JP5762148B2 - CZTS thin film solar cell manufacturing method - Google Patents

CZTS thin film solar cell manufacturing method Download PDF

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JP5762148B2
JP5762148B2 JP2011125620A JP2011125620A JP5762148B2 JP 5762148 B2 JP5762148 B2 JP 5762148B2 JP 2011125620 A JP2011125620 A JP 2011125620A JP 2011125620 A JP2011125620 A JP 2011125620A JP 5762148 B2 JP5762148 B2 JP 5762148B2
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酒井　紀行
紀行 酒井
広紀 杉本
広紀 杉本
誉 廣井
誉 廣井
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本発明は、ＣＺＴＳ系薄膜太陽電池の製造方法に関し、特に、光電変換効率の高いＣＺＴＳ系薄膜太陽電池を製造するための方法に関する。   The present invention relates to a method for producing a CZTS-based thin film solar cell, and more particularly to a method for producing a CZTS-based thin film solar cell having high photoelectric conversion efficiency.

近年、ｐ型光吸収層として、一般にＣＺＴＳと呼ばれるカルコゲナイド系の化合物半導体を用いた薄膜太陽電池が注目されている。このタイプの太陽電池は、材料が比較的安価で、また太陽光に適したバンドギャップエネルギーを有するので、高効率の太陽電池を安価に製造できるとの期待がある。ＣＺＴＳは、Ｃｕ，Ｚｎ，Ｓｎ，Ｓを含む、Ｉ2−ＩＩ−ＩＶ−ＶＩ4族化合物半導体であり、代表的なものとして、Ｃｕ2ＺｎＳｎＳ4等がある。 In recent years, a thin film solar cell using a chalcogenide-based compound semiconductor generally called CZTS has attracted attention as a p-type light absorption layer. Since this type of solar cell is relatively inexpensive and has a band gap energy suitable for sunlight, it is expected that a highly efficient solar cell can be manufactured at low cost. CZTS is an I 2 -II-IV-VI 4 group compound semiconductor containing Cu, Zn, Sn, and S. Typical examples include Cu 2 ZnSnS 4 .

ＣＺＴＳ系薄膜太陽電池は、基板上に金属の裏面電極層を形成し、その上にｐ型ＣＺＴＳ系光吸収層を形成し、さらにｎ型高抵抗バッファ層、ｎ型透明導電膜を順次積層して形成される。金属の裏面電極層材料としては、モリブデン（Ｍｏ）またはチタン（Ｔｉ）、クロム（Ｃｒ）等の高耐蝕性でかつ高融点金属が用いられる。ｐ型ＣＺＴＳ系光吸収層は、例えば、モリブデン（Ｍｏ）の金属裏面電極層を形成した基板上に、Ｃｕ−Ｚｎ−ＳｎあるいはＣｕ−Ｚｎ−Ｓｎ−Ｓのプリカーサ膜をスパッタ法等により形成し、これを硫化水素雰囲気中で硫化することにより、形成される（例えば特許文献１参照）。   In a CZTS thin film solar cell, a metal back electrode layer is formed on a substrate, a p-type CZTS light absorption layer is formed thereon, and an n-type high resistance buffer layer and an n-type transparent conductive film are sequentially laminated. Formed. As the metal back electrode layer material, high corrosion resistance and high melting point metal such as molybdenum (Mo), titanium (Ti), chromium (Cr) or the like is used. The p-type CZTS light absorption layer is formed by, for example, forming a Cu—Zn—Sn or Cu—Zn—Sn—S precursor film on a substrate on which a molybdenum (Mo) metal back electrode layer is formed by sputtering or the like. This is formed by sulfiding in a hydrogen sulfide atmosphere (see, for example, Patent Document 1).

特開２０１０−２１５４９７号公報JP 2010-215497 A

上述したように、ＣＺＴＳ系薄膜太陽電池はその潜在的な可能性は高いが、現在のところ実用に耐え得る高い光電変換効率を有する製品は得られておらず、製造技術の一層の進歩が求められている。本発明は係る点に関してなされたもので、特に、優れた結晶品質を有するｐ型ＣＺＴＳ系光吸収層を形成することによって、高い光電変換効率を有するＣＺＴＳ系薄膜太陽電池の製造を可能とすることを課題とする。   As described above, CZTS-based thin-film solar cells have high potential, but at present, products with high photoelectric conversion efficiency that can withstand practical use have not been obtained, and further progress in manufacturing technology is required. It has been. The present invention has been made with respect to this point, and in particular, by forming a p-type CZTS light absorption layer having excellent crystal quality, it is possible to manufacture a CZTS thin film solar cell having high photoelectric conversion efficiency. Is an issue.

前記課題を解決するために、本発明の第１の態様では、基板上に金属裏面電極層を形成し、前記金属裏面電極層上にｐ型ＣＺＴＳ系光吸収層を形成し、前記ｐ型ＣＺＴＳ系光吸収層上にｎ型高抵抗バッファ層を形成し、前記ｎ型高抵抗バッファ層の形成後の前記基板を酸素含有雰囲気中でアニールし、前記アニール後、前記ｎ型高抵抗バッファ層上にｎ型透明導電膜を形成する、各ステップを備える、ＣＺＴＳ系薄膜太陽電池の製造方法を提供する。   In order to solve the above problems, in the first aspect of the present invention, a metal back electrode layer is formed on a substrate, a p-type CZTS-based light absorption layer is formed on the metal back electrode layer, and the p-type CZTS is formed. Forming an n-type high-resistance buffer layer on the light-absorbing layer, annealing the substrate after the formation of the n-type high-resistance buffer layer in an oxygen-containing atmosphere, and after the annealing, on the n-type high-resistance buffer layer A method for producing a CZTS-based thin film solar cell, comprising the steps of forming an n-type transparent conductive film is provided.

上記第１の態様において、前記酸素含有雰囲気を大気としても良い。   In the first aspect, the oxygen-containing atmosphere may be air.

さらに、前記ｎ型高抵抗バッファ層の形成前の基板に対して、更なるアニールを行っても良い。   Further, the substrate before the formation of the n-type high resistance buffer layer may be further annealed.

さらに、前記アニール又は前記更なるアニールを、雰囲気温度１３０℃以上でかつ３０分以上行うようにしても良い。   Further, the annealing or the further annealing may be performed at an ambient temperature of 130 ° C. or higher and for 30 minutes or longer.

本発明の製造方法では、金属裏面電極層とｐ型ＣＺＴＳ系光吸収層及びｎ型高抵抗バッファ層が形成された基板を、酸素含有雰囲気中でアニールする。このアニールによって、雰囲気中の酸素が極薄い薄膜であるｎ型高抵抗バッファ層を透過してｐ型ＣＺＴＳ系光吸収層中に導入され、該層中に存在するＶＩ族元素起因の結晶欠陥に捕獲される。その結果、結晶欠陥が不活性化され、ｐ型ＣＺＴＳ系光吸収層の結晶品質が向上するので、製造後の太陽電池の光電変換効率が向上する。   In the manufacturing method of the present invention, the substrate on which the metal back electrode layer, the p-type CZTS light absorption layer, and the n-type high resistance buffer layer are formed is annealed in an oxygen-containing atmosphere. By this annealing, oxygen in the atmosphere passes through the n-type high-resistance buffer layer, which is a very thin thin film, and is introduced into the p-type CZTS-based light absorption layer, resulting in crystal defects caused by group VI elements present in the layer. Be captured. As a result, crystal defects are inactivated and the crystal quality of the p-type CZTS light absorption layer is improved, so that the photoelectric conversion efficiency of the solar cell after manufacture is improved.

本発明の一実施形態に係る製造方法によって形成されたＣＺＴＳ系薄膜太陽電池の断面構造を示す概略図。Schematic which shows the cross-section of the CZTS type thin film solar cell formed by the manufacturing method concerning one embodiment of the present invention. ＣＺＴＳ系薄膜太陽電池のｎ型高抵抗バッファ層及びｎ型透明導電膜の一般的な製造工程を説明するための図。The figure for demonstrating the general manufacturing process of the n-type high resistance buffer layer and n-type transparent conductive film of a CZTS type thin film solar cell. 本発明の一実施形態に係るｎ型高抵抗バッファ層及びｎ型透明導電膜の製造工程を説明するための図。The figure for demonstrating the manufacturing process of the n-type high resistance buffer layer and n-type transparent conductive film which concerns on one Embodiment of this invention. 本発明の他の実施形態に係るｎ型高抵抗バッファ層及びｎ型透明導電膜の製造工程を説明するための図。The figure for demonstrating the manufacturing process of the n-type high resistance buffer layer and n-type transparent conductive film which concerns on other embodiment of this invention.

以下に、図面を参照して本発明の種々の実施形態を説明するが、これらの実施形態は単に一例であって本発明を限定するものでは無い。また、全図面を通して、同じ符号は同一または類似の構成要素を示すので、重複した説明は行わない。更に、各図は本発明の説明のみを目的としており、従って各層の図面上の大きさが実際の縮尺に対応するものではない。   Various embodiments of the present invention will be described below with reference to the drawings, but these embodiments are merely examples and do not limit the present invention. Moreover, since the same code | symbol shows the same or similar component through all the drawings, the overlapping description is not performed. Further, each drawing is for the purpose of illustrating the present invention only, and therefore the size of each layer on the drawing does not correspond to the actual scale.

図１は、本発明の方法で製造したＣＺＴＳ系薄膜太陽電池の構造を示す概略断面図である。図１において、１はガラス基板、２はＭｏ等の金属を材料とする金属裏面電極層、３はｐ型ＣＺＴＳ系光吸収層、４はｎ型高抵抗バッファ層、５はｎ型透明導電膜を示す。ｐ型ＣＺＴＳ系光吸収層３は、Ｃｕ、Ｚｎ、Ｓｎを含む金属プリカーサ膜を金属裏面電極層２上に形成した後、これを５００℃〜６５０℃の硫化水素および／またはセレン化水素雰囲気中で硫化および／またはセレン化して形成される。   FIG. 1 is a schematic cross-sectional view showing the structure of a CZTS-based thin film solar cell manufactured by the method of the present invention. In FIG. 1, 1 is a glass substrate, 2 is a metal back electrode layer made of a metal such as Mo, 3 is a p-type CZTS light absorption layer, 4 is an n-type high resistance buffer layer, and 5 is an n-type transparent conductive film. Indicates. The p-type CZTS light absorption layer 3 is formed in a hydrogen sulfide and / or hydrogen selenide atmosphere at 500 ° C. to 650 ° C. after a metal precursor film containing Cu, Zn, and Sn is formed on the metal back electrode layer 2. It is formed by sulfurization and / or selenization.

少なくともＣｕ、Ｚｎ、Ｓｎを含む金属プリカーサ膜を硫化水素雰囲気中で硫化することによって、Ｃｕ2ＺｎＳｎＳ4からなるｐ型ＣＺＴＳ系光吸収層３が形成される。一方、この金属プリカーサ膜をセレン化水素雰囲気中でセレン化することによって、Ｃｕ2ＺｎＳｎＳｅ4からなるｐ型ＣＺＴＳ系光吸収層３が形成される。或いは、同じ金属プリカーサ膜をセレン化しかつ硫化することによって、Ｃｕ2ＺｎＳｎ（Ｓ，Ｓｅ）4からなるｐ型ＣＺＴＳ系光吸収層３が形成される。 By sulfiding a metal precursor film containing at least Cu, Zn, and Sn in a hydrogen sulfide atmosphere, the p-type CZTS light absorption layer 3 made of Cu 2 ZnSnS 4 is formed. On the other hand, the metal precursor film is selenized in a hydrogen selenide atmosphere to form a p-type CZTS light absorption layer 3 made of Cu 2 ZnSnSe 4 . Alternatively, the same metal precursor film is selenized and sulfided to form the p-type CZTS light absorption layer 3 made of Cu 2 ZnSn (S, Se) 4 .

図２の（ａ）及び（ｂ）は、ｐ型ＣＺＴＳ系光吸収層３上に、ｎ型高抵抗バッファ層４及びｎ型透明導電膜５を形成してＣＺＴＳ系薄膜太陽電池を完成する、一般的な工程を示す。図２（ａ）に示すように、金属裏面電極層２上にｐ型ＣＺＴＳ系光吸収層３が形成されると、その上に、ｎ型高抵抗バッファ層４を形成する。ｎ型高抵抗バッファ層４は、例えば、Ｃｄ、Ｚｎ、Ｉｎを含む化合物の薄膜（膜厚３ｎｍ〜５０ｎｍ程度）であり、代表的にはＣｄＳ、ＺｎＯ、ＺｎＳ、Ｚｎ（ＯＨ）2、Ｉｎ2Ｏ3、Ｉｎ2Ｓ3、あるいはこれらの混晶であるＺｎ（Ｏ、Ｓ、ＯＨ）で形成される。この層は、一般的には溶液成長法（ＣＢＤ法）により製膜されるが、ドライプロセスとして有機金属気相成長法（ＭＯＣＶＤ法）、原子層堆積法（ＡＬＤ法）も適用可能である。なお、ＣＢＤ法とは、プリカーサとなる化学種を含む溶液に基材を浸し、溶液と基材表面との間で不均一反応を進行させることによって薄膜を基材上に析出させるものである。 2 (a) and 2 (b), an n-type high resistance buffer layer 4 and an n-type transparent conductive film 5 are formed on the p-type CZTS light absorption layer 3 to complete a CZTS-based thin film solar cell. A general process is shown. As shown in FIG. 2A, when the p-type CZTS light absorption layer 3 is formed on the metal back electrode layer 2, the n-type high resistance buffer layer 4 is formed thereon. The n-type high resistance buffer layer 4 is, for example, a thin film (thickness of about 3 nm to 50 nm) of a compound containing Cd, Zn, and In, typically CdS, ZnO, ZnS, Zn (OH) 2 , In 2. It is formed of O 3 , In 2 S 3 , or Zn (O, S, OH) which is a mixed crystal thereof. This layer is generally formed by a solution growth method (CBD method), but a metal organic chemical vapor deposition method (MOCVD method) or an atomic layer deposition method (ALD method) can also be applied as a dry process. In the CBD method, a thin film is deposited on a base material by immersing the base material in a solution containing a chemical species that serves as a precursor and causing a heterogeneous reaction between the solution and the base material surface.

ｎ型高抵抗バッファ層４の形成後、図２（ｂ）に示すように、ｎ型透明導電膜５が形成されてＣＺＴＳ系薄膜太陽電池が構成される。ｎ型透明導電膜５としては、ｎ型の導電性を有し、禁制帯幅が広く透明でかつ低抵抗の材料によって、膜厚０．０５から２．５μｍ程度に形成される。代表的には酸化亜鉛系薄膜（ＺｎＯ）あるいはＩＴＯ薄膜がある。ＺｎＯ膜の場合、ＩＩＩ族元素（例えばＡｌ、Ｇａ、Ｂ）をドーパントとして添加することで低抵抗膜とすることができる。ｎ型透明導電膜５は、ＭＯＣＶＤ法以外に、スパッタ法（ＤＣ、ＲＦ）等で形成することもできる。   After the formation of the n-type high resistance buffer layer 4, as shown in FIG. 2B, an n-type transparent conductive film 5 is formed to constitute a CZTS-based thin film solar cell. The n-type transparent conductive film 5 is formed with a film thickness of about 0.05 to 2.5 μm by a transparent material with n-type conductivity, wide forbidden band width, and low resistance. Typically, there is a zinc oxide thin film (ZnO) or an ITO thin film. In the case of a ZnO film, a low resistance film can be formed by adding a group III element (eg, Al, Ga, B) as a dopant. The n-type transparent conductive film 5 can also be formed by sputtering (DC, RF) or the like other than MOCVD.

以上の工程を経て完成されたＣＺＴＳ系薄膜太陽電池では、一般に、あまり高い光電変換効率を得ることが出来ない。本発明者等は、その原因がｐ型ＣＺＴＳ系光吸収層３の結晶品質にあるのではないかと考えた。ｐ型ＣＺＴＳ系光吸収層３には、一般に、ＶＩ族元素（Ｓ、Ｓｅ等）に起因する多くの結晶欠陥が存在し、その結晶品質を低下させている。そこで、ｐ型ＣＺＴＳ系光吸収層３中に形成された、ＶＩ族元素起因の結晶欠陥を効果的に不活性化することが出来れば、その結晶品質を改善し、太陽電池の光電変換効率を向上させることが可能となる。本発明は、このような知見に基づいて、以下のような方法を提案する。   In general, a CZTS-based thin film solar cell completed through the above steps cannot have a very high photoelectric conversion efficiency. The present inventors considered that the cause may be the crystal quality of the p-type CZTS-based light absorption layer 3. The p-type CZTS-based light absorption layer 3 generally has many crystal defects due to group VI elements (S, Se, etc.), and its crystal quality is degraded. Therefore, if the crystal defects due to the group VI element formed in the p-type CZTS light absorption layer 3 can be effectively inactivated, the crystal quality is improved, and the photoelectric conversion efficiency of the solar cell is improved. It becomes possible to improve. The present invention proposes the following method based on such knowledge.

図３の（ａ）〜（ｃ）は、本発明の一実施形態に係るＣＺＴＳ系薄膜太陽電池の製造方法における、ｐ型光吸収層３上にｎ型高抵抗バッファ層４を形成した後の工程を示す。即ち、図３（ａ）に示すように、金属裏面電極２上に形成されたｐ型ＣＺＴＳ系光吸収層３に、例えば、図２を参照して説明した方法によりｎ型高抵抗バッファ層４を形成した後、図３（ｂ）に示すように、基板を、酸素含有雰囲気中、例えば大気中でアニールを行うことを特徴とする。ｎ型高抵抗バッファ層４は、３ｎｍ〜５０ｎｍ程度の極薄い薄膜であるため、このアニールによって、雰囲気中に含まれる酸素ガスが比較的容易にこれを透過し、ｐ型ＣＺＴＳ系光吸収層３中に達する。   FIGS. 3A to 3C are views after the n-type high-resistance buffer layer 4 is formed on the p-type light absorption layer 3 in the method for manufacturing a CZTS-based thin film solar cell according to an embodiment of the present invention. A process is shown. That is, as shown in FIG. 3A, the n-type high resistance buffer layer 4 is applied to the p-type CZTS light absorption layer 3 formed on the metal back electrode 2 by, for example, the method described with reference to FIG. After forming, as shown in FIG. 3B, the substrate is annealed in an oxygen-containing atmosphere, for example, in the air. Since the n-type high-resistance buffer layer 4 is an extremely thin thin film of about 3 nm to 50 nm, the oxygen gas contained in the atmosphere is relatively easily transmitted by this annealing, and the p-type CZTS light absorption layer 3 Reach inside.

このようにして、ｐ型ＣＺＴＳ系光吸収層３中に導入された酸素は、ＶＩ族元素に起因する結晶欠陥に捕獲されこれを不活性化する。その結果、ｐ型ＣＺＴＳ系光吸収層３の結晶品質が改善される。その後、図３（ｃ）に示すように、ｎ型高抵抗バッファ層４上に、例えば、図２を参照して説明した方法により、ｎ型透明導電膜５を形成する。   In this way, oxygen introduced into the p-type CZTS-based light absorption layer 3 is captured by the crystal defects caused by the group VI element and inactivated. As a result, the crystal quality of the p-type CZTS light absorption layer 3 is improved. Thereafter, as shown in FIG. 3C, the n-type transparent conductive film 5 is formed on the n-type high resistance buffer layer 4 by, for example, the method described with reference to FIG.

以下の表１に、上記第１の実施形態によって製造されたＣＺＴＳ系薄膜太陽電池サンプルの光電変換効率を示す。実験１サンプルはアニール時間を３０分とし、実験２サンプルはアニール時間を１２０分としている。何れのサンプルも、アニール温度は１３０℃であり、アニール雰囲気は大気とした。比較のために、従来例１サンプルとしてアニールを行わないＣＺＴＳ系薄膜太陽電池の光電変換効率を示してある。なお、従来例１サンプル、実験１サンプル及び実験２サンプルとも、アニール工程以外は同じ製造工程を経て形成されており、ｐ型ＣＺＴＳ系光吸収層３はＣｕ2ＺｎＳｎＳ4で形成され、ｎ型高抵抗バッファ層４はＣｄＳで形成されている。その他の製造条件については、表３を参照して後述する。

Figure 0005762148
Table 1 below shows the photoelectric conversion efficiency of the CZTS-based thin film solar cell sample manufactured according to the first embodiment. The sample for Experiment 1 has an annealing time of 30 minutes, and the sample for Experiment 2 has an annealing time of 120 minutes. In all the samples, the annealing temperature was 130 ° C., and the annealing atmosphere was air. For comparison, the photoelectric conversion efficiency of a CZTS-based thin film solar cell that is not annealed is shown as a conventional example 1 sample. The conventional example 1 sample, the experiment 1 sample, and the experiment 2 sample are formed through the same manufacturing process except the annealing process, and the p-type CZTS-based light absorption layer 3 is formed of Cu 2 ZnSnS 4 and has an n-type high height. The resistance buffer layer 4 is made of CdS. Other manufacturing conditions will be described later with reference to Table 3.
Figure 0005762148

表１より明らかなように、本発明に従ってアニール後のｎ型高抵抗バッファ層４上にｎ型透明導電膜５を形成した実験１サンプル、実験２サンプルでは、アニールを行わない従来例１サンプルに比べて光電変換効率が２０％程度、向上している。また、実験１サンプルと実験２サンプルとの比較から、アニール時間は３０分以上が望ましいと推定される。この実験結果から、本発明に係るｎ型高抵抗バッファ層４の形成後のアニールが、光電変換効率の向上に効果のあることが実証された。   As is apparent from Table 1, in the experiment 1 sample and the experiment 2 sample in which the n-type transparent conductive film 5 is formed on the n-type high resistance buffer layer 4 after annealing according to the present invention, the conventional example 1 sample in which annealing is not performed is used. In comparison, the photoelectric conversion efficiency is improved by about 20%. Further, from the comparison between the experiment 1 sample and the experiment 2 sample, it is estimated that the annealing time is preferably 30 minutes or more. From this experimental result, it was proved that annealing after the formation of the n-type high resistance buffer layer 4 according to the present invention is effective in improving the photoelectric conversion efficiency.

図４の（ａ）〜（ｄ）は、本発明の他の実施形態に係る製造工程の一部を示し、この実施形態では、図４（ａ）に示すように、ｐ型ＣＺＴＳ系光吸収層３を形成した後であってｎ型高抵抗バッファ層４を形成する前に、基板に対し、酸素含有雰囲気中での第１回目のアニールを行う。その後、図４（ｂ）に示すように、アニール後のｐ型ＣＺＴＳ系光吸収層３上に、例えば図２を参照して説明した方法により、ｎ型高抵抗バッファ層４を形成する。   FIGS. 4A to 4D show a part of a manufacturing process according to another embodiment of the present invention. In this embodiment, as shown in FIG. 4A, p-type CZTS light absorption is performed. After the layer 3 is formed and before the n-type high resistance buffer layer 4 is formed, the substrate is first annealed in an oxygen-containing atmosphere. Thereafter, as shown in FIG. 4B, the n-type high resistance buffer layer 4 is formed on the annealed p-type CZTS light absorption layer 3 by the method described with reference to FIG. 2, for example.

本実施形態では、ｎ型高抵抗バッファ層４の形成後、図４（ｃ）に示すように第２回目のアニールを行い、その後、図４（ｄ）に示すようにｎ型高抵抗バッファ層５を形成する。第２回目のアニールも第１回目のアニールと同様に、酸素含有雰囲気中、例えば大気中で行う。本実施形態では、このように、ｎ型高抵抗バッファ層４の製膜の前後に２回のアニールを行うことにより、ｐ型ＣＺＴＳ系光吸収層３中にさらに効果的に酸素を導入することを特徴とする。   In the present embodiment, after the n-type high resistance buffer layer 4 is formed, the second annealing is performed as shown in FIG. 4C, and then the n-type high resistance buffer layer is shown in FIG. 4D. 5 is formed. Similar to the first annealing, the second annealing is performed in an oxygen-containing atmosphere, for example, in the air. In the present embodiment, oxygen is more effectively introduced into the p-type CZTS light absorption layer 3 by performing annealing twice before and after the formation of the n-type high resistance buffer layer 4 in this manner. It is characterized by.

表２に、実験３サンプルの光電変換効率の測定結果を示す。実験３サンプルは、第２の実施形態に従って、ｎ型高抵抗バッファ層４の形成前と形成後の２回、アニールを行ったものであり、その他の製造条件については、従来例１サンプル、実験１サンプル及び実験２サンプルと同じとしている。第１回目（ｎ型高抵抗バッファ層４の形成前）と第２回目（ｎ型高抵抗バッファ層４の形成後）のアニールは、温度１３０℃の大気中で３０分間に亘って行われた。

Figure 0005762148
Table 2 shows the measurement results of the photoelectric conversion efficiency of the experiment 3 samples. The experiment 3 sample was annealed twice before and after the formation of the n-type high-resistance buffer layer 4 in accordance with the second embodiment. It is the same as 1 sample and 2 experiments. The first annealing (before the formation of the n-type high resistance buffer layer 4) and the second annealing (after the formation of the n-type high resistance buffer layer 4) were performed in an atmosphere at a temperature of 130 ° C. for 30 minutes. .
Figure 0005762148

表２から明らかなように、ｎ型高抵抗バッファ層４を形成する前後で２回のアニールを実施した実験３サンプルでは、従来例１サンプル、実験１サンプル及び実験２サンプルに比べてさらに光電変換効率が改善されている。従って、ｎ型高抵抗バッファ層４を形成する前後の２回のアニールが、光電変換効率の向上に効果のあることが実証された。   As is apparent from Table 2, in the experiment 3 sample in which the annealing was performed twice before and after forming the n-type high resistance buffer layer 4, the photoelectric conversion was further performed as compared with the conventional sample 1, the experiment 1 sample, and the experiment 2 sample. Efficiency has been improved. Therefore, it was proved that annealing twice before and after forming the n-type high resistance buffer layer 4 is effective in improving the photoelectric conversion efficiency.

以下の表３に、従来例１サンプル、実験１サンプル、実験２サンプル及び実験３サンプルの製造方法を要約する。

Figure 0005762148
Table 3 below summarizes the manufacturing method of the conventional example 1 sample, the experiment 1 sample, the experiment 2 sample, and the experiment 3 sample.
Figure 0005762148

表４に、図３に示す本発明の実施形態、即ち、ｎ型高抵抗バッファ層４の形成後にのみ１回のアニールを行う製造方法に従って製造された他のサンプル、即ち、従来例２サンプルと実験例４サンプルについて、その光電変換効率の測定結果を示す。従来例２サンプルと実験４サンプルは、ｎ型高抵抗バッファ層４の形成後のアニール工程を除いて同一の製造条件で形成されており、従来例１サンプル、実験１〜実験３サンプルとは異なってｎ型高抵抗バッファ層４の組成をＺｎ（Ｓ，Ｏ，ＯＨ）としている。なお、従来例２サンプル及び実験４サンプルは、ｎ型高抵抗バッファ層４をＺｎ（Ｓ，Ｏ，ＯＨ）で形成したこと以外、表３に記載する製造条件に基づいて製造されたものであるが、ＣＺＴＳ系化合物Ｃｕ2ＺｎＳｎＳ4におけるＺｎとＳｎの組成比が、従来例１サンプル、実験１サンプル、実験２サンプル及び実験３サンプルの場合とは異なる。

Figure 0005762148
Table 4 shows another embodiment of the present invention shown in FIG. 3, that is, another sample manufactured according to the manufacturing method in which annealing is performed only after the formation of the n-type high-resistance buffer layer 4, that is, the conventional example 2 sample. The measurement result of the photoelectric conversion efficiency about the sample of Experimental Example 4 is shown. The conventional example 2 sample and the experimental 4 sample are formed under the same manufacturing conditions except for the annealing step after the formation of the n-type high resistance buffer layer 4 and are different from the conventional example 1 sample and the experimental 1 to experimental 3 sample. Thus, the composition of the n-type high resistance buffer layer 4 is Zn (S, O, OH). In addition, the conventional example 2 sample and the experiment 4 sample were manufactured based on the manufacturing conditions described in Table 3 except that the n-type high resistance buffer layer 4 was formed of Zn (S, O, OH). However, the composition ratio of Zn and Sn in the CZTS compound Cu 2 ZnSnS 4 is different from those of the conventional example 1 sample, the experiment 1 sample, the experiment 2 sample, and the experiment 3 sample.
Figure 0005762148

表４から明らかなように、ｎ型高抵抗バッファ層４をＺｎ（Ｓ，Ｏ，ＯＨ）で構成した場合であっても、従来例２サンプルに対して実験４サンプルの光電変換効率がかなり向上している。このことからも、ｎ型高抵抗バッファ層４の形成後のアニールに、光電変換効率を改善する効果を認めることが出来る。   As is apparent from Table 4, even when the n-type high-resistance buffer layer 4 is made of Zn (S, O, OH), the photoelectric conversion efficiency of the experimental 4 samples is significantly improved over the conventional 2 samples. doing. Also from this, the effect of improving the photoelectric conversion efficiency can be recognized in the annealing after the formation of the n-type high resistance buffer layer 4.

実験１〜実験４サンプルは、組成がＣｕ2ＺｎＳｎＳ4のｐ型ＣＺＴＳ系光吸収層３を有するが、本発明はこの事例に限定されるものではなく、Ｃｕ2ＺｎＳｎＳｅ4又はＣｕ2ＺｎＳｎ（Ｓ，Ｓｅ）4であっても、同様の効果が得られることは明らかである。さらに、ｐ型ＣＺＴＳ系光吸収層３を形成するための金属プリカーサ膜も、表３に示すＺｎＳの代わりにＺｎを用いても良く、Ｓｎの代わりにＳｎＳであっても良い。さらに、Ｚｎ、Ｓｎ、Ｃｕを順次製膜する以外に、ＺｎとＳｎを予め合金化した蒸着源を用いても良い。製膜方法として、ＥＢ蒸着以外にスパッタ法を用いても良い。 The samples of Experiment 1 to Experiment 4 have the p-type CZTS light absorption layer 3 having a composition of Cu 2 ZnSnS 4 , but the present invention is not limited to this example, and Cu 2 ZnSnSe 4 or Cu 2 ZnSn (S , Se) 4 , it is clear that the same effect can be obtained. Furthermore, the metal precursor film for forming the p-type CZTS light absorption layer 3 may also use Zn instead of ZnS shown in Table 3, or SnS instead of Sn. Further, in addition to the sequential deposition of Zn, Sn, and Cu, an evaporation source in which Zn and Sn are alloyed in advance may be used. As a film forming method, a sputtering method may be used in addition to EB vapor deposition.

さらに、基板１、金属裏面電極層２、ｎ型高抵抗バッファ層４及びｎ型透明導電膜５も、表３に記載する事例に限定されない。例えば、基板１として、青板ガラス、低アルカリガラス等のガラス基板の他に、ステンレス板等の金属基板、ポリイミド樹脂基板等を用いることができる。金属裏面電極層２の形成方法としては、表２に記載するＤＣスパッタ法以外に、電子ビーム蒸着法、電子層堆積法（ＡＬＤ法）等がある。金属裏面電極層２の材料としては、高耐蝕性でかつ高融点金属、例えばクロム（Ｃｒ）、チタン（Ｔｉ）等を用いても良い。   Further, the substrate 1, the metal back electrode layer 2, the n-type high resistance buffer layer 4 and the n-type transparent conductive film 5 are not limited to the examples described in Table 3. For example, as the substrate 1, in addition to a glass substrate such as blue plate glass or low alkali glass, a metal substrate such as a stainless plate, a polyimide resin substrate, or the like can be used. As a method for forming the metal back electrode layer 2, there are an electron beam evaporation method, an electron layer deposition method (ALD method) and the like in addition to the DC sputtering method described in Table 2. As a material for the metal back electrode layer 2, a high corrosion resistance and high melting point metal such as chromium (Cr), titanium (Ti), or the like may be used.

ｎ型透明導電膜５としては、ｎ型の導電性を有し、禁制帯幅が広く透明でかつ低抵抗の材料を用いて、膜厚０．０５から２．５μｍ程度に形成される。代表的には酸化亜鉛系薄膜（ＺｎＯ）あるいはＩＴＯ薄膜がある。ＺｎＯ膜の場合、ＩＩＩ族元素（例えばＡｌ、Ｇａ、Ｂ）をドーパントとして添加することで低抵抗膜とする。ｎ型透明導電膜５は、ＭＯＣＶＤ法以外に、スパッタ法（ＤＣ、ＲＦ）等で形成することもできる。   The n-type transparent conductive film 5 is formed to have a film thickness of about 0.05 to 2.5 μm by using a material having n-type conductivity, wide forbidden band width, transparent and low resistance. Typically, there is a zinc oxide thin film (ZnO) or an ITO thin film. In the case of a ZnO film, a low resistance film is formed by adding a group III element (for example, Al, Ga, B) as a dopant. The n-type transparent conductive film 5 can also be formed by sputtering (DC, RF) or the like other than MOCVD.

１ ガラス基板
２ 金属裏面電極層
３ ｐ型ＣＺＴＳ系光吸収層
４ ｎ型高抵抗バッファ層
５ ｎ型透明導電膜 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Metal back electrode layer 3 p-type CZTS type light absorption layer 4 n-type high resistance buffer layer 5 n-type transparent conductive film

Claims (3)

基板上に金属裏面電極層を形成し、
前記金属裏面電極層上に、ｐ型ＣＺＴＳ系光吸収層を形成し、
前記ｐ型ＣＺＴＳ系光吸収層上にｎ型高抵抗バッファ層を形成し、
前記ｎ型高抵抗バッファ層の形成後の前記基板を大気中において雰囲気温度１３０℃以上で且つ３０分以上に亘ってアニールし、
前記アニール後、前記ｎ型高抵抗バッファ層上にｎ型透明導電膜を形成する、各ステップを備え、前記ｎ型高抵抗バッファ層はＺｎ（Ｓ，Ｏ，ＯＨ）で形成されている、ＣＺＴＳ系薄膜太陽電池の製造方法。 Forming a metal back electrode layer on the substrate;
Forming a p-type CZTS-based light absorption layer on the metal back electrode layer;
Forming an n-type high-resistance buffer layer on the p-type CZTS-based light absorption layer;
Annealing the substrate after the formation of the n-type high-resistance buffer layer in the atmosphere at an ambient temperature of 130 ° C. or more and for 30 minutes or more;
After the annealing, to form an n-type transparent conductive film on the n-type high-resistance buffer layer, comprising the steps, the n-type high-resistance buffer layer that is formed by Zn (S, O, OH) , CZTS Of manufacturing thin-film solar cell. 請求項１に記載の方法において、前記ｐ型ＣＺＴＳ系光吸収層を形成する工程後に、前記ｐ型ＣＺＴＳ系光吸収層が形成された基板に対して、大気中において雰囲気温度１３０℃以上でかつ３０分以上に亘ってアニールを行ってから、前記ｎ型高抵抗バッファ層を形成する工程を行うことを特徴とする、ＣＺＴＳ系薄膜太陽電池の製造方法。   2. The method according to claim 1, wherein after the step of forming the p-type CZTS light absorption layer, an atmospheric temperature of 130 ° C. or higher in the atmosphere with respect to the substrate on which the p-type CZTS light absorption layer is formed, and A method for producing a CZTS-based thin film solar cell, comprising performing the step of forming the n-type high-resistance buffer layer after annealing for 30 minutes or more. 請求項１または２に記載の方法において、前記ｎ型高抵抗バッファ層の膜厚は３ｎｍ−５０ｎｍである、ＣＺＴＳ系薄膜太陽電池の製造方法。3. The method according to claim 1, wherein the n-type high resistance buffer layer has a thickness of 3 nm to 50 nm.
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