JPH02143468A - Solar cell - Google Patents

Abstract

PURPOSE:To manufacture an integrated solar cell in high efficiency and having sufficiently effective space regardless of the specific resistance of semiconductor films by a method wherein the cells are isolated by the bumps of substrates comprising ceramics etc., as well as the grooves cut by physical removal of the semiconductor films. CONSTITUTION:A ceramic substrate 1 is sectioned into equispaces by square sectional bumps 11'. First, Si powder is heaped up on the substrate 1' to be heated and melted down in H2 so that the substrate 1' may be doped with the Si powder to give the specific resistance of 0.001OMEGAcm. Secondly, active layers 3'. in the same conductivity type and the specific resistance of 0.1-1.0OMEGAcm are formed on semiconductor films 2' by liquid deposition process. Thirdly, fine crystalline hydrogenated Si films 4 in inverse conductivity type to that of the films 3' are laminated on the films 3' to make pn junctions. Fourthly, the films 3', 4' are deposited only on the parts above Si underneath layers. Fifthly, grooves 12 reaching the semiconductor films 2' are cut in parallel with the bumps 11'. Finally, the sectional regions 13' by the grooves 12' and the bumps 11' are melted down linearly into conductive channels 13' by laser beams to be communicated with the semiconductor films 2 so that cells A, B may be connected by paste 5' to be covered with reflection preventive films 15' for the completion of an integrated poly Si solar cell.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to the structure of a solar cell using a polycrystalline material, and particularly relates to a solar cell structure in which a plurality of power generation regions are connected in series on - substrates. The present invention aims to reduce the cost of integrated solar cells.

[Conventional technology]

Figure 2a) is a plan view of the conventional integrated polycrystalline solar cell shown in U, S, P, 4,042,418, Figure 2b
) is also a sectional view. In the figure, 1 is an insulating substrate such as ceramic or glass, 2 is a metal thin film such as Cu or A1 deposited on one surface of the insulating substrate 1, and 3 is a first semiconductor film responsible for power generation (e.g. Cu25), 4 is a second semiconductor film forming a junction with the first semiconductor film 3 (for example, C
d5), 5 is a metal part such as AI or Ag that is partially deposited on the surface of the second semiconductor film 4, and 6 is also deposited on the surface part of the second semiconductor film 4 and is electrically connected to the metal part 5. It is a conductive paste made of, for example, carbon powder, which has an atomic contact and contains a diffused atomic source (such as Zn).

For example, the part sandwiched by the thin lines indicated by A constitutes one unit solar cell by a junction made of semiconductor films 3 and 4 and metal parts 2 and 5 that are in electrical contact with each of these and serve as electrodes. ing. B is another unit solar cell having a similar configuration.

When the temperature of the diffusion source atoms contained in the conductor paste 6 is increased to diffuse them into the semiconductors 3 and 4, the resistance of this portion decreases and a conductive portion 7 (hatching) is formed between the metal thin film 2 and the conductor base 6. ) is formed. This conductive portion 7 connects the metal portion 5 of the unit solar cell A and the metal thin film 2 of the unit solar cell B. Additionally, each unit solar cell is provided with electrical connections similar to those of adjacent unit solar cells. In this case, if the electrical resistance between the gap a and the gap is small, the output of each unit solar cell will be consumed by the resistance of this part, and sufficient output will not be obtained. In order to avoid such inconvenience, the resistivity of the semiconductor films 3 and 4 should be set sufficiently high (1 to 100Ω).
cm) or when the specific resistance is low, it is necessary to widen the gaps a and b.

[Problem to be solved by the invention]

The condition of increasing the specific resistance of the semiconductor films 3 and 4 imposes an unfavorable design condition on a solar cell using thin film polycrystalline silicon (Si), which is low in cost and has excellent characteristics. In other words, the specific resistance of high-efficiency thin film polycrystalline St is 1
It is desirable that Ωc be 11 or less.

Furthermore, increasing the gaps a and b increases the ineffective area that does not contribute to power generation, which has the disadvantage of reducing the output per unit area, that is, the efficiency.

The present invention was made in order to solve the above-mentioned conventional problems, and uses Si, which is a material with relatively low resistivity, low cost, and no pollution problems, and has sufficient effectiveness. The purpose of this invention is to provide an integrated polycrystalline solar cell that can secure a large area and provide high efficiency.

[Means to solve the problem]

In the solar cell according to the present invention, linear protrusions are formed on an insulating substrate so that a semiconductor portion formed on the substrate is divided into small parts, and the semiconductor portion is formed in a region of each recess between the protrusions. A semiconductor layer is formed on the portion to form a solar cell, and in order to separate the surface corresponding to the gap a in Fig. 2, a groove is formed by scribing with a dicing saw, etc. The power generation region and the connection region are electrically connected by the semiconductor portion, and the connection region of one solar cell and the main power generation region of the other solar cell are connected via the protrusion. It is electrically connected.

[Effect]

In this invention, the insulating substrate is divided into a plurality of parts having equal areas by the bank-like protrusions, and the semiconductor part formed thereon is brought into a molten state and gathered at the lower part of the substrate, so that the semiconductor part A solar cell having a semiconductor layer thereon can be formed electrically independently in each depression formed by the protrusion. Further, the solar cell is divided into a main power generation region and a connection region by a groove formed in a part thereof, and the connection region and the main power generation region are electrically connected by a semiconductor portion on the surface in contact with the substrate, and the surface The connecting area of the solar cell in one recessed part is electrically connected to the main power generation area of the solar cell in the other adjacent recessed part through the above-mentioned protrusion. In this way, series connection of unit solar cells is possible. In addition, separation by protrusions reduces the distance between units,
A sufficient effective area can be secured and high efficiency can be obtained.

Furthermore, by making the semiconductor portion used as the substrate-side conductive film thick, a margin for processing accuracy in the thickness direction can be secured, and separation of the surface layer using a dicing saw can be realized.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1A is a perspective view of a substrate of a solar cell according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view thereof.The manufacturing method of this embodiment will be explained using FIG.

Reference numeral 1- denotes a substrate made of ceramic (for example, alumina, etc.), which is divided into small parts of equal area by protruding banks 11' having a roughly square cross section of 0.1 to 0.5 mm square. For example, Si powder is placed on the substrate 1-, melted by heating in a reducing atmosphere, and cooled. The amount of impurities is n even if it is p-type.
Regardless of the type, adjust the specific resistance to 0.001 Ωcm. As a result, 512- dissolves between the banks 11- and 11- to form a film, as shown in FIG. 1C). This semiconductor film 2' is used as a lower electrode and is not an active layer for power generation. The active layer 3- for power generation is formed by a method called liquid phase growth, by placing the substrate on which the semiconductor film 2 is formed at the bottom of a solution of Si and Sn,
By gradually cooling the 5iSn solution, which has become supersaturated at a temperature between 0.degree. In this case, the semiconductor film 3' is preferably of the same conductivity type as the semiconductor film 2- and has a specific resistance in the range of 0.1 to 1.0 Ωc1.

Subsequently, a semiconductor film 4' made of a microcrystalline hydrogenated silicon film of a conductivity type opposite to that of the semiconductor film 3- is deposited as shown in FIG. 1e) to form a pn junction. This converts impurity gas such as PH3 (n-type) or B2 Ha (p-type) into SiH
, and H2 in addition to glow discharge decomposition. Alternatively, BCl2 (p-type)
Alternatively, a gas such as POCI (n-type) is brought into contact with the surface of the semiconductor film 3, and the surface is irradiated and heated with an ArF excimer laser to perform doping, thereby forming a semiconductor film 4- of the opposite conductivity type. It is also possible to do so.

The semiconductor films 3' and 4' are deposited only on the portions where the underlying layer is St. Next, using, for example, a dicing saw, a hole 77412- parallel to the embankment 11' is dug as shown in FIG. 1f).

This groove 12 cuts the semiconductor films 4' and 3- so as to reach the semiconductor film 2', but does not cut the semiconductor film 2'.

This is done by making the semiconductor film 2- sufficiently thick (100~
500 μm).

A fine region 13- separated by the groove 12- and the bank 11- is irradiated and swept with a laser beam (for example, an Ar laser) as shown in FIG. The conductive path 13- is melted in a dotted or linear shape so as to be electrically connected to the semiconductor film 2-. That is, the semiconductor film 2' and the semiconductor film 4' are short-circuited by the molten semiconductor.

Furthermore, adjacent cells A and B are connected in series (electrically connected)
In order to do this, the silver paste 5- is patterned, printed, and fired. In that case, as shown in Fig. 1h), the surface of the laser-melted portion 13- in the section of cell A and the wider power generation region 14- of the semiconductor film 4'' of cell B separated by the groove 12'. For example, a comb-like electrode 5' is formed to connect the two.Thereafter, an antireflection film 15' (for example, a TiO2 film) is formed by a known method to complete an integrated polycrystalline Sf solar cell.

When the junction is formed with a microcrystalline semiconductor film 4', the antireflection film 15' is an IT film formed by vapor deposition or sputtering.
It is desirable to use O. In this case, the semiconductor film 4-
Since the ITO is formed after forming the groove 12' and before forming the groove 12', there is no anti-reflection film 15' shown in Figure 1h), which is sandwiched between the semiconductor film 4' and the electrode 5'. layered (
(not shown).

Further, with such a structure, a pin junction solar cell made of amorphous silicon is formed in a layered manner on the semiconductor film 4', and then ITO is formed as the antireflection film 15', and then the groove 12- is formed, and the above-mentioned process is subsequently performed. By performing the steps as in the embodiment, it is possible to realize an integrated type solar cell having a structure in which two power generation layers are laminated.

〔Effect of the invention〕

As described above, according to the present invention, in a solar cell, adjacent cells are separated by a groove formed by physically removing a semiconductor film and a protrusion on a substrate such as a ceramic. This has the effect of realizing a solar cell with an integrated structure that has a sufficient effective area and can achieve high efficiency regardless of the specific resistance of the solar cell.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, in which a) is a perspective view of a substrate, b) is a cross-sectional view of the substrate, C) to h) are views sequentially showing cross-sections in each manufacturing process, and FIG. The figure shows a conventional solar cell. In the figure, 1.1" is the substrate, 2.2- is the substrate side electrode,
3.3'' is a first semiconductor layer which becomes a power generation part, 4.4- is a second semiconductor layer of the opposite conductivity type to the first semiconductor layer 3, 5 is an upper electrode, and 6 is a part of an electrode. 7 is a diffusion source layer, 7 is a conductive path by diffusion, 11″ is a protrusion provided on the substrate, 1
2- is a groove, 13- is a conductive path melted by laser, 14'' is a power generation area, and 15' is an anti-reflection film. Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1) A semiconductor portion serving as a conductive layer is formed in each recessed portion of a substrate made of an insulator having a plurality of recesses formed by a plurality of protrusions, and a semiconductor portion is formed on the semiconductor portion of the recessed portion. A layer is formed and a solar cell is formed electrically independently in each recessed part, and the solar cell is divided into a main power generation area and a connection area by a groove formed in a part of the solar cell, and the connection area and the connection area are divided into a main power generation area and a connection area. The main power generation area is electrically connected by the semiconductor part on the surface in contact with the substrate and electrically separated by the groove on the surface part, and includes the connection area of the solar cell in one recessed part and the other area adjacent to this. A solar cell characterized in that the recessed portion of the solar cell is electrically connected to the main power generation area of the solar cell through the projection.