JP3984761B2 - Photovoltaic element, manufacturing method thereof, and manufacturing apparatus thereof - Google Patents

Description

【００７５】
このような膜堆積を帯状基板の長さ４００ｍにわたって連続的に行った後、各チャンバーへの放電電力の供給と、原料ガスの導入と、帯状基板の加熱とを停止し、各室内を十分にパージし、帯状基板と装置内部を充分冷却した後、装置を大気開放し、半導体積層膜が形成されて巻き取り室のボビンに巻き取られた帯状基板を取り出した。
【００７６】
更に、取り出した帯状基板を連続モジュール化装置によって連続的に加工し、本発明の装置で形成した半導体積層膜の上に、透明電極として全面に６０ｎｍのＩＴＯ薄膜を形成し、集電電極として一定間隙に細線状のＡｇ電極を形成し、３５ｃｍ角のｎｉｐｎｉｐ構造の２層タンデム構造の太陽電池モジュールを連続的に作成した。
【００７７】
そして、作成した太陽電池モジュールについて、ＡＭ１．５（１００ｍＷ／ｃｍ²）の疑似太陽光照射下にて、２５℃の温度で特性評価を行なった。
【００７８】
特性評価の結果、作成した太陽電池モジュールの平均光電変換効率は、チャンバー１０４、１０７にバイアス電圧を印加しなかった場合の太陽電池モジュールの平均光電変換効率を１とした比較で、１．４倍になっていた。
【００７９】
また、作成した太陽電池モジュールの短絡による特性不良発生率をみたところ、チャンバー１０４、１０７に直流電圧を印加しなかった時の良品率を１００とした比較で、チャンバー１０４に３００Ｖ、チャンバー１０７に１００Ｖを印加した時の良品率９５、チャンバー１０４に１００Ｖ、チャンバー１０７に３００Ｖを印加した時の良品率は３５であった。
【００８０】
直流電圧の組み合わせを変えて太陽電池モジュールを製造した場合の変換効率と良品率の変化を表２に示す。
【００８１】
【表２】

【００８２】
これから、本発明の方法によって、タンデム構造の光起電力素子の変換効率と良品率の両立が図れることが確認された。
【００８３】
（実施例２）
図２は、本実施例で用いた本発明の方法を実現する装置を示す模式図である。図２に示した装置は、図１の装置に更にＲＦ周波数のチャンバーが３室追加されており、ｉ型層が、基板側からＶＨＦ周波数、ＶＨＦ周波数、ＲＦ周波数の高周波プラズマＣＶＤ法で堆積されたｎｉｐｎｉｐｎｉｐ、またはｐｉｎｐｉｎｐｉｎの３層タンデム構造の光起電力素子の半導体積層膜を製造できる。
【００８４】
図２において、２０１は帯状基板、２０２は巻き出し室、２０３、２０４、２０５、２０６、２０７、２０８はチャンバー、２２０、２２１、２２２は１３．５６ＭＨｚのＲＦ周波数のプラズマＣＶＤのチャンバー、２０９は巻き取り室、２１０はガスゲートである。
【００８５】
本実施例では、図２に示す装置を用い、本発明の方法により、ステンレス基板上に９層のシリコン系非単結晶膜からなるｎｉｐｎｉｐ構造の３層タンデム構造の太陽電池を製造した。
【００８６】
３層あるｉ型層は、基板側からＶＨＦ周波数、ＶＨＦ周波数、ＲＦ周波数の高周波プラズマＣＶＤ法で堆積し、ＶＨＦ周波数のチャンバー２０４、２０７の成膜室には正の直流電圧を印加した。また、印加する直流電圧は堆積順に低くなるように設定した。
【００８７】
具体的には、基板が先に通過するＶＨＦ周波数のチャンバー２０４のバイアス電極にはアース電位の帯状基板に対し正の向きに直流電圧２００Ｖを印加し、基板が後に通過するＶＨＦ周波数のチャンバー２０７のバイアス電極にはアース電位の帯状基板に対し正の向きに直流電圧１００Ｖを印加した。
【００８８】
各チャンバーの成膜条件を表１に示す。
【００８９】
【表３】

【００９０】
以下、実施例１と同様にして、本発明の方法により、ステンレス基板上に９層のシリコン系非単結晶膜からなるｎｉｐｎｉｐｎｉｐ構造の３層タンデム構造の太陽電池モジュールを製造した。
【００９１】
そして、作成した太陽電池モジュールについて、Ａｍ１．５（１００ｍＷ／ｃｍ²）の疑似太陽光照射下にて、２５℃の温度で特性評価を行った。
【００９２】
特性評価の結果、作成した太陽電池モジュールの平均光電変換効率は、チャンバー２０４、２０７に直流電圧を印加しなかった場合の太陽電池モジュールの平均光電変換効率を１とした比較で、１．４倍になっていた。
【００９３】
また、作成した太陽電池モジュールの短絡による特性不良発生率をみたところ、チャンバー２０４、２０７に直流電圧を印加しなかった時の良品率を１００とした比較で、チャンバー２０４に２００Ｖ、チャンバー２０７に１００Ｖを印加した時の良品率は９８と殆ど変化なく良好だった。
【００９４】
これから、本発明の方法によって、タンデム構造の光起電力素子の変換効率と良品率の両立が図られることが確認された。
【００９５】
（実施例３）
放電室２０４、２０７における放電周波数を、２０ＭＨｚに変えた以外は実施例２と同様にして、３５ｃｍ角のｎｉｐｎｉｐｎｉｐ構造の３層タンデム構造の太陽電池モジュールを連続的に製造した。
【００９６】
そして、作成した太陽電池モジュールについて、Ａｍ１．５（１００ｍＷ／ｃｍ²）の疑似太陽光照射下にて、２５℃の温度で特性評価を行った。
【００９７】
特性評価の結果、作成した太陽電池モジュールの平均光電変換効率は、チャンバー２０４、２０７に直流電圧を印加しなかった場合の太陽電池モジュールの平均光電変換効率を１とした比較で１．２５倍になっていた。
【００９８】
また、作成した太陽電池モジュールの短絡による特性不良発生率をみたところ、チャンバー２０４、２０７に直流電圧を印加しなかった時の良品率を１００とした比較で、チャンバー２０４に２００Ｖ、チャンバー２０７に１００Ｖを印加した時の良品率１００と変化なく良好であった。
【００９９】
これから、本発明の方法によって、タンデム構造の光起電力素子の変換効率と良品率の両立が図られることが確認された。
【０１００】
（実施例４）
放電室２０４、２０７における放電周波数を、５００ＭＨｚに変えた以外は実施例２と同様にして、３５ｃｍ角のｎｉｐｎｉｐｎｉｐ構造の３層タンデム構造の太陽電池モジュールを連続的に製造した。
【０１０１】
そして、作成した太陽電池モジュールについて、Ａｍ１．５（１００ｍＷ／ｃｍ²）の疑似太陽光照射下にて、２５℃の温度で特性評価を行った。
【０１０２】
特性評価の結果、作成した太陽電池モジュールの平均光電変換効率は、チャンバー２０４、２０７に直流電圧を印加しなかった場合の太陽電池モジュールの平均光電変換効率を１とした比較で、１．４５倍になっていた。
【０１０３】
また、作成した太陽電池モジュールの短絡による特性不良発生率をみたところ、チャンバー２０４、２０７に直流電圧を印加しなかった時の良品率を１００とした比較で、チャンバー２０４に２００Ｖ、チャンバー２０７に１００Ｖを印加した時の良品率は９５と殆ど変化なく良好であった。
【０１０４】
これから、本発明の方法によって、タンデム構造の光起電力素子の変換効率と良品率の両立が図られることが確認された。
【０１０５】
（実施例５）
放電室２０４、２０７に印加する直流電圧をそれぞれ、２００Ｖ、１５０Ｖに変えた以外は実施例２と同様にして、３５ｃｍ角のｎｉｐｎｉｐｎｉｐ構造の３層タンデム構造の太陽電池モジュールを連続的に製造した。
【０１０６】
そして、作成した太陽電池モジュールについて、Ａｍ１．５（１００ｍＷ／ｃｍ²）の疑似太陽光照射下にて、２５℃の温度で特性評価を行った。
【０１０７】
特性評価の結果、作成した太陽電池モジュールの平均光電変換効率は、チャンバー２０４、２０７に直流電圧を印加しなかった場合の太陽電池モジュールの平均光電変換効率を１とした比較で１．４３倍になっていた。
【０１０８】
また、作成した太陽電池モジュールの短絡による特性不良発生率をみたところ、チャンバー２０４、２０７に直流電圧を印加しなかった時の良品率を１００とした比較で、チャンバー２０４に２００Ｖ、チャンバー２０７に１５０Ｖを印加した時の良品率は９３と殆ど変化なく良好であった。
【０１０９】
これから、本発明の方法によって、タンデム構造の光起電力素子の変換効率と良品率の両立が図られることが確認された。
【０１１０】
【発明の効果】
以上説明したように、本発明によれば、ＶＨＦ周波数の高周波電力で堆積膜の形成を行なうｉ型層の成膜室には、基板に対して正の直流電圧が印加され、基板側が負の直流電界が形成されるため、高速堆積時の堆積膜の膜質の向上を図ることができる。
【０１１１】
また、ＶＨＦ周波数の高周波電力で堆積膜の形成を行うｉ型層において、積層順が後の層ほど印加する直流電圧が低く設定されるので、比較的高抵抗で堆積膜厚の厚いｉ型層が堆積され、基板上の堆積膜表面が高抵抗になってきても、印加される直流電圧が堆積膜が積層されるに伴って低く設定されるので、直流電圧印加電極からスパーク等の異常放電を生じたり、堆積膜表面がチャージアップして製造途中の半導体膜が絶縁破壊を起こしたりすることがなく、製造する光起電力素子が特性不良を起こすことがないので、大面積で高効率低劣化のタンデム構造の光起電力素子を製造することができる。
【図面の簡単な説明】
【図１】本発明の光起電力素子の製造方法を実現する装置の構成の一例を示す模式的断面図である。
【図２】本発明の光起電力素子の製造方法を実現する装置の構成の一例を示す模式的断面図である。
【符号の説明】
１０１ 帯状基板
１０２ 巻き出し室
１０３、１０４、１０５、１０６、１０７、１０８ チャンバー
１０９ 巻き取り室
１１０ ガスゲート
１１１ ゲートガス導入管
１１２ 原料ガス導入管
１１３ 排気管
１１４ 平板電極
１１５ 棒状電極
１１６ ＲＦ周波数の高周波電源
１１７ ＶＨＦ周波数の高周波電源
１１８ 直流バイアス電極
１１９ 直流電源
２０１ 帯状基板
２０２ 巻き出し室
２０３、２０４、２０５、２０６、２０７、２０８、２２０、２２１、２２２ チャンバー
２０９ 巻き取り室
２１０ ガスゲート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photovoltaic element having a tandem structure made of a silicon-based non-single-crystal semiconductor on a substrate, a manufacturing method thereof, and a manufacturing apparatus thereof. For example, amorphous silicon, amorphous silicon germanium, amorphous silicon carbide, microcrystalline silicon, etc. The present invention relates to a photovoltaic device such as a tandem solar cell, a manufacturing method thereof, and a manufacturing apparatus thereof.
[0002]
[Prior art]
With amorphous silicon, a semiconductor film having a large area can be formed by a plasma CVD method, and a semiconductor device having a large area can be formed relatively easily as compared with crystalline silicon or polycrystalline silicon. For this reason, amorphous silicon films are often used in semiconductor devices that require a large area, specifically, solar cells, photoconductor drums for copying machines, image sensors for facsimiles, thin film transistors for liquid crystal displays, and the like.
[0003]
These devices have a larger area than a device made of a crystalline semiconductor such as an LSI or CCD. For example, in the case of a solar cell, if the photoelectric conversion efficiency is 10%, the power for ordinary households can be covered. In order to obtain an output of 3 kW, an area of about 30 square meters is required per household, and one photovoltaic device is also a considerably large area.
[0004]
In order to form an amorphous silicon film, SiH is generally used. _Four And Si ₂ H ₆ A plasma CVD method is used in which a raw material gas containing Si or the like is decomposed into a plasma state by high-frequency discharge to form a film on a substrate placed in the plasma.
[0005]
Conventionally, when an amorphous silicon film is formed by plasma CVD, a high frequency of RF frequency (around 13.56 MHz) has been generally used.
[0006]
However, in recent years, plasma CVD using a VHF frequency has attracted attention. For example, Amorphous Silicon Technology 1992 p15-p26 (Materials Research Society Symposium Processing Volumes 258) can increase the discharge frequency from 13.56 MHz RF to VHF frequency. It has been reported that a good deposited film can be formed.
[0007]
US Pat. No. 4,406,765 discloses a high-frequency plasma CVD method in which a DC electric field is applied. It is said that a high-quality amorphous semiconductor can be obtained by applying an appropriate DC electric field together with an electric field due to a high frequency in the plasma CVD method. In this case, the DC voltage to be applied varies in suitability depending on the type of deposited film, discharge conditions, and the like.
[0008]
Conventionally, a continuous plasma CVD apparatus employing a roll-to-roll method has been disclosed in US Pat. No. 4,400,409 as a continuous production apparatus for amorphous silicon semiconductor devices. Yes.
[0009]
According to this apparatus, a plurality of glow discharge chambers are provided, and each glow discharge chamber is arranged along a path through which a sufficiently long strip-shaped substrate having a desired width is sequentially penetrated, so that the electrical conductivity required in each glow discharge chamber is obtained. A large-area device having a semiconductor junction can be continuously formed by continuously transporting the substrate in the longitudinal direction while depositing and forming a mold type semiconductor film. If a roll-to-roll type continuous plasma CVD apparatus is used in this way, devices can be manufactured continuously for a long time without stopping the manufacturing apparatus, so that high productivity can be obtained.
[0010]
[Problems to be solved by the invention]
However, when trying to introduce a film formation method of VHF frequency into this roll-to-roll type plasma CVD apparatus, it is possible to use light in a wider wavelength range and obtain a high photoelectric conversion efficiency, especially compared to a single structure. In addition, since the film thickness of the i-type layer can be reduced, the following problems occur when an attempt is made to introduce a VHF frequency film formation method into the i-type layer of a photovoltaic element having a tandem structure with little light degradation. there were.
[0011]
First, when using a VHF frequency plasma CVD method for a roll-to-roll system for forming a deposited film over a large area, it is generally used at an RF frequency to generate a uniform discharge over a large area. When a flat discharge electrode having a large area is used, there is a problem that a uniform plasma cannot be obtained in a large area without impedance at the VHF frequency.
[0012]
In addition, if a rod-shaped radial antenna is used, the impedance matches, but the area ratio between the discharge electrode and the counter electrode, which was approximately 1 on the parallel plate, becomes extremely small in the area on the discharge electrode side, and the area balance is lost, resulting in a small area. In the case of the parallel plate, the absolute value of the self-bias of the discharge electrode, which should become smaller as the frequency increases, is increased conversely, and a positive and undesirable DC electric field is formed on the substrate side. Therefore, when the VHF frequency plasma CVD method is to be adopted in a roll-to-roll system apparatus that forms a deposited film in a large area, the influence of positive self-bias on the substrate side is eliminated and the large area is good. In order to obtain a film, it was necessary to control the DC electric field by applying a DC voltage or the like.
[0013]
However, in a tandem photovoltaic device, when applying such a VHF frequency plasma CVD method to an i-type layer that requires a relatively thick film for photoelectric conversion, a high-quality film is formed. In order to obtain this, it is necessary to apply a DC voltage as described above. However, if a high DC voltage is applied to the film forming chamber, abnormal discharge such as sparks may occur from the DC voltage applying electrode to the film forming chamber, or the surface of the deposited film may There has been a problem that the photovoltaic device to be manufactured is liable to cause a characteristic failure because the semiconductor film in the process of being charged up causes dielectric breakdown.
[0014]
In view of the above problems, the object of the present invention is to manufacture a photovoltaic device having a tandem structure by a roll-to-roll method capable of continuously forming a deposited film over a large area. An object of the present invention is to provide a photovoltaic device having a large area, high efficiency and low degradation, a tandem structure photovoltaic device, a manufacturing method thereof, and a manufacturing apparatus therefor, by solving the problems in applying the plasma CVD method to an i-type layer.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the photovoltaic device manufacturing method of the present invention manufactures a photovoltaic device having a tandem structure made of a silicon-based non-single crystal semiconductor on a substrate by passing the substrate through a plurality of deposition chambers. In the method of manufacturing a photovoltaic device, the i-type layer of the photovoltaic device having a tandem structure introduces a gas containing Group III and / or Group V atoms, which will be described later in <Plasma CVD>. Or a film is formed under the condition of introducing a small amount of Group III and / or Group V atoms such that the Fermi level is located near the center of the band gap. Among the i-type layers, a plurality of i-type layers are deposited by a plasma CVD method using high-frequency power at a VHF frequency, and a plurality of i-type layers deposited by a plasma CVD method using high-frequency power at a VHF frequency. In the film forming chamber, a DC voltage having a positive direction with respect to the substrate is applied, and the DC voltage is set to a lower voltage in the film forming chamber of the later layer in the stacking order. .
[0016]
In the method for manufacturing a photovoltaic element, the photovoltaic element is preferably produced as a photovoltaic element having a three-layer tandem structure of nipnipnip or pinpinpin.
[0017]
In addition, the second i-type layer and the third i-type layer from the light incident side of the photovoltaic element having the three-layer tandem structure are made of non-single-crystal silicon germanium by plasma CVD using high-frequency power of VHF frequency. Is preferably deposited as.
[0018]
Furthermore, the substrate is preferably a strip substrate.
[0019]
In addition, it is preferable to adopt a roll-to-roll method in which a roll-shaped substrate continuously moves in a plurality of film formation chambers.
[0020]
The photovoltaic element of the present invention is manufactured by any one of the methods described above.
[0021]
The photovoltaic device manufacturing apparatus of the present invention manufactures a photovoltaic device that passes a substrate through a plurality of film forming chambers and manufactures a photovoltaic device having a tandem structure made of a silicon-based non-single crystal semiconductor on the substrate. The apparatus has a film formation chamber in which a plurality of i-type layers among the i-type layers of photovoltaic elements having a tandem structure are deposited by a plasma CVD method using high-frequency power of a VHF frequency, and the plurality of i-type layers In the film formation chamber for depositing, a means for applying a DC voltage in the positive direction with respect to the substrate is provided, and the means for applying this DC voltage is set to a lower voltage in the film formation chamber of the later layer in the stacking order. It is characterized by that.
[0022]
The positive orientation is preferred.
[0023]
In the photovoltaic device manufacturing apparatus, the means for applying the positive DC voltage is preferably formed by a DC bias electrode and a DC power source for applying a DC voltage thereto.
[0024]
Moreover, it is preferable that the photovoltaic element is formed as a photovoltaic element having a three-layer tandem structure of nipnipnip or pinpinpin.
[0025]
Furthermore, in the film formation chamber in which the second i-type layer and the third i-type layer from the light incident side of the photovoltaic device having the three-layer tandem structure perform a plasma CVD method using high-frequency power of the VHF frequency, It is preferably deposited as non-single crystal silicon germanium.
[0026]
And it is preferable that the said board | substrate is a strip | belt-shaped board | substrate.
[0027]
In addition, it is preferably formed as a roll-to-roll apparatus in which a rolled substrate continuously moves in a plurality of film forming chambers.
[0028]
According to the present invention, a positive DC voltage is applied to the substrate and a negative DC electric field is formed on the substrate side in the i-type film forming chamber in which the deposited film is formed with the high frequency power of the VHF frequency. Therefore, the film quality of the deposited film during high-speed deposition can be improved.
[0029]
In addition, in an i-type layer that forms a deposited film with high-frequency power of VHF frequency, the DC voltage applied is set lower as the layer is stacked later, so that the i-type layer having a relatively high resistance and a thick deposited film thickness. Even if the surface of the deposited film on the substrate becomes high resistance, the applied DC voltage is set lower as the deposited film is stacked, so abnormal discharge such as sparks from the DC voltage application electrode. And the surface of the deposited film is not charged up, and the semiconductor film being manufactured does not cause dielectric breakdown, and the photovoltaic element to be manufactured does not cause characteristic failure.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings, but the present invention is not limited to these embodiments.
[0031]
FIG. 1 is a schematic cross-sectional view showing an example of an apparatus for realizing the method for producing a photovoltaic element of the present invention. In the apparatus shown in FIG. 1, a photovoltaic device having a two-layer tandem structure made of a silicon-based non-single-crystal semiconductor is manufactured on a substrate by passing it through six film forming chambers while continuously moving the belt-like substrate. The layer structure of a photovoltaic device having a two-layer tandem structure made of a silicon-based non-single-crystal semiconductor is generally nipnip or pinpin. In this apparatus, two i-type semiconductor layers are deposited by a plasma CVD method at a VHF frequency and stacked. A lower positive DC voltage is applied to the i-type layer in the later order in the deposition chamber.
[0032]
In FIG. 1, a long belt-like substrate 101 is pulled out from a coiled state in an unwinding chamber 102, and sequentially passes through chambers 103, 104, 105, 106, 107, and 108, and is wound up (not shown). The coil is wound up in a winding chamber 109 having a mechanism. The unwinding chamber 102, the chambers 103 to 108, and the winding chamber 109 are connected to adjacent chambers by gas gates 110.
[0033]
Each of the gas gates 110 through which the belt-like substrate 101 passes is provided with a gate gas introduction pipe 111 in the vicinity of the central portion in the substrate transfer direction. ₂ The gas flow from the center of the gas gate to the adjacent chamber is formed by introducing a gas such as He, He, etc., preventing the mixing of the source gas in the adjacent chamber and separating the source gas.
[0034]
Each chamber 103 to 108 is provided with a source gas introduction pipe 112, an exhaust pipe 113, a plate electrode 114 or a rod-like electrode 115, and a substrate heater 119, and a silicon-based non-single-crystal semiconductor film is formed on the surface of the moving belt-like substrate 101. Laminated.
[0035]
In the apparatus shown in FIG. 1, among the chambers 103 to 108, the discharge frequency of the chambers 104 and 107 is 105 MHz of the VHF frequency, and the discharge frequency of the other chambers 103, 105, 106, and 108 is 13.56 MHz of the RF frequency. is there.
[0036]
In the chambers 104 and 107 having the VHF frequency, the high frequency power is radiated from the rod-like electrode 115 connected to the high frequency power source 117 having the VHF frequency. On the other hand, in the RF frequency chamber, the high frequency power is radiated from the plate electrode 114 connected to the RF frequency high frequency power source 116.
[0037]
In addition, a DC bias electrode 118 is provided in the film forming chambers of the VHF frequency chambers 104 and 107 in addition to the rod-shaped electrode 115, and a DC voltage is applied from a DC power source 119.
[0038]
In FIG. 1, the moving direction 120 of the substrate is from left to right, and in the chambers 104 and 107 in which the i-type semiconductor layer is deposited with the high frequency power of the VHF frequency, the deposited films are stacked on the substrate in the order of 104 and 107. Is called.
[0039]
In the present invention, the direct-current voltage V1 applied to the chamber 104 and the direct-current voltage V2 applied to the chamber 107 are set to have a relationship of V1>V2> 0, so that the deposited film is formed with high-frequency power of the VHF frequency. In the i-type layer deposition chamber, a positive DC voltage is applied to the substrate and a negative DC electric field is formed on the substrate side, so that the quality of the deposited film during high-speed deposition is improved.
[0040]
In addition, in an i-type layer that forms a deposited film with high-frequency power of VHF frequency, the DC voltage applied is set lower as the layer is stacked later, so that the i-type layer having a relatively high resistance and a thick deposited film thickness. Even if the surface of the deposited film on the substrate becomes high resistance, the applied DC voltage is set lower as the deposited film is stacked, so abnormal discharge such as sparks from the DC voltage application electrode. And the surface of the deposited film is not charged up, and the semiconductor film being manufactured does not cause dielectric breakdown, and the photovoltaic element to be manufactured does not cause characteristic failure.
[0041]
Hereinafter, the manufacturing method of the photovoltaic device according to the present invention will be further described.
[0042]
<DC bias voltage>
In the present invention, the direct current voltage applied to the film formation chamber is a positive voltage with respect to the substrate potential, and preferably has a good film quality in the deposited semiconductor film from the range of 0 to 500 V, more preferably 50 to 400 V. The voltage is set so that sparks and charge-up do not occur.
[0043]
<DC bias voltage application method>
In the present invention, as a method of applying a DC voltage to the film forming chamber, a method of providing a bias electrode for applying a bias separately from the VHF discharge electrode in the film forming chamber, or a method of superimposing a DC voltage together with high frequency power on the VHF discharge electrode. And applying it. The method of superimposing and applying a DC voltage together with the high frequency power to the VHF discharge electrode requires a small number of electrodes and simplifies the structure of the film forming chamber. However, the choke is prevented from entering the DC voltage application circuit. It is necessary to cut off the high frequency by means such as a coil and cut off the direct current with a capacitor or the like so that no direct current flows into the high frequency power supply.
[0044]
<VHF frequency>
In the present invention, the VHF frequency used for the plasma CVD method is a frequency of 30 MHz to 500 MHz. Within that range, select a relatively high frequency region if you want to increase the deposition rate by increasing the plasma density, and select a relatively low frequency region if you want a longer area uniformity using longer wavelengths. To use.
[0045]
<Striped substrate>
As a material of the belt-like substrate suitably used in the present invention, it can be moved when forming a semiconductor layer, has little deformation and distortion at a temperature required for film deposition, has a desired strength, and has conductivity. Those are preferred. Specific examples include a metal thin film such as stainless steel, aluminum, and iron, or a surface of a heat resistant resin such as polyimide and Teflon that has been subjected to a conductive treatment.
[0046]
<Plasma CVD method>
In the present invention, a plasma CVD method using a high frequency of the VHF frequency is performed in at least two film forming chambers. The discharge frequency in the other film forming chamber may be an RF frequency or a microwave frequency.
[0047]
The source gas introduced into the film formation chamber and used as the raw material for the semiconductor film is a gas containing a gasatable compound containing at least silicon atoms when the deposited film is, for example, a silicon-based non-single-crystal film. It may contain a compound that can be gasified, a compound that can be gasified containing carbon atoms, and a mixed gas of the compound.
[0048]
Specifically, as a gasifiable compound containing a silicon atom, a chain or cyclic silane compound is used. Specifically, for example, SiH _Four , Si ₂ H ₆ , SiF _Four , SiFH _Three , SiF ₂ H ₂ , SiF _Three H, Si _Three H ₈ , SiD _Four , SiHD _Three , SiH ₂ D ₂ , SiH _Three D, SiFD _Three , SiF ₂ D ₂ , Si ₂ D _Three H _Three , (SiF ₂ ) _Five , (SiF ₂ ) ₆ , (SiF ₂ ) _Four , Si ₂ F ₆ , Si _Three F ₈ , Si ₂ H ₂ F _Four , Si ₂ H _Three F _Three , SiCl _Four , (SiCl ₂ ) _Five , SiBr _Four , (SiBr ₂ ) _Five , Si ₂ Cl ₆ , SiHCl _Three , SiH ₂ Br ₂ , SiH ₂ Cl ₂ , Si ₂ Cl _Three F _Three And those that can be easily gasified. Here, D represents deuterium.
[0049]
When the deposited film is amorphous silicon germanium, a gasifiable compound containing germanium atoms as a raw material gas is specifically GeH. _Four , GeD _Four , GeF _Four , GeFH _Three , GeF ₂ H ₂ , GeF _Three H, GeHD _Three , GeH ₂ D ₂ , GeH _Three D, Ge ₂ H ₆ , Ge ₂ D ₆ Etc.
[0050]
In addition, when the deposited film is amorphous silicon carbide, as a gasification compound that specifically contains carbon atoms as a source gas, CH _Four , CD _Four , C _n H _{2n + 2} (N is an integer), C _n H _2n (N is an integer), C ₂ H ₂ , C ₆ H ₆ , CO ₂ , CO and the like.
[0051]
Examples of the substance introduced into the p-type layer or the n-type layer for valence electron control include Group III atoms and Group V atoms in the periodic table.
[0052]
As a material effectively used as a starting material for introducing a group III atom, specifically, for introducing a boron atom, B ₂ H ₆ Boron hydride such as BF _Three And boron halides.
[0053]
Specifically, as a starting material for introducing a group V atom, specifically, PH for introducing a phosphorus atom can be used. _Three Phosphorus hydrides such as PF _Five And the like. In addition to AsH _Three Etc. can also be mentioned.
[0054]
Further, the gasifiable compound is H. ₂ , He, Ne, Ar, Xe, Kr or the like may be appropriately diluted with a gas such as He, Ne, Ar, Xe, or Kr.
[0055]
<Tandem structure photovoltaic device>
In the present invention, a tandem photovoltaic element refers to a photovoltaic element having a structure in which a plurality of photovoltaic elements are connected in series.
[0056]
In a tandem photovoltaic device, a plurality of photovoltaic devices with different light absorption wavelength ranges can be stacked so that the band gap becomes narrower in order from the light incident direction, so that a wider wavelength range of incident light can be utilized. As a result, the photoelectric conversion efficiency is improved.
[0057]
Moreover, in a photovoltaic device having a tandem structure, since the light is absorbed by a plurality of photoelectric conversion layers, the film thickness of each photoelectric conversion layer can be reduced, and a photodegradation phenomenon called the Stebler-Lonsky effect is caused. Can be suppressed.
[0058]
Examples of the layer structure of a photovoltaic element having a tandem structure made of a silicon-based non-single-crystal semiconductor include a nipnip or pinpin two-layer tandem structure and a nipnipnip or pinpinpin three-layer tandem structure. Among these, the three-layer tandem structure is excellent in that a wider light wavelength range can be utilized.
[0059]
In the case of a photovoltaic element having a three-layer tandem structure, the light after passing through the first photoactive layer is transmitted to the second photoactive layer from the light incident side. Since the light after passing through the second photoactive layer is incident, it is necessary to increase the film thickness in the order of first <second <third. Further, if the band gaps of the second and third photoactive layers are made narrower than the first, it is possible to suppress the film thickness from increasing. However, since the film thickness tends to be thicker than that of the first photoactive layer, it is continuously increased. Application of high speed deposition is desirable for manufacturing.
[0060]
As described above, when photovoltaic elements with tandem structure made of silicon-based non-single crystal are stacked with a plurality of photovoltaic elements having different light absorption wavelength ranges so that the band gap is narrowed in order from the light incident direction. Examples of the material having a narrow band gap include non-single-crystal silicon germanium, non-single-crystal silicon tin, and microcrystalline silicon.
[0061]
【Example】
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[0062]
Example 1
In this example, a solar cell having a nipnip two-layer tandem structure composed of six layers of silicon-based non-single crystal film on a stainless steel substrate was manufactured by the method of the present invention using the manufacturing apparatus having the configuration shown in FIG. .
[0063]
The two i-type layers were deposited by applying a DC voltage to the film formation chamber by a plasma CVD method with a VHF frequency, and the applied DC voltage was set to be lower in the order of deposition.
[0064]
In the apparatus shown in FIG. 1, first, a stainless steel substrate 101 (SUS430-BA) having a length of 500 m, a width of 356 mm, and a thickness of 0.15 mm is passed through a gas gate 110 from a bobbin wound in a coil shape of the unwind chamber 102. Then, the chambers 103, 104, 105, 106, 107, 108 were passed through the bobbin of the winding chamber 109 so as to be wound in a coil shape, and the tension was applied without tension by a tension applying mechanism (not shown).
[0065]
Next, the chambers 102 to 109 were evacuated once to 1 Pa or less by the exhaust means of each chamber. While continuously evacuating, 100 sccm of He gas was introduced from the gas introduction pipe 112 connected to the gas supply means (not shown) of each chamber, and the opening degree of the exhaust valve (not shown) of the exhaust pipe 113 was adjusted. The internal pressure of the chamber was maintained at 100 Pa.
[0066]
In this state, the belt-like substrate was continuously moved at a moving speed of 600 mm per minute by a substrate transfer mechanism (not shown) connected to the bobbin of the winding chamber 109.
[0067]
Next, heating was controlled by the substrate heater 119 provided in each plasma discharge chamber and a substrate temperature monitor (not shown) so that the belt-like substrate 101 moving in each chamber had a predetermined temperature.
[0068]
When the substrate 101 is uniformly heated in each chamber, the introduction of the He gas is stopped while continuing the heating, and the gas to the gas introduction pipe 112 is changed to SiH. _Four Switched to source gas containing.
[0069]
Further, each gas gate 110 is supplied with H as a gas for separating a source gas from a gate gas introduction pipe 111 connected to a gas supply means (not shown). ₂ 1000 sccm of each was introduced.
[0070]
Next, high frequency power of RF frequency and VHF frequency is supplied from a high frequency power source to the discharge electrodes 114 and 115 of each chamber, discharge is generated in each chamber, the source gas is plasma-decomposed, and the moving strip substrate 101 is moved over A stacked film of a silicon-based non-single crystal film was deposited to form a semiconductor film of a solar battery having a two-layer tandem structure made of a silicon-based non-single crystal semiconductor.
[0071]
The discharge frequencies of the chambers 104 and 107 were 105 MHz and the discharge electrodes were rod-shaped, the discharge frequencies of the chambers 103, 105, 106 and 108 were 13.56 MHz and the discharge electrodes were flat.
[0072]
Furthermore, a DC voltage of 300 V is applied to the bias electrode of the VHF frequency chamber 104 through which the substrate passes first in a positive direction with respect to the belt substrate at the ground potential, and the bias electrode of the chamber 107 at VHF frequency through which the substrate passes later is applied. Applied a DC voltage of 100 V in a positive direction with respect to the belt-like substrate at the ground potential.
[0073]
Table 1 shows the film forming conditions of each chamber.
[0074]
[Table 1]

[0075]
After such film deposition is continuously performed over the length of the strip-shaped substrate of 400 m, the supply of discharge power to each chamber, introduction of the source gas, and heating of the strip-shaped substrate are stopped, After purging and sufficiently cooling the band-shaped substrate and the inside of the apparatus, the apparatus was opened to the atmosphere, and the band-shaped substrate having the semiconductor laminated film formed thereon and taken up on the bobbin in the winding chamber was taken out.
[0076]
Furthermore, the strip-shaped substrate taken out is continuously processed by a continuous modularization apparatus, and a 60 nm ITO thin film is formed on the entire surface as a transparent electrode on the semiconductor laminated film formed by the apparatus of the present invention. A thin-line Ag electrode was formed in the gap, and a solar cell module having a 35 cm square nipnip structure and a two-layer tandem structure was continuously formed.
[0077]
And about the created solar cell module, AM1.5 (100 mW / cm ² ) Was evaluated at 25 ° C. under simulated sunlight irradiation.
[0078]
As a result of the characteristic evaluation, the average photoelectric conversion efficiency of the produced solar cell module is 1.4 times compared with the average photoelectric conversion efficiency of the solar cell module when the bias voltage is not applied to the chambers 104 and 107 as 1. It was.
[0079]
Further, when the occurrence rate of characteristic defects due to short-circuiting of the created solar cell module was observed, the non-defective product rate when the DC voltage was not applied to the chambers 104 and 107 was compared with 100, and the chamber 104 was 300 V and the chamber 107 was 100 V. The non-defective rate was 95 when the voltage was applied, the non-defective rate was 35 when 100 V was applied to the chamber 104 and 300 V was applied to the chamber 107.
[0080]
Table 2 shows changes in conversion efficiency and yield rate when solar cell modules are manufactured by changing the combination of DC voltages.
[0081]
[Table 2]

[0082]
From this, it was confirmed that the conversion efficiency and the yield rate of the photovoltaic element having the tandem structure can be achieved by the method of the present invention.
[0083]
(Example 2)
FIG. 2 is a schematic diagram showing an apparatus for realizing the method of the present invention used in this embodiment. The apparatus shown in FIG. 2 has three RF frequency chambers added to the apparatus shown in FIG. 1, and the i-type layer is deposited from the substrate side by the high-frequency plasma CVD method with VHF frequency, VHF frequency, and RF frequency. Further, a semiconductor laminated film of a photovoltaic element having a three-layer tandem structure of nipnipnip or pinpinpin can be manufactured.
[0084]
In FIG. 2, 201 is a belt-like substrate, 202 is an unwinding chamber, 203, 204, 205, 206, 207 and 208 are chambers, 220, 221, and 222 are plasma CVD chambers with an RF frequency of 13.56 MHz, and 209 is a winding. The take-up chamber 210 is a gas gate.
[0085]
In this example, a solar cell having a three-layer tandem structure having a nipnip structure composed of nine silicon non-single crystal films on a stainless steel substrate was manufactured by the method of the present invention using the apparatus shown in FIG.
[0086]
Three i-type layers were deposited from the substrate side by a high-frequency plasma CVD method with VHF frequency, VHF frequency, and RF frequency, and a positive DC voltage was applied to the film forming chambers of the chambers 204 and 207 with VHF frequency. Further, the DC voltage to be applied was set to be lower in the order of deposition.
[0087]
Specifically, a DC voltage of 200 V is applied to the bias electrode of the VHF frequency chamber 204 through which the substrate passes first in a positive direction with respect to the belt substrate at the ground potential, and the VHF frequency chamber 207 through which the substrate passes later. A DC voltage of 100 V was applied to the bias electrode in a positive direction with respect to the belt-like substrate having the ground potential.
[0088]
Table 1 shows the film forming conditions of each chamber.
[0089]
[Table 3]

[0090]
Hereinafter, in the same manner as in Example 1, a solar cell module having a three-layer tandem structure having a nipnipnip structure composed of nine layers of silicon-based non-single-crystal films on a stainless steel substrate was manufactured by the method of the present invention.
[0091]
And about the created solar cell module, Am1.5 (100 mW / cm ² ) Was evaluated at a temperature of 25 ° C. under simulated sunlight irradiation.
[0092]
As a result of the characteristic evaluation, the average photoelectric conversion efficiency of the produced solar cell module is 1.4 times compared with the average photoelectric conversion efficiency of the solar cell module when the DC voltage is not applied to the chambers 204 and 207 as 1. It was.
[0093]
Further, when the occurrence rate of characteristic failure due to short circuit of the created solar cell module was observed, the non-defective product rate when the DC voltage was not applied to the chambers 204 and 207 was set to 100, and the chamber 204 was 200 V and the chamber 207 was 100 V. The non-defective rate was 98, which was almost unchanged.
[0094]
From this, it was confirmed that the conversion efficiency and the yield rate of the photovoltaic device having the tandem structure can be achieved by the method of the present invention.
[0095]
(Example 3)
A 35-cm square nipnipnip structure three-layer tandem solar cell module was continuously manufactured in the same manner as in Example 2 except that the discharge frequency in the discharge chambers 204 and 207 was changed to 20 MHz.
[0096]
And about the created solar cell module, Am1.5 (100 mW / cm ² ) Was evaluated at a temperature of 25 ° C. under simulated sunlight irradiation.
[0097]
As a result of the characteristic evaluation, the average photoelectric conversion efficiency of the created solar cell module is 1.25 times higher than the average photoelectric conversion efficiency of the solar cell module when the DC voltage is not applied to the chambers 204 and 207. It was.
[0098]
Further, when the occurrence rate of characteristic failure due to short circuit of the created solar cell module was observed, the non-defective product rate when the DC voltage was not applied to the chambers 204 and 207 was set to 100, and the chamber 204 was 200 V and the chamber 207 was 100 V. The non-defective product rate was 100 and no change when applied.
[0099]
From this, it was confirmed that the conversion efficiency and the yield rate of the photovoltaic device having the tandem structure can be achieved by the method of the present invention.
[0100]
(Example 4)
A 35 cm square nipnipnip structure three-layer tandem solar cell module was continuously manufactured in the same manner as in Example 2 except that the discharge frequency in the discharge chambers 204 and 207 was changed to 500 MHz.
[0101]
And about the created solar cell module, Am1.5 (100 mW / cm ² ) Was evaluated at a temperature of 25 ° C. under simulated sunlight irradiation.
[0102]
As a result of the characteristic evaluation, the average photoelectric conversion efficiency of the produced solar cell module is 1.45 times in comparison with the average photoelectric conversion efficiency of the solar cell module when the DC voltage is not applied to the chambers 204 and 207 as 1. It was.
[0103]
Further, when the occurrence rate of characteristic failure due to short-circuiting of the created solar cell module was observed, the non-defective product rate when a DC voltage was not applied to the chambers 204 and 207 was set to 100, and the chamber 204 was 200 V and the chamber 207 was 100 V. The non-defective rate when 95 was applied was as good as 95 with almost no change.
[0104]
From this, it was confirmed that the conversion efficiency and the yield rate of the photovoltaic device having the tandem structure can be achieved by the method of the present invention.
[0105]
(Example 5)
A 35 cm square nipnipnip structure three-layer tandem solar cell module was continuously manufactured in the same manner as in Example 2 except that the DC voltages applied to the discharge chambers 204 and 207 were changed to 200 V and 150 V, respectively.
[0106]
And about the created solar cell module, Am1.5 (100 mW / cm ² ) Was evaluated at a temperature of 25 ° C. under simulated sunlight irradiation.
[0107]
As a result of the characteristic evaluation, the average photoelectric conversion efficiency of the created solar cell module is 1.43 times compared with the average photoelectric conversion efficiency of the solar cell module when the DC voltage is not applied to the chambers 204 and 207 as 1. It was.
[0108]
Further, when the occurrence rate of characteristic failure due to short circuit of the created solar cell module was observed, the non-defective product rate when a DC voltage was not applied to the chambers 204 and 207 was set to 100, and the chamber 204 was 200 V and the chamber 207 was 150 V. The non-defective rate was 93, with almost no change.
[0109]
From this, it was confirmed that the conversion efficiency and the yield rate of the photovoltaic device having the tandem structure can be achieved by the method of the present invention.
[0110]
【The invention's effect】
As described above, according to the present invention, a positive DC voltage is applied to the substrate and the substrate side is negative in the i-type film forming chamber for forming the deposited film with high-frequency power of the VHF frequency. Since a direct current electric field is formed, the film quality of the deposited film during high-speed deposition can be improved.
[0111]
In addition, in an i-type layer that forms a deposited film with high-frequency power of VHF frequency, the DC voltage applied is set lower as the layer is stacked later, so that the i-type layer having a relatively high resistance and a thick deposited film thickness. Even if the deposited film surface on the substrate becomes high resistance, the applied DC voltage is set lower as the deposited film is stacked, so abnormal discharge such as spark from the DC voltage application electrode. And the surface of the deposited film does not charge up and the semiconductor film in the process of causing breakdown does not cause a failure of the characteristics of the photovoltaic device to be manufactured. A photovoltaic device having a degraded tandem structure can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of the configuration of an apparatus for realizing a method for producing a photovoltaic element of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of the configuration of an apparatus for realizing the method for manufacturing a photovoltaic element of the present invention.
[Explanation of symbols]
101 Strip board
102 Unwinding room
103, 104, 105, 106, 107, 108 Chamber
109 Winding room
110 Gas Gate
111 Gate gas introduction pipe
112 Raw material gas introduction pipe
113 Exhaust pipe
114 Plate electrode
115 Rod electrode
116 RF power supply with RF frequency
117 High frequency power supply with VHF frequency
118 DC bias electrode
119 DC power supply
201 Strip substrate
202 Unwinding room
203, 204, 205, 206, 207, 208, 220, 221, 222 Chamber
209 Winding room
210 gas gate

Claims (12)

In the method for manufacturing a photovoltaic device, the substrate is passed through a plurality of film formation chambers, and a photovoltaic device having a tandem structure made of a silicon-based non-single crystal semiconductor is manufactured on the substrate.
Among the i-type layers of the tandem structure photovoltaic element, a plurality of i-type layers are deposited by a plasma CVD method using high-frequency power of a VHF frequency,
In addition, a DC voltage in a positive direction with respect to the substrate is applied to a plurality of i-type layer deposition chambers deposited by a plasma CVD method using high-frequency power at a VHF frequency, and the DC voltage is applied later in the stacking order. A method for manufacturing a photovoltaic device, characterized in that the voltage is set to be lower in a film forming chamber of the layer. The method for manufacturing a photovoltaic device according to claim 1, wherein the photovoltaic device is produced as a photovoltaic device having a three-layer tandem structure of nipnipnip or pinpinpin. The second i-type layer and the third i-type layer from the light incident side of the photovoltaic device having the three-layer tandem structure are deposited as non-single-crystal silicon germanium by plasma CVD using high-frequency power at the VHF frequency. The method of manufacturing a photovoltaic element according to claim 2, wherein The method for manufacturing a photovoltaic element according to claim 1, wherein the substrate is a belt-like substrate. The method for manufacturing a photovoltaic device according to any one of claims 1 to 4, wherein a roll-to-roll method is employed in which a roll-shaped substrate continuously moves in a plurality of film forming chambers. A photovoltaic element manufactured by the method according to claim 1. In a photovoltaic device manufacturing apparatus for manufacturing a photovoltaic device having a tandem structure made of a silicon-based non-single crystal semiconductor on a substrate through a plurality of film formation chambers,
A film forming chamber for depositing a plurality of i-type layers among the i-type layers of the tandem photovoltaic element by a plasma CVD method using high-frequency power of a VHF frequency;
In the film formation chamber for depositing the plurality of i-type layers, a means for applying a DC voltage in the positive direction with respect to the substrate is provided, and the means for applying the DC voltage is used to form a layer whose order is later. The photovoltaic device manufacturing apparatus is characterized in that the voltage is set to be lower in the chamber. 8. A photovoltaic element manufacturing apparatus according to claim 7, wherein said means for applying a positive direct current voltage is formed by a direct current bias electrode and a direct current power source for applying a direct current voltage thereto. apparatus. 9. The photovoltaic device manufacturing apparatus according to claim 7, wherein the photovoltaic device is formed as a photovoltaic device having a three-layer tandem structure of nipnipnip or pinpinpin. In the film formation chamber in which the second i-type layer and the third i-type layer from the light incident side of the photovoltaic element having the three-layer tandem structure perform plasma CVD using high-frequency power of the VHF frequency. The photovoltaic device manufacturing apparatus according to claim 9, wherein the photovoltaic element is deposited as crystalline silicon germanium. The photovoltaic device manufacturing apparatus according to claim 7, wherein the substrate is a belt-like substrate. The apparatus for manufacturing a photovoltaic element according to any one of claims 7 to 11, wherein the apparatus is formed as a roll-to-roll apparatus in which a rolled substrate continuously moves in a plurality of film forming chambers.

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