JPH11251609A - Photovoltaic element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate superior photoelectric conversion characteristics without preventing the movement of carriers due to inverse junction, by providing inverse conduction-type semiconductor layers on both the main surfaces of a substrate, and providing rectifying junction on the entire surface of the substrate including a side surface. SOLUTION: A second semiconductor layer 7 is formed on one main surface of an n-type substrate 1. Then, a first semiconductor layer 3 is formed on the other. In this case, n/p/n rectifying junction where the second and first semiconductor layers 7 and 3 are successively laminated on the substrate 1 is formed at a peripheral end part on one main surface that becomes a light incidence side as in A. An n/n/p rectifying junction is formed also at a peripheral end part on the other main surface that becomes a light transmission side as in B. When the first semiconductor layer 3 is formed on one main surface of the n-type substrate 1, and then the second semiconductor layer 7 is formed on the other, the inverse junction of n/p/n where the second and first semiconductor layers 7 and 3 are successively laminated is formed on the substrate 1 at the periphery end part on one main surface of the light incidence side as in A, and the inverse junction of n/p/n is formed at the periphery end part on the other of the light transmission side as in B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technique for manufacturing a photovoltaic element having high photoelectric conversion efficiency.

[0002]

2. Description of the Related Art In recent years, in photovoltaic elements such as solar cells and optical sensors, in order to achieve both high conversion efficiency and low production cost, crystalline semiconductors such as monocrystalline silicon and polycrystalline silicon have been used. Alternatively, a photovoltaic element formed by combining with a semiconductor such as silicon having microcrystals has been studied (for example, see JP-A-5-102504).

FIG. 4 is a sectional view of the element structure of such a photovoltaic element. Reference numeral 1 denotes a substrate made of a crystalline semiconductor such as n-type single crystal or polycrystalline silicon; An intrinsic semiconductor layer having a thickness of about 100 ° and made of an amorphous semiconductor such as intrinsic amorphous or microcrystalline silicon,
Reference numeral 3 denotes a first semiconductor layer formed on the intrinsic semiconductor layer and made of a non-crystalline semiconductor such as p-type amorphous or microcrystalline silicon having a conductivity type opposite to that of the substrate 1 and having a thickness of about 100 °. On the first semiconductor layer 3, there are formed a light-transmissive electrode 4 made of a light-transmissive conductive material such as SnO ₂ or ITO, and a collecting electrode 5 made of a comb-shaped conductive material such as Ag or Al. Have been.

On the other main surface of the substrate 1, an intrinsic semiconductor layer 6 having a thickness of about 100 ° made of an amorphous semiconductor such as intrinsic amorphous or microcrystalline silicon, or an n-type amorphous or A film thickness of about 20 made of an amorphous semiconductor such as crystalline silicon
A second semiconductor layer 7 of 0 °, a light-transmitting electrode 8 made of a light-transmitting conductive material such as SnO ₂ , ITO, and a collecting electrode 9 made of a comb-shaped conductive material such as Ag or Al are sequentially formed. ing.

In such a photovoltaic device, the intrinsic semiconductor layer 2 provided on one main surface of the substrate 1, the first semiconductor layer 3, the intrinsic semiconductor layer 6 on the other main surface, and the second semiconductor layer 7 are formed. Is also composed of an amorphous or microcrystalline non-crystalline semiconductor. Therefore, since the formation of each of the layers 2, 3, 6, and 7 can be performed at a temperature of about 200 ° C. by using the plasma CVD method, the conventional method of forming a pn junction is 100%.
The manufacturing cost can be reduced as compared with a crystal-based photovoltaic element that required a high temperature of 0 ° C. or higher, and a photovoltaic element that is comparable in characteristics can be obtained.

[0006]

In manufacturing a photovoltaic device having the structure shown in FIG. 4, a cleaned substrate 1 is introduced into a plasma CVD apparatus, and one main surface of the substrate 1 is manufactured. The intrinsic semiconductor layer 2 and the first semiconductor layer 3 are formed thereon.
In addition, the intrinsic semiconductor layer 6 and the second semiconductor layer 7 are formed on the other main surface of the substrate 1 by the plasma CVD method.

However, it is difficult for such a conventional method to obtain a photovoltaic element having high photoelectric conversion characteristics with good reproducibility.

[0008]

In order to solve the above-mentioned problems, a photovoltaic device according to the present invention is a photovoltaic device comprising semiconductor layers having opposite conductivity types on both main surfaces of a substrate. An electromotive element, wherein a rectifying junction is provided on the entire surface of the substrate including a side surface.

Further, the substrate is made of a crystalline semiconductor, and both of the semiconductor layers are made of an amorphous or microcrystalline semiconductor, and an amorphous material is provided between both main surfaces of the substrate and the semiconductor layer. Characterized in that an intrinsic semiconductor layer made of a crystalline or microcrystalline semiconductor is interposed.

Further, a method of manufacturing a photovoltaic element according to the present invention is a method of manufacturing a photovoltaic element comprising semiconductor layers having opposite conductivity types on both main surfaces of a substrate, Forming one semiconductor layer having the same conductivity type as that of the substrate on the one main surface of the substrate, and then forming the other semiconductor layer on the other main surface of the substrate. And

Further, the substrate is made of a crystalline semiconductor, and the semiconductor layer is made of an amorphous or microcrystalline semiconductor. In addition, an amorphous or microcrystalline semiconductor is provided between the substrate and the semiconductor layer. A step of forming an intrinsic semiconductor layer made of a crystalline semiconductor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 6 is an element structure diagram for each step for explaining a step of manufacturing the photovoltaic element shown in FIG.

First, in the step shown in FIG.
An intrinsic semiconductor layer 6 made of intrinsic amorphous or microcrystalline silicon on one main surface of a substrate 1 made of n-type single crystal silicon of about 500 μm using a plasma CVD method;
A second semiconductor layer 7 made of n-type amorphous or microcrystalline silicon having the same conductivity type as the substrate is sequentially formed.

Next, in the step shown in FIG. 1B, the intrinsic semiconductor layer 2 made of intrinsic amorphous or microcrystalline silicon and the p-type semiconductor layer 2 are formed on the other main surface of the substrate 1 by plasma CVD. A first semiconductor layer 3 made of a type of amorphous or microcrystalline silicon is sequentially formed.

Finally, light-transmitting conductive films 4 and 8 made of ITO or SnO ₂ are formed on the first semiconductor layer 3 and the second semiconductor layer 7, respectively. Collector electrodes 5 and 9 each having a comb shape are formed, and the photovoltaic element having the configuration shown in FIG. 4 is completed.

According to the present invention, it is possible to obtain a photovoltaic element having good photoelectric conversion characteristics with good reproducibility. The reason will be described in detail below.

FIG. 2 is an explanatory view for explaining the reason why a photovoltaic element having a good photoelectric conversion characteristic can be obtained with good reproducibility according to the present invention. FIG. A photovoltaic element manufactured by forming a second semiconductor layer having the same conductivity type as that of the substrate above, and FIG. The main part enlarged sectional view of the photovoltaic element manufactured by forming the 1st semiconductor layer which shows a type | mold is each shown. For simplicity, the intrinsic semiconductor layers 2 and 6
Is omitted.

In general, when a thin film is to be formed on one surface of a substrate by using a plasma CVD method, the thin film is formed so as to wrap around on the side surface and the other surface of the substrate.

Therefore, in the case where the second semiconductor layer 7 is formed first on the other main surface of the n-type substrate 1 and then the first semiconductor layer 3 is formed on one main surface of the substrate 1 As shown in A of FIG. 2A, n / n is obtained by sequentially laminating the second semiconductor layer 7 and the first semiconductor layer 3 on the substrate 1 at the peripheral end on one main surface on the light incident side. An n / p rectifying junction is formed. Also, a rectifying junction of n / n / p is formed at the peripheral end on the other main surface on the light transmission side, as shown by B.

On the other hand, when the first semiconductor layer 3 is formed first on one main surface of the n-type substrate 1 and then the second semiconductor layer 7 is formed on the other main surface of the substrate 1, , FIG. 2 (B)
As shown in FIG. 1A, an n / p / n reverse junction formed by sequentially laminating the first semiconductor layer 3 and the second semiconductor layer 7 on the substrate 1 is formed at the peripheral end on one main surface on the light incident side. Will be formed. In addition, a reverse junction of n / p / n is formed at the peripheral end portion on the other main surface which is on the light transmission side as shown in B.

In these cases, in the case of FIG. 2A corresponding to the present invention, the joints formed at the peripheral ends A and B on both main surfaces of the substrate 1 are both n / n Since the rectifying junction is / p, the photoelectric conversion characteristics are not significantly affected.

However, in the case of FIG.
Both peripheral edges A and B on both main surfaces of the substrate 1 have n / p / n
Is formed, and this reverse junction acts as a barrier that hinders the movement of carriers, so that the photoelectric conversion characteristics are degraded. Particularly in a case where using a B ₂ H ₆ as a doping gas at the time of forming the first semiconductor layer, B ₂ H ₆ gas decomposition products of B ₂ H ₆ from decomposing even at room temperature over the entire surface of the substrate 1 is As a result, an n / p / n reverse junction is formed on the entire surface of the other main surface of the substrate 1, so that the influence is further increased.

As described in detail above, according to the present invention, one semiconductor layer having the same conductivity type as that of the substrate is formed first on one main surface of the substrate, and then the other semiconductor layer of the substrate is formed. The other semiconductor layer having the opposite conductivity type is formed on the surface. Therefore, the obtained photovoltaic element is a photovoltaic element in which semiconductor layers having opposite conductivity types are provided on both main surfaces of the substrate, and a rectifying junction is formed on the entire surface of the substrate including side surfaces. Will be prepared. From this, it is considered that there is no adverse effect such as suppression of carrier movement due to the reverse junction, and a photovoltaic element having good photoelectric conversion characteristics can be obtained with good reproducibility. (Embodiment) FIG. 3 is a schematic view of the structure of a plasma CVD apparatus for manufacturing a photovoltaic device according to the present invention. In the figure,
P, I, and N are a P chamber, an I chamber, and an N chamber that are reaction chambers for forming the first semiconductor layer, the intrinsic semiconductor layer, and the second semiconductor layer, respectively. Then, the substrate 1 is moved between these reaction chambers P, I, and N by a transfer system (not shown).

In the P chamber P, the I chamber I, and the N chamber N, an exhaust system (not shown) is independently provided, and a reaction gas required for forming each semiconductor layer by a reaction gas supply system (not shown). In the P chamber P, SiH ₄ , H ₂ , B ₂ H ₆ and I
The chamber I contains SiH ₄ and H ₂ , and the N chamber N contains SiH ₄ and P 2
H ₃ is introduced respectively. In each of the reaction chambers P, I and N, RF electrodes P1, I1 and N1 and ground electrodes P2 and I are provided.
2 and N2 are arranged opposite to each other. L is an auxiliary chamber for loading and unloading substrates.

Next, a process of manufacturing the photovoltaic device shown in FIG. 4 using such a plasma CVD device will be described.

First, the substrate 1 made of n-type single crystal silicon having a thickness of about 500 μm was introduced into the auxiliary chamber L with the other main surface side as a film forming surface, and was evacuated to a vacuum of about 10 ⁻⁶ Torr. In this state, the substrate 1 is heated to a temperature of about 250 ° C. to degas moisture and the like attached to the substrate 1.

Next, the substrate 1 is transferred into the reaction chamber I by a transfer system (not shown), and is kept at a substrate temperature of, for example, about 180 ° C., and SiH is supplied from a source gas supply system (not shown).
₄ and H ₂ are supplied at a flow rate of, for example, 20 SCCM, respectively, and the inside of the reaction chamber is, for example, 50 mTorr by an exhaust system (not shown).
And maintain a pressure of about

In this state, 50 m is applied to the RF electrode I1.
High frequency power is applied at a power density of about W / cm ² to generate plasma of SiH ₄ and H ₂ gas between the opposing RF electrode I1 and ground electrode I2, and radicals generated in this plasma are An intrinsic semiconductor layer 6 made of amorphous silicon and having a thickness of about 50 ° is deposited on the other main surface.

Then, the supply of the high-frequency power applied to the RF electrode I1 and the supply of the SiH ₄ gas into the reaction chamber I are stopped, and the inside of the reaction chamber I is released by an exhaust system (not shown).
The substrate 1 is evacuated to a degree of vacuum of about 0 ^-7 Torr, and the substrate 1 is transferred into the n chamber N by a transfer system (not shown).

In the n chamber N, the substrate is kept at a substrate temperature of, for example, about 180 ° C., and a SiH ₄ gas and a PH ₃ gas are supplied, for example, by a source gas supply system (not shown).
SCCM is supplied, and the reaction chamber is maintained at a pressure of, for example, about 200 mTorr by an exhaust system (not shown).

In this state, 50 m is applied to the RF electrode N1.
The RF power is applied at a W / cm ² about the power density, SiH between RF electrodes N1 and the grounding electrode N ₂ facing ₄ and P
A plasma of H ₃ gas is generated, and radicals generated in the plasma are deposited on the intrinsic semiconductor layer 6 to form a second semiconductor layer 7 of n-type amorphous silicon having a thickness of about 200 °. .

Next, the supply of the high-frequency power applied to the RF electrode N1 and the supply of the SiH4 and PH3 gases into the n-chamber N are stopped, and the n-chamber N is supplied by an exhaust system (not shown).
The inside is evacuated to a degree of vacuum of about 10 ⁻⁷ Torr, and the substrate 1 is transferred to the auxiliary chamber L by a transfer system (not shown).

Then, after lowering the temperature of the substrate 1 in the auxiliary chamber L, the substrate 1 is taken out. Through the above steps, the intrinsic semiconductor layer 6 and the second semiconductor layer 7 are laminated on the other main surface of the substrate.

Next, the substrate 1 on which the intrinsic semiconductor layer 6 and the second semiconductor layer 7 are laminated on the other principal surface is introduced into the auxiliary chamber L again with the one principal surface side as a film formation surface.

Then, the substrate 1 is heated at a temperature of about 250 ° C. in a state of being evacuated to a degree of vacuum of about 10 ⁻⁶ Torr, and the moisture and the like adhering to the substrate 1 are degassed.

Next, the substrate 1 is transferred into the reaction chamber I by a transfer system (not shown), and is kept at a substrate temperature of, for example, about 180 ° C., and SiH is supplied from a source gas supply system (not shown).
₄ and H ₂ are supplied at a flow rate of, for example, 20 SCCM, respectively, and the inside of the reaction chamber is, for example, 50 mTorr by an exhaust system (not shown).
And maintain a pressure of about

In this state, 50 m is applied to the RF electrode I1.
High frequency power is applied at a power density of about W / cm ² to generate plasma of SiH ₄ and H ₂ gas between the opposing RF electrode I1 and ground electrode I2, and radicals generated in this plasma are An intrinsic semiconductor layer 2 made of amorphous silicon and having a thickness of about 50 ° is deposited on one main surface.

Next, the supply of the high-frequency power applied to the RF electrode I1 and the supply of the SiH ₄ gas into the reaction chamber I are stopped, and the inside of the reaction chamber I is reduced to 1 by an exhaust system (not shown).
Evacuation is performed to a degree of vacuum of about 0 ^-7 Torr, and the substrate 1 is transferred into the P chamber P by a transfer system (not shown).

In the P chamber P, the substrate is maintained at a substrate temperature of, for example, about 180 ° C., and SiH ₄ , B ₂ H _6, and H ₂ gases are supplied from a source gas supply system (not shown) to, for example, 10 SCCM, 100 SCCM, 100 SCCM.
The reaction chamber is maintained at a pressure of, for example, about 200 mTorr by an exhaust system (not shown). The B ₂ H ₆ gas used was diluted to 1000 ppm with H ₂ .

In this state, 50 m is applied to the RF electrode N1.
High frequency power is applied at a power density of about W / cm ² , and SiH ₄ , B is applied between the opposing RF electrode N1 and ground electrode N2.
A plasma of ₂ H ₆ and H ₂ gas is generated, and radicals generated in the plasma are deposited on the intrinsic semiconductor layer 2 to form a first semiconductor layer made of p-type amorphous silicon having a thickness of about 200 °. Form 3

Next, the supply of the high-frequency power applied to the RF electrode N1 and the introduction of SiH ₄ , B ₂ H ₆ and H
₍₂₎ The supply of gas is stopped, and the inside of the p chamber P is evacuated to a degree of vacuum of about 10 ⁻⁷ Torr by an exhaust system (not shown).
The substrate 1 is transported to the auxiliary chamber L by a transport system (not shown).

Then, the substrate 1 is taken out after the temperature of the substrate 1 is lowered in the auxiliary chamber L. Through the above steps, the intrinsic semiconductor layer 2 and the first semiconductor layer 3 are formed on one main surface of the substrate, and the intrinsic semiconductor layer 6 and the second semiconductor layer 7 are formed on the other main surface.

Then, light-transmitting conductive films 4 and 8 made of ITO and having a thickness of about 700 ° are formed on the first semiconductor layer 3 and the second semiconductor layer 7 by sputtering, respectively. , 8 are formed by screen printing to form comb-shaped collector electrodes 5 and 9 made of Ag to complete the photovoltaic element having the structure shown in FIG.

At this time, as described above, the intrinsic semiconductor layers 2, 6, and
A laminate of the first semiconductor layer 3 and the second semiconductor layer 7 is formed, and there is a possibility that the first semiconductor layer 3 and the second semiconductor layer 7 may be short-circuited at this portion. In order to prevent this, a separation groove for joining and separating may be provided on the peripheral end or side surface on one main surface or the other main surface of the substrate.

Using the above manufacturing method, 20 photovoltaic elements having the structure shown in FIG. 4 were formed, and their photoelectric conversion characteristics were measured. For comparison, the order in which the intrinsic semiconductor layer 2 and the first semiconductor layer 3 are formed first on one main surface of the substrate 1, and then the intrinsic semiconductor layer 6 and the second semiconductor layer 7 are formed on the other main surface. 2
Zero photovoltaic elements were manufactured, and their photoelectric conversion characteristics were measured.

Table 1 also shows the photoelectric conversion characteristics of the photovoltaic devices of this embodiment and the comparative example. In the table, each parameter of the photoelectric conversion characteristic is an average value of 20 photovoltaic elements, and is shown as a relative value where the value according to the present embodiment is 1.

[0047]

[Table 1]

As is clear from the table, the photovoltaic device manufactured according to the present example exhibited better values for each parameter, and a value improved by about 18% in conversion efficiency was obtained.

In the above-described embodiment, the semiconductor device having the intrinsic semiconductor layers 2 and 6 has been described. However, the present invention is not limited to this, and the present invention can be applied to the semiconductor device without the intrinsic semiconductor layers 2 and 6.

However, as disclosed in Japanese Patent Application Laid-Open No. 5-102504, in order to improve the interface characteristics between the first and second semiconductor layers 3 and 7 made of amorphous or microcrystal and the substrate 1. Preferably, an intrinsic semiconductor layer having a thickness of about 250 ° or less is provided. In the above description, a substrate having n-type is used as the substrate 1. However, it is needless to say that the present invention can be applied to a photovoltaic element using a substrate having p-type.

[0051]

As described above, according to the present invention, one semiconductor layer having the same conductivity type as that of the substrate is first formed on one main surface of the substrate, and then the other semiconductor layer of the substrate is formed. The other semiconductor layer having the opposite conductivity type is formed on the main surface. Therefore,
The obtained photovoltaic element is a photovoltaic element in which semiconductor layers having opposite conductivity types are provided on both main surfaces of the substrate, and a rectifying junction is provided on the entire surface of the substrate including side surfaces. Becomes From this, it is considered that there is no adverse effect such as suppression of carrier movement due to the reverse junction, and a photovoltaic element having good photoelectric conversion characteristics can be obtained with good reproducibility.

[Brief description of the drawings]

FIG. 1 is an element structure diagram for each step for explaining a manufacturing method of the present invention.

FIG. 2 is an explanatory diagram for explaining an effect of the present invention. .

FIG. 3 is a schematic diagram illustrating the configuration of a plasma CVD apparatus.

FIG. 4 is a sectional view of an element structure of a conventional photovoltaic element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2, 6 ... Intrinsic semiconductor layer, 3 ... First semiconductor layer,
4, 8: translucent conductive film, 5, 9: collecting electrode, 7: second semiconductor layer

Claims (6)

[Claims] 1. A photovoltaic element comprising semiconductor layers having opposite conductivity types on both main surfaces of a substrate, wherein a rectifying junction is provided on the entire surface of the substrate including side surfaces. Photovoltaic element. 2. The photovoltaic device according to claim 1, wherein said substrate is made of a crystalline semiconductor, and said semiconductor layers are both made of an amorphous or microcrystalline semiconductor. 3. The photovoltaic device according to claim 2, wherein an intrinsic semiconductor layer made of an amorphous or microcrystalline semiconductor is interposed between both principal surfaces of said substrate and said semiconductor layer. . 4. A method for manufacturing a photovoltaic element comprising: semiconductor layers having opposite conductivity types on both main surfaces of a substrate, wherein the semiconductor layer is provided on one main surface of the substrate. Forming a semiconductor layer having the same conductivity type as that of the substrate, and then forming the other semiconductor layer on the other main surface of the substrate. 5. The method according to claim 4, wherein the substrate is made of a crystalline semiconductor, and the semiconductor layer is made of an amorphous or microcrystalline semiconductor. 6. The method according to claim 5, further comprising the step of forming an intrinsic semiconductor layer made of an amorphous or microcrystalline semiconductor between the substrate and the semiconductor layer. Method.