (3 mW / cm ² , pseudo-sunlight).

  Under low illumination conditions, using the LED solar simulator Iris-06 (manufactured by Cell System Co., Ltd.) as the light source, various daylighting filters (for example, mesh filters with different aperture ratios) of ordinary white light of general LED lighting ) To reduce the light amount to a desired light amount, and the light amount at that time was measured using a spectroradiometer MSR-7000N (manufactured by Opt Research Co., Ltd.). Under high illumination conditions, various light reduction filters are combined to reduce the desired amount of light under irradiation conditions within ± 10% of spectral characteristics approximating AM1.5 at 400 nm to 800 nm and within ± 5% of illumination distribution within the irradiation range The light was emitted and the amount of light at that time was measured using a spectroradiometer MSR-7000N. External wiring is connected to DSC and various characteristics (short circuit current density Jsc, open circuit voltage Voc, curve factor FF) obtained by IV tracer ADCMT6246 (manufactured by ADCC) and irradiation energy obtained by spectroradiometer The conversion efficiency was determined. The results are shown in Table 3.

As can be seen from the results in Table 3, the conversion efficiency at low illuminance decreases as the I ₃ ^- concentration increases. From the viewpoint of conversion efficiency at low illuminance, the I ₃ ^- concentration is preferably 0.05 M or less. I ₃ ^- it is low concentration, the conversion efficiency in the low illuminance is high, the photoanode redox couple (I ^- and I ₃ ^-) frequency reverse electron transfer occurs to is because low. As a result, it is possible to obtain a relatively high open circuit voltage Voc even at low illuminance. On the other hand, the conversion efficiency at high illuminance decreases when the I ₃ ^- concentration falls below 0.02M. In order to obtain high conversion efficiency even at high illuminance, it can be said that the I ₃ ⁻ concentration is preferably more than 0.02M. From these facts, in order to obtain a DSC that operates effectively in a wide illumination range from low illumination to high illumination, it is preferable that the I ₃ ^- concentration in the electrolyte medium be 0.02 M or more and 0.05 M or less I understand that. Also, when the I ₃ ^- concentration in the electrolyte medium is 0.02 M, the DSC with a metal oxide layer thickness of 8 nm has almost the same excellent performance as the DSC with a metal oxide layer thickness of 2 nm Know that

  Next, with reference to Tables 4 to 8 and FIG. 11, the illuminance dependency of the output voltage (operating voltage) of the DSC cell and module used in the solar charger according to the embodiment of the present invention will be described. FIG. 11 is a graph showing the illuminance dependency of the output voltage (operating voltage) of the DSC module. The DCS module used here has a structure in which seven DSCs 100 are connected in series. Therefore, the output voltage of the DSC module is seven times the output voltage of the DSC cell that constitutes the DSC module.

Table 4 shows ordinary DSC without metal oxide layer, Table 5 shows DSC with metal oxide layer (thickness 4 nm), Table 6 shows DSC with adjusted concentration of I ₃ ^- concentration (0.02 M), table 7, the metal oxide layer (thickness 4 nm) and I ₃ ^- the DSC was performed to adjust the concentration (0.02 M), shows the output voltage at various illuminance. Tables 5 to 7 also show the difference from the output voltage of the conventional DSC. Table 8 shows, for each DSC, the difference between the output voltage when the illuminance is 4 mW / cm ² and the output voltage when the illuminance is 0.3 mW / cm ² (ΔV (@ 4-0.3 mW / cm ² ) Is shown.

From the comparison of Tables 4 and 5-7, from Table 8 and FIG. 11, the illuminance dependence of the output voltage by providing a metal oxide layer or by adjusting the I ₃ ^- concentration within the above-mentioned predetermined range It can be seen that the sex can be reduced. That is, a drop in output voltage at low illuminance can be suppressed. Furthermore, it is understood that the decrease of the output voltage at low illuminance can be further suppressed by providing the metal oxide layer and adjusting the I ₃ ^- concentration within the above-mentioned predetermined range. As shown in Table 7, the value of ΔVop (V) of DSC in which the metal oxide layer is provided and the I ₃ ^- concentration is adjusted within the above-mentioned predetermined range is ΔVop ^{MO of} DSC in which the metal oxide layer is provided. Compared to the simple sum (ΔVop ^MO + ΔVop ^IC ) of the DSC ΔVop ^IC (see Table 6) with I ₃ ^- concentration adjusted within the above given range (refer to Table 5), the illuminance is 4 mW / cm ² In all cases, a large value is taken, that is, by providing the metal oxide layer and adjusting the I ₃ ^- concentration within the above-mentioned predetermined range, synergistic effects can be obtained, each applied alone It can be seen that the effect of suppressing the decrease in output voltage is greater than that.

  Although the above embodiment illustrates a solar charger using a DSC module having a monolithic integrated structure, the solar charger according to an embodiment of the present invention may use a DSC module having another type of integrated structure it can. For example, Sharp Giken Report No. 100, February 2010, pages 32-35 discloses a DSC module having a W integrated structure and a Z integrated structure together with a monolithic integrated structure. The configuration in which the metal oxide layer 16 is provided to the DSC module 200 W having the W integrated structure and the DSC module 200 Z having the Z integrated structure will be described with reference to FIGS. 12 and 13. 12 and 13, components having substantially the same functions as the components of the DSC module 200 shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 12 is a cross-sectional view schematically showing the structure of another DSC module 200W used in a solar charger according to an embodiment of the present invention.

  The DSC 200 W has a W integrated structure. The W-type integrated structure forms the photoelectric conversion layer 18 alternately on two substrates 12 and 32 on which TCO and / or conductive layer (transparent conductive layer 14 and / or counter electrode 34) are formed at predetermined locations. Have a structure in which a plurality of DSC cells are connected in series by bonding the two substrates 12 and 32 so that the photoelectric conversion layers 18 on the two substrates 12 and 32 are alternately arranged. . In the cross section of this module, since the connection form of the DSC cells connected in series resembles W of the alphabet, it is called a W-type integrated structure. The DSC 200 W also has the metal oxide layer 16 between the TCO and / or the conductive layer (the transparent conductive layer 14 and / or the counter electrode 34) and the photoelectric conversion layer 18. The metal oxide layer 16 has the above-mentioned features, and suppresses the generation of the leak current and the output current from being reduced more than necessary.

  FIG. 13 is a cross-sectional view schematically showing the structure of still another DSC module 200Z used for a solar charger according to an embodiment of the present invention.

  The DSC 200Z has a Z integrated structure. In the Z-type integrated structure, the photoelectric conversion layer 18 is formed on the substrate 12 or 32 on which the TCO (transparent conductive layer 14) is formed, and the counter electrode 34 is formed on the substrate 32 or 12 on which another TCO is formed. A plurality of DSC cells are connected in series by bonding the substrate 12 or 32 on which the photoelectric conversion layer 18 is formed. A connection layer 35 is formed on one or both of the substrates 12 and 32, and adjacent DSC cells are connected in series via the connection layer 35. The connection layer 35 can be formed of the same material as the transparent conductive layer 14 or the counter electrode 34, or various conductive materials (for example, silver, copper, carbon) used for general electrical wiring. In the cross section of this module, since the connection form of the DSC cells connected in series resembles the letter Z, it is called a Z-type integrated structure. The DSC 200 </ b> Z also has the metal oxide layer 16 between the TCO (transparent conductive layer 14) and the photoelectric conversion layer 18. The metal oxide layer 16 has the above-mentioned features, and suppresses the generation of the leak current and the output current from being reduced more than necessary.

  In the DSC 200 W or DSC 200 Z, the catalyst layer 24 is formed on the FTO layer (transparent conductive oxide layer) using two FTO layer-attached glass substrates, and the conductive layer (for example, Ti layer) on the catalyst layer 24 34 may be formed.

  This specification discloses the solar charger according to the items 1 to 10 below.

[Item 1]
A dye-sensitized solar cell module comprising a plurality of dye-sensitized solar cells;
A structure electrically connected directly to and integrated with a mobile electronic device, the light receiving surface of the dye-sensitized solar cell module being integrated with the mobile electronic device and using the mobile electronic device Have a structure to expose,
The dye-sensitized solar cell module includes a substrate, an electrolyte medium, a transparent conductive layer provided on the electrolyte medium side of the substrate, and a metal oxide layer formed on the electrolyte medium side of the transparent conductive layer. A porous semiconductor layer provided on the electrolyte medium side of the metal oxide layer, and a sensitizing dye supported on the porous semiconductor layer,
A solar charger, wherein the electric resistance of the metal oxide layer is smaller than the electric resistance of the porous semiconductor layer and larger than the electric resistance of the transparent conductive layer.
[Item 2]
The solar charger according to item 1, wherein the metal oxide layer is a non-porous layer.
[Item 3]
The solar charger according to Item 1 or 2, wherein the thickness of the metal oxide layer does not exceed 10 nm.
[Item 4]
The solar charger according to any one of Items 1 to 3, wherein the metal oxide layer is a thermal oxide film.
[Item 5]
5. Solar charger according to any of the preceding claims, wherein the metal oxide layer is a titanium oxide layer.
[Item 6]
The electrolyte medium, I ^- and I ₃ ^- and a, I ₃ ^- concentration is less 0.02M ultra 0.05 M, solar charger as described in any one of 1 to 5.
[Item 7]
7. A solar charger according to any of the preceding claims, further comprising a voltage stabilization circuit between the output of the dye-sensitized solar cell module and the mobile electronic device.
[Item 8]
7. A solar charger according to any of the preceding claims, wherein the solar charger is configured to output the output of the dye-sensitized solar cell module directly to the mobile electronic device.
[Item 9]
9. A solar charger according to any of items 1 to 8, wherein the plurality of dye-sensitized solar cells comprises two or more dye-sensitized solar cells connected in series.
[Item 10]
The solar charger according to any one of Items 1 to 9, wherein the plurality of dye-sensitized solar cells share the substrate.

  The solar charger of the present invention is suitably used to charge mobile electronic devices represented by mobile phones, smart phones, tablet PCs, and electronic book terminals.

12, 32 substrate 14 transparent conductive layer 34 counter electrode 15 photoanode 16 metal oxide layer 18a porous semiconductor layer 18 photoelectric conversion layer 42 electrolyte medium 100, 100a, 100b, 100c DSC
200, 200a, 200b, 200c DSC module 200A, 200B, 200C Solar charger 300 Mobile electronic device (e-book terminal)

Claims (4)

A dye-sensitized solar cell module comprising a plurality of dye-sensitized solar cells;
A structure electrically connected directly to and integrated with a mobile electronic device, the light receiving surface of the dye-sensitized solar cell module being integrated with the mobile electronic device and using the mobile electronic device Have a structure to expose,
The dye-sensitized solar cell module includes a substrate, an electrolyte medium, a transparent conductive layer provided on the electrolyte medium side of the substrate, and a metal oxide layer formed on the electrolyte medium side of the transparent conductive layer. A porous semiconductor layer provided on the electrolyte medium side of the metal oxide layer, and a sensitizing dye supported on the porous semiconductor layer,
The electrical resistance of the metal oxide layer, the porous semiconductor layer smaller than the electrical resistance of, and much larger than the electric resistance of the transparent conductive layer,
The electrolyte medium, I ^- and I ₃ ^- and a, I ₃ ^- concentration is less 0.02M ultra 0.05 M, solar charger.   The solar charger according to claim 1, wherein the thickness of the metal oxide layer does not exceed 10 nm. An output of the dye-sensitized solar cell module, further comprising, solar charger according to claim 1 or 2 a voltage stabilizing circuit between said mobile electronic device. The solar charger according to any one of claims 1 to 3 , wherein the output of the dye-sensitized solar cell module is configured to be output directly to the mobile electronic device.

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