JP5025938B2 - Dye-sensitized solar cell, counter electrode thereof, and method of manufacturing the counter electrode - Google Patents

Description

  The present invention relates to a dye-sensitized solar cell, a counter electrode thereof, and a method of manufacturing the counter electrode, and more particularly, a dye-sensitized solar cell in which an electrolyte is sealed between a photoelectrode and a counter electrode, the counter electrode, and The present invention relates to a method for manufacturing the counter electrode.

  In recent years, from the viewpoint of environmental problems, solar cells that convert light energy into electrical energy have attracted attention. In particular, dye-sensitized solar cells have attracted attention because they can reduce manufacturing costs. Conventional dye-sensitized solar cells were poor in practicality due to low photoelectric conversion efficiency, but recently, a large amount of dye is adsorbed by making the semiconductor electrode porous to increase the surface area. In addition, a technique for improving photoelectric conversion efficiency has been developed (for example, see Patent Document 1).

  As schematically shown in FIG. 7, the dye-sensitized solar cell using such a technique is composed of a photoelectrode 102, a counter electrode 103, and an electrolytic solution 104 enclosed between them. A dye-sensitized solar cell 101 is known.

  The photoelectrode 102 of the dye-sensitized solar cell 101 includes a substrate member 105, a transparent electrode film 106 formed on the surface of the substrate member 105, titanium oxide formed on the transparent electrode film 106, and the like. A porous semiconductor electrode film 107 is formed, and a dye is adsorbed to the porous semiconductor electrode film 107. The porous semiconductor electrode film 107 is formed by applying a suspension containing semiconductor particles on the transparent electrode film 106, drying it, and baking it.

  On the other hand, the counter electrode 103 of the dye-sensitized solar cell 101 includes a counter substrate member 108, a conductive material film 110 formed on the counter substrate member 108, and platinum coated on the conductive material film 110. It is comprised from the electroconductive catalyst material film | membrane 112 which consists of catalysts, such as (refer patent document 2).

  The substrate member 105 and the counter substrate member 108 are disposed so that the conductive catalyst material film 112 and the porous semiconductor electrode film 107 are opposed to each other with a predetermined interval therebetween. The conductive catalyst material film 112 and the porous semiconductor electrode film An electrolyte solution 104 is enclosed between 107 to form a dye-sensitized solar cell 101.

  In this dye-sensitized solar cell 101, when light enters from the photoelectrode 102 side, the sensitizing dye adsorbed on the surface of the porous semiconductor electrode film 107 is excited by absorbing light in the visible region. Electrons generated by the excitation of the dye are moved through the porous semiconductor electrode film 107 and reach the transparent electrode film 106. The electrons that have moved to the transparent electrode film 106 move to the conductive material film 110 via an external circuit that conducts the transparent electrode film 106 and the conductive material film 110 (not shown). Electrons that have moved to the conductive material film 110 move to the electrolytic solution 104 through the conductive catalyst material film 112, and are carried from the counter electrode 103 side to the photoelectrode 102 side by ions in the electrolytic solution 104, thereby being porous. Returning to the sensitizing dye of the semiconductor electrode film 107. Electric energy is extracted by repeating such an action.

JP-T-5-504023 (first page, FIG. 1) JP 2002-298936 A (paragraph number 0018)

  In such a conventional dye-sensitized solar cell 101, in order to reduce the cost by reducing the amount of expensive catalyst such as platinum used in the conductive catalyst material film 112 of the counter electrode 103, A conductive material film 110 made of a corrosion-resistant conductive material (for example, a metal oxide such as tin oxide or indium tin oxide (hereinafter referred to as “ITO”) known as a conductive oxide) is formed. A conductive catalyst material film 112 made of a catalyst such as platinum is thinly coated on the conductive material film 110.

  In addition, it is desired that light can be incident not only from the photoelectrode 102 side but also from the counter electrode 103 side to produce a so-called see-through type solar cell that is substantially transparent as a whole. Even if the counter substrate member 108 of the counter electrode 103 is formed of a transparent material and the conductive material film 110 is formed of transparent ITO in order to manufacture such a so-called see-through type solar cell, the conductive material film Since the conductive catalyst material film 112 coated on 110 is made of a metal such as platinum that hardly transmits light, it is necessary to transmit light by a method such as thinning the conductive catalyst material film 112.

  However, if the conductive catalyst material film 112 is made too thin, there is a problem that the catalytic ability of the counter electrode 103 is lowered and the photoelectric conversion efficiency is lowered. That is, there is a problem that the photoelectric conversion efficiency decreases as the conductive catalyst material film 112 is made thinner in order to improve the transmittance of the counter electrode 103.

  Therefore, in view of such conventional problems, the present invention can improve the transmittance of the counter electrode of the dye-sensitized solar cell and prevent a decrease in photoelectric conversion efficiency of the dye-sensitized solar cell. An object of the present invention is to provide a dye-sensitized solar cell, a counter electrode thereof, and a method of manufacturing the counter electrode.

  As a result of intensive studies to solve the above problems, the present inventor has found that a transparent conductive material formed on a substrate member in a dye-sensitized solar cell in which an electrolyte is sealed between a photoelectrode and a counter electrode. By forming a conductive catalyst material film on a part of the surface of the film, the transmittance of the counter electrode of the dye-sensitized solar cell can be improved and the photoelectric conversion efficiency of the dye-sensitized solar cell can be reduced. The inventors have found that this can be prevented, and have completed the present invention.

  That is, the counter electrode of the dye-sensitized solar cell according to the present invention is formed on the counter substrate member, the transparent conductive material film formed on the counter substrate member, and a part of the surface of the transparent conductive material film. And a portion of the surface of the transparent conductive material excluding a part thereof is not covered with the conductive catalyst material film. In the counter electrode of the dye-sensitized solar cell, the partial area of the surface of the transparent conductive material film on which the conductive catalyst material film is formed is 95% or less of the entire area of the surface of the transparent conductive material film. Is preferred. Further, the conductive catalyst material film may be formed by a plurality of island-like portions separated from each other at a predetermined interval. Further, the conductive catalyst material film may be formed on a part of the surface of the transparent conductive material film via the corrosion-resistant metal material film, and the conductive catalyst material film is substantially the same planar shape as the corrosion-resistant metal material film. It is preferable to have. Further, the corrosion-resistant metal material film is preferably a film made of titanium, and the conductive catalyst material film is preferably a film made of platinum.

  Further, a dye-sensitized solar cell according to the present invention includes the above-described counter electrode, a photoelectrode provided with a porous semiconductor electrode film that is disposed opposite to the counter electrode and adsorbs or carries the sensitizing dye, and these And an electrolyte sealed between the counter electrode and the photoelectrode.

  Furthermore, the manufacturing method of the counter electrode of the dye-sensitized solar cell according to the present invention includes a step of forming a transparent conductive material film on a counter substrate member, and a conductive catalyst on a part of the surface of the transparent conductive material film. And a step of forming a material film. In the method of manufacturing the counter electrode of the dye-sensitized solar cell, the partial area of the surface of the transparent conductive material film on which the conductive catalyst material film is formed is equal to the total area of the surface of the transparent conductive material film. It is preferably 95% or less. The step of forming the conductive catalyst material film is preferably a step of forming a conductive catalyst material film by disposing a mask having a predetermined shape on the transparent conductive material film. The step of forming the conductive catalyst material film may be a step of forming a corrosion-resistant metal material film on a part of the surface of the transparent conductive material film and forming the conductive catalyst material film on the corrosion-resistant metal material film. . In this case, after the step of forming the conductive catalyst material film forms a corrosion-resistant metal material film by disposing a mask having a predetermined shape on the transparent conductive material film, the conductive catalyst material film with the mask disposed It is preferable that it is a process of forming. Further, as a mask, a mask made of a plate-like body having a plurality of openings spaced from each other at a predetermined interval may be used. Further, the corrosion-resistant metal material film is preferably a film made of titanium, and the conductive catalyst material film is preferably a film made of platinum.

  ADVANTAGE OF THE INVENTION According to this invention, while the transmittance | permeability of the counter electrode of a dye-sensitized solar cell can be improved, the fall of the photoelectric conversion efficiency of a dye-sensitized solar cell can be prevented.

  Hereinafter, embodiments of a dye-sensitized solar cell, a counter electrode thereof, and a method of manufacturing the counter electrode according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 schematically shows an embodiment of a dye-sensitized solar cell according to the present invention. As shown in FIG. 1, the dye-sensitized solar cell 1 of the present embodiment includes a photoelectrode 2, a counter electrode 3, and an electrolyte 4 enclosed between them.

  The photoelectrode 2 is formed on a transparent (light transmissive) substrate member 5, a transparent electrode film 6 formed on the surface of the substrate member 5, and the transparent electrode film 6 to adsorb and carry a sensitizing dye. And a porous semiconductor electrode film 7 to be formed. The substrate member 5 is made of a transparent resin material such as acrylic, polyethylene terephthalate (PET), polyethylene naphthalene (PEN), polyolefin, polycarbonate (PC), or a transparent glass material. When the substrate member 5 is formed of a transparent resin material, it can be formed by injection molding, heat compression molding, extrusion molding, or the like.

  On the other hand, the counter electrode 3 includes a transparent counter substrate member 8, a transparent conductive material film 10 formed on the counter substrate member 8, and a corrosion resistance formed on a part of the surface of the transparent conductive material film 10. The metal material film 11 and a conductive catalyst material film 12 formed on the corrosion-resistant metal material film 11 are configured. The counter substrate member 8 is formed of a transparent resin material such as acrylic, polyethylene terephthalate (PET), polyethylene naphthalene (PEN), polyolefin, polycarbonate (PC), or a transparent glass material. When the counter substrate member 8 is formed of a transparent resin material, it can be formed by injection molding, heat compression molding, extrusion molding, or the like.

  The transparent conductive material film 10 is made of a metal oxide such as tin oxide or zinc oxide known as a conductive oxide, and is preferably made of indium tin oxide (ITO). The corrosion-resistant metal material film 11 is made of titanium, tantalum, a titanium alloy or a tantalum alloy, and is preferably made of titanium. The conductive catalyst material film 12 is made of platinum, carbon, or palladium, and is preferably made of platinum.

  As shown in FIGS. 2 and 3, in this embodiment, the surface of the transparent conductive material film 10 is separated from each other at a predetermined interval (about 1 to 5000 μm, preferably 300 μm or less) (thickness is 0 to 0). A large number of substantially hexagonal corrosion-resistant metal material films 11 (about 20 nm, preferably about 10 nm) are formed, and on these corrosion-resistant metal material films 11, the same shape (thickness as the respective corrosion-resistant metal material films 11). A conductive catalyst material film 12 (about 1 to 100 nm, preferably about 50 nm) is formed. In addition, the space | interval (separation distance) between the adjacent corrosion-resistant metal material film 11 and the electroconductive catalyst material film | membrane 12 can be suitably set in consideration of photoelectric conversion efficiency, and the corrosion-resistant metal material film 11 and the electroconductive catalyst material The distance (width) between the parallel side surfaces of the film 12 facing each other can be set as appropriate based on the above-mentioned separation distance and the required transmittance. For example, a portion where the separation distance is 20 μm, the thickness of the corrosion-resistant metal material film 11 is 10 nm, the thickness of the conductive catalyst material film 12 is 50 nm, and the corrosion-resistant metal material film 11 and the conductive catalyst material film 12 are formed. In order to obtain a transmittance of 50% when the transmittance of the portion that hardly transmits light and where the corrosion-resistant metal material film 11 and the conductive catalyst material film 12 are not formed is about 90%, the corrosion-resistant metal material film 11 and the conductive catalyst material film 12 may have a width of about 40 μm.

  Note that the planar shapes of the corrosion-resistant metal material film 11 and the conductive catalyst material film 12 are not limited to hexagons, and may be other polygonal shapes or other shapes such as circular shapes. Further, the corrosion-resistant metal material film 11 and the conductive catalyst material film 12 are only required to be formed on a part of the surface of the transparent conductive material film 10, and do not need to be composed of a large number of parts separated from each other. It may have a continuous shape such as a shape or a honeycomb shape.

  The dye-sensitized solar cell 1 having the above-described structure can be manufactured as follows.

  First, in a vacuum apparatus in which argon gas and a small amount of oxygen gas are introduced (not shown), ITO is used as a target material, and sputtering treatment is performed using plasma generated by high frequency discharge. A transparent electrode film 6 made of ITO is formed on the surface of the substrate member 5.

Next, a porous semiconductor electrode film 7 made of titanium dioxide (TiO ₂ ) or the like is formed on the transparent electrode film 6 thus formed. The porous semiconductor electrode film 7 can be formed by applying a suspension containing semiconductor particles on the transparent electrode film 6, drying the applied suspension, and firing the suspension. A sensitizing dye (for example, ruthenium complex) having a photoelectric conversion function is adsorbed and supported on the porous semiconductor electrode film 7 thus formed. The porous semiconductor electrode film 7 may be formed by zinc oxide or the like instead of titanium dioxide, or may be formed by an electrodeposition method or a hydrothermal treatment method instead of the firing method.

  In addition, in a vacuum apparatus (not shown) in which argon gas and a small amount of oxygen gas are introduced (not shown), ITO is used as a target material, and sputtering treatment is performed using plasma generated by high-frequency discharge. A transparent conductive material film 10 made of ITO is formed on the surface of the counter substrate member 8.

  Next, as shown in FIG. 4, a mask 20 made of a plate-like body having substantially regular hexagonal openings having substantially the same size and spaced apart from each other at a predetermined interval is disposed on the transparent conductive material film 10. On the transparent conductive material film 10, a number of substantially regular hexagonal corrosion-resistant metal material films 11 having substantially the same size and spaced apart from each other at a predetermined interval are formed. When the corrosion-resistant metal material film 11 made of titanium is formed, titanium is used as a target material and a sputtering process is performed by plasma generated by high frequency discharge. The shape of the opening of the mask 20 does not need to be a hexagon, and may be another shape such as another polygon or a circle. Further, the corrosion-resistant metal material film 11 may be formed by vapor deposition or ion plating instead of sputtering.

  Next, the conductive catalyst material film 12 is formed on each corrosion-resistant metal material film 11 while the mask 20 is disposed on the transparent conductive material film 10. When the conductive catalyst material film 12 made of platinum is formed, platinum is used as a target material, and a sputtering process is performed using plasma generated by direct current discharge.

  The porous semiconductor electrode film 7 of the photoelectrode 2 thus formed and the conductive catalyst material film 12 of the counter electrode 3 are arranged so as to face each other, and the porous semiconductor electrode film 7 and the conductive catalyst material film 12 are The electrolyte 4 is encapsulated in between to complete the dye-sensitized solar cell 1 of the present embodiment (see FIG. 1). In addition, as the electrolyte 4, a redox electrolyte solution containing an oxidation-reduction pair such as an iodine-iodine compound or a bromine-bromine compound can be usually used. In addition to the liquid electrolyte, an electrolyte solidified with a gelling agent or a P-type semiconductor (CuI) may be used as the electrolyte 4.

In the dye-sensitized solar cell 1 formed in this manner, when sunlight enters the photoelectrode 2 from the outside, the sensitizing dye adsorbed and supported on the porous semiconductor film 7 is excited, and the sensitizing dye Electrons transition from the ground state to the excited state. The excited electrons of the sensitizing dye are injected into the conduction band of TiO ₂ constituting the porous semiconductor electrode film 7, move to the transparent electrode film 6, and pass through an external circuit (not shown) from the transparent electrode film 6. Then, it moves to the corrosion-resistant metal material film 11 of the counter electrode 3. The electrons that have moved to the corrosion-resistant metal material film 11 move to the electrolyte 4 side through the conductive catalyst material film 12, and are carried by ions in the electrolyte 4 to return to the sensitizing dye. Electric energy is extracted by repeating such an action.

  Hereinafter, examples of the dye-sensitized solar cell, the counter electrode thereof, and the method of manufacturing the counter electrode according to the present invention will be described in detail.

[Example 1]
First, a substrate member with ITO in which a transparent electrode film (ITO film) 6 made of ITO is formed on a substrate member 5 made of polyethylene naphthalate (PEN) (having a rectangular planar shape with a side length of 5 cm, A plate member having a thickness of 125 μm and an electric resistance value of 10Ω / □ was prepared. After applying a titania coating paste for low-temperature film formation to a thickness of 50 μm on the ITO film 6 of the substrate member with ITO, the film is heated at 150 ° C. for 5 minutes to have a thickness of 5 μm on the ITO film 6. A semiconductor electrode film 7 was formed, and then a ruthenium complex dye was adsorbed on the porous semiconductor electrode film 7. Thus, the photoelectrode 2 in which the porous semiconductor electrode film 7 on which the sensitizing dye was adsorbed and supported was formed on the ITO film 6 was produced.

  Further, the counter substrate member with ITO in which the transparent conductive material film 10 made of ITO is formed on the counter substrate member 8 made of polyethylene terephthalate (PET) (having a rectangular planar shape with a side length of 5 cm, A plate member having a thickness of 125 μm was prepared. On the transparent conductive material film 10 of the counter substrate member with ITO, a number of substantially regular hexagonal openings with a distance between parallel side surfaces facing each other of about 50 μm are spaced apart from each other at a constant distance (about 20 μm). The formed plate-like stainless steel mask 20 is disposed and subjected to sputtering treatment, so that a substantially regular hexagonal planar shape with a distance between parallel side surfaces facing each other of about 50 μm is formed from titanium having a thickness of about 10 nm. A number of corrosion-resistant metal material films 11 were formed. Next, the conductive catalyst material film 12 made of platinum having a thickness of about 50 nm was formed on each corrosion-resistant metal material film 11 by performing a sputtering process with the mask 20 placed. The sheet resistance of the conductive film as the counter electrode 3 formed in this way was 10Ω / □, and the transmittance was 47%.

  The porous semiconductor electrode film 7 of the photoelectrode 2 thus formed and the conductive catalyst material film 12 of the counter electrode 3 are arranged so as to face each other, and the porous semiconductor electrode film 7 and the conductive catalyst material film 12 are In the meantime, a redox electrolyte solution was sealed as the electrolyte 4 to prepare the dye-sensitized solar cell 1 of this example.

The dye-sensitized solar cell 1 thus produced was irradiated with pseudo-sunlight having a light irradiation energy of 10 mW / cm ² using a solar simulator, and a battery characteristic test was performed. Further, as a comparative example, FIG. 7 shows the same configuration except that the counter electrode 103 is used instead of the counter electrode 3, that is, the conductive catalyst material film 112 is formed on the entire surface of the counter electrode 103. A conventional dye-sensitized solar cell 101 was produced and subjected to the same battery characteristic test. The results are shown in FIGS. 5 and 6 and Table 1. FIG. 5 shows an experiment on current-voltage characteristics when the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example are irradiated with light from the surface side (photoelectrode side). The results are shown in comparison, and FIG. 5 shows the current when the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example are irradiated with light from the back surface side (opposite electrode side). The experimental result about a voltage characteristic is compared and shown. In Table 1, Isc is a current (short-circuit current) flowing between both terminals when the output terminal of the dye-sensitized solar cell is short-circuited, and Voc is when the output terminal of the dye-sensitized solar cell is opened. Voltage between both terminals (open voltage), f. f. Is a value obtained by dividing the maximum output Pmax (= Imax · Vmax) by the product of the open circuit voltage Voc and the current density Jsc (short circuit current Isc per 1 cm ² ) (fill factor) ff = Pmax / Voc · Jsc ), Η represents a value (conversion efficiency) expressed as a percentage by multiplying 100 by a value obtained by dividing the maximum output Pmax by the irradiation light quantity (W) (per 1 cm ² ).

  As shown in FIG. 5 and Table 1, when light was irradiated from the surface side (photoelectrode side) of the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example, In the dye-sensitized solar cell 1 of the example, the short-circuit current is not so much reduced as compared to the dye-sensitized solar cell 101 of the comparative example (in contrast to 0.640 mA in the comparative example, this In the example, 0.622 mA) and the fill factor has not changed (both are 0.589), so the conversion efficiency has not decreased so much (2.43% in the comparative example, whereas this example) Then 2.34%). On the other hand, as shown in FIG. 6 and Table 1, when light is irradiated from the back side (counter electrode side) of the dye-sensitized solar cell 1 of this example and the dye-sensitized solar cell 101 of the comparative example, The dye-sensitized solar cell 101 of the comparative example does not generate power because it hardly transmits light. However, the dye-sensitized solar cell 1 of this example has a transmittance of 47% and a relatively short circuit current. (0.228 mA) and the fill factor is very high (0.584), so the conversion efficiency is also very high (0.77%) compared to the comparative example (conversion efficiency is almost 0%).

[Examples 2 and 3]
The transmittance is 68% (implemented) in the same manner as in Example 1 except that the interval between the parallel side surfaces of the opening of the mask 20 is about 30 μm (Example 2) and about 10 μm (Example 3). Example 2) and a counter electrode 3 having a transmittance of 89% (Example 3) were produced, and the same battery characteristic test as in Example 1 was performed. The results are shown in FIGS. 5 and 6 and Table 1.

  As shown in FIGS. 5 and 6 and Table 1, in Examples 2 and 3, as in Example 1, when light was irradiated from the surface side (photoelectrode side) of the dye-sensitized solar cell 1 When the light is irradiated from the back side (opposite electrode side) of the dye-sensitized solar cell 1 even though the conversion efficiency is not so much lower than that of the comparative example, the conversion efficiency is comparative example (conversion It can be seen that the efficiency is very high as compared to (approximately 0%).

  A plurality of dye-sensitized solar cells each having a counter electrode according to the present invention are connected in series, or a plurality of solar cell arrays connected in series are connected in parallel to form a dye-sensitized solar cell assembly. If constituted, desired electrical energy can be obtained. In addition, so-called see-through dye-sensitized solar cells can also be produced.

It is sectional drawing which shows typically embodiment of the dye-sensitized solar cell by this invention. It is sectional drawing which shows typically the counter electrode of the dye-sensitized solar cell shown in FIG. It is a top view of the counter electrode of the dye-sensitized solar cell shown in FIG. It is a top view of the mask used for manufacture of the counter electrode of the dye-sensitized solar cell shown in FIG. It is a figure which compares and shows the experimental result about the current-voltage characteristic when light injects from the photoelectrode side of the dye-sensitized solar cell of an Example and a comparative example. It is a figure which compares and shows the experimental result about the current-voltage characteristic at the time of making light enter from the counter electrode side of the dye-sensitized solar cell of an Example. It is sectional drawing which shows the conventional dye-sensitized solar cell typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Dye-sensitized solar cell, 2 ... Photoelectrode, 3 ... Counter electrode, 4 ... Electrolyte, 5 ... Substrate member, 6 ... Transparent electrode film (ITO film), 7 ... Porous semiconductor electrode film, 8 ... Counter substrate Member: 10 ... Transparent conductive material film, 11 ... Corrosion-resistant metal material film, 12 ... Conductive catalyst material film, 20 ... Mask

Claims (7)

A counter substrate member, a transparent conductive material film formed on the counter substrate member, and a plurality of islands formed on a part of the surface of the transparent conductive material film so as to be separated from each other at a predetermined interval And a portion of the surface of the transparent conductive material excluding a part of the surface of the transparent conductive material is not covered with the conductive catalyst material film. Counter electrode. The partial area of the surface of the transparent conductive material film on which the conductive catalyst material film is formed is 95% or less of the entire area of the surface of the transparent conductive material film, Item 2. The counter electrode of the dye-sensitized solar cell according to Item 1. 3. The dye-sensitized solar according to claim 1, wherein the conductive catalyst material film is formed on a part of the surface of the transparent conductive material film via a corrosion-resistant metal material film. The counter electrode of the battery. The counter electrode of the dye-sensitized solar cell according to claim 3, wherein the conductive catalyst material film has substantially the same planar shape as the corrosion-resistant metal material film. The counter electrode of the dye-sensitized solar cell according to claim 3 or 4, wherein the corrosion-resistant metal material film is a film made of titanium. The counter electrode of the dye-sensitized solar cell according to any one of claims 1 to 5, wherein the conductive catalyst material film is a film made of platinum. A counter electrode according to any one of claims 1 to 6, a photoelectrode including a porous semiconductor electrode film disposed opposite to the counter electrode and adsorbing or carrying a sensitizing dye, and the counter electrode A dye-sensitized solar cell comprising an electrolyte encapsulated between photoelectrodes.

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