JP3777281B2 - Compound semiconductor solar cell and manufacturing method thereof - Google Patents

Compound semiconductor solar cell and manufacturing method thereof Download PDF

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JP3777281B2
JP3777281B2 JP36768799A JP36768799A JP3777281B2 JP 3777281 B2 JP3777281 B2 JP 3777281B2 JP 36768799 A JP36768799 A JP 36768799A JP 36768799 A JP36768799 A JP 36768799A JP 3777281 B2 JP3777281 B2 JP 3777281B2
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layer
type semiconductor
semiconductor layer
solar cell
copper
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JP2001148490A (en
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健司 竹内
良雄 小沼
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Shinko Electric Industries Co Ltd
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Shinko Electric Industries Co Ltd
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy
    • Y02E10/541CuInSe2 material PV cells
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

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Description

【0001】
【発明の属する技術分野】
本発明は化合物半導体太陽電池及びその製造方法に関し、更に詳細にはpn接合の化合物半導体太陽電池及びその製造方法に関する。
【0002】
【従来の技術】
図4に示すpn接合の光吸収層を有する化合物半導体太陽電池がある。図4において、図4(a)は化合物半導体太陽電池の正面図であり、図4(b)は化合物半導体太陽電池の縦断面図である。この化合物半導体太陽電池(以下、単に太陽電池と称することがある)は、ガラス基板100上に電極膜としてモリブデン層102が形成されている。このモリブデン層102上には、p形半導体層104とn形半導体層106とが順次積層されて形成されており、n形半導体層106上に透明電極108が形成されている。更に、透明電極108上には櫛形電極110が形成されている。この櫛形電極110は、図4(a)に示す様に、電極が枝別れ状(櫛形状)に形成されているものである。
【0003】
かかる図4に示す太陽電池は、図5に示す方法で製造できる。先ず、ガラス基板100の一面側に、モリブデン層102から成る電極膜を蒸着又はスパッタリングで形成した後、インジウム層103を室温下での蒸着によって形成し、更にインジウム層103上に銅層105を室温下での蒸着によって形成する〔図5(a)の工程〕。
このインジウム層103と銅層105とから成る金属膜を、硫化水素雰囲気中で加熱処理する硫化処理を施してCuInS2のp形半導体層104とした後、p形半導体層104に生成された硫化物(CuxY)等の不純物を取り除きp形半導体層104の特性を適正化して安定した特性とすべく、KCNが5〜10重量%含有されたKCN溶液によってp形半導体層104の表面を洗浄するKCN処理を施す〔図5(b)の工程〕。
更に、p形半導体層104上には、化学的溶液析出法によりn形半導体層106を形成し〔図5(c)の工程〕、更にn形半導体層106上にスパッタリングによりZnO:Al又はIn23から成る透明電極108を形成する〔図5(d)の工程〕。
その後、透明電極108上に、アルミニウムから成る櫛形電極110を形成した後、モリブデン層102上に電極端子を形成し、図4に示す太陽電池を得ることができる。
【0004】
【発明が解決しようとする課題】
図4に示す太陽電池においては、KCN処理前のp形半導体層104を形成するインジウム(In)と銅(Cu)とのCu/In原子濃度比率(以下、単にCu/In原子濃度比率と記載する場合は、KCN処理前のp形半導体層を形成するインジウム(In)と銅(Cu)とのCu/In原子濃度比率を示表する)を可及的に高くすることによって、p形半導体層104内の結晶性を向上でき、その発電効率を向上できる。
しかしながら、現状においては、KCN処理直前のp形半導体層104のCu/In原子濃度比率は、最終的に得られる太陽電池の歩留まり率等の観点から略1.6が限界である。p形半導体層104のCu/In原子濃度比率が1.6を超えて高くすると、KCN処理工程において、p形半導体層104が電極膜102から剥離し易くなるからである。
そこで、本発明の課題は、主として銅(Cu)及びインジウム(In)によって形成されて成るp形半導体層を具備するpn接合の化合物半導体太陽電池において、KCN処理前のp形半導体層を形成するインジウム(In)と銅(Cu)とのCu/In原子濃度比率を、従来のものよりも高くし得る化合物半導体太陽電池及びその製造方法を提供することにある。
【0005】
【課題を解決するための手段】
本発明者等は、前記課題を解決すべく検討した結果、基板の一面側に形成した電極膜とp形半導体層との間に、金又は白金族から成る薄膜金属層を形成することによって、KCN処理前のp形半導体層のCu/In原子濃度比率を1.8以上にできることを知り、本発明に到達した。
すなわち、本発明は、基板の一面側に形成された電極膜上に、p形半導体層とn形半導体層とが順次形成されてなる化合物半導体太陽電池において、該p形半導体層が、CuInS 2 又はCuInSe 2 から成り、KCN溶液によって洗浄されて硫化銅やセレン化銅等の不純物が除去された半導体層であり、且つ前記電極膜とp形半導体層との間に、前記p形半導体層よりも薄い貴金属から成る薄膜金属層が形成されていることを特徴とする化合物半導体太陽電池にある。
かかる本発明において、薄膜金属層の厚さを、2nm以上、特に好適には薄膜金属層の厚さを5〜200nmとすることによって、化合物半導体太陽電池の製造コストの低減を図ることができる。
更に、電極膜を、ガラス基板の一面側に形成したモリブデン(Mo)から成る電極膜とすることにより、発電効率を従来の太陽電池よりも向上できる。
【0006】
また、本発明は、基板の一面側に形成された電極膜上にインジウム層と銅層とを積層して金属膜を形成した後、前記金属膜に硫化処理又はセレン化処理を施してCuInS2又はCuInSe2から成るp形半導体層を形成し、次いで、前記p形半導体層をKCN溶液で洗浄して、硫化銅やセレン化銅等の不純物を除去するKCN処理を施した後、前記p形半導体層上にn型半導体層を形成して化合物半導体太陽電池を製造する際に、該電極膜の表面に、前記p形半導体層よりも薄い貴金属から成る薄膜金属層を形成した後、前記薄膜金属層の表面にインジウム層と銅層とから成る金属膜を形成することを特徴とする化合物半導体太陽電池の製造方法にある。
【0007】
かかる本発明において、インジウム層と銅層とから成る金属膜を、KCN処理を施す前のp形半導体層を形成するインジウム(In)と銅(Cu)とのCu/In原子濃度比率が1.8以上となるように形成することによって、最終的に得られる太陽電池の特性を向上できる。
尚、本発明の薄膜金属層としては、金(Au),白金(Pt)又はパラジウム(Pd)によって形成した薄膜金属層が好ましい。
【0008】
本発明においては、KCN処理を施す前のp形半導体層のCu/In原子濃度比率を1.8以上としても、KCN処理工程にいて、電極膜からのp形半導体層の剥離を防止できる。このため、p形半導体層のCu/In原子濃度比率を、従来の化合物半導体太陽電池よりも高くでき、p形半導体層内の結晶性を向上できる結果、本発明に係るpn接合の化合物半導体太陽電池の発電効率を、従来の化合物半導体太陽電池の発電効率よりも向上できる。
【0009】
【発明の実施の形態】
本発明に係る化合物半導体太陽電池の一例を図1に示す。図1において、図1(a)は太陽電池の正面図であり、図1(b)は太陽電池の斜視図である。図1に示す太陽電池は、基板としてのガラス基板10上に電極膜としてモリブデン層12が形成されている。このモリブデン層12上には、CuInS2のp形半導体層14とn形半導体層16とが順次積層されており、n形半導体層16上に透明電極18が形成されている。更に、透明電極18上には櫛形電極20が形成されている。この櫛形電極20は、図1(a)に示す様に、電極が枝別れ状(櫛形状)に形成されているものである。
かかる太陽電池において、モリブデン層12とp形半導体層14との間には、貴金属から成る薄膜金属層22が形成されている。この薄膜金属層22は、金(Au),白金(Pt)又はパラジウム(Pd)によって形成することが好ましく、且つ図1(b)に示す様に、太陽電池を構成する層及び膜のいずれよりも薄く、厚さは2nm程度で有効である。但し、実用的には、薄膜金属層22の厚さを5〜200nmの範囲内とすることが好ましく、特に薄膜金属層22の厚さを5〜20nmとすることが好ましい。
また、p形半導体層14は、後述するKCN処理を施す前のp形半導体層のCu/In原子濃度比率を1.8以上とすることができる。モリブデン層12上に直接p型半導体層14を形成した従来の化合物半導体太陽電池では、KCN処理前のp形半導体層のCu/In原子濃度比率が1.6を超えて高くなり、その膜厚が2μm以上となると、KCN処理工程において、モリブデン層12からp型半導体層が剥離する現象が発生し易くなる。この様に、Cu/In原子濃度比率を1.8以上とした図1に示す化合物半導体太陽電池のp形半導体層では、その厚さを6〜8μmとすることができる。
尚、Cu/In原子濃度比率が1.6程度である従来の化合物半導体太陽電池のp形半導体層では、その厚さは2μm程度である。
【0010】
図1に示す太陽電池は、図2に示す製造方法で製造できる。先ず、基板としてのガラス基板10の一面側に、電極膜としてのモリブデン層12をスパッタリングによって形成した後〔図2(a)の工程〕、厚さが5〜100nm(好ましくは5〜20nm)の貴金属から成る薄膜金属層22をモリブデン層12上に形成する〔図2(b)の工程〕。この薄膜金属層22は、金(Au),白金(Pt)又はパラジウム(Pd)の蒸着、スパッタリング、又は電解めっきによって形成することが好ましい。
更に、インジウム層13を、薄膜金属層22上に室温下での蒸着によって形成した後、銅層15を室温下での蒸着によってインジウム層13上に形成する〔図2(c)の工程〕。この際、インジウム層13及び銅層15の厚さを、KCN処理前のp形半導体層のCu/In原子濃度比率が1.8以上となるように制御する。
次いで、形成したインジウム層13及び銅層15から成る金属膜に、硫化水素雰囲気中で加熱処理する硫化処理を施すことによって、CuInS2のp形半導体層14を形成する〔図2(d)の工程〕。この硫化処理は、アルゴンガス等の不活性ガス中に硫化水素(H2S)が5vol %加えられた気体を、540℃の温度雰囲気下で約2時間ほど流すことによって施すことができる。
ここで、図2においては、インジウム層13を形成した後に銅層15を形成しているが、銅層15を形成した後にインジウム層13を形成してもよい。
更に、図2では、インジウム層13及び銅層15を蒸着によって形成しているが、スパッタリングやめっきによって形成してもよく、蒸着、スパッタリング、及びめっきを併用してもよい。
【0011】
その後、最適なpn接合の太陽電池が得られるように、p形半導体層14に生成された硫化物(CuxY)等の不純物を取り除きp形半導体層14の特性を適正化して安定した特性とすべく、KCNが5〜10重量%含有されたKCN溶液によってp形半導体層14の表面を洗浄するKCN処理を施す。このKCN処理は、KCNが5〜10重量%含有された室温(常温)程度のKCN溶液中に、p形半導体層14の表面を1〜5分間程度浸漬することによって行うことができる。
かかるKCN処理の工程において、薄膜金属層22上に形成したp型半導体層では、KCN処理前のp型半導体層のCu/In原子濃度比率を1.8以上としても、モリブデン層12からのp形半導体層の剥離現象は発生しない。
他方、モリブデン層102上に直接p形半導体層104が形成されている図5に示す従来の太陽電池では、KCN処理前のp型半導体層のCu/In原子濃度比率が1.6を超えて高くなると、モリブデン層からp形半導体層が剥離する現象が発生する。
【0012】
この様に形成したp形半導体層14上には、化学的溶液析出法によってn形半導体層16を形成する〔図2(e)の工程〕。かかるn形半導体層16は、ZnSO4(0.1mol/リットル)、チオ尿素(0.6mol/リットル)及びNH3水溶液(3mol/リットル)が混合されて80℃に維持された混合液に、p形半導体層14を形成したガラス基板10を約10分間程浸漬することによって形成できる。
この工程はn型半導体層14がZnSの場合であり、n型半導体層14をCdSとする場合は、ヨウ化カドミウム(0.0015mol/リットル)、NH3水溶液(1.0mol/リットル)及びヨウ化アンモニウム(0.01mol/リットル)を混合した液に基板を入れ、加温して約40℃になったところで、チオ尿素(0.15mol/リットル)を入れ、80℃で5分間浸漬することによって形成できる。
更に、n形半導体層16上に、AlがドープされたZnOから成る透明電極18を形成する〔図2(f)の工程〕。
その後、透明電極18上に、アルミニウムによって櫛形電極20を形成した後、モリブデン層12上に電極端子23を形成して図1に示す太陽電池を得ることができる。
この電極端子23は、モリブデン層12上で電極端子23を形成する部位を予め保護用のレジスト又はマスクにより被覆しておき、p型半導体層14、n形半導体層16、透明電極18を形成した後、保護用のレジスト又はマスクを除去することによって形成できる。
【0013】
図1に示す太陽電池のI−V特性を図3の曲線Aとして示す。AM1.5(100mW/cm2)の条件により測定した結果である。
曲線AのI−V特性を呈する太陽電池は、その受光面積(有効面積)が0.25cm2であって、ガラス基板10上に形成された厚さ約1μmのモリブデン層12、厚さ5nmの白金(Pt)から成る薄膜金属層22、厚さ約2.5μmで且つKCN処理前のCu/In原子濃度比率が3.0であったCuInS2から成るp形半導体層14、厚さ80〜120nmのZnSによるn型半導体層16及びAlがドープされたZnOから成る厚さ約1μmの透明電極18によって構成されている。
尚、n型半導体層16としてCdS、InSを使用した場合も同様である。
【0014】
他方、図5に示す従来の太陽電池のI−V特性を、図3に曲線Bとして併記する。曲線BのI−V特性を呈する太陽電池は、その受光面積(有効面積)が0.25cm2であって、ガラス基板100上に形成された厚さ約1μmのモリブデン層102、厚さ約2μmで且つKCN処理前のCu/In原子濃度比率が1.6であったCuInS2から成るp形半導体層104、厚さ80〜120nmのZnSによるn型半導体層106及びAlがドープされたZnOから成る厚さ約1μmの透明電極108によって構成されている。
図3から明らかな様に、図1に示す太陽電池の光量100mW/cm2下におけるI−V特性は、図5に示す従来の太陽電池のI−V特性よりも良好であり、図3に示すI−V特性から導かれる発電効率は11.0%である。一方、図5に示す従来の太陽電池の発電効率は9.7%であった。
【0015】
以上の説明では、インジウム層13と銅層15とから成る金属層に、硫化水素雰囲気中で加熱処理する硫化処理を施すことによって、CuInS2のp形半導体層14を形成したが、インジウム層13と銅層15とから成る金属層に、セレン化水素雰囲気中で加熱処理するセレン化処理を施し、CuInSe2のp形半導体層14を形成する場合も、本発明を適用することができる。
また、p形半導体層14を形成するCuInS2又はCuInSe2中に、微量のガリウム(Ga)が含有されていてもよい。この様に、微量のガリウム(Ga)が含有されているp形半導体層14を形成するには、例えば図2に示す方法において、ガラス基板10の基板面に形成したモリブデン層12上にガリウム層をガリウム(Ga)又は硫化ガリウム(GaS)のスパッタリング又は蒸着によって形成した後、インジウム層13と銅層15とを形成するか、或いはモリブデン層12上にインジウム層13と銅層15とを形成した後、同様にしてガリウム層を形成し、次いで、硫化水素雰囲気中で加熱処理する硫化処理を施すことによって、微量のガリウム(Ga)を含有するCuInS2から成るp形半導体層14を形成できる。同様のp形半導体層14は、ガラス基板10の基板面に形成したモリブデン層12上にインジウム層13を形成した後、銅(Cu)−ガリウム(Ga)合金層をスパッタリング又は蒸着によって形成し、次いで、硫化水素雰囲気中で加熱処理する硫化処理を施しても形成できる。
或いは、ガラス基板10の基板面に形成したモリブデン層12上に、銅(Cu)、インジウム(In)、セレン(Se)、及び微量のガリウム(Ga)を加熱しつつ同時蒸着することによって、微量のガリウム(Ga)を含有するCuInSe2から成るp形半導体層14を形成できる。
【発明の効果】
本発明によれば、KCN処理直前のp形半導体層のCu/In原子濃度比率を、従来のpn接合の化合物半導体太陽電池よりも高くでき、p形半導体層内の結晶性を向上できるため、本発明に係るpn接合の化合物半導体太陽電池の発電効率は、従来のpn接合の化合物半導体太陽電池の発電効率よりも向上できる。その結果、pn接合の化合物半導体太陽電池の普及を図ることができる。
【図面の簡単な説明】
【図1】本発明に係る化合物半導体太陽電池の一例を説明するための正面図及び斜視図である。
【図2】図1に示す化合物半導体太陽電池の製造方法の一例を説明するための工程図である。
【図3】図1に示す太陽電池のI−V特性を示すグラフである。
【図4】従来の化合物半導体太陽電池の一例を説明するための正面図及び縦断面図である。
【図5】図4に示す従来の化合物半導体太陽電池の製造方法の一例を説明するための工程図である。
【符号の説明】
10 ガラス基板
12 モリブデン層(電極膜)
13 インジウム層
14 p形半導体層
15 銅層
16 n形半導体層
18 透明電極層
20 櫛形電極
22 薄膜金属層
[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compound semiconductor solar cell and a manufacturing method thereof, and more particularly to a pn junction compound semiconductor solar cell and a manufacturing method thereof.
[0002]
[Prior art]
There is a compound semiconductor solar cell having a light absorption layer of a pn junction shown in FIG. 4A is a front view of the compound semiconductor solar battery, and FIG. 4B is a longitudinal sectional view of the compound semiconductor solar battery. In this compound semiconductor solar cell (hereinafter sometimes simply referred to as a solar cell), a molybdenum layer 102 is formed as an electrode film on a glass substrate 100. A p-type semiconductor layer 104 and an n-type semiconductor layer 106 are sequentially stacked on the molybdenum layer 102, and a transparent electrode 108 is formed on the n-type semiconductor layer 106. Further, a comb electrode 110 is formed on the transparent electrode 108. As shown in FIG. 4A, the comb-shaped electrode 110 has electrodes that are branched (comb-shaped).
[0003]
The solar cell shown in FIG. 4 can be manufactured by the method shown in FIG. First, an electrode film made of a molybdenum layer 102 is formed on one surface side of the glass substrate 100 by vapor deposition or sputtering, and then an indium layer 103 is formed by vapor deposition at room temperature, and a copper layer 105 is formed on the indium layer 103 at room temperature. It forms by vapor deposition below [the process of Fig.5 (a)].
The metal film composed of the indium layer 103 and the copper layer 105 is subjected to a sulfidation process in which a heat treatment is performed in a hydrogen sulfide atmosphere to form a CuInS 2 p-type semiconductor layer 104, and then the sulfide generated in the p-type semiconductor layer 104. The surface of the p-type semiconductor layer 104 is removed by a KCN solution containing 5 to 10% by weight of KCN in order to remove impurities such as Cu x S Y and optimize the characteristics of the p-type semiconductor layer 104 to achieve stable characteristics. A KCN process is performed to wash [step of FIG. 5B].
Further, an n-type semiconductor layer 106 is formed on the p-type semiconductor layer 104 by a chemical solution deposition method (step of FIG. 5C), and ZnO: Al or In is further sputtered on the n-type semiconductor layer 106. A transparent electrode 108 made of 2 O 3 is formed [step of FIG. 5 (d)].
Thereafter, a comb electrode 110 made of aluminum is formed on the transparent electrode 108, and then an electrode terminal is formed on the molybdenum layer 102, whereby the solar cell shown in FIG. 4 can be obtained.
[0004]
[Problems to be solved by the invention]
In the solar cell shown in FIG. 4, the Cu / In atomic concentration ratio between indium (In) and copper (Cu) forming the p-type semiconductor layer 104 before the KCN treatment (hereinafter simply referred to as Cu / In atomic concentration ratio). In this case, the p-type semiconductor is formed by increasing the Cu / In atomic concentration ratio of indium (In) and copper (Cu) forming the p-type semiconductor layer before KCN treatment as much as possible. The crystallinity in the layer 104 can be improved, and the power generation efficiency can be improved.
However, at present, the limit of the Cu / In atomic concentration ratio of the p-type semiconductor layer 104 immediately before the KCN treatment is approximately 1.6 from the viewpoint of the yield rate of the finally obtained solar cell. This is because if the Cu / In atomic concentration ratio of the p-type semiconductor layer 104 is increased to exceed 1.6, the p-type semiconductor layer 104 is easily peeled from the electrode film 102 in the KCN treatment process.
Accordingly, an object of the present invention is to form a p-type semiconductor layer before KCN treatment in a pn junction compound semiconductor solar cell having a p-type semiconductor layer formed mainly of copper (Cu) and indium (In). An object of the present invention is to provide a compound semiconductor solar cell and a method for manufacturing the same, in which the Cu / In atomic concentration ratio of indium (In) and copper (Cu) can be made higher than that of the conventional one.
[0005]
[Means for Solving the Problems]
As a result of studying the above problems, the present inventors have formed a thin metal layer made of gold or platinum group between the electrode film formed on one side of the substrate and the p-type semiconductor layer, Knowing that the Cu / In atomic concentration ratio of the p-type semiconductor layer before KCN treatment can be 1.8 or more, the present invention has been achieved.
That is, according to the present invention, in a compound semiconductor solar cell in which a p-type semiconductor layer and an n-type semiconductor layer are sequentially formed on an electrode film formed on one surface of a substrate, the p-type semiconductor layer is CuInS 2. Or a semiconductor layer made of CuInSe 2 and washed with a KCN solution to remove impurities such as copper sulfide and copper selenide , and between the electrode film and the p-type semiconductor layer, from the p-type semiconductor layer The thin film metal layer made of a thin noble metal is formed in the compound semiconductor solar cell.
In the present invention, the manufacturing cost of the compound semiconductor solar battery can be reduced by setting the thickness of the thin film metal layer to 2 nm or more, and particularly preferably setting the thickness of the thin film metal layer to 5 to 200 nm.
Further, an electrode film, the electrode film and be Rukoto consisting of molybdenum formed on one surface side of a glass substrate (Mo), the power generation efficiency can be improved than conventional solar cells.
[0006]
In the present invention, a metal film is formed by laminating an indium layer and a copper layer on an electrode film formed on one surface of a substrate, and then the metal film is subjected to sulfidation or selenization to form CuInS 2 Alternatively, a p-type semiconductor layer made of CuInSe 2 is formed, and then the p-type semiconductor layer is washed with a KCN solution and subjected to KCN treatment for removing impurities such as copper sulfide and copper selenide, and then the p-type semiconductor layer is formed. When a compound semiconductor solar cell is manufactured by forming an n-type semiconductor layer on a semiconductor layer, a thin film metal layer made of a noble metal thinner than the p-type semiconductor layer is formed on the surface of the electrode film, and then the thin film In the method of manufacturing a compound semiconductor solar cell, a metal film including an indium layer and a copper layer is formed on the surface of the metal layer.
[0007]
In the present invention, a metal film composed of an indium layer and a copper layer has a Cu / In atomic concentration ratio of 1. (indium (In) and copper (Cu)) forming a p-type semiconductor layer before KCN treatment. By forming so that it becomes 8 or more, the characteristic of the solar cell finally obtained can be improved.
The thin film metal layer of the present invention is preferably a thin film metal layer formed of gold (Au), platinum (Pt) or palladium (Pd).
[0008]
In the present invention, even if the Cu / In atomic concentration ratio of the p-type semiconductor layer before the KCN treatment is set to 1.8 or more, the p-type semiconductor layer can be prevented from peeling from the electrode film in the KCN treatment step. Therefore, the Cu / In atomic concentration ratio of the p-type semiconductor layer can be made higher than that of the conventional compound semiconductor solar cell, and the crystallinity in the p-type semiconductor layer can be improved. As a result, the pn junction compound semiconductor solar according to the present invention The power generation efficiency of the battery can be improved over the power generation efficiency of the conventional compound semiconductor solar battery.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An example of a compound semiconductor solar cell according to the present invention is shown in FIG. 1, FIG. 1 (a) is a front view of a solar cell, and FIG. 1 (b) is a perspective view of the solar cell. In the solar cell shown in FIG. 1, a molybdenum layer 12 is formed as an electrode film on a glass substrate 10 as a substrate. A CuInS 2 p-type semiconductor layer 14 and an n-type semiconductor layer 16 are sequentially stacked on the molybdenum layer 12, and a transparent electrode 18 is formed on the n-type semiconductor layer 16. Further, a comb-shaped electrode 20 is formed on the transparent electrode 18. As shown in FIG. 1 (a), the comb-shaped electrode 20 has electrodes formed in a branched shape (comb shape).
In such a solar cell, a thin film metal layer 22 made of a noble metal is formed between the molybdenum layer 12 and the p-type semiconductor layer 14. The thin metal layer 22 is preferably formed of gold (Au), platinum (Pt), or palladium (Pd), and as shown in FIG. 1B, from any of the layers and films constituting the solar cell. It is also effective with a thickness of about 2 nm. However, practically, it is preferable that the thickness of the thin film metal layer 22 is in the range of 5 to 200 nm, and it is particularly preferable that the thickness of the thin film metal layer 22 is 5 to 20 nm.
Further, the p-type semiconductor layer 14 can have a Cu / In atomic concentration ratio of 1.8 or more in the p-type semiconductor layer before the KCN treatment described later. In the conventional compound semiconductor solar battery in which the p-type semiconductor layer 14 is formed directly on the molybdenum layer 12, the Cu / In atomic concentration ratio of the p-type semiconductor layer before the KCN treatment is higher than 1.6, and the film thickness is increased. When the thickness is 2 μm or more, a phenomenon that the p-type semiconductor layer is peeled off from the molybdenum layer 12 easily occurs in the KCN treatment step. Thus, the p-type semiconductor layer of the compound semiconductor solar cell shown in FIG. 1 having a Cu / In atomic concentration ratio of 1.8 or more can have a thickness of 6 to 8 μm.
Note that the p-type semiconductor layer of the conventional compound semiconductor solar cell having a Cu / In atomic concentration ratio of about 1.6 has a thickness of about 2 μm.
[0010]
The solar cell shown in FIG. 1 can be manufactured by the manufacturing method shown in FIG. First, after forming a molybdenum layer 12 as an electrode film on one surface side of a glass substrate 10 as a substrate by [spattering in FIG. 2A], the thickness is 5 to 100 nm (preferably 5 to 20 nm). A thin film metal layer 22 made of a noble metal is formed on the molybdenum layer 12 [step of FIG. 2 (b)]. The thin metal layer 22 is preferably formed by vapor deposition, sputtering, or electrolytic plating of gold (Au), platinum (Pt), or palladium (Pd).
Further, after the indium layer 13 is formed on the thin metal layer 22 by vapor deposition at room temperature, the copper layer 15 is formed on the indium layer 13 by vapor deposition at room temperature [step of FIG. 2 (c)]. At this time, the thicknesses of the indium layer 13 and the copper layer 15 are controlled so that the Cu / In atomic concentration ratio of the p-type semiconductor layer before the KCN treatment is 1.8 or more.
Next, a CuInS 2 p-type semiconductor layer 14 is formed by subjecting the formed metal film composed of the indium layer 13 and the copper layer 15 to a sulfidation process in which a heat treatment is performed in a hydrogen sulfide atmosphere [see FIG. Process]. This sulfurization treatment can be performed by flowing a gas in which 5 vol% of hydrogen sulfide (H 2 S) is added to an inert gas such as argon gas in a temperature atmosphere of 540 ° C. for about 2 hours.
In FIG. 2, the copper layer 15 is formed after the indium layer 13 is formed. However, the indium layer 13 may be formed after the copper layer 15 is formed.
Furthermore, in FIG. 2, although the indium layer 13 and the copper layer 15 are formed by vapor deposition, they may be formed by sputtering or plating, or vapor deposition, sputtering, and plating may be used in combination.
[0011]
Thereafter, in order to obtain an optimal pn junction solar cell, impurities such as sulfide (Cu x S Y ) generated in the p-type semiconductor layer 14 are removed and the characteristics of the p-type semiconductor layer 14 are optimized and stabilized. In order to obtain the characteristics, a KCN treatment for cleaning the surface of the p-type semiconductor layer 14 with a KCN solution containing 5 to 10% by weight of KCN is performed. This KCN treatment can be performed by immersing the surface of the p-type semiconductor layer 14 in a KCN solution containing about 5 to 10% by weight of KCN at room temperature (room temperature) for about 1 to 5 minutes.
In such a KCN processing step, in the p-type semiconductor layer formed on the thin metal layer 22, even if the Cu / In atom concentration ratio of the p-type semiconductor layer before the KCN processing is set to 1.8 or more, the p-type semiconductor layer is formed from the molybdenum layer 12. The peeling phenomenon of the shaped semiconductor layer does not occur.
On the other hand, in the conventional solar cell shown in FIG. 5 in which the p-type semiconductor layer 104 is formed directly on the molybdenum layer 102, the Cu / In atomic concentration ratio of the p-type semiconductor layer before the KCN treatment exceeds 1.6. When the height is increased, a phenomenon occurs in which the p-type semiconductor layer is separated from the molybdenum layer.
[0012]
On the p-type semiconductor layer 14 thus formed, an n-type semiconductor layer 16 is formed by a chemical solution deposition method (step shown in FIG. 2E). The n-type semiconductor layer 16 is a mixture of ZnSO 4 (0.1 mol / liter), thiourea (0.6 mol / liter) and NH 3 aqueous solution (3 mol / liter) and maintained at 80 ° C. It can be formed by immersing the glass substrate 10 on which the p-type semiconductor layer 14 is formed for about 10 minutes.
This process is performed when the n-type semiconductor layer 14 is ZnS. When the n-type semiconductor layer 14 is CdS, cadmium iodide (0.0015 mol / liter), NH 3 aqueous solution (1.0 mol / liter) and iodine are used. Place the substrate in a solution mixed with ammonium fluoride (0.01 mol / liter), and when heated to about 40 ° C, add thiourea (0.15 mol / liter) and immerse at 80 ° C for 5 minutes. Can be formed.
Further, a transparent electrode 18 made of ZnO doped with Al is formed on the n-type semiconductor layer 16 [step of FIG. 2 (f)].
Then, after forming the comb-shaped electrode 20 with aluminum on the transparent electrode 18, the electrode terminal 23 is formed on the molybdenum layer 12, and the solar cell shown in FIG. 1 can be obtained.
In this electrode terminal 23, the part where the electrode terminal 23 is formed on the molybdenum layer 12 is previously covered with a protective resist or mask, and the p-type semiconductor layer 14, the n-type semiconductor layer 16, and the transparent electrode 18 are formed. Thereafter, it can be formed by removing the protective resist or mask.
[0013]
The IV characteristic of the solar cell shown in FIG. 1 is shown as curve A in FIG. It is the result measured under the conditions of AM1.5 (100 mW / cm 2 ).
The solar cell exhibiting the IV characteristic of the curve A has a light receiving area (effective area) of 0.25 cm 2 , a molybdenum layer 12 having a thickness of about 1 μm formed on the glass substrate 10, and a thickness of 5 nm. Thin film metal layer 22 made of platinum (Pt), p-type semiconductor layer 14 made of CuInS 2 having a thickness of about 2.5 μm and a Cu / In atomic concentration ratio before KCN treatment of 3.0, thickness 80˜ The n-type semiconductor layer 16 made of 120 nm ZnS and the transparent electrode 18 made of Al doped ZnO and having a thickness of about 1 μm.
The same applies to the case where CdS or InS is used as the n-type semiconductor layer 16.
[0014]
On the other hand, the IV characteristic of the conventional solar cell shown in FIG. The solar cell exhibiting the IV characteristic of curve B has a light receiving area (effective area) of 0.25 cm 2 , a molybdenum layer 102 having a thickness of about 1 μm formed on the glass substrate 100, and a thickness of about 2 μm. And a p-type semiconductor layer 104 made of CuInS 2 having a Cu / In atomic concentration ratio of 1.6 before KCN treatment, an n-type semiconductor layer 106 of ZnS having a thickness of 80 to 120 nm, and ZnO doped with Al. The transparent electrode 108 having a thickness of about 1 μm is formed.
As is clear from FIG. 3, the IV characteristic of the solar cell shown in FIG. 1 under the light amount of 100 mW / cm 2 is better than the IV characteristic of the conventional solar cell shown in FIG. The power generation efficiency derived from the IV characteristics shown is 11.0%. On the other hand, the power generation efficiency of the conventional solar cell shown in FIG. 5 was 9.7%.
[0015]
In the above description, the p-type semiconductor layer 14 of CuInS 2 is formed by subjecting the metal layer composed of the indium layer 13 and the copper layer 15 to heat treatment in a hydrogen sulfide atmosphere to form the p-type semiconductor layer 14 of CuInS 2. The present invention can also be applied to the case where the metal layer made of copper and the copper layer 15 is subjected to a selenization treatment in which a heat treatment is performed in a hydrogen selenide atmosphere to form the CuInSe 2 p-type semiconductor layer 14.
Further, a trace amount of gallium (Ga) may be contained in CuInS 2 or CuInSe 2 forming the p-type semiconductor layer 14. Thus, in order to form the p-type semiconductor layer 14 containing a small amount of gallium (Ga), for example, in the method shown in FIG. 2, a gallium layer is formed on the molybdenum layer 12 formed on the substrate surface of the glass substrate 10. Is formed by sputtering or vapor deposition of gallium (Ga) or gallium sulfide (GaS), and then the indium layer 13 and the copper layer 15 are formed, or the indium layer 13 and the copper layer 15 are formed on the molybdenum layer 12. Thereafter, a p-type semiconductor layer 14 made of CuInS 2 containing a trace amount of gallium (Ga) can be formed by forming a gallium layer in the same manner and then performing a sulfidation treatment in which heat treatment is performed in a hydrogen sulfide atmosphere. A similar p-type semiconductor layer 14 is formed by forming an indium layer 13 on the molybdenum layer 12 formed on the substrate surface of the glass substrate 10, and then forming a copper (Cu) -gallium (Ga) alloy layer by sputtering or vapor deposition. Subsequently, it can also be formed by performing a sulfidation treatment in which a heat treatment is performed in a hydrogen sulfide atmosphere.
Alternatively, a small amount of copper (Cu), indium (In), selenium (Se), and a small amount of gallium (Ga) are simultaneously deposited on the molybdenum layer 12 formed on the substrate surface of the glass substrate 10 while heating. The p-type semiconductor layer 14 made of CuInSe 2 containing gallium (Ga) can be formed.
【The invention's effect】
According to the present invention, the Cu / In atomic concentration ratio of the p-type semiconductor layer immediately before the KCN treatment can be made higher than that of a conventional compound semiconductor solar cell with a pn junction, and the crystallinity in the p-type semiconductor layer can be improved. The power generation efficiency of the pn junction compound semiconductor solar cell according to the present invention can be improved more than the power generation efficiency of the conventional pn junction compound semiconductor solar cell. As a result, pn junction compound semiconductor solar cells can be widely used.
[Brief description of the drawings]
FIG. 1 is a front view and a perspective view for explaining an example of a compound semiconductor solar battery according to the present invention.
FIG. 2 is a process diagram for explaining an example of a method for producing the compound semiconductor solar battery shown in FIG.
FIG. 3 is a graph showing IV characteristics of the solar cell shown in FIG. 1;
FIG. 4 is a front view and a longitudinal sectional view for explaining an example of a conventional compound semiconductor solar battery.
5 is a process diagram for explaining an example of a method for producing the conventional compound semiconductor solar battery shown in FIG. 4. FIG.
[Explanation of symbols]
10 Glass substrate 12 Molybdenum layer (electrode film)
13 Indium layer 14 p-type semiconductor layer 15 copper layer 16 n-type semiconductor layer 18 transparent electrode layer 20 comb-shaped electrode 22 thin film metal layer

Claims (8)

基板の一面側に形成された電極膜上に、p形半導体層とn形半導体層とが順次形成されてなる化合物半導体太陽電池において、
該p形半導体層が、CuInS 2 又はCuInSe 2 から成り、KCN溶液によって洗浄されて硫化銅やセレン化銅等の不純物が除去された半導体層であり、
且つ前記電極膜とp形半導体層との間に、前記p形半導体層よりも薄い貴金属から成る薄膜金属層が形成されていることを特徴とする化合物半導体太陽電池。
In a compound semiconductor solar cell in which a p-type semiconductor layer and an n-type semiconductor layer are sequentially formed on an electrode film formed on one surface side of a substrate,
The p-type semiconductor layer is made of CuInS 2 or CuInSe 2 and is a semiconductor layer that has been washed with a KCN solution to remove impurities such as copper sulfide and copper selenide ,
A thin film metal layer made of a noble metal thinner than the p-type semiconductor layer is formed between the electrode film and the p-type semiconductor layer.
薄膜金属層の厚さが、2nm以上である請求項1記載の化合物半導体太陽電池。  The compound semiconductor solar battery according to claim 1, wherein the thickness of the thin metal layer is 2 nm or more. 薄膜金属層の厚さが、5〜200nmである請求項2記載の化合物半導体太陽電池。  The compound semiconductor solar battery according to claim 2, wherein the thin metal layer has a thickness of 5 to 200 nm. 薄膜金属層が、金(Au),白金(Pt)又はパラジウム(Pd)によって形成されている請求項1〜3のいずれか一項記載の化合物半導体太陽電池。  The compound semiconductor solar cell according to any one of claims 1 to 3, wherein the thin-film metal layer is formed of gold (Au), platinum (Pt), or palladium (Pd). 電極膜が、ガラス基板の一面側に形成されたモリブデン(Mo)から成る電極膜である請求項1〜4のいずれか一項記載の化合物半導体太陽電池。Electrode film, a compound semiconductor solar cell according to one of the electrode film Der Ru請 Motomeko 1-4 composed of molybdenum formed on one surface side of a glass substrate (Mo). 基板の一面側に形成された電極膜上にインジウム層と銅層とを積層して金属膜を形成した後、前記金属膜に硫化処理又はセレン化処理を施してCuInS2又はCuInSe2から成るp形半導体層を形成し、
次いで、前記p形半導体層をKCN溶液で洗浄して、硫化銅やセレン化銅等の不純物を除去するKCN処理を施した後、前記p形半導体層上にn型半導体層を形成して化合物半導体太陽電池を製造する際に、
該電極膜の表面に、前記p形半導体層よりも薄い貴金属から成る薄膜金属層を形成した後、
前記薄膜金属層の表面にインジウム層と銅層とから成る金属膜を形成することを特徴とする化合物半導体太陽電池の製造方法。
A metal film is formed by laminating an indium layer and a copper layer on an electrode film formed on one side of the substrate, and then the metal film is subjected to sulfidation or selenization to form p made of CuInS 2 or CuInSe 2. Forming a semiconductor layer,
Next, the p-type semiconductor layer is washed with a KCN solution and subjected to KCN treatment for removing impurities such as copper sulfide and copper selenide, and then an n-type semiconductor layer is formed on the p-type semiconductor layer to form a compound. When manufacturing semiconductor solar cells,
After forming a thin film metal layer made of a noble metal thinner than the p-type semiconductor layer on the surface of the electrode film,
A method for producing a compound semiconductor solar cell, comprising forming a metal film comprising an indium layer and a copper layer on a surface of the thin film metal layer.
薄膜金属層を、金(Au),白金(Pt)又はパラジウム(Pd)によって形成する請求項6記載の化合物半導体太陽電池の製造方法。  The method for producing a compound semiconductor solar cell according to claim 6, wherein the thin film metal layer is formed of gold (Au), platinum (Pt), or palladium (Pd). インジウム層と銅層との金属膜を、前記KCN処理を施す前のp形半導体層を形成するインジウム(In)と銅(Cu)とのCu/In原子濃度比率が1.8以上となるように形成する請求項6又は請求項7記載の化合物半導体太陽電池の製造方法。  The metal film of the indium layer and the copper layer is formed so that the Cu / In atomic concentration ratio of indium (In) and copper (Cu) forming the p-type semiconductor layer before the KCN treatment is 1.8 or more. The manufacturing method of the compound semiconductor solar cell of Claim 6 or Claim 7 formed in this.
JP36768799A 1999-03-29 1999-12-24 Compound semiconductor solar cell and manufacturing method thereof Expired - Fee Related JP3777281B2 (en)

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