JP2000353816A - Manufacture of thin film solar battery module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a highly integrated thin film module and greatly improve its power generation, especially a current, by adjusting a substrate temperature in each layer laser scribe process within a certain range of a set value. SOLUTION: A transparent electrode 2 consisting of SnO2 is formed in a surface of a glass substrate 1. A bus bar electrode formation region is formed in an outside of a unit cell (string) at both ends. An entire circumference of a circumferential edge of the glass substrate 1 is subjected to laser scribe for electrically separating a circumferential edge of the glass substrate 1 and an active part of a solar battery cell. A scribe interval in a laser scribe process of each layer is set by using a substrate whose substrate temperature is a room temperature (25 deg.C). If a glass substrate temperature in a scribe process of the semiconductor layer 4 is not higher than 35 deg.C, that is, the difference between it and a substrate temperature (25 deg.C) during scribe interval setting is 10 deg.C or lower, scribe of the semiconductor layer 4 can be performed highly precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film solar cell module, and more particularly to an improvement in a laser scribe process.

[0002]

2. Description of the Related Art A thin-film solar cell module has a structure in which a number of unit cells each composed of a transparent electrode, a semiconductor layer and a back electrode are connected in series on a glass substrate. In order to connect a large number of unit cells in series, a step of separating each of the layers sequentially formed on the glass substrate into a string at a predetermined pitch by scribing using a laser processing machine is performed. At this time, in order to avoid a short circuit between the transparent electrode and the back electrode in the unit cell due to a shift of the laser processing machine, the scribe line of the transparent electrode and the scribe line of the semiconductor layer are processed while being shifted. Also, in order to prevent the back electrode of one unit cell from being disconnected from the transparent electrode of an adjacent unit cell due to a shift of the laser processing machine, the scribe line of the semiconductor layer and the scribe line of the back electrode are shifted. Process.

In the current thin film solar cell module, for example, the scribe line width of the transparent electrode layer is set to about 50 μm, the scribe line width of the semiconductor layer is set to about 100 μm, and the scribe line width of the back electrode layer is set to about 100 μm. Is 250 μm. Conventionally, the gap between the scribe lines of each layer is designed to be large in order to allow for the deviation of the laser processing machine. For this reason, the width of the separation region (from one end of the scribe line of the transparent electrode to the other end of the scribe line of the back electrode) between two adjacent unit cells is about 500 μm, which is essentially necessary. The width was almost twice as large as 250 μm, which is an important processing width. This separation region does not contribute to power generation, but merely hinders high integration of unit cells, and thus causes power loss in the thin-film solar cell module.

On the other hand, by grasping the accuracy of the laser processing machine and strictly controlling the operation of the laser processing machine, the interval between the scribe lines of each layer is made much narrower than before so that the separation region can be formed. The width can be reduced.

However, despite the strict control of the operation of the laser beam machine, the distance between the scribe line of the transparent electrode and the scribe line of the semiconductor layer becomes much narrower than a design value. It has been found that a defect in which two scribe lines overlap may occur. This defect mainly occurs at the end of the scribe when the scribe of the semiconductor layer formed on one glass substrate by the CVD method is started from one end and ended at the other end. Was. Therefore, it could be expected that the cause of this defect was not due to the displacement of the laser processing machine, but to another reason.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for scribing each layer constituting a thin-film solar cell module with high accuracy, thereby reducing the area of a separation region between unit cells to thereby reduce the thickness of a thin-film solar cell module. An object of the present invention is to achieve high integration of a battery module and significantly improve its power generation characteristics (especially, current).

[0007]

The method of manufacturing a thin-film solar cell module according to the present invention comprises the steps of forming a transparent electrode layer on a substrate and performing laser scribing, and forming a semiconductor layer on the transparent electrode layer and performing laser scribing. And a step of forming a back electrode layer on the semiconductor layer and performing laser scribing on the semiconductor layer, wherein the scribing substrate temperature in each layer laser scribing step is within a set value ± 10 ° C. It is characterized by adjusting to.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The present inventors have investigated the cause of the defect that the distance between the scribe line of the transparent electrode layer and the scribe line of the semiconductor layer is much smaller than the designed value as described above. As a result, as described below, it has been found that this defect is caused by the fact that the temperature of the substrate is not controlled during the scribing process.

The scribing of the transparent electrode layer is performed by obtaining a glass substrate having a transparent electrode layer formed on the surface in advance.
It can be considered that the substrate temperature during the scribe step is substantially equal to room temperature. On the other hand, the scribing of the semiconductor layer is performed after the semiconductor layer is formed on the transparent electrode by the CVD method.
The substrate temperature during the scribe process is much higher than room temperature. At this time, the dimensions of the glass substrate have expanded due to thermal expansion. In this state, if the semiconductor layer is scribed at a predetermined pitch in order to separate the semiconductor layer into unit cells (strings) having a designed width, the above-described defect occurs. In other words, on the end side where the scribe started,
The distance between the scribe line of the transparent electrode and the scribe line of the semiconductor layer is almost as designed. However, the scribe line of the transparent electrode is located at a position extending laterally from the initial position due to the thermal expansion of the glass substrate on the end side where the scribing is completed. On the other hand, the semiconductor layers are scribed at a predetermined pitch as designed. For this reason, the scribe line of the semiconductor layer approaches the scribe line of the transparent electrode on the end side where the scribe is completed, and the interval between the two becomes much smaller than the design value.

The scribing of the back electrode is performed after the back electrode is formed on the semiconductor layer by a sputtering method. Since the temperature of the glass substrate after sputtering does not rise so much, the scribing step of the back surface electrode can be performed almost as designed.
During the back electrode scribing step, the glass substrate is at a lower temperature than during the semiconductor layer scribing step, so the scribe line of the semiconductor layer may be present at a position shrunk in the lateral direction from the position immediately after the scribing. high. Therefore, in contrast to the above, on the end side where the scribe is completed, the interval between the scribe line of the semiconductor layer and the scribe line of the back electrode tends to be wider than the design value.

The present invention has been made based on the above findings. The present invention improves the accuracy of the interval between the scribe lines of each layer by adjusting the substrate temperature at the time of scribing in the laser scribing step of each layer constituting the thin-film solar cell module to within a set value ± 10 ° C. is there. If the accuracy of the scribing process can be improved in this way, the width of the isolation region between the unit cells can be reduced, the thin-film solar cell module can be highly integrated, and the power generation characteristics (particularly, current) can be greatly improved.

The set value of the substrate temperature adjustment in the present invention is the substrate temperature when the scribe line interval is set, and the temperature may be the same in all laser scribe steps or may be different. However, the temperature range to be adjusted is ± 10
° C, preferably ± 5 ° C, more preferably ± 2
It is within ° C. Examples of the set value for adjusting the substrate temperature include, but are not limited to, the room temperature around the laser scribe step. Even if the substrate temperature entering a certain laser scribing process is higher than room temperature by 10 ° C. or more and the substrate is in a thermally expanded state, if the substrate temperature can be adjusted and controlled, setting the scribe line interval in consideration of the substrate state with high accuracy. Scribing is possible.

Next, each layer constituting the thin-film solar cell module will be described in more detail. The thin-film solar cell module of the present invention has a structure in which a transparent electrode, a semiconductor layer (a photoelectric conversion unit), and a back electrode are formed on a glass substrate.

The material of the transparent electrode disposed on the glass substrate preferably has a high transmittance of 80% or more with respect to light having a wavelength of 500 to 1200 nm.
A transparent conductive oxide film including one or more layers selected from O ₂ and ZnO is used. Among these materials, SnO ₂ is particularly suitable from the viewpoint of transmittance, conductivity and chemical stability, and ITO is also suitable from the viewpoint of processability, conductivity and transmittance. Transparent electrode is vacuum evaporation, thermal CVD
Alternatively, it is formed on a glass substrate by a method such as sputtering.

The semiconductor layer (photoelectric conversion unit) formed on the transparent electrode includes, for example, a photoelectric conversion unit including an amorphous silicon-based photoelectric conversion layer, a photoelectric conversion unit including a crystalline silicon-based photoelectric conversion layer, and one or more photoelectric conversion units. A tandem-type photoelectric conversion unit in which an amorphous silicon-based photoelectric conversion layer and at least one crystalline silicon-based photoelectric conversion layer are stacked, a photoelectric conversion unit including a CdS / CdTe-based photoelectric conversion layer, and a photoelectric conversion unit including a CuInS ₂ -based photoelectric conversion layer A conversion unit. In the following, a silicon-based thin-film photoelectric conversion unit will be mainly described as an example.

The photoelectric conversion unit includes a one conductivity type layer, a photoelectric conversion layer, and a reverse conductivity type layer. The one conductivity type layer may be a p-type layer or an n-type layer, and correspondingly, the opposite conductivity type layer may be an n-type layer or a p-type layer. Each semiconductor layer has a base temperature of 40
It is deposited at a temperature of 0 ° C. or lower by a plasma CVD method. As the plasma CVD method, a generally well-known parallel plate type RF plasma CVD may be used,
A plasma CVD method using a high-frequency power supply from an RF band having a frequency of 150 MHz or less to a VHF band may be used.

The one conductivity type layer is, for example, a p-type silicon-based thin film doped with boron as a conductivity type determining impurity atom. The impurity atoms are not particularly limited, and may be aluminum or the like in the case of a p-type layer. As the semiconductor material of the one conductivity type layer, amorphous silicon, an alloy material such as amorphous silicon carbide or amorphous silicon germanium, polycrystalline silicon or microcrystalline silicon partially containing amorphous or Alloy materials can also be used. If necessary, the crystallization fraction and carrier concentration can be controlled by irradiating the deposited one-conductivity-type layer with pulsed laser light (laser annealing).

A photoelectric conversion layer is deposited on the one conductivity type layer. As the photoelectric conversion layer, a non-doped (intrinsic semiconductor) polycrystalline silicon film, a microcrystalline silicon film or an amorphous silicon film, or a weak p-type or weak n-type containing a small amount of impurities and having a sufficient photoelectric conversion function Silicon-based thin film materials can be used. The semiconductor material forming the photoelectric conversion layer is not limited to the above materials, and an alloy material such as silicon carbide or silicon germanium can be used. The thickness of the photoelectric conversion layer is generally 0.5 to 2 so that necessary and sufficient photoelectric conversion can be performed.
It is formed in a range of 0 μm.

A reverse conductivity type layer is formed on the photoelectric conversion layer. This reverse conductivity type layer is made of, for example, an n-type silicon-based thin film doped with phosphorus as a conductivity type determining impurity atom. The impurity atoms are not particularly limited, and may be nitrogen or the like in the n-type layer. Further, as the semiconductor material of the opposite conductivity type layer, amorphous silicon, alloy material such as amorphous silicon carbide or amorphous silicon germanium, polycrystalline silicon or microcrystalline silicon partially containing amorphous or Alloy materials can also be used.

A back electrode is formed on the semiconductor layer (photoelectric conversion unit). The back electrode includes, for example, a transparent conductive oxide film and a light-reflective metal electrode. The transparent conductive oxide film is formed as necessary, but enhances the adhesion between the photoelectric conversion unit and the light-reflective metal electrode, increases the reflection efficiency of the light-reflective metal electrode, and allows the photoelectric conversion unit to be protected from chemical changes. It is preferable to form it because it has a function of preventing it.

The transparent conductive oxide film is made of ITO, SnO ₂ ,
It is preferably formed of at least one selected from ZnO and the like, and a film containing ZnO as a main component is particularly preferable. The thickness of the transparent conductive oxide film mainly composed of ZnO is 5
0 nm to 1 μm, and the specific resistance is 1.5
It is preferably at most × 10 ⁻³ Ωcm.

The light reflective metal electrodes are made of Ag, Au, Al,
It is preferable to form with one kind selected from Cu and Pt, or an alloy containing these. For example, Ag having high light reflectivity is 100 to 330 ° C., more preferably 200 to 330 ° C.
It can be formed by vacuum evaporation at a temperature of ~ 300 ° C. It is also preferable to form the film at room temperature by a sputtering method.

[0024]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view of a thin-film solar cell module.
FIG. 2 is a plan view. This thin-film solar cell module
48 unit cells (strings) are connected in series. The thin-film solar cell modules shown in these figures are manufactured as follows.

A glass substrate 1 having a transparent electrode 2 made of SnO _{2 on its} surface is prepared. This glass substrate 1 has dimensions of 460 mm × 920 mm and a dimensional accuracy of ± 2 m.
m. The glass substrate 1 is carried into a clean room whose temperature has been adjusted to 25 ° C.

This glass substrate 1 is placed on an XY laser machine.
It was placed on a table and irradiated with a YAG laser beam having a Q switch frequency of 10 kHz and an average output of 3 W to form a transparent electrode 2
Is scribed, and a transparent electrode scribe line 3 and an alignment mark 10 are formed as shown in FIG. The width of the transparent electrode scribe line 3 is about 40 μm.

Next, this glass substrate 1 is placed in a separation-type plasma CVD apparatus, and a p-type silicon layer, an i-type silicon layer, and an n-type silicon layer are sequentially deposited at a substrate temperature of 200 ° C. to form a pin junction. The constituent semiconductor layer 4 is formed. The glass substrate 1 taken out of the CVD apparatus is set on the XY table of the laser processing machine again, and XY correction and θ correction are performed by the XY table with reference to the alignment marks 10 provided at the corners of the glass substrate 1. The second harmonic light of a YAG laser having a Q switch frequency of 10 kHz and an average output of 0.8 W is applied to the transparent electrode scribe line 3 for about 150
The semiconductor layer 4 is scribed by irradiating a position shifted by μm. FIG. 1 shows a semiconductor scribe line 5. The width of the semiconductor scribe line 5 is about 80 μm.

Next, the glass substrate, the ZnO target and the Ag target are set in a magnetron sputtering apparatus. First, the argon gas pressure was set to 2 mtorr.
r, the substrate temperature was set to 200 ° C., and the discharge power was 200 W
And a ZnO target is sputtered to form a ZnO layer having a thickness of 1000 °. Next, an argon gas pressure of 2 mtorr and a film formation temperature of room temperature were set,
An Ag target is sputtered with a DC discharge at a discharge power of 200 W to form an Ag layer having a thickness of 2000 mm. In this manner, the back electrode 6 in which the ZnO layer and the Ag layer are laminated
To form

The glass substrate 1 taken out of the magnetron sputtering apparatus is set again on the XY table of the laser beam machine, and the XY correction and θ are performed by the XY table with reference to the alignment marks 10 provided at the corners of the glass substrate 1.
Make corrections. A second-harmonic light of a YAG laser having a Q switch frequency of 10 kHz and an average output of 0.8 W is applied to a position shifted by about 300 μm from the transparent electrode scribe line 3 to scribe the back electrode 6. FIG. 1 shows a back electrode scribe line 7. The width of the back electrode scribe line 7 is about 80 μ
m.

Next, unit cells (strings) 1 at both ends
A busbar electrode formation region is secured outside of the first and the first. In addition, in order to electrically separate the peripheral portion of the glass substrate 1 from the active portion of the solar cell, the peripheral portion of the glass substrate 1 is laser scribed over the entire circumference. Further, a bus bar electrode 12 is formed, and a wiring (not shown) for taking out the electrode is connected.

In the above-described step of forming the semiconductor layer 4, the substrate immediately after the completion of the formation of the semiconductor layer and taken out of the CVD apparatus is at a high temperature, and is cooled to room temperature over time. In the scribing step of the semiconductor layer 4, the leaving time until the glass substrate 1 is taken out of the CVD apparatus and placed in a laser processing machine is changed in a range of 10 minutes to 40 minutes, and the temperature of the glass substrate 1 is different. I went in. The scribing interval in the laser scribing step for each layer was set using a substrate having a substrate temperature of room temperature (25 ° C.). The temperature of the glass substrate 1 was measured by a surface thermometer. The interval S1 between the first (scribe start end) transparent electrode scribe line 3 and the semiconductor scribe line 5, the 48th (scribe end end) transparent electrode scribe line 3 and the semiconductor scribe line 5
The difference (S1-S48) from the interval S48 was determined. The glass substrate temperature at the time of scribing the transparent electrode 2 is room temperature (25 ° C.)
, Which is the same as the substrate temperature at the time of setting the scribe interval, and it may be considered that the scribe is performed at the set interval. Table 1 shows the results. FIG. 3 shows that the glass substrate temperature is 50.
FIG. 4 shows the state of the scribe start end and the end of the scribe when the glass substrate temperature is 28 to 29 ° C. FIG.

[0033]

[Table 1]

As can be seen from Table 1 and FIGS. 3 and 4,
As the temperature of the glass substrate at the time of scribing the semiconductor layer 4 increases, the value of (S1-S48) increases. this is,
The main reason is that as the glass substrate temperature at the time of scribing the semiconductor layer 4 is higher, the interval S48 between the 48th transparent electrode scribe line 3 and the semiconductor scribe line 5 becomes smaller. The allowable value of (S1-S48) is about 20 μm. The glass substrate temperature in the scribing step of the semiconductor layer 4 is 3
It can be seen that if the difference from the substrate temperature (25 ° C.) at the time of setting the scribe interval is 10 ° C. or less, the scribing of the semiconductor layer 4 can be performed with high accuracy.

Regarding the scribing step of the back electrode 6, the temperature of the glass substrate is almost room temperature (25 ° C.) irrespective of the standing time until the glass substrate 1 is taken out of the sputtering apparatus and set in a laser beam machine. Thus, the back electrode 6 could be scribed with high accuracy. However, when the sputtering conditions of the back electrode 6 are changed, it is necessary to determine the set value of the substrate temperature adjustment in the back electrode scribing step and set the scribe interval at the substrate temperature.

[0036]

As described in detail above, the layers of the thin-film solar cell module can be scribed with high accuracy by using the method of the present invention. Therefore, the area of the isolation region between the unit cells is reduced, the thin film solar cell module is highly integrated, and the power generation characteristics (in particular, the current) can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a thin-film solar cell module.

FIG. 2 is a plan view of the thin-film solar cell module.

FIG. 3 is a diagram illustrating a state of a scribe start end and a scribe end end when a glass substrate temperature is 50 ° C.

FIG. 4 is a diagram showing a state of a scribe start end and a scribe end end when a glass substrate temperature is 28 to 29 ° C.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Transparent electrode 3 ... Transparent electrode scribe line 4 ... Semiconductor layer 5 ... Semiconductor scribe line 6 ... Backside electrode 7 ... Backside electrode scribe line 10 ... Alignment mark 11 ... Unit cell (string) 12 ... Bus bar electrode

Claims (3)

[Claims] A step of forming a transparent electrode layer on a substrate and performing laser scribing; a step of forming a semiconductor layer on the transparent electrode layer and performing laser scribing; A method of manufacturing a thin film solar cell module having a scribing step, wherein the substrate temperature at the time of scribing in the laser scribing step of each layer is adjusted within a set value ± 10 ° C. 2. The adjustment range of the substrate temperature during scribing is ± 5.
The method for manufacturing a thin-film solar cell module according to claim 1, wherein the temperature is within ° C. 3. The adjustment range of the substrate temperature during scribing is ± 2.
The method for manufacturing a thin-film solar cell module according to claim 1, wherein the temperature is within ° C.