JP5135744B2 - Dye-sensitized solar cell - Google Patents

Description

The present invention relates to a dye-sensitized solar cells.

  The dye-sensitized solar cell operates by a mechanism different from that of a silicon semiconductor pn junction, and has an advantage of high conversion efficiency and low cost.

As shown in FIG. 2, an electrolytic solution 25 is sealed inside a general cell of this solar battery.

In FIG. 2, a transparent conductive layer 22 is connected to a glass substrate 21 to which sunlight is irradiated to constitute an electrode. The transparent conductive layer 22 is connected to the semiconductor layer 24 by a sealing agent 23 such as a resin, and holds the electrolytic solution 25 in a space formed by the transparent conductive layer 22, the sealing agent 23, and the semiconductor layer 24 ( For example, see Patent Document 1.)
JP 2000-173680 A

In the configuration of the solar cell, the gap between both electrodes is only fixed with a sealing agent 23 such as a resin.
(1) The adhesion strength between the two electrodes is weak.
(2) Since the electrolytic solution 25 and the sealant 23 are in direct contact, the solvent of the electrolytic solution is volatilized.
(3) The sealing agent 23 deteriorates due to the corrosiveness of the electrolytic solution 25, and as a result, the electrolytic solution 25 leaks out.
There are problems such as. Therefore, it is difficult to maintain a stable state in the long term.

  In addition, since the electrolytic solution 25 is corrosive, a conductive material such as copper or gold cannot be used, and a material obtained by depositing platinum on transparent conductive glass is used as the reducing layer. Therefore, a glass substrate is used for both electrodes, and as a result, the sealing technique is limited.

  Further, in order to efficiently output the photoelectrically converted current to the outside, it is necessary to reduce the surface resistance of the transparent conductive layer. However, when the film thickness is increased in order to reduce the surface resistance, the transmitted sunlight is reduced, and these are in a so-called trade-off relationship. When increasing the light receiving area and increasing the transmitted sunlight, the integrated line 31 is required as shown in FIG. However, since the electrolyte is corrosive, it is necessary to protect the integrated line 31 with a protective material 32 such as glass, and the effective area of light reception is reduced.

  Then, the electrolyte solution sealing technique in a solar cell which can solve the said subject is provided.

Accordingly, in order to solve the above-mentioned problems, the invention described in claim 1 is a dye-sensitized solar cell comprising a reduction electrode formed by forming a platinum film on the surface of stainless steel or titanium, and the cell A working electrode on which a transparent conductive film is formed after forming a titanium lattice having an electrolytic solution resistance on a surface of the glass substrate facing the reducing electrode, the glass substrate having a Kovar frame for welding to the glass substrate; The electrolytic solution is held between the reduction electrode and the working electrode, and the Kovar frame and the cell are welded and sealed .

Further, the invention described in claim 2 is characterized in that the titanium lattice is engraved in the glass substrate , and a film thickness of 50 μm or more is secured on the titanium lattice.

The invention according to claim 3 is characterized in that the Kovar frame and the cell are sealed by YAG laser welding.

The invention of claim 4 is characterized in that engraved the V-shaped groove in the vicinity of the welding interface between the glass substrate at the outermost peripheral portion of the Kovar frame.

The invention described in Claim 5 is characterized in that thickened collar around the laser welds of the Kovar frame.

The invention according to claim 6, characterized in that engraved grooves in collar around the laser welds of the Kovar frame.

According to the invention described in claim 1, Ri can der to provide a cell structure that does not cause corrosion due to the electrolyte solution at a low cost, also the sheet resistance of the working electrode is reduced, the energy conversion efficiency is improved .

According to the second aspect of the present invention, the thickness of the titanium lattice can be increased, the surface resistance of the working electrode is reduced, and the energy conversion efficiency is improved.

According to the third aspect of the present invention, it is possible to reduce welding distortion and reduce costs.

According to the invention described in claims 4 , 5, and 6 , the stress at the time of laser welding for the purpose of cell sealing is relaxed, and the yield can be improved.

(Embodiment 1)
In the dye-sensitized solar cell, photoelectric conversion is performed by an oxidation-reduction reaction of iodine, and platinum is effective as a catalyst for reducing iodine, and is practically used.

  However, since platinum is very expensive, if the electrode is made of platinum alone, the manufacturing cost increases. Therefore, a reduction electrode was formed by forming a platinum thin film layer (2 μm or less) on titanium having good adhesion to platinum by a technique such as plating, vacuum deposition, or sputtering.

  The corrosion rate of this electrode is shown in Table 1.

  As shown in Table 1, an electrode in which a platinum thin film layer was formed on titanium exhibited the same corrosion resistance as an electrode made of platinum alone.

  Therefore, by using an electrode in which a thin film layer of platinum is formed on titanium, it is possible to provide an electrode having the same corrosion resistance as an electrode made of platinum alone at a low cost.

(Embodiment 2)
The dye-sensitized solar cell performs photoelectric conversion by an oxidation-reduction reaction of iodine, and platinum is effective and used as a catalyst for reducing this iodine.

  However, since platinum is very expensive, if the electrode is made of platinum alone, the manufacturing cost increases. Therefore, a reduction electrode was obtained by platinum plating (less than 2 μm) on stainless steel using a pulse power source.

  The corrosion rate of this electrode is shown in Table 1.

  As shown in Table 1, the electrode in which platinum plating was formed on stainless steel showed the same corrosion resistance as the electrode made of platinum alone.

  Therefore, by using an electrode in which platinum plating is formed on stainless steel, it is possible to provide an electrode having the same corrosion resistance as an electrode made of platinum alone at a low cost.

(Embodiment 3)
Regarding the connection between the reduction electrode and the cell container, titanium is relatively difficult to machine, and therefore, the reduction electrode was formed by depositing platinum on a flat plate titanium. A solar cell is assembled by YAG welding this electrode and a stainless steel part processed to form the solar cell, and it has been considered impossible until now. The electric wire was examined.

(Example 3-1)
Photoelectric conversion is performed on the surface of the working electrode, which is also the light receiving glass, facing the reduction electrode, but a transparent conductive layer is formed to take out the converted electrons to the outside. However, since this transparent conductive layer has a high surface resistance, the voltage loss is large and the conversion efficiency is lowered. Therefore, before forming the transparent conductive film, after forming a titanium grid having an electrolytic solution resistance directly on the glass substrate by vacuum deposition or sputtering, the transparent conductive film is formed and the surface resistance is increased. I tried to reduce it.

  Table 2 shows the surface resistance of the working electrode.

As shown in Table 2, when the current working electrode is compared, the sheet resistance is reduced by about 0.4 (Ω / cm ² ).

(Example 3-2)
The film thickness of the titanium grid of Example 1 needs to be thinner than the distance between the electrodes in order to prevent short-circuiting of the electrodes, and the distance needs to be 50 μm or less from the viewpoint of efficiency. In order to draw out the performance of this titanium lattice more, engraving was made on a glass substrate by laser engraving or the like, and an attempt was made to reduce resistance by securing a film thickness of 50 μm or more.

Table 2 shows the surface resistance of the working electrode. As shown in Table 2, when the current working electrode is compared, the sheet resistance is reduced by about 0.6 (Ω / cm ² ).

(Embodiment 4)
Conventionally, the electrolyte solution is sealed by welding with an electron beam, but this technique has a problem that it is inferior in mass productivity because it requires a high vacuum. Therefore, welding in the atmosphere was examined.

Example 4
FIG. 1 shows a cell configuration of a dye-sensitized solar cell (reference numeral 15 is a titanium lattice, and reference numeral 16 is an output terminal). The distance between the electrodes of the Kovar 11 framed glass substrate (working electrode) 12 and the stainless steel or titanium metal cell (reduction electrode) 13 needs to be maintained at about 25 μm.

  Therefore, joining was attempted by YAG laser welding, which requires only a small amount of heat input and a local heat effect and can suppress welding distortion as much as possible.

  By employing this welding technique, the stress on the glass-kovar interface 14 was relaxed, crack fracture at this interface was reduced, and the production speed was improved.

  Further, the stress remaining in the glass portion of the glass substrate with kovar varies. In the conventional Kovar cross-sectional shape, during laser welding, a glass substrate having a large residual stress cracked at the glass-Kovar interface, resulting in a decrease in yield.

(Embodiment 5)
Table 3 shows the Kovar shape that performs shape analysis of Kovar and relaxes the stress generated at the glass-Kovar interface during laser welding.

  As shown in Table 3, the outermost peripheral portion on the Kovar side has a structure having a thinner rib than the glass welded portion, and the outermost peripheral portion of this collar is an electron beam welded portion, so that unnecessary welding stress is not generated. The structure.

  Since this stress has a force that warps upward (maximum stress) and a force that warps downward (minimum stress), the absolute value of each of the maximum and minimum values is preferably as small as possible.

  In Example 5-1, a V-shaped groove was carved in the vicinity of the glass weld interface. In this case, the absolute value of the maximum stress increases by 3 MPa and the absolute value of the minimum stress decreases by 7 MPa compared with the current state. Further, there is an effect that processing is easy and the yield is good.

  In Example 5-2, the collar near the laser welded portion is thickened. In this case, the absolute value of the maximum stress is reduced by 2 MPa and the absolute value of the minimum stress is reduced by 3 MPa as compared with the current state. In addition, there is an effect that the machining is the easiest and the yield is good compared to others.

  In Example 5-3, a groove is carved into the collar near the laser weld. In this case, the absolute value of the maximum stress is reduced by 4 MPa and the absolute value of the minimum stress is reduced by 4 MPa as compared with the current state. Moreover, although processing is difficult, there exists an effect that there is the least stress.

The cell block diagram of a dye-sensitized solar cell. The cell block diagram of a dye-sensitized solar cell. Current collection explanatory drawing of a dye-sensitized solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Kovar 12 ... Light-receiving surface 13 ... Metal cell 14 ... Glass-Kovar interface 21 ... Glass base material 22 ... Transparent conductive layer 23 ... Sealant 24 ... Semiconductor layer 25 ... Electrolyte solution

Claims (6)

A cell comprising a reducing electrode made of a platinum film formed on the surface of stainless steel or titanium, and a glass substrate with a Kovar frame for welding to the cell, the surface of the glass substrate facing the reducing electrode is resistant to electrolysis. And a working electrode on which a transparent conductive film is formed after forming a liquid titanium lattice,
  A dye-sensitized solar cell, wherein an electrolytic solution is held between the reduction electrode and the working electrode, and the Kovar frame and the cell are welded and sealed. The titanium grating creates engraved on the glass substrate, a dye-sensitized solar cell according to claim 1, characterized in that to ensure a film thickness of at least 50μm into the titanium lattice. The dye-sensitized solar cell according to claim 1 or 2, wherein the Kovar frame and the cell are sealed by YAG laser welding. The dye-sensitized solar cell according to any one of claims 1 to 3, characterized in that engraved the V-shaped groove in the vicinity of the welding interface between the glass substrate at the outermost peripheral portion of the Kovar frame. The dye-sensitized solar cell according to any one of claims 1 to 3, wherein a collar near a laser welding portion of the Kovar frame is thickened. The dye-sensitized solar cell according to any one of claims 1 to 3, wherein a groove is carved into a collar in the vicinity of a laser welded portion of the Kovar frame .

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