JP2003017719A - Photo-electric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem about the fact that a photo-electric conversion device using conventional spherical crystalline semiconductor particles is low in conversion efficiency. SOLUTION: A large number of first conductivity spherical crystalline semiconductor particles 3 are arranged on a board 1 which is to serve as one of electrodes, an insulating material layer 2 is interposed between the spherical crystalline semiconductor particles 3, and a second conductivity semiconductor layer 4 and a protective film 5 are formed on the spherical crystalline semiconductor particles 3 for the formation of a photo-electric conversion device. An acute projection 6 is provided to each of the first conductivity spherical crystalline semiconductor particles 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion device used for solar power generation, and more particularly to a photoelectric conversion device using spherical crystalline semiconductor particles.

[0002]

2. Description of the Related Art The advent of low-cost next-generation solar cells using silicon-saving raw materials is strongly desired. FIG. 2 shows a conventional photoelectric conversion device using grain-shaped or spherical silicon crystal particles, which is advantageous in saving resources (see, for example, Japanese Patent No. 2641800). In this photoelectric conversion device, a low melting point metal layer 9 is formed on a substrate 1, and an average particle size of 20 μm is formed on the low melting point metal layer 9.
First-conductivity-type spherical crystalline semiconductor particles 3 having a size of 50 μm or more are provided, and second-conductivity-type amorphous semiconductor layer 8 and transparent conductive layer 7 are provided on the spherical-crystalline crystalline semiconductor particles 3 with the low melting point metal. A photoelectric conversion device formed between the layer 9 and the insulating layer 2 is disclosed.

Further, as shown in FIG. 3, an aluminum film 10 is formed around a steel substrate 11, crushed silicon particles 12 having a particle size of 300 μm or more and 1000 μm or less are bonded to the aluminum film 10, and an insulator 13, an n-type is formed. Silicon part 14,
It is disclosed that the transparent conductive layer 15 is sequentially formed (see, for example, US Pat. No. 4,514,580).

[0004]

However, in the conventional photoelectric conversion device shown in FIG. 2, the average particle size is 20 μm or more.
There is a problem in that semiconductor particles having a particle size of 0 μm or less are used, but since the average particle size is too small, light cannot be sufficiently absorbed and the conversion efficiency becomes low. In addition, there is no specific description about a suitable shape of semiconductor particles.

In the conventional photoelectric conversion device shown in FIG. 3, crushed silicon particles having a particle size of 300 μm or more and 1000 μm or less are used, but the shape of the crushed silicon particles cannot be controlled at all, and the surface of the silicon particles is further crushed. There is a problem in that the surface becomes defective due to damage, resulting in low conversion efficiency.

The present invention has been made in view of the above problems in the prior art, and an object thereof is to provide a photoelectric conversion device having excellent characteristics.

[0007]

In order to achieve the above object, according to the photoelectric conversion device of the present invention, a large number of spherical crystalline semiconductor particles of the first conductivity type are arranged on a substrate which is one of the electrodes. In the photoelectric conversion device, an insulating material is interposed between the spherical crystalline semiconductor particles, and a semiconductor layer of the second conductivity type is formed on the spherical crystalline semiconductor particles. The particles are characterized by having a convex portion.

In the photoelectric conversion device described above, it is desirable that the convex portions of the spherical crystalline semiconductor particles have a sharp shape.

In the photoelectric conversion device described above, the length of the convex portion is preferably 1/20 or more and not more than the particle diameter of the spherical crystalline semiconductor particles.

In the above photoelectric conversion device, it is desirable that the spherical crystalline semiconductor particles have a particle size of 100 μm or more and 400 μm or less.

In the photoelectric conversion device, it is desirable that the spherical crystalline semiconductor particles are silicon.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a photoelectric conversion device according to the present invention, in which 1 is a substrate, 2 is an insulating material,
3 is a spherical crystalline semiconductor particle of the first conductivity type, 4 is a semiconductor layer of the second conductivity type, 5 is a protective film, and 6 is a sharp convex portion.

As the substrate 1, metal, ceramic, resin or the like is used. The substrate 1 also serves as a lower electrode as long as it has conductivity as a characteristic, and when the material is a metal, the substrate 1 has a single layer or a multi-layer with another metal. When the substrate 1 is an insulator such as ceramic or resin, it is necessary to form a conductive layer on the surface thereof.

The insulating material 2 is filled between the semiconductor particles 3 in order to separate the positive electrode and the negative electrode. For example, SiO ₂ , Al ₂
It is formed using a glass slurry containing O ₃ , PbO, ZnO or the like as an arbitrary component. It is formed by applying it to an arbitrary thickness by a screen printing method or the like, and heating and baking. A resin material such as epoxy or polyimide may be used as the insulating material 2.

The spherical crystalline semiconductor particles 3 of the first conductivity type are
It is made of a semiconductor material such as silicon or germanium, and is preferably silicon. The semiconductor particles 3 have convex portions 6
It is a shape having. Using the semiconductor particles 3 having the convex portions 6 has an effect of improving conversion efficiency. The cause is that the convex portions 6 enter the gaps between the semiconductor particles 3 and easily absorb more light, or the light incident on the top of the semiconductor particles 3 is generated by the convex portions 6. It is considered that the stress is easily relaxed in the process of forming the semiconductor particles 3 due to the effect of scattering and leading to the adjacent semiconductor particles 3, and crystals with few defects are formed. Furthermore, it becomes possible to further arrange the arrangement of particles by a vacuum suction method using this convex portion or an arrangement method by electromagnetic force.

The shape of the convex portion 6 is preferably a sharp shape. The sharp shape refers to a convex portion having a narrow tip, and is not limited to the shape in which the convex portion 6 has an acute angle, and a diameter of a part of the particles is smaller than the particle diameter. Also includes a shape having a curved surface. The sharp shape may be present at multiple points of the grain. The length of the convex portion 6 is preferably not less than 1/20 of the particle diameter and not more than the particle diameter. When the length of the convex portion 6 is 1/20 or less of the particle diameter, the effect of improving the conversion efficiency becomes small, which is not preferable, and when the length of the convex portion 6 is equal to or larger than the particle diameter, the convex portion 6 6 is not preferable because it easily breaks during handling.

The particle size of the semiconductor particles 3 is preferably 100 μm or more and 400 μm or less. If it is 100 μm or less, it is not preferable because it cannot absorb light sufficiently and the conversion efficiency is lowered. It is not preferable because the amount of the semiconductor raw material is decreased and the amount of the semiconductor raw material used is increased to increase the cost. In addition, the convex portion 6
Even in the case of the photoelectric conversion device in which the semiconductor particles 3 having the convex portions and the semiconductor particles 3 having no convex portion are mixed, if the ratio of the semiconductor particles having the convex portions 6 is 5% or more, the effect of improving the conversion efficiency is obtained. Was confirmed. However, the smaller the proportion of the semiconductor particles having the convex portions 6 is, the smaller the effect of improving the conversion efficiency is. Therefore, the proportion of the semiconductor particles having the convex portions 6 is more preferably 30% or more.

The semiconductor particles 3 can be formed by a vapor phase growth method, an atomizing method, a direct current plasma method or the like, but a melt dropping method of dropping the melt in a non-contact environment is preferable. The shape and size of the convex portion 6 can be changed by controlling the temperature during dropping.

The semiconductor layer 4 of the second conductivity type is VHF-CV.
For example, by D method, plasma CVD method, catalytic CVD method or the like, a minute amount of a vapor phase of a phosphorus-based compound exhibiting an n-type or a vapor phase of a boron-based compound exhibiting a p-type is introduced into a vapor phase of a silane compound to form a semiconductor layer. To do. Further, it may be formed by diffusing into the semiconductor particles in the vapor phase of the phosphorus compound exhibiting the n-type or in the vapor phase of the boron compound exhibiting the p-type. The trace element concentration of the second conductivity type semiconductor layer 4 is, for example, 1 × 10 ¹⁴ to 10 ¹⁴
It is about ²² atm / cm ³ .

A protective film 5 may be provided on the semiconductor layer 4 of the second conductivity type. As the protective film 5, silicon nitride, titanium oxide, tin oxide, indium oxide, or the like is formed by a sputtering method, a plasma CVD method, or the like. It is also possible to have a role such as multiple reflection effect, antireflection effect, weather resistance improvement, and low resistance.

Further, a silver or copper paste may be formed thereon as an auxiliary electrode in an appropriate pattern.

[0022]

EXAMPLES Next, specific examples of the photoelectric conversion device of the present invention will be described. First, the insulating material 2 is formed on the substrate 1.
Aluminum was used for the substrate 1. The insulating material 2 was formed to a thickness of 60 μm using a glass paste. Next, a crystalline p-type silicon particle 3 having an average particle size of 160 μm is densely placed on the surface of the layer.
Layered. Table 1 shows the results of evaluation of the conversion efficiency by changing the shape of the p-type silicon particles.

Next, the substrate 1, the insulating material 2 and the crystalline p-type silicon particles 3 were heated to 600 ° C., the silicon particles 3 were submerged in the insulating material 2 and brought into contact with the substrate 1. Next, an n-type crystalline silicon layer 4 was formed on the silicon particles 3 and the insulating material 2 using silane, hydrogen and phosphine by a plasma CVD method. The substrate temperature during film formation is 300
C. and pressure were 1 Pa. Adjust the flow rate of phosphine,
The concentration of phosphorus added to the n-type crystalline silicon layer 4 is 1 × 10
^The film thickness was set to ¹⁹ atm / cm ³ and the film thickness was set to 100 nm. A protective film 5 made of tin oxide was formed thereon to a thickness of 100 nm.

[0024]

[Table 1]

As can be seen from the above results, the use of semiconductor particles having a sharp convex shape is suitable because the conversion efficiency is improved. Further, it is more preferable that the length of the convex shape is 8 μm or more (1/20 of the particle size) and 160 μm or less (particle size).

Next, the results of evaluation of conversion efficiency by changing the shape of crystalline p-type silicon particles having an average particle diameter of 360 μm are summarized in Table 2.

[0027]

[Table 2]

As can be seen from the above results, conversion efficiency is improved when semiconductor particles having a sharp convex shape are used. Further, it is more preferable that the length of the convex shape is 18 μm or more (1/20 of the particle size) and 360 μm or less (particle size).

From the results shown in Tables 1 and 2, it is more preferable that the length of the convex shape is 1/20 or more of the particle diameter and less than or equal to the particle diameter.

Next, Table 3 shows the results of evaluating the conversion efficiency by changing the particle size of the crystalline p-type silicon particles. The silicon particles used had a sharp convex portion having a length of 1/4 of the particle diameter.

[0031]

[Table 3]

As can be seen from the above results, it is more preferable that the particle size of the silicon particles is 100 μm or more and 400 μm or less.

[0033]

As described above, according to the photoelectric conversion device of the present invention, a large number of first-conductivity-type spherical crystalline semiconductor particles are provided on the substrate which is one of the electrodes, and the spherical crystalline semiconductor In a photoelectric conversion device in which an insulating material is interposed between particles and a semiconductor layer of the second conductivity type is formed on the spherical crystalline semiconductor particles, the spherical crystalline semiconductor particles of the first conductivity type have sharp convex portions. With this, high conversion efficiency can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a photoelectric conversion device of the present invention.

FIG. 2 is a cross-sectional view showing a conventional photoelectric conversion device.

FIG. 3 is a cross-sectional view showing another conventional photoelectric conversion device.

[Explanation of symbols]

1 ... substrate 2 ... Insulating material 3 ... Spherical crystalline semiconductor particles of the first conductivity type 4 ... Second conductivity type semiconductor layer 5 ... Protective film 6 ... Convex part 7 ... Transparent conductive layer 8 ... Amorphous semiconductor layer 9 ... Low melting point metal layer 10 ... Aluminum film 11 ... Steel substrate 12 ... Crushed silicon particles 13 ... Insulator 14 ... n type silicon part 15 ... Transparent conductive layer

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Claims (5)

[Claims] 1. A large number of spherical crystalline semiconductor particles of the first conductivity type are provided on a substrate to be one of the electrodes, and an insulating substance is interposed between the spherical crystalline semiconductor particles, and the spherical crystalline semiconductor particles are formed. A photoelectric conversion device having a second-conductivity-type semiconductor layer formed thereon, wherein the first-conductivity-type spherical crystalline semiconductor particles have a convex portion. 2. The photoelectric conversion device according to claim 1, wherein the convex portion of the spherical crystalline semiconductor particle has a sharp shape. 3. The photoelectric conversion device according to claim 1, wherein the length of the convex portion is 1/20 or more and not more than the particle diameter of the spherical crystalline semiconductor particles. 4. The particle size of the spherical crystalline semiconductor particles is 10.
3. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device has a thickness of 0 μm or more and 400 μm or less. 5. The photoelectric conversion device according to claim 1, wherein the spherical crystalline semiconductor particles are silicon.