JP2997366B2 - Solar cell element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell device, and more particularly to a solar cell device having an electrode formed only on the back side of a silicon substrate.

[0002]

2. Description of the Related Art A solar cell device is shown in FIG.
As shown in FIG.
⁺ Region 32 is formed to form a pn junction, and electrodes 33 and 34 are formed on n ⁺ region 32 on one main surface side of silicon substrate 31 and on the other main surface side, respectively. It is. In FIG. 3, reference numeral 35 denotes an antireflection film. However, in such a solar cell element, the electrode 33 is provided on the light receiving surface side.
As a result, the incident light is blocked by the light receiving surface side electrode 33 and a loss due to shadow occurs, and a recombination loss of the carrier occurs in the light receiving surface side electrode 33 and the light receiving surface side high concentration layer 32 portion. There is a problem of doing.

Therefore, in order to reduce the light shadow area on the light receiving surface side and to suppress the recombination of carriers at the light receiving surface side electrode portion, as shown in FIG. Arranged solar cell elements have also been proposed. That is, only the concave and convex portions 42 and the antireflection film 43 are formed on one main surface side of the p-type silicon substrate 41, and the n ⁺ region 44 and the p ⁺ region 45 are formed on the other main surface side in the silicon substrate 41. Then, the electrodes 46 and 47 are formed so as to be in point contact with the n ⁺ region 44 and the p ⁺ region 45, respectively. With this configuration, since there is no electrode on the light receiving surface side of the silicon substrate 41, the light shadow area becomes zero, and the recombination of carriers can be suppressed by reducing the contact area with the electrode.

However, in this solar cell element, if the silicon substrate 41 has a large specific resistance, the series resistance increases when the solar cell element is formed, and the efficiency is greatly reduced due to the influence of surface recombination. There's a problem.

Therefore, as shown in FIG. 5, a large number of through holes 52 are formed in a p-type silicon substrate 51, and an n ⁺ region 53 is formed continuously with the light receiving surface side of the silicon substrate 51 and in the through hole 52. The electrode 5 is formed on each of the p ⁺ region 54 on the back side and the n ⁺ region 55 on the back side of the through hole.
A solar cell element in which the light-shading area on the light-receiving surface side of the silicon substrate 51 is reduced by forming the layers 6 and 57 has also been proposed (for example, see JP-A-1-51282). Such a through hole 52 is formed by, for example, a YAG laser or the like.
Forming the through-holes 52 by irradiating a laser in a spot-like manner is complicated and time-consuming, the cost of the solar cell element becomes extremely high, and the n ⁺ region is precisely formed in the vicinity of these through-holes 52. There is a problem that it is difficult to form and the production yield is reduced. In FIG. 5, reference numeral 58 denotes an antireflection film formed on the light receiving surface side of the p-type silicon substrate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to prevent a reduction in efficiency due to a light-shading area and to prevent a recombination loss of a carrier, thereby realizing a low-cost and high-efficiency solar cell. It is an object to provide a battery element.

[0007]

According to the present invention, a linear through-hole is provided in a p-type silicon substrate having an uneven portion on the light-receiving surface side, and an n-type through hole is provided near the through-hole on the back surface of the silicon substrate.
⁺ Region is provided, and an electron conduction region connected to the n ⁺ region from the light receiving surface side of the silicon substrate via the through hole portion is provided in the silicon substrate, and the light receiving surface side of the silicon substrate and the through hole are provided. A passivation film and an antireflection film, a p ⁺ region is provided in a portion other than the portion where the n ⁺ region is formed on the back side of the silicon substrate, and electrodes are formed on the n ⁺ region and the p ⁺ region. Thus, the above object is achieved.

[0008]

As described above, since there is no electrode on the light receiving surface side of the silicon substrate, light loss and carrier recombination loss are reduced. Furthermore, by forming an uneven portion on the light receiving surface side of the silicon substrate and forming a linear through hole in the silicon substrate, the surface area of the silicon substrate is increased, and the time required for forming the through hole is significantly increased. This facilitates formation of the through hole and the n ⁺ region around the through hole. Therefore, a highly efficient solar cell element can be manufactured at low cost without lowering the manufacturing yield.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a perspective view showing one embodiment of a solar cell element according to the present invention, and 1 shows a p-type silicon substrate as a whole.

The silicon substrate 1 is formed of a silicon substrate having a specific resistance of about 0.4 to 10 Ω · cm and a thickness of about 50 to 200 μm containing a p-type impurity such as boron. This silicon substrate 1 may be a single crystal silicon substrate formed by a pulling method or the like, or may be a polycrystalline silicon substrate formed by a casting method or the like.

In the silicon substrate 1, a linear through hole 1a is formed. This through hole 1a increases the surface area (light receiving area) of the silicon substrate 1 and
It is formed to guide a minority carrier (electron) described later to the back surface side of the silicon substrate 1. This line-shaped through hole 1a
Is formed to have a width of about 30 to 100 μm and a length excluding both ends of the silicon substrate 1. The through hole 1a is not limited to being formed continuously from the vicinity of one end of the silicon substrate 1 to the vicinity of another end, but may be formed intermittently. Further, this through hole 1a is not limited to the case where the through hole 1a is formed perpendicular to the surface of the silicon
The incident light may be efficiently taken into the silicon substrate 1 by forming it at a certain angle with respect to the surface.

On the light receiving surface side of the silicon substrate 1, a pyramid-shaped uneven portion 1b is formed by texture processing. The pyramid-shaped uneven portion 1b is formed to reduce the reflection loss of irradiation light on the surface of the silicon substrate 1. In addition, not only the pyramid-shaped uneven portion but also a large number of V-shaped grooves may be formed. When a V-shaped groove is formed on the surface of the silicon substrate 1, it is formed by a photolithography technique using a sodium hydroxide solution or the like. In FIG. 1, reference numeral 3 denotes an electrode in an n ⁺ region, and reference numeral 4 denotes an electrode in a p ⁺ region.

FIG. 2 is a partial sectional view of a solar cell element according to the present invention. In the silicon substrate 1, a linear through hole 1a is formed to be inclined. An n ⁺ region 5 is selectively formed near the through hole 1a on the back surface side of the silicon substrate 1. This n ⁺ region 5 is made of phosphorus (P)
It contains semiconductor impurities such as arsenic and arsenic (As) at a high concentration. In a portion other than the portion where the n ⁺ region 5 is formed on the back surface side of the silicon substrate 1, ap ⁺ region 6 serving as a BSF (back surface electric field) layer is formed at an appropriate distance from the n ⁺ region 5 portion. Have been. This p ⁺ region 6 is formed by containing an aluminum element or the like at a high concentration.

In the silicon substrate 1 at the light-receiving surface side of the silicon substrate 1 and the through hole 1a, an electron conduction region 7 is provided.
Are formed. The electron conduction region 7 includes an n layer, a heterojunction layer, an inversion layer, or the like, and is formed so as to be connected to the n ⁺ region 5 formed on the back surface side.
That is, it is for efficiently separating electrons and holes generated near the surface and guiding electrons guided to the front surface of the silicon substrate 1 to the n ⁺ region 5 formed on the back surface side of the silicon substrate 1. When the electron conduction region 7 is formed of an n-layer, an n-type semiconductor impurity such as phosphorus (P) or arsenic (As) may be diffused into the surface of the silicon substrate 1. When the electron conduction region 7 is formed of a heterojunction layer, for example, an amorphous silicon carbide layer or the like may be formed on the surface of the silicon substrate 1. Further, when the electron conduction region 7 is formed of an inversion layer, the electron attracting layer 8 is formed of, for example, a silicon nitride film having a charge density of about 3 × 10 ¹¹ to 2 × 10 ¹³ cm ^{−2 on} the surface of the silicon substrate 1. May be formed. In addition,
When the electron conduction region 7 is formed of an n-layer or a heterojunction layer, the electron attracting layer 8 is not always necessary.

[0015] On the surface side including the through-hole 1a of the silicon substrate 1 is a passivation film 2 made of silicon oxide (SiO _X) film is formed on a thickness of about 50 Å. In FIG. 2, reference numeral 9 denotes an antireflection film made of a magnesium fluoride layer or the like. Further, on n ⁺ region 5 formed on the back surface side of silicon substrate 1, electrode 3 made of Al or the like, which is in point contact with n ⁺ region 5, and p ⁺ region 6
And electrodes 4 made of Al or the like, which are in point contact with each other. The electrode 3 of the n ⁺ region 5 and the p ⁺ region 6
The electrode 4 may be formed in a comb-tooth shape so as to merge with each other at the opposing portions on the back surface side of the silicon substrate 1. The electrode 3 in the n ⁺ region 5 and the electrode 4 in the p ⁺ region 6 are
It also serves as R (backside antireflection layer).

In the above-described solar cell element, when the electron conduction region 7 is constituted by an inversion layer, it is formed by the following steps. First, the p-type silicon substrate 1 is cleaned with HCl or the like. Next, YAG narrowed down to about 10 μm
Using a laser or the like, the linear through hole 1a is formed to be inclined. Next, in order to remove the damaged layer, the surface of the silicon substrate 1 is lightly etched using a mixed solution of hydrofluoric acid and nitric acid. Next, a pyramid-shaped uneven portion 1b is formed on the light receiving surface side of the silicon substrate 1. The pyramid-shaped uneven portion 1b is formed by a texturing process using a sodium hydroxide solution or the like. Next, the light receiving surface and the n region of the through hole, the n ⁺ region on the back surface, and the p ⁺ region are formed by ion implantation or thermal diffusion. Next, a passivation film 2 made of a silicon oxide film or the like is formed by plasma CVD.
A predetermined portion on the rear surface side (portion for forming the n ⁺ region and p ⁺ region electrodes) is removed by etching or thermal oxidation. Next, electrodes 3 and 4 made of Al or the like are formed on n ⁺ region 5 and p ⁺ region 6 by screen printing or vapor deposition. Finally, an electron attracting layer 8 made of a silicon nitride film or the like and an antireflection film 9 made of a magnesium fluoride film or the like are formed by plasma CVD or the like.

[0017]

As described above, in the solar cell element according to the present invention, a linear through-hole is provided in a p-type silicon substrate having an uneven portion on the light-receiving surface side, and the through-hole is formed on the back side of the silicon substrate. An n.sup. ⁺ Region is provided near the hole, and the n.sup. ⁺
An electron conduction region connected to the region is provided in the silicon substrate, a passivation film and an antireflection film are provided on the light receiving surface side of the silicon substrate and the through hole, and the n ⁺ region on the back surface side of the silicon substrate is formed. Since the p ⁺ region is provided in a portion other than the portion described above, and electrodes are formed on the n ⁺ region and the p ⁺ region, there is no electrode on the light receiving surface side of the silicon substrate, and carrier reclamation near the electrode is not performed. In addition to eliminating coupling loss, there is an electron conduction region on the light-receiving surface side of the silicon substrate, so current can be collected effectively, and voltage and current characteristics can be improved at lower cost compared to conventional configurations. it can. Further, since the through hole is formed in a line shape, the time required for forming the through hole is significantly reduced, and the formation of the through hole and the n ⁺ region around the through hole is facilitated. Therefore, a highly efficient solar cell element can be manufactured at low cost without lowering the manufacturing yield.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a solar cell element according to the present invention.

FIG. 2 is a sectional view of a solar cell element according to the present invention.

FIG. 3 is a view showing a conventional solar cell element.

FIG. 4 is a view showing another conventional solar cell element.

FIG. 5 is a view showing another conventional solar cell element.

[Explanation of symbols]

1 ... p-type silicon substrate, 1a ... through-hole, 1b.
..Uneven portions, 2 ... passivation film, 3 ... n ⁺
, P ⁺ region, 5... N ⁺ region, 6... P ⁺ region, 7... Electron conduction region, 9.
..Anti-reflection film.

Claims (1)

(57) [Claims] A linear through hole is provided in a p-type silicon substrate having an uneven portion on a light receiving surface side, and an n ⁺ region is provided near the through hole on the back surface side of the silicon substrate. The conduction region of electrons connected to the n ⁺ region from the surface side through the through hole portion is connected to the silicon substrate.
Provided within the passivation film and the antireflection film is provided between the light-receiving surface side of the silicon substrate in the through holes, the p ⁺ region provided in a portion other than the n ⁺ region is formed portion of the silicon substrate backside A solar cell element comprising electrodes formed on the n ⁺ region and the p ⁺ region.