JPH09306553A - Photo-electric conversion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photo-electric conversion secondary battery having a photo-electric conversion function together with a secondary battery function in the same structure by filling the specified oxidation-reduction solution between a coloring matter adsorbed compound semiconductor layer and a transparent conductor layer. SOLUTION: A photo-electric conversion secondary battery has such structure that a coloring matter adsorbed compound semiconductor is interposed between a transparent conductor formed on the surface of a transparent supporting body and a counter electrode, and an oxidation-reduction solution whose oxidation species is colored and reduction species is colorless is filled between the transparent conductor and the compound semiconductor, and a metal species is filled between the counter electrode and the compound semiconductor. As the transparent supporting body, for example, transparent plastic for optics is used, and as the transparent conductor, for example, fluorine-doped tin oxide is used. The coloring matter adsorbed compound semiconductor is obtained in such a way that a compound semiconductor fine particle dispersion solution is applied to a metal species/counter electrode, baked, then immersed in a coloring matter solution. As the metal species, Al, Mg or the like is used. As the oxidation-reduction solution, iodine/tetrapropyle ammonium iodide (I2 /I<-> ) system is listed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a secondary battery which performs photoelectric conversion by utilizing the photoelectrochemical effect of a compound semiconductor.

[0002]

2. Description of the Related Art As a secondary battery that is repeatedly discharged and charged,
Lead acid batteries, alkaline batteries, nickel-cadmium batteries, etc. are known. This type of storage battery includes a positive electrode active material, a negative electrode active material, and an electrolyte existing between both materials. The negative electrode active material emits electrons to the external circuit during the discharge process and is itself oxidized. The positive electrode active material receives the emitted electrons and is reduced. At the interface between the negative electrode active material and the positive electrode active material and the electrolyte, an electrochemical reaction for transferring electrons between the active chamber and the ions proceeds. For example, Pb (H ₂ SO ₄ ) | diaphragm | (H ₂ SO ₄ ) P
In a bO ₂ type lead storage battery, Pb → Pb ²⁺ + 2e on the negative electrode side.
^- + SO ₄ ^2- , Pb ²⁺ + SO ₄ ^2- → PbSO ₄ , PbO ₂ + 4H ⁺ + SO ₄ ^2- + 2e ⁻ → PbSO ₄ + on the positive electrode side
2H ₂ O, PbO ₂ + 2H ₂ SO ₄ + P as the whole reaction formula
The discharge reaction of b → 2PbSO ₄ + 2H ₂ O proceeds. Charging goes through the opposite reaction process. In this respect, the photovoltaic cell converts light energy into electric energy by utilizing the photoelectrochemical effect of the compound semiconductor.

[0003]

An external power source such as a commercial power source, a generator, or a photovoltaic cell is required to charge the secondary battery which can be repeatedly discharged and charged in this way. At this time, if the battery is charged when the discharge is insufficient, the memory effect of reducing the storage capacity, the destruction due to overcharge, and the like occur, and thus charge management is required. Further, since the photovoltaic cell itself does not have a power storage function, electric power is supplied only during light irradiation, and a storage battery is separately required for continuous use. Therefore, charge management of this storage battery is required. The present invention has been devised to solve such a problem, and a redox solution in which an oxidizing species is colored and a reducing species is colorless is filled between the dye adsorbing compound semiconductor layer and the transparent conductor layer. Accordingly, it is an object of the present invention to provide a photoelectric conversion secondary battery having the same structure and having both a photoelectric conversion function and a secondary battery function.

[0004]

In order to achieve the object, a photoelectric conversion type secondary battery of the present invention has a structure in which a transparent conductor and a counter electrode formed on the surface of a transparent support as shown in FIG. A compound semiconductor layer in which a dye is adsorbed is sandwiched between, and a redox solution in which an oxidizing species is colored and a reducing species is colorless is filled between the transparent conductor and the compound semiconductor layer, and the counter electrode and the compound It is characterized in that a metal species is filled between the semiconductor layer and the semiconductor layer. As the transparent support, non-alkali glass, optical transparent plastics such as PMMA, PC and PVC are used. A transparent conductor layer is formed on the surface of this transparent support by a sputtering method, a spray method or the like. As the transparent conductor layer, fluorine-doped tin oxide (SnO ₂
F), Sn-doped indium oxide (ITO), or the like is used.

The dye-adsorbed compound semiconductor exhibits a photoelectric conversion function and an electrochemical diaphragm function by a wet-type photovoltaic cell, and a compound semiconductor fine particle dispersion is applied on a metal species / counter electrode and baked at 450 to 550 ° C. Is prepared by immersing in a dye solution. Metal type / counter electrode is A
A normal electrode is coated with 1, Mg or the like. The metal species is basically selected according to the type of the redox solution with reference to the standard electrode potential. For example, I
₂ / I ^- in the redox solution system, the standard electrode potential (VSNH
E, 25 ° C.) is +0.536 V, so Al ³⁺ /Al:-1.66 having a standard electrode potential lower than that potential.
A battery is formed by selecting a metal species such as 2V, Mg ²⁺ / Mg: -2.363V. This compound semiconductor layer / metal species /
The counter electrode and the transparent conductor described above are bonded together, and a redox solution in which the oxidizing species are colored and the reducing species is colorless is injected between the compound semiconductor layer / metal species / counter electrode and the transparent conductor layer. As this kind of redox solution, there is an iodine / tetrapropylammonium iodide (I ₂ / I ⁻ ) system.

[0006]

In the process of investigating and researching a dye-sensitized wet photocell, the present inventors have found that the device having the structure shown in FIG. 1 has both the function of a secondary cell and the photoelectric conversion function. When aluminum is used as a metal species and I ₂ / I ⁻ system is used as a redox solution, the secondary battery function and the photoelectric conversion function are assumed to be exhibited by the following mechanism. It The reaction of 2Al → 2Al ³⁺ + 6e ^{− in} the metal species on the counter electrode side and the reaction of 3I ₂ + 6e ⁻ → 6I ^{− in} the redox solution on the transparent conductor side proceed. This reaction is continued until the oxidation of the metallic species or the reduction of the oxidizing species present in the redox solution is completed, and discharging is performed.

When this system is irradiated with light from the transparent support side, a photoelectric conversion reaction occurs. This photoelectric conversion reaction originates from the dye-sensitized wet-type photocell, and is the result of the dye absorbing the irradiation light generating and transferring charges at the interface with the semiconductor compound. At this time, a redox reaction occurs between the dye and the redox solution. Expressing these reaction formulas, the generation of excitation and charge of the dye ^{6dye + 6hν → 6dye * → 6dye} + + 6e - metal species reducing 2Al ³⁺ + 6e ^- → 2Al (reduction of the oxidized dye) redox oxidation solution 6dye ^{+ +} 6I ^- → 6dye + 3I ₂ . In addition, hν is the light energy irradiated,
Indicates a dye, 6dye ^* indicates a dye in an excited state by light absorption, and dye ⁺ indicates a dye in an oxidized state. These reactions are continued and charged until the light irradiation is stopped, or the oxidation of the redox solution or the reduction of the metal oxide species is completed.

The color of the redox solution affects the charging reaction. For example, in a redox system in which the reducing species are colored, the irradiation light is absorbed by the colored reducing species and the dye cannot be sufficiently excited. Therefore, the light charging reaction is hindered. On the other hand, a redox system in which the oxidizing species are colored and the reducing species are colorless exhibits a hue change according to the charge capacity. Then, when a large amount of charge is required, the light is effectively colored because it has a light color and is effectively excited. In addition, when charging is not required, it is difficult for the irradiation light to pass therethrough, so that the dye is not irradiated and overcharging is prevented. Since the metal species formed on the counter electrode is usually a metal such as Al or Mg, the metal oxide species become mononuclear ions. Therefore, the original film shape may not be completely returned when it is reduced. In such a case, a decrease in the maximum charge capacity can be prevented by fixing to the counter electrode with an inclusion compound capable of binding to a multivalent ion species. As an inclusion compound capable of binding to a multivalent ion species,
There are macrocyclic organometallic complexes represented by phthalocyanines, zeolites with ion exchange of metal species, and intercalation compounds. Of these, an inorganic inclusion compound such as zeolite is preferable because it involves a firing treatment.

[0009]

Example An aluminum thin plate was used as a metal species / counter electrode, and a titanium oxide semiconductor fine particle dispersion liquid was applied. As the titanium oxide semiconductor fine particle dispersion liquid, an anatase type titanium oxide having an average particle diameter of 7 mm was uniformly dispersed in a solvent at a ratio of 30% by weight. After coating, it was baked at 450 ° C. for 0.5 hours. The obtained titanium oxide semiconductor layer / aluminum counter electrode was attached to an ITO transparent conductor layer having a non-alkali glass as a transparent support, and iodine / iodine was provided between the titanium oxide semiconductor layer / aluminum counter electrode and the ITO transparent conductor layer. A photoelectric conversion secondary battery was constructed by injecting a tetrapropylammonium (I ₂ / I ⁻ ) based redox solution. The initial electromotive force of this photoelectric conversion secondary battery has an open circuit voltage of 0.65.
V, the short circuit current was 0.052 mA. 10 in the dark
When short-circuited for a period of time, the open circuit voltage was 85% and the short-circuit current was 9
% And the discharge took place. After that, when light was irradiated for 10 hours using a 250 W halogen lamp, the open voltage was 100% and the short-circuit current was recovered to 68% with respect to the initial values, and charging was performed. FIG. 2 shows the charging effect at this time.

[0010]

As described above, in the photoelectric conversion secondary battery of the present invention, the dye adsorbing compound semiconductor layer is sandwiched between the transparent conductor layer and the counter electrode, and the oxidizing species are colored and the reducing species are colorless. The redox solution is filled between the transparent conductor layer and the semiconductor layer. Due to this structure, the hue changes according to the charging capacity, the irradiation light effectively excites the dye during charging, and it is difficult for the irradiation light to pass through when charging is not required, so overcharging is prevented. It Since it has both discharging and charging functions in this way, it is possible to continuously generate electricity by utilizing the photoelectric conversion function.

[Brief description of drawings]

FIG. 1 Photoelectric conversion secondary battery having both charging and discharging functions

FIG. 2 is a charging effect of the photoelectric conversion type secondary battery prepared in the example.

Claims (1)

[Claims] 1. A compound semiconductor layer on which a dye is adsorbed is sandwiched between a transparent conductor formed on the surface of a transparent support and a counter electrode, and an oxidizing species is present between the transparent conductor and the compound semiconductor layer. Fill with a redox solution that is colored and the reducing species are colorless,
A photoelectric conversion secondary battery, wherein a metal species is filled between the counter electrode and the compound semiconductor layer.