JP2004127579A - Manufacturing method of metal-metal oxide composite electrode, photoelectric transducing element and photoelectric cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a metal-metal oxide composite electrode suitable for a photoelectric transducing element; and to provide a die-sensitized photoelectric transducing element having an oxide layer with high mechanical strength, and a large photocurrent. <P>SOLUTION: This manufacturing method of a metal-metal oxide composite electrode is characterized by that other metals are substantially removed from an alloy containing two or more kinds of metals by leaving one kind of metal, and the one kind of metal that has been left is oxidized. <P>COPYRIGHT: (C)2004,JPO

Description

【００３２】
（ｂ）　メチン色素
好ましいメチン色素は、シアニン色素、メロシアニン色素、スクワリリウム色素等のポリメチン色素である。好ましいポリメチン色素の例としては、特開平１１−３５８３６号公報、同１１−１５８３９５号公報、同１１−１６３３７８号公報、同１１−２１４７３０号公報、同１１−２１４７３１号公報、欧州特許第８９２４１１号明細書及び同第９１１８４１号明細書に記載の色素が挙げられる。これらのポリメチン色素の合成法については、エフ・エム・ハーマー（Ｆ．　Ｍ．　Ｈａｍｅｒ）著「ヘテロサイクリック・コンパウンズ−シアニンダイズ・アンド・リレィティド・コンパウンズ（Ｈｅｔｅｒｏｃｙｃｌｉｃ　Ｃｏｍｐｏｕｎｄｓ　−　Ｃｙａｎｉｎｅ　Ｄｙｅｓ　ａｎｄ　Ｒｅｌａｔｅｄ　Ｃｏｍｐｏｕｎｄｓ）」，　ジョン・ウィリー・アンド・サンズ（Ｊｏｈｎ　Ｗｉｌｅｙ　＆　Ｓｏｎｓ）社，　ニューヨーク，　ロンドン，　１９６４年、デー・エム・スターマー（Ｄ．　Ｍ．　Ｓｔｕｒｍｅｒ）著「ヘテロサイクリック・コンパウンズ−スペシャル・トピックス・イン・ヘテロサイクリック・ケミストリー（Ｈｅｔｅｒｏｃｙｃｌｉｃ　Ｃｏｍｐｏｕｎｄｓ　−　Ｓｐｅｃｉａｌｔｏｐｉｃｓ　ｉｎ　Ｈｅｔｅｒｏｃｙｃｌｉｃ　Ｃｈｅｍｉｓｔｒｙ）」，　ジョン・ウィリー・アンド・サンズ（Ｊｏｈｎ　Ｗｉｌｅｙ　＆　Ｓｏｎｓ）社，　ニューヨーク，ロンドン，　１９７７年，　第１８章，　第１４節，　ｐ．８２〜５１５、「ロッズ・ケミストリー・オブ・カーボン・コンパウンズ（Ｒｏｄｄ’ｓ　Ｃｈｅｍｉｓｔｒｙ　ｏｆ　Ｃａｒｂｏｎ　Ｃｏｍｐｏｕｎｄｓ）」，　第２版，　エルセビア・サイエンス・パブリック・カンパニー・インク（Ｅｌｓｅｖｉｅｒ　Ｓｃｉｅｎｃｅ　Ｐｕｂｌｉｓｈｉｎｇ　Ｃｏｍｐａｎｙ　Ｉｎｃ．）社，　ニューヨーク，　１９７７年，　第ＩＶ巻，　ｐａｒｔ　Ｂ，　第１５章，　ｐ．３６９−４２２、英国特許第１，０７７，６１１号明細書、「Ｕｋｒａｉｎｓｋｉｉ　Ｋｈｉｍｉｃｈｅｓｋｉｉ　Ｚｈｕｒｎａｌ」，　第４０巻，　第３号，　ｐ．２５３−２５８、「ダイズ・アンド・ピグメンツ（Ｄｙｅｓ　ａｎｄ　Ｐｉｇｍｅｎｔｓ）」，　第２１巻，　ｐ．２２７−２３４、これらの引用文献等に記載されている。
【００３３】
（４）　金属酸化物への色素の吸着
金属酸化物に色素を吸着させる際には、色素の溶液中によく乾燥した複合電極を浸漬する方法、又は色素の溶液を複合電極に塗布する方法を用いることができる。前者の方法の場合、浸漬法、ディップ法、ローラ法、エアーナイフ法等が利用可能である。浸漬法を用いる場合、色素の吸着は室温で行ってもよいし、特開平７−２４９７９０号公報に記載されているように加熱還流して行ってもよい。後者の方法の場合、ワイヤーバー法、スライドホッパー法、エクストルージョン法、カーテン法、スピン法、スプレー法等が利用できる。また、インクジェット法等によって色素を画像状に塗布し、この画像そのものを光電変換素子とすることもできる。複合電極に半導体微粒子層を形成する場合は、形成した半導体微粒子層に上記の方法で色素を吸着させることができる。
【００３４】
色素の溶液（吸着液）に用いる溶媒は、好ましくはアルコール類（メタノール、エタノール、ｔ−ブチルアルコール、ベンジルアルコール等）、ニトリル類（アセトニトリル、プロピオニトリル、３−メトキシプロピオニトリル等）、ニトロメタン、ハロゲン化炭化水素（ジクロロメタン、ジクロロエタン、クロロホルム、クロロベンゼン等）、エーテル類（ジエチルエーテル、テトラヒドロフラン等）、ジメチルスルホキシド、アミド類（Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセタミド等）、Ｎ−メチルピロリドン、１，３−ジメチルイミダゾリジノン、３−メチルオキサゾリジノン、エステル類（酢酸エチル、酢酸ブチル等）、炭酸エステル類（炭酸ジエチル、炭酸エチレン、炭酸プロピレン等）、ケトン類（アセトン、２−ブタノン、シクロヘキサノン等）、炭化水素（へキサン、石油エーテル、ベンゼン、トルエン等）又はこれらの混合溶媒である。
【００３５】
色素の吸着量は、複合電極の単位面積（１ｍ^２）当たり０．０１〜１００　ｍｍｏｌとするのが好ましい。また色素の金属酸化物に対する吸着量は、金属酸化物１ｇ当たり０．０１〜１ｍｍｏｌであるのが好ましい。このような色素の吸着量とすることにより金属酸化物の増感効果が十分に得られる。色素の吸着量が少なすぎると増感効果が不十分となり、色素の吸着量が多すぎると半導体に付着していない色素が浮遊し、増感効果が低減する。色素の吸着量を増やすためには、吸着前に複合電極を加熱処理するのが好ましい。複合電極表面に水が吸着するのを避けるために、加熱処理後は常温に戻さずに複合電極の温度が６０〜１５０℃の間で素早く色素の吸着を行うのが好ましい。
【００３６】
色素間の凝集等の相互作用を低減するために、界面活性剤としての性質を持つ無色の化合物を色素吸着液に添加し、金属酸化物に共吸着させてよい。このような無色の化合物の例としては、カルボキシル基やスルホ基を有するステロイド化合物（コール酸、デオキシコール酸、ケノデオキシコール酸、タウロデオキシコール酸等）や、下記のようなスルホン酸塩類等が挙げられる。
【００３７】
【化２】

【００３８】
未吸着の色素は、吸着工程後、速やかに洗浄により除去するのが好ましい。洗浄は湿式洗浄槽中でアセトニトリル、アルコール系溶剤のような有機溶媒等を用いて行うのが好ましい。
【００３９】
色素を吸着させた後、アミン類、４級アンモニウム塩、少なくとも１つのウレイド基を有するウレイド化合物、少なくとも１つのシリル基を有するシリル化合物、アルカリ金属塩、アルカリ土類金属塩等を用いて複合電極の表面を処理してもよい。好ましいアミン類の例としてはピリジン、４−ｔ−ブチルピリジン、ポリビニルピリジン等が挙げられる。好ましい４級アンモニウム塩の例としてはテトラブチルアンモニウムヨージド、テトラヘキシルアンモニウムヨージド等が挙げられる。これらは有機溶媒に溶解して用いてもよく、液体の場合はそのまま用いてもよい。
【００４０】
（Ｂ）　電荷輸送層
電荷輸送層は、色素の酸化体に電子を補充する機能を有する電荷輸送材料を含有する。本発明で用いる電荷輸送材料は、（ｉ）イオンが関わる電荷輸送材料であっても、（ｉｉ）固体中のキャリアー移動が関わる電荷輸送材料であってもよい。（ｉ）イオンが関わる電荷輸送材料としては、酸化還元対イオンを含有する溶融塩電解質組成物、酸化還元対のイオンが溶解した溶液（電解液）、酸化還元対の溶液をポリマーマトリクスのゲルに含浸したいわゆるゲル電解質組成物、固体電解質組成物等が挙げられ、（ｉｉ）固体中のキャリアー移動が関わる電荷輸送材料としては、電子輸送材料や正孔（ホール）輸送材料等が挙げられる。これらの電荷輸送材料は複数併用してもよい。本発明では、電荷輸送層に溶融塩電解質組成物又はゲル電解質組成物を用いるのが好ましい。
【００４１】
（１）　溶融塩電解質組成物
溶融塩電解質組成物は溶融塩を含む。溶融塩電解質組成物は常温で液体であるのが好ましい。主成分である溶融塩は室温において液状であるか、又は低融点の電解質であり、その一般的な例としては国際公開第９５／１８４５６号パンフレット、特開平８−２５９５４３号公報、「電気化学」，　１９９７年，　第６５巻，　第１１号，　ｐ．９２３等に記載のピリジニウム塩、イミダゾリウム塩、トリアゾリウム塩等が挙げられる。溶融塩の融点は５０℃以下であるのが好ましく、２５℃以下であるのが特に好ましい。溶融塩の具体例は特開２００１−３２００６８号公報の段落番号００６６〜００８２に詳しく記載されている。
【００４２】
溶融塩は単独で使用しても２種以上混合して使用してもよい。また、ＬｉＩ、ＮａＩ、ＫＩ、ＬｉＢＦ_４、ＣＦ_３ＣＯＯＬｉ、ＣＦ_３ＣＯＯＮａ、ＬｉＳＣＮ、ＮａＳＣＮ等のアルカリ金属塩を併用することもできる。アルカリ金属塩の添加量は、組成物全体に対して２質量％以下であるのが好ましく、１質量％以下がさらに好ましい。また、溶融塩電解質組成物に含まれるアニオンの５０モル％以上がヨウ化物イオンであることが好ましい。
【００４３】
通常、溶融塩電解質組成物はヨウ素を含有する。ヨウ素の含有量は、溶融塩電解質組成物全体に対して０．１〜２０質量％であるのが好ましく、０．５〜５質量％であるのがより好ましい。
【００４４】
溶融塩電解質組成物の揮発性は低いことが好ましく、溶媒を含まないことが好ましい。溶媒を添加する場合でも、溶媒の添加量は溶融塩電解質組成物全体に対して３０質量％以下に留めることが好ましい。溶融塩電解質組成物は後述のようにゲル化して使用してもよい。
【００４５】
（２）　電解液
電解液は電解質、溶媒及び添加物から構成されることが好ましい。電解液に用いる電解質の例としては、Ｉ_２とヨウ化物（ＬｉＩ、ＮａＩ、ＫＩ、ＣｓＩ、ＣａＩ_２等の金属ヨウ化物、テトラアルキルアンモニウムヨーダイド、ピリジニウムヨーダイド、イミダゾリウムヨーダイド等の４級アンモニウム化合物ヨウ素塩等）の組み合わせ、Ｂｒ_２と臭化物（ＬｉＢｒ、ＮａＢｒ、ＫＢｒ、ＣｓＢｒ、ＣａＢｒ_２等の金属臭化物、テトラアルキルアンモニウムブロマイド、ピリジニウムブロマイド等の４級アンモニウム化合物臭素塩等）の組み合わせ、フェロシアン酸塩−フェリシアン酸塩やフェロセン−フェリシニウムイオン等の金属錯体、ポリ硫化ナトリウム、アルキルチオール−アルキルジスルフィド等のイオウ化合物、ビオロゲン色素、ヒドロキノン−キノン等が挙げられる。中でも、Ｉ_２とＬｉＩ又はピリジニウムヨーダイド、イミダゾリウムヨーダイド等の４級アンモニウム化合物ヨウ素塩を組み合わせた電解質が好ましい。電解質は混合して用いてもよい。
【００４６】
電解液中の電解質濃度は好ましくは０．１〜１０　Ｍであり、より好ましくは０．２〜４Ｍである。また、電解液にヨウ素を添加する場合の好ましいヨウ素の添加濃度は０．０１〜０．５　Ｍである。
【００４７】
電解液に使用する溶媒は、粘度が低くイオン移動度を向上したり、若しくは誘電率が高く有効キャリアー濃度を向上したりして、優れたイオン伝導性を発現できる化合物であることが望ましい。このような溶媒の例としては、エチレンカーボネート、プロピレンカーボネート等のカーボネート化合物、３−メチル−２−オキサゾリジノン等の複素環化合物、ジオキサン、ジエチルエーテル等のエーテル化合物、エチレングリコールジアルキルエーテル、プロピレングリコールジアルキルエーテル、ポリエチレングリコールジアルキルエーテル、ポリプロピレングリコールジアルキルエーテル等の鎖状エーテル類、メタノール、エタノール、エチレングリコールモノアルキルエーテル、プロピレングリコールモノアルキルエーテル、ポリエチレングリコールモノアルキルエーテル、ポリプロピレングリコールモノアルキルエーテル等のアルコール類、エチレングリコール、プロピレングリコール、ポリエチレングリコール、ポリプロピレングリコール、グリセリン等の多価アルコール類、アセトニトリル、グルタロジニトリル、メトキシアセトニトリル、プロピオニトリル、ベンゾニトリル等のニトリル化合物、ジメチルスルホキシド、スルフォラン等の非プロトン極性物質、水等が挙げられる。これらの溶媒は混合して用いることもできる。
【００４８】
また、「ジャーナル・オブ・ジ・アメリカン・セラミック・ソサイエティ（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ａｍｅｒｉｃａｎ　Ｃｅｒａｍｉｃ　Ｓｏｃｉｅｔｙ）」，　１９９７年，　第８０巻，　第１２号，　ｐ．３１５７−３１７１に記載されているようなｔｅｒｔ−ブチルピリジンや、２−ピコリン、２，６−ルチジン等の塩基性化合物を前述の溶融塩電解質組成物や電解液に添加することが好ましい。塩基性化合物を電解液に添加する場合の好ましい濃度範囲は０．０５〜２Ｍである。溶融塩電解質組成物に添加する場合、塩基性化合物はイオン性基を有することが好ましい。溶融塩電解質組成物全体に対する塩基性化合物の質量比は好ましくは１〜４０質量％であり、より好ましくは５〜３０質量％である。
【００４９】
（３）　ゲル電解質組成物
本発明では、ポリマー添加、オイルゲル化剤添加、多官能モノマー類を含む重合、ポリマーの架橋反応等の手法により、前述の溶融塩電解質組成物や電解液をゲル化（固体化）させて使用することもできる。ポリマー添加によりゲル化する場合は、「ポリマー・エレクトロライト・レビューズ（Ｐｏｌｙｍｅｒ　Ｅｌｅｃｔｒｏｌｙｔｅ　Ｒｅｖｉｅｗｓ）−１及び２」（Ｊ．　Ｒ．　ＭａｃＣａｌｌｕｍとＣ．　Ａ．　Ｖｉｎｃｅｎｔの共編、ＥＬＳＥＶＩＥＲ　ＡＰＰＬＩＥＤ　ＳＣＩＥＮＣＥ）に記載された化合物を使用することができるが、特にポリアクリロニトリル及びポリフッ化ビニリデンが好ましく使用できる。オイルゲル化剤添加によりゲル化する場合は「工業科学雑誌（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ　ｏｆＪａｐａｎ，　Ｉｎｄｕｓｔｒｉａｌ　Ｃｈｅｍｉｓｔｒｙ　Ｓｅｃｔｉｏｎｓ）」，　１９４３年，　第４６巻，　ｐ．７７９、「ジャーナル・オブ・ジ・アメリカン・ケミカル・ソサイエティ（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ａｍｅｒｉｃａｎ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ）」，　１９８９年，　第１１１巻，　ｐ．５５４２、「ジャーナル・オブ・ザ・ケミカル・ソサイエティ，　ケミカル・コミュニケーションズ（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ，　Ｃｈｅｍｉｃａｌ　Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ）」，　１９９３年，　ｐ．３９０、「Ａｎｇｅｗａｎｄｔｅ　Ｃｈｅｍｉｅ　Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｅｄｉｔｉｏｎ　ｉｎ　Ｅｎｇｌｉｓｈ」，　１９９６年，　第３５巻，　ｐ．１９４９、「ケミストリー・レターズ（Ｃｈｅｍｉｓｔｒｙ　Ｌｅｔｔｅｒｓ）」，　１９９６年，　ｐ．８８５、及び「ジャーナル・オブ・ザ・ケミカル・ソサイエティ，　ケミカル・コミュニケーションズ（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ，　Ｃｈｅｍｉｃａｌ　Ｃｏｍｍｕｎｉｃａｔｉｏｎｓ）」，　１９９７年，　ｐ．５４５に記載されている化合物を使用することができるが、アミド構造を有する化合物を使用するのが好ましい。電解液をゲル化した例は特開平１１−１８５８６３号公報に、溶融塩電解質をゲル化した例は特開２０００−５８１４０号公報にも記載されており、これらも本発明に適用できる。
【００５０】
また、ポリマーの架橋反応によりゲル化させる場合、架橋可能な反応性基を含有するポリマー及び架橋剤を併用することが望ましい。この場合、好ましい架橋可能な反応性基は、アミノ基、含窒素複素環（ピリジン環、イミダゾール環、チアゾール環、オキサゾール環、トリアゾール環、モルホリン環、ピペリジン環、ピペラジン環等）であり、好ましい架橋剤は、窒素原子に対して求電子反応可能な２官能以上の試薬（ハロゲン化アルキル類、ハロゲン化アラルキル類、スルホン酸エステル類、酸無水物、酸クロライド類、イソシアネート化合物、α，β−不飽和スルホニル化合物、α，β−不飽和カルボニル化合物、α，β−不飽和ニトリル化合物等）である。特開２０００−１７０７６号公報及び同２０００−８６７２４号公報に記載されている架橋技術も適用できる。
【００５１】
（４）　正孔輸送材料
本発明では、溶融塩等のイオン伝導性電解質のかわりに、有機固体正孔輸送材料、無機固体正孔輸送材料、或いはこの両者を組み合わせた材料を使用することができる。
【００５２】
（ａ）　有機正孔輸送材料
本発明において好ましく使用できる有機正孔輸送材料の例としては、ジェイ・ハーゲン（Ｊ．　Ｈａｇｅｎ）等著，　「シンセティック・メタル（Ｓｙｎｔｈｅｔｉｃ　Ｍｅｔａｌ）」，１９９７年，　第８９巻，　ｐ．２１５−２２０、「ネイチャー（Ｎａｔｕｒｅ）」，　１９９８年，　第３９５巻，　第８号　Ｏｃｔ．，　ｐ５８３−５８５、国際公開第９７／１０６１７号パンフレット、特開昭５９−１９４３９３号公報、特開平５−２３４６８１号公報、米国特許第４，９２３，７７４号明細書、特開平４−３０８６８８号公報、米国特許第４，７６４，６２５号明細書、特開平３−２６９０８４号公報、同４−１２９２７１号公報、同４−１７５３９５号公報、同４−２６４１８９号公報、同４−２９０８５１号公報、同４−３６４１５３号公報、同５−２５４７３号公報、同５−２３９４５５号公報、同５−３２０６３４号公報、同６−１９７２号公報、同７−１３８５６２号公報、同７−２５２４７４号公報、同１１−１４４７７３号公報等に記載の芳香族アミン類、特開平１１−１４９８２１号公報、同１１−１４８０６７号公報、同１１−１７６４８９号公報等に記載のトリフェニレン誘導体類等が挙げられる。また、「アドバンスド・マテリアルズ（Ａｄｖａｎｃｅｄ　Ｍａｔｅｒｉａｌｓ）」，　１９９７年，　第９巻，　第７号，　ｐ．５５７、「Ａｎｇｅｗａｎｄｔｅ　Ｃｈｅｍｉｅ　Ｉｎｔｅｒｎａｔｉｏｎａｌ　Ｅｄｉｔｉｏｎ　ｉｎ　Ｅｎｇｌｉｓｈ」，　１９９５年，　第３４巻，　第３号，　ｐ．３０３−３０７、「ジャーナル・オブ・ジ・アメリカン・ケミカル・ソサイエティ（Ｊｏｕｒｎａｌ　ｏｆ　ｔｈｅ　Ａｍｅｒｉｃａｎ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ）」，　１９９８年，　第１２０巻，　第４号，ｐ．６６４−６７２等に記載のオリゴチオフェン化合物、Ｋ．　Ｍｕｒａｋｏｓｈｉ，　ｅｔ　ａｌ．，　「ケミストリー・レターズ（Ｃｈｅｍｉｓｔｒｙ　Ｌｅｔｔｅｒｓ）」，　１９９７年，　ｐ．４７１に記載のポリピロール、ＮＡＬＷＡ著「ハンドブック・オブ・オーガニック・コンダクティブ・モレキュールズ・アンド・ポリマーズ（Ｈａｎｄｂｏｏｋ　ｏｆ　Ｏｒｇａｎｉｃ　Ｃｏｎｄｕｃｔｉｖｅ　Ｍｏｌｅｃｕｌｅｓ　ａｎｄ　Ｐｏｌｙｍｅｒｓ）」，　第１，２，３，４巻，　ＷＩＬＥＹ出版に記載のポリアセチレン及びその誘導体、ポリ（ｐ−フェニレン）及びその誘導体、ポリ（ｐ−フェニレンビニレン）及びその誘導体、ポリチエニレンビニレン及びその誘導体、ポリチオフェン及びその誘導体、ポリアニリン及びその誘導体、ポリトルイジン及びその誘導体等の導電性高分子も好ましく使用することができる。
【００５３】
「ネイチャー（Ｎａｔｕｒｅ）」，　１９９８年，　第３９５巻，　第８号　Ｏｃｔ．，　ｐ．５８３−５８５に記載されているように、ドーパントレベルをコントロールするためにトリス（４−ブロモフェニル）アミニウムヘキサクロロアンチモネートのようなカチオンラジカルを含有する化合物を正孔輸送材料に添加してもよい。また、酸化物半導体表面のポテンシャル制御（空間電荷層の補償）を行うためにＬｉ［（ＣＦ_３ＳＯ_２）_２Ｎ］のような塩を添加してもよい。
【００５４】
（ｂ）　無機正孔輸送材料
無機正孔輸送材料としてはｐ型無機化合物半導体を用いることができ、そのバンドギャップは好ましくは２ｅＶ以上、より好ましくは２．５ｅＶ以上である。また、ｐ型無機化合物半導体のイオン化ポテンシャルは、色素の正孔を還元するためには色素吸着電極のイオン化ポテンシャルより小さいことが必要である。使用する色素によってｐ型無機化合物半導体のイオン化ポテンシャルの好ましい範囲は異なるが、一般に好ましくは４．５〜５．５　ｅＶ、より好ましくは４．７〜５．３　ｅＶである。好ましいｐ型無機化合物半導体は１価の銅を含む化合物半導体であり、その例としてはＣｕＩ、ＣｕＳＣＮ、ＣｕＩｎＳｅ_２、Ｃｕ（Ｉｎ，Ｇａ）Ｓｅ_２、ＣｕＧａＳｅ_２、Ｃｕ２Ｏ、ＣｕＳ、ＣｕＧａＳ_２、ＣｕＩｎＳ_２、ＣｕＡｌＳｅ_２等が挙げられる。中でも、ＣｕＩ及びＣｕＳＣＮが好ましく、ＣｕＩが最も好ましい。他のｐ型無機化合物半導体の例としては、ＧａＰ、ＮｉＯ、ＣｏＯ、ＦｅＯ、Ｂｉ_２Ｏ_３、ＭｏＯ_２、Ｃｒ_２Ｏ_３等が挙げられる。
【００５５】
（５）　電荷輸送層の形成
電荷輸送層は２通りの方法のいずれかにより形成できる。１つは感光層の上に先に対極を貼り合わせておき、その間隙に液状の電荷輸送層を挟み込む方法である。もう１つは感光層上に直接電荷輸送層を付与する方法で、対極はその後付与することになる。
【００５６】
前者の方法の場合、電荷輸送層を挟み込む際には、浸漬等による毛管現象を利用する常圧プロセス又は常圧より低い圧力にして間隙の気相を液相に置換する真空プロセスを利用できる。
【００５７】
後者の方法において、湿式の電荷輸送層を用いる場合は、通常未乾燥のまま対極を付与しエッジ部の液漏洩防止措置を施す。またゲル電解質組成物を用いる場合には、これを湿式で塗布した後で重合等の方法により固体化してよい。固体化は対極を付与する前に行っても後に行ってもよい。電解液、湿式有機正孔輸送材料、ゲル電解質組成物等からなる電荷輸送層を形成する場合は、前述の半導体微粒子層の形成方法と同様の方法を利用できる。
【００５８】
固体電解質組成物や固体正孔輸送材料を用いる場合には、真空蒸着法やＣＶＤ法等のドライ成膜処理で電荷輸送層を形成し、その後対極を付与することもできる。有機正孔輸送材料は真空蒸着法、キャスト法、塗布法、スピンコート法、浸漬法、電解重合法、光電解重合法等により電極内部に導入することができる。無機固体化合物はキャスト法、塗布法、スピンコート法、浸漬法、電解析出法、無電解メッキ法等により電極内部に導入することができる。
【００５９】
（Ｃ）　対極
対極は導電性材料からなる対極導電層の単層構造でもよいし、対極導電層と支持基板から構成されていてもよい。本発明では色素増感光電変換素子は対極側から光を照射するので、対極導電層に用いるのは透明性の高い金属酸化物（インジウム−スズ複合酸化物、フッ素ドープ酸化スズ等）である。これに金属（白金、金、銀、銅、アルミニウム、マグネシウム、インジウム等）、炭素、等を少量併用しても良い。対極に用いる基板は、好ましくはガラス基板又はプラスチック基板であり、これに上記の導電剤を塗布又は蒸着して用いることができる。対極導電層の厚さは光透過率によって制限される。光透過率は３０％以上が好ましく、５０％以上がより好ましい。対極導電層の表面抵抗は低い程よく、好ましくは５０Ω／□以下、より好ましくは２０Ω／□以下である。
【００６０】
対極は電荷輸送層上に直接導電剤を塗布、メッキ又は蒸着（ＰＶＤ、ＣＶＤ）するか、導電層を有する基板の導電層側を貼り付けて設置すればよい。対極の抵抗を下げる目的で金属リードを用いても良い。金属リードは白金、金、ニッケル、チタン、アルミニウム、銅、銀等の金属からなるのが好ましく、アルミニウム又は銀からなるのが特に好ましい。透明基板上に金属リードを蒸着、スパッタリング等で設置し、その上にフッ素をドープした酸化スズ、ＩＴＯ膜等からなる透明対極導電層を設けるのが好ましい。また、透明対極導電層を透明基板に設けた後、透明対極導電層上に金属リードを設置することも好ましい。金属リード設置による入射光量の低下は、好ましくは１０％以内、より好ましくは１〜５％とする。
【００６１】
（Ｄ）　光電変換素子の内部構造の具体例
上述のように、光電変換素子の内部構造は目的に合わせ様々な形態が可能である。光電変換素子の内部構造を大きく２つに分けると、両面から光の入射が可能な構造と、片面からのみ光の入射が可能な構造とがある。光電変換素子の好ましい内部構造の例を、前述の図１及び図２〜図４に示す。図２に示す構造は、導電層１０、感光層２０の上に電荷輸送層３０、透明対極導電層４０ａを設け、この上に一部に金属リード１１を設けた透明基板５０ａを金属リード１１側を内側にして配置したものである。図３に示す構造は、導電層１０の両面に感光層２０、電荷輸送層３０、及び透明対極導電層４０ａを設け、この上に透明基板５０ａを配置したものである。図４に示す構造は、導電層１０、感光層２０の上に固体の電荷輸送層３０を設け、この上に一部対極導電層４０又は金属リード１１を有するものである。
【００６２】
［３］　光電池
本発明の光電池は、上記本発明の光電変換素子に外部負荷で仕事をさせるようにしたものである。光電池のうち、電荷輸送材料が主としてイオン輸送材料からなる場合を特に光電気化学電池と呼び、また、太陽光による発電を主目的とする場合を太陽電池と呼ぶ。
【００６３】
光電池の側面は、構成物の劣化や内容物の揮散を防止するためにポリマーや接着剤等で密封するのが好ましい。導電性支持体及び対極にリードを介して接続する外部回路自体は公知のものでよい。
【００６４】
本発明の光電変換素子を太陽電池に適用する場合も、そのセル内部の構造は基本的に上述した光電変換素子の構造と同じである。また、本発明の光電変換素子を用いた色素増感型太陽電池は、従来の太陽電池モジュールと基本的には同様のモジュール構造をとりうる。太陽電池モジュールは、一般的には金属、セラミック等の支持基板の上にセルが構成され、その上を充填樹脂や保護ガラス等で覆い、支持基板の反対側から光を取り込む構造をとるが、支持基板に強化ガラス等の透明材料を用い、その上にセルを構成してその透明の支持基板側から光を取り込む構造とすることも可能である。具体的には、スーパーストレートタイプ、サブストレートタイプ、ポッティングタイプと呼ばれるモジュール構造、アモルファスシリコン太陽電池等で用いられる基板一体型モジュール構造等が知られており、本発明の光電変換素子を用いた色素増感型太陽電池も使用目的や使用場所及び環境により、適宜モジュール構造を選択できる。具体的には、特願平１１−８４５７号、特開２０００−２６８８９２号公報等に記載の構造や態様とすることが好ましい。
【００６５】
【実施例】
以下、本発明を実施例によって具体的に説明するが、本発明はそれらに限定されるものではない。
【００６６】
実施例１
（１）　ＴｉＯ_２微粒子塗布電極（比較用電極Ａ）の作製
内側をテフロン（登録商標）でコーティングしたステンレス製容器にＴｉＯ_２微粒子（日本アエロジル社製、Ｐ−２５）１５　ｇ、水４５　ｇ、トリトンＸ−１００（アルドリッチ社製）１ｇ、及び直径０．５　ｍｍのジルコニアビーズ（（株）ニッカトー製）３０　ｇを入れ、サンドグラインダーミル（（株）アイメックス製）を用いて１５００　ｒｐｍで２時間分散させた。分散物からジルコニアビーズを濾過し、ＴｉＯ_２微粒子塗布液を得た。
【００６７】
フッ素をドープした酸化スズをコーティングした透明導電性ガラス（日本板硝子（株）製、表面抵抗約１０　Ω／ｃｍ^２、長さ１００　ｍｍ、幅１９　ｍｍ、厚さ１．１　ｍｍ）の導電面側にドクターブレードを用いて上記ＴｉＯ_２微粒子塗布液を塗布した。２５℃で３０分間乾燥した後、電気炉（ヤマト科学（株）製マッフル炉ＦＰ−３２型）を用いて４５０℃で３０分間焼成し、ＴｉＯ_２微粒子塗布電極（比較用電極Ａ）を得た。塗布、焼成前後の質量変化より比較用電極ＡのＴｉＯ_２の塗布量を求めたところ９ｇ／ｍ^２であった。
【００６８】
（２）　チタン−酸化チタン複合電極Ｅ−１及びＥ−２の作製
長さ２０　ｍｍ、幅１０　ｍｍ、厚さ５ｍｍのチタン−アルミニウム合金（（株）高純度化学研究所製、チタン含有率７０質量％及びアルミニウム含有率３０質量％）を７．０　ｍｍｏｌの水酸化ナトリウム水溶液中に８０℃で２０時間浸漬した後、中性の水で洗浄し、Ｘ線表面分析（ＸＰＳ）によりチタンとアルミニウムの比率を測定した。この操作を何回か繰り返し、チタンに対するアルミニウムの比率が５質量％以下になった時点でこの操作を終了し、多孔性の金属チタン電極を得た。得られたチタン電極の長手方向の上端をソースメジャーユニット２３８型（ケースレー製）の＋端子に接続し、下から１４　ｍｍまでを石英セルの中に入れた２Ｍ希硫酸中に浸漬した。同じセル中に浸漬した白金ワイヤーをソースメジャーユニットの−端子に接続し、５Ｖの電圧で電解酸化し、複合電極Ｅ−１を得た。また、上記と同じチタン−アルミニウム合金の長手方向の上端をソースメジャーユニット２３８型（ケースレー製）の＋端子に接続し、下から１４　ｍｍまでを石英セルの中に入れた７．０　ｍｏｌ／Ｌの水酸化ナトリウム水溶液中に浸漬し、同じセル中に浸漬した白金ワイヤーをソースメジャーユニットの−端子に接続し、３５Ｖの電圧でアルミニウムを除去しながら電解酸化することによって、複合電極Ｅ−２を得た。これらの複合電極のＸ線回折（ＸＲＤ）を測定したところ、どちらも金属チタンの他にアナターゼ型ＴｉＯ_２が検出された。
【００６９】
（３）　ＴｉＯ_２膜の機械的強度の評価
比較用電極Ａを１０　ｍｍ×１９　ｍｍの大きさにカットし、塗布面側にマイラーテープ（日東電工（株）製）を貼り、指の腹でよく擦って圧着した。次にこのテープを剥がしたところ、かなりの量のＴｉＯ_２が剥離してテープの粘着面に付着していることを確認した。一方、複合電極Ｅ−１及びＥ−２について同様の実験を行ったところ、テープの粘着面にＴｉＯ_２は全く付着しなかった。このことから、複合電極Ｅ−１及びＥ−２はＴｉＯ_２微粒子を塗布、焼成した電極よりもＴｉＯ_２層の機械的強度が高いことがわかる。
【００７０】
実施例２
（１）　比較用チタン−酸化チタン複合電極Ｂの作製
長さ２０　ｍｍ、幅１０　ｍｍ、厚さ０．２５　ｍｍのチタン板（アルドリッチ社製）の長手方向の上端をソースメジャーユニット２３８型（ケースレー社製）の＋端子に接続し、下から１４　ｍｍまでを石英セルの中に入れた２Ｍ希硫酸中に浸漬した。同じセル中に浸漬した白金ワイヤーをソースメジャーユニットの−端子に接続し、５Ｖの電圧で電解酸化した。初め１０　ｍＡを越える電解電流が流れたのち急激に減衰し、５分後には５０μＡ以下となった。その後、５Ｖの印加電圧でさらに３時間通電した。得られた電極を４５０℃で３０分間焼成し、比較用電極Ｂを得た。
【００７１】
（２）　色素の吸着
焼成直後の電極（比較用電極Ｂ、複合電極Ｅ−１及びＥ−２）を下記の色素（Ｄ−１）０．３ミリモル／リットルを含む溶液（吸着液）に１６時間浸漬した。吸着温度は２５℃とし、吸着液の溶媒としてはエタノール、ｔ−ブタノール、アセトニトリルを１：１：２（体積比）で混合した溶媒を用いた。色素の染着した比較用電極Ｂ、複合電極Ｅ−１及びＥ−２をエタノール、アセトニトリルで順次洗浄し、それぞれ色素増感電極ＤＢ、ＤＥ−１及びＤＥ−２を得た。
【００７２】
【化３】

【００７３】
（３）　対極の作製
フッ素をドープした酸化スズをコーティングした透明導電性ガラス（日本板硝子（株）製、表面抵抗約１０　Ω／ｃｍ^２）を長さ２０　ｍｍ、幅１２　ｍｍにカットし、ＪＥＥ−４Ｃ型真空蒸着装置（日本電子（株）製）を用いて、導電ガラスの透明性を失わない程度に白金を蒸着した。この白金蒸着導電ガラスの透過率は５５０　ｎｍの光に対して７０％であった。
【００７４】
（４）　光電変換素子の作製
図５に示すように、作製した色素増感電極１０１、ポリエチレンスペーサーフィルム（厚さ：２５μｍ）１０３、白金蒸着導電ガラス１０２を重ね、両ガラスの隙間に電解液（ヨウ化１，３−ジメチルイミダゾリウム０．６５モル／リットル、ヨウ素０．０５モル／リットル、及びｔ−ブチルピリジン０．１モル／リットルのアセトニトリル溶液）を加えた。あふれ出た過剰の電解液を紙でふき取り、２枚の電極をクリップで固定することにより、表１に示す光電変換素子ＣＢ、ＣＥ−１及びＣＥ−２を得た。
【００７５】
【表１】

【００７６】
（５）　光電変換効率の測定
５００　Ｗのキセノンランプ（ウシオ（株）製）の光を分光フィルター（Ｏｒｉｅｌ社製、ＡＭ１．５Ｄ）を通すことにより模擬太陽光を発生させた。光の強度は垂直面において８７　ｍＷ／ｃｍ^２であった。光電変換素子の白金蒸着導電ガラスの端部に銀ペーストを塗布して正極とし、この正極と色素増感電極（負極）を電流電圧測定装置（ケースレーＳＭＵ２３８型）に接続した。模擬太陽光を垂直に照射しながら、発生した光電流を測定した。表２に本発明の光電変換素子ＣＥ−１、ＣＥ−２及び比較用光電変換素子ＣＢの光電流の値を示す。
【００７７】
（６）　色素吸着量の測定
色素増感電極の活性領域（１０　ｍｍ×１０　ｍｍ、光電流測定に用いた領域）を０．１Ｎ水酸化ナトリウム水溶液に浸漬し溶出した色素を分光法で定量した。このとき裏面を含むその他の領域は、色素が吸着していても溶出しないように、マイラーテープを貼ってマスクした。
【００７８】
【表２】

【００７９】
表２の結果から、チタン−アルミニウム合金からアルミニウムを溶解除去して得られたチタン電極を電解酸化したチタン−酸化チタン複合電極Ｅ−１を用いた本発明の光電変換素子ＣＥ−１は、単なるチタンプレートを電解酸化した比較電極Ｂを用いた光電変換素子ＣＢよりも光電流が大きく、優れた光電変換素子であることがわかる。また、チタン−酸化チタン複合電極Ｅ−１及びＥ−２を用いた色素増感電極ＤＥ−１及びＤＥ−２は、比較用色素増感電極ＤＢに比べて色素吸着量が多い。これは表面粗度が高いためであると考えられ、光電流の大きい原因であると推定できる。
【００８０】
実施例３
合金の種類及び合金中の金属Ａの含有率（Ａ含率：質量％）を表３に示すように変えた以外実施例１のＥ−２と同様の方法で複合電極Ｅ−３〜８を作製した。これらの電極を実施例１と同様の方法で機械的強度を調べたところ、ＴｉＯ_２の脱落は見られず、機械的強度の高い電極であることがわかった。次に、実施例２と同様の方法で光電変換素子（ＣＥ−３〜ＣＥ−８）を作製し、光電流及び色素吸着量を測定した。ＣＥ−３〜ＣＥ−８、及び対照としてＣＥ−２の測定結果を表３に示す。
【００８１】
【表３】

【００８２】
表３から複合電極に用いる金属Ａとしてはチタンが好ましく、合金に含まれる除去する金属Ｂとしてはアルミニウムが好ましいことがわかる。
【００８３】
【発明の効果】
以上詳述したように、本発明の方法によれば、少なくとも二種以上の金属を含む合金中から一種の金属以外を除去し、残された一種の金属を酸化することにより、機械的強度が高く表面粗度の大きい金属−金属酸化物複合電極が得られる。この金属−金属酸化物複合電極を用いることにより酸化物半導体膜の機械的強度が高く、かつ光電流の大きい色素増感光電変換素子が得られる。
【図面の簡単な説明】
【図１】本発明の好ましい一実施例による光電変換素子の構造を示す部分断面図である。
【図２】本発明の好ましい別の実施例による光電変換素子の構造を示す部分断面図である。
【図３】本発明の好ましいさらに別の実施例による光電変換素子の構造を示す部分断面図である。
【図４】本発明の好ましいさらに別の実施例による光電変換素子の構造を示す部分断面図である。
【図５】実施例２で作製した光電変換素子の構成を示す分解図である。
【符号の説明】
１０・・・導電層
１１・・・金属リード
２０・・・感光層
２１・・・半導体微粒子
２２・・・色素
２３・・・電荷輸送材料
３０・・・電荷輸送層
４０ａ・・・透明対極導電層
５０ａ・・・透明基板
１０１・・・色素増感電極
１０２・・・白金蒸着導電ガラス
１０３・・・ポリエチレンスペーサーフィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a metal-metal oxide composite electrode, a photoelectric conversion element including the metal-metal oxide composite electrode produced by the method, and a photovoltaic cell.
[0002]
[Prior art]
Photoelectric conversion elements are used in various optical sensors, copiers, photovoltaic power generation devices and the like. Various systems such as those using metals, semiconductors, organic pigments and dyes, and combinations of these have been put to practical use as photoelectric conversion elements.
[0003]
For example, a photoelectric conversion element using semiconductor fine particles sensitized with a dye (hereinafter referred to as “dye-sensitized photoelectric conversion element”), and a material and a manufacturing technique for producing the photoelectric conversion element are disclosed (for example, (See Patent Documents 1 to 9 and Non-Patent Documents 1 to 3.) According to these technologies, an excellent photoelectric conversion element can be obtained simply by preparing a coating film using oxide semiconductor fine particles and adsorbing a dye, so that a photoelectric conversion element with high cost performance can be obtained.
[0004]
However, the adhesion between the oxide semiconductor fine particles and the transparent electrode as a support thereof is not necessarily high, and there is a problem of peeling of the oxide semiconductor fine particles. On the other hand, a method of forming an oxide layer on a metal surface by electrolytic oxidation is known. If this method is used, a metal electrode as a conductive support and a metal oxide layer firmly adhered thereto can be formed, so that the problem of mechanical strength should be solved. However, when this technique is applied to metals such as titanium, niobium, and tungsten that are suitable for dye-sensitized photoelectric conversion elements, a strong oxide film can be obtained, but the ratio of surface area to the projected area (surface roughness) is small, and small light There was a problem that only current could be taken out. As described above, although a dye-sensitized photoelectric conversion element having a high mechanical strength of an oxide semiconductor film and a large photocurrent that can be taken out is desired, it has not been realized so far.
[0005]
[Patent Document 1]
US Pat. No. 4,927,721
[Patent Document 2]
US Pat. No. 4,684,537
[Patent Document 3]
US Pat. No. 5,084,365
[Patent Document 4]
US Pat. No. 5,350,644
[Patent Document 5]
US Pat. No. 5,463,057
[Patent Document 6]
US Pat. No. 5,525,440
[Patent Document 7]
International Publication No. 98/50393 Pamphlet
[Patent Document 8]
JP 7-249790 A
[Patent Document 9]
Japanese National Patent Publication No. 10-504521
[Non-Patent Document 1]
“Journal of the American Ceramic Society”, 1997, Vol. 80, p. 3157-3171
[Non-Patent Document 2]
“Accounts of Chemical Research”, 2000, Vol. 33, p. 269-277
[Non-Patent Document 3]
“Journal of the American Chemical Society”, 1993, 115, p. 6832
[0006]
[Problems to be solved by the invention]
The first object of the present invention is to provide a metal-metal oxide composite electrode having high mechanical strength and high surface roughness, and the second object of the present invention is to provide high mechanical strength and high photocurrent. To provide a large dye-sensitized photoelectric conversion element and a photovoltaic cell using the same.
[0007]
[Means for Solving the Problems]
As a result of diligent research in view of the above object, the present inventors have developed a metal-metal oxide composite electrode having high mechanical strength and high surface roughness according to the following (1) to (11), and dye sensitization having a large photocurrent. It discovered that a photoelectric conversion element and a photovoltaic cell could be obtained, and came up with this invention.
(1) A metal-metal oxide characterized in that one kind of metal is left out of an alloy containing at least two kinds of metals and other metals are substantially removed and the remaining one kind of metal is oxidized. A method for producing a composite electrode.
(2) The manufacturing method according to (1), wherein the one kind of metal left in the alloy is titanium, niobium, or tungsten.
(3) The production method according to (1) or (2), wherein titanium is used as the one kind of metal remaining without being removed to produce a titanium-titanium oxide composite electrode.
(4) The alloy includes a metal A selected from the group consisting of titanium, niobium and tungsten and a metal B selected from the group consisting of aluminum, zinc, tin and indium, and substantially contains a metal other than the metal A. After the removal, the metal A is oxidized, The manufacturing method according to any one of (1) to (3).
(5) The manufacturing method according to any one of (1) to (4), wherein the alloy includes only two kinds of metals.
(6) The method according to any one of (1) to (5), wherein a metal containing aluminum is removed from the alloy.
(7) A manufacturing method characterized by removing a metal other than the one kind of metal contained in the alloy by immersing it in a basic solution.
(8) The method according to any one of (1) to (7), wherein the one kind of metal left in the alloy is oxidized by electrolytic oxidation.
(9) The method according to (8), wherein an applied voltage in the electrolytic oxidation is 20 to 70V.
(10) A dye-sensitized photoelectric conversion element comprising a metal-metal oxide composite electrode produced by the method according to any one of (1) to (9), a dye, and a charge transport material.
(11) A photovoltaic cell using the dye-sensitized photoelectric conversion element according to (10).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The main point of the present invention is that the surface roughness is improved by oxidizing the surface of the remaining porous metal by removing one metal from the alloy containing at least two kinds of metals and substantially removing other metals. It is to obtain a large metal-metal oxide composite electrode. The method will be described in detail below.
[0009]
[1] Method for producing metal-metal oxide composite electrode
(A) Alloy
The metal-metal oxide composite electrode (hereinafter abbreviated as “composite electrode”) according to the method of the present invention uses an alloy containing at least metal A and metal B, and preferably an alloy composed of these two kinds of metals. Examples of the metal A include metals such as titanium, niobium, and tungsten, and examples of the metal B include metals such as aluminum, zinc, tin, and indium. The ratio of metal A (titanium, niobium, tungsten, etc.) in the alloy to the entire alloy is preferably 30% by mass or more, and more preferably 50% by mass or more. When the intended use of the composite electrode is a dye-sensitized photoelectric conversion element, titanium is particularly preferable as the metal A, and aluminum is particularly preferable as the metal B to be removed. Therefore, a titanium-aluminum alloy is preferable as the alloy. The shape of the alloy is preferably a plate shape, and the thickness is preferably 0.01 to 10 mm, more preferably 0.1 to 1 mm.
[0010]
(B) Preparation method
The composite electrode manufacturing method of the present invention includes a step of removing a metal (for example, metal B) other than the metal A contained in the alloy (hereinafter referred to as “removal step”), and an oxidation step of the remaining metal A ( Hereinafter, it is referred to as an “oxidation step”). Each process will be described below.
[0011]
(1) Removal process
The step of removing a metal other than metal A from the alloy can be performed by utilizing the difference in chemical and physical properties between metal A and the metal to be removed. For example, using the difference in solubility between metal A and metal B in an acidic solution or basic solution, immersing the metal B in a solution that dissolves easily (dissolution method), or using the difference in melting point And a method of melting and removing the metal B (melting method). As the removal method, the former dissolution method is preferable, and when removing aluminum, removal with a basic solution is preferable. In the case of the dissolution method, immersion in a basic solution or an acidic solution is preferable. Preferred bases used in the basic solution include alkali metal hydroxides, tetraalkylammonium hydroxides, and the like. Preferable acids used for the acidic solution include sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, acetic acid, oxalic acid and the like, and anhydrides may be used. The base and the acid are used at a concentration of 1 mmol / L or more, preferably 10 mmol / L to 10 mol / L.
[0012]
The immersion conditions vary depending on the metal to be removed, and the temperature is preferably 20 ° C. or higher, and the time is preferably 10 minutes or longer. Furthermore, conditions other than these (pressure, application, light irradiation, etc.) may be added. The removal process substantially removes the other metal in the alloy leaving a kind of metal (metal A). Here, “substantially remove” means that in addition to removing all metals other than metal A, metals other than metal A may remain within a range not impairing the effects of the present invention. To do. In the present invention, it is preferable to remove 100% of the metal other than the metal A by the removing step, but other metals within 5% by mass relative to the metal A may remain. By these methods, porous metal A can be obtained from an alloy containing metal A and metal B.
[0013]
(2) Oxidation process
The electrode surface made of the porous metal A formed by the above removal step is oxidized to produce a porous composite electrode. Preferable methods include a method in which a metal surface is fired and oxidized (firing method), a method in which a metal electrode is connected to a power source as an anode (electrolytic method) and the like (electrolytic method). In the case of the firing method, firing is preferably performed at 150 to 700 ° C. in an air or oxygen atmosphere. When titanium is used as the metal, the firing temperature is preferably 350 to 550 ° C., and the firing time is preferably about 5 minutes to 3 hours.
[0014]
In the case of the electrolysis method, the electrolysis voltage is usually 0.1 to 200 V, preferably 5 to 100 V, more preferably 20 to 70 V. If the electrolysis voltage exceeds 80 V, there is a danger, so the preferred range is set relatively low. However, if there is a device that can avoid the danger, the higher the electrolysis voltage, the better. A three-pole system using a reference electrode in the electrolysis may be used, or a two-pole system may be used without using a reference electrode. When the electrolytic voltage is 5 V or higher, it is not necessary to use a reference electrode. The counter electrode is not particularly limited, but is preferably a noble metal with low reactivity (for example, gold, platinum, etc.), carbon or the like.
[0015]
The electrolyte solution can be either aqueous or non-aqueous, but is preferably aqueous. Examples of electrolytes include acids (sulfuric acid, nitric acid, perchloric acid, methanesulfonic acid, oxalic acid, acetic acid, phosphoric acid, carbonic acid, boric acid, trifluoromethanesulfonic acid, trifluoroacetic acid, etc.), alkalis (lithium hydroxide, hydroxide) Sodium, potassium hydroxide, calcium hydroxide, tetrabutylammonium hydroxide, etc.) and salts formed by neutralizing the above acid and alkali (sodium sulfate, lithium nitrate, potassium perchlorate, etc.). As the acid, a strong acid (sulfuric acid, nitric acid, perchloric acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc.) is particularly preferable.
[0016]
The electrolysis temperature and electrolysis time can be appropriately determined according to the conditions. Typical conditions are an electrolysis temperature of 5 to 70 ° C. and an electrolysis time of 1 minute to 24 hours. The removal step and the oxidation step are preferably performed simultaneously. For example, it is preferable to produce a composite electrode by performing electrolytic oxidation while immersing the alloy in a basic or acidic solution.
[0017]
[2] Photoelectric conversion element
The produced composite electrode can be preferably used for a dye-sensitized photoelectric conversion element. The dye-sensitized photoelectric conversion element is preferably formed by laminating a conductive layer 10, a photosensitive layer 20, a charge transport layer 30, and a transparent counter electrode conductive layer 40a in this order as shown in FIG. In the present invention, the metal portion of the composite electrode is used for the conductive layer 10, and the metal oxide portion of the composite electrode is used for the photosensitive layer 20. In order to impart strength to the photoelectric conversion element, a transparent substrate 50a may be provided as a base of the transparent counter electrode conductive layer 40a. In this specification, a layer composed of the counter electrode conductive layer 40 and an optional substrate 50 is called a “counter electrode”, and the counter electrode needs to be transparent. Among such photoelectric conversion elements, a photoelectric cell is connected to an external load to perform electrical work (power generation), and an optical sensor is formed for the purpose of sensing optical information. Among photovoltaic cells, those in which the charge transport material is mainly composed of an ion transport material are called photoelectrochemical cells, and those whose main purpose is power generation by sunlight are called solar cells.
[0018]
In the photoelectric conversion element shown in FIG. 1, the light incident on the photosensitive layer 20 containing the metal oxide sensitized by the dye excites the dye and the high energy electrons in the excited dye and the like are conducted by the metal oxide. It is passed to the belt and further diffused to reach the conductive layer 10. At this time, the dye is an oxidant. In the photovoltaic cell, the electrons in the conductive layer 10 return to the oxidant of the dye through the transparent counter electrode conductive layer 40a and the charge transport layer 30 while working in the external circuit, and the dye is regenerated. The photosensitive layer 20 functions as a negative electrode, and the transparent counter electrode conductive layer 40a functions as a positive electrode. At the boundary of each layer (for example, the boundary between the conductive layer 10 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transport layer 30, the boundary between the charge transport layer 30 and the transparent counter electrode conductive layer 40a, etc.) The components may be diffusively mixed with each other. Hereinafter, each layer and structure will be described in detail.
[0019]
(A) Conductive layer and photosensitive layer
The metal-metal oxide composite electrode adsorbs an appropriate sensitizing dye, whereby the metal portion becomes a conductive layer and the metal oxide portion becomes a photosensitive layer. The metal oxide dye-sensitized in the photosensitive layer acts as a photoreceptor, absorbs light and separates charges to generate electrons and holes. Light absorption and the generation of electrons and holes thereby occur mainly in the dye, and the metal oxide is responsible for receiving and transmitting these electrons. That is, a metal oxide is an n-type semiconductor that provides an anode current due to conductor electrons under photoexcitation.
[0020]
(1) Semiconductor
You may apply | coat the dispersion liquid or colloidal solution containing semiconductor fine particles on a composite electrode in the range which does not reduce film | membrane intensity | strength. In this case, the coated semiconductor fine particles also carry a dye and act as a photoreceptor. The thickness of the coated semiconductor fine particle film is preferably 5 μm or less, more preferably 2 μm or less in order to maintain mechanical strength. Semiconductor fine particles are compounds having a perovskite structure (strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate, etc.), TiO₂, SnO₂, WO₃, ZnO, Nb₂O₅, In₂O₃Etc., preferably ZnO, SnO₂, WO₃TiO₂Or Nb₂O₅And most preferably TiO₂It is. The semiconductor fine particles may have any crystal form of anatase type, rutile type and brookite type.
[0021]
The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably 5 to 200 nm, more preferably 8 to 100 nm. It is. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 10 μm.
[0022]
Examples of preferable coating methods include the roller method and dip method as application systems, the air knife method and blade method as metering systems, and Japanese Patent Publication No. 58-4589 as the application and metering can be made the same part. Examples thereof include a disclosed wire bar method, a slide hopper method, an extrusion method, and a curtain method described in US Pat. Nos. 2,681,294, 2,761,419, 2,761791, and the like. Moreover, a spin method and a spray method are also preferable as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. A film forming method may be selected from these according to the liquid viscosity and the wet thickness.
[0023]
After the semiconductor fine particles are applied on the composite electrode, heat treatment is preferably performed in order to bring the semiconductor fine particles into electronic contact with each other and to improve the coating strength and the adhesion to the composite electrode. The heating temperature in the heat treatment is preferably 40 to 700 ° C, more preferably 100 to 600 ° C. The heating time is about 10 minutes to 10 hours. When using a substrate having a low melting point or softening point such as a polymer film, high temperature treatment is not preferable because it causes deterioration of the substrate. Also from the viewpoint of cost, it is preferable to perform the heat treatment at the lowest possible temperature. When the heat treatment is performed in the presence of small semiconductor fine particles of 5 nm or less, mineral acid, or the like, the heating temperature can be lowered.
[0024]
A pressure treatment may be performed instead of the heat treatment. Regarding the method of pressure treatment, “Journal of photochemistry and photobiology” by Lindstrom et al., 2001 (Elsevier), vol. 145, p. 107-112. When the pressure treatment is performed, a binder such as a polymer is not used in the semiconductor fine particle coating solution.
[0025]
After the heat treatment or pressure treatment, for example, chemical plating treatment using a titanium tetrachloride aqueous solution or electrochemical plating treatment using a titanium trichloride aqueous solution as described in US Pat. No. 5,084,365 is performed. May be.
[0026]
(2) Processing
In the present invention, the semiconductor fine particles used for the photosensitive layer may be treated with a solution of a metal compound. As the metal compound, for example, a metal alkoxide or halide selected from the group consisting of scandium, yttrium, lanthanoid, zirconium, hafnium, niobium, tantalum, gallium, indium, germanium, and tin can be used. The metal compound solution (treatment liquid) is usually an aqueous solution or an alcohol solution. Note that “treatment” means an operation of bringing the semiconductor fine particles into contact with the treatment liquid for a certain period of time before adsorbing the pigment to the semiconductor fine particles. The metal compound may or may not be adsorbed on the semiconductor fine particles after contact. The treatment is preferably performed after the semiconductor fine particle layer is formed.
[0027]
As a specific method for the treatment, a method of immersing semiconductor fine particles in the treatment liquid (immersion method) is a preferred example. Moreover, the method (spray method) which sprays a process liquid in a spray form for a fixed time is also applicable. Although the temperature (immersion temperature) of the process liquid at the time of performing an immersion method is not specifically limited, Typically, it is -10-70 degreeC, Preferably it is 0-40 degreeC. The treatment time is also not particularly limited, and is typically 1 minute to 24 hours, preferably 30 minutes to 15 hours. After the immersion, the semiconductor fine particles may be washed with a solvent such as distilled water. Moreover, you may bake in order to strengthen the coupling | bonding of the substance adhering to semiconductor fine particle by the immersion process. The firing conditions may be set similarly to the above-described heat treatment conditions.
[0028]
(3) Dye
The sensitizing dye used in the photosensitive layer is not particularly limited as long as it has absorption characteristics in the visible range and near-infrared range and can sensitize a semiconductor. However, a metal complex dye, a methine dye, a porphyrin dye, and a phthalocyanine dye Can be preferably used, and among them, metal complex dyes are particularly preferable. Phthalocyanines, naphthalocyanines, metal phthalocyanines, metal naphthalocyanines, porphyrins such as tetraphenylporphyrin and tetraazaporphyrin, metal porphyrins, derivatives thereof, and the like can also be used. Dyes used for dye lasers can also be used in the present invention. Moreover, in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, two or more kinds of dyes can be used in combination. In this case, it is possible to select the dye to be used in combination and its ratio so as to match the wavelength range and intensity distribution of the target light source.
[0029]
The dye preferably has a suitable interlocking group having an adsorption ability to the surface of the metal oxide. Examples of preferred linking groups include —COOH group, —OH group, —SO₂H group, -P (O) (OH)₂Group and -OP (O) (OH)₂And chelating groups having π conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. Among them, -COOH group, -P (O) (OH)₂Group and -OP (O) (OH)₂The group is particularly preferred. These bonding groups may form a salt with an alkali metal or the like, or may form an internal salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case where the methine chain forms a squarylium ring or a croconium ring, this part may be used as a linking group. Hereinafter, preferred sensitizing dyes used in the photosensitive layer will be specifically described.
[0030]
(A) Metal complex dye
The metal atom of the metal complex dye used in the present invention is preferably ruthenium Ru. Examples of ruthenium complex dyes include U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440. JP-A-7-249790, JP-A-10-504512, WO98 / 50393 pamphlet, JP-A-2000-26487, and the like. Specific examples of preferable metal complex dyes include those described in paragraph numbers 0051 to 0057 of JP-A No. 2001-320068. The most typical metal complex dyes include the following D-1 and D-2.
[0031]
[Chemical 1]

[0032]
(B) Methine dye
Preferred methine dyes are polymethine dyes such as cyanine dyes, merocyanine dyes and squarylium dyes. Examples of preferred polymethine dyes include JP-A-11-35836, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730, JP-A-11-214731, and European Patent 892411. And dyes described in JP-A-911841. For the synthesis method of these polymethine dyes, “FM Hemer” “Heterocyclic Compounds-Cyanine Soybeans and Relaminated Compounds” John Wiley & Sons, New York, London, 1964, by D.M. Sturmer, “Heterocyclic Compounds-Special Topics in Heterocycle” Click Chemistry (Heterocyclic Compounds-Specialtopics in Hete ocyclic Chemistry) ", John Wiley & Sons (John Wiley & Sons), Inc., New York, London, 1977, Chapter 18, Section 14, p. 82-515, “Rod's Chemistry of Carbon Compounds”, 2nd edition, Elsevier Science Public Inc., New York, Inc., New York, Inc. 1977, Volume IV, part B, Chapter 15, p. 369-422, British Patent No. 1,077,611, “Ukrainski Kimicheskii Zhurnal”, Vol. 40, No. 3, p. 253-258, “Dies and Pigments”, Vol. 21, p. 227-234, these references, etc.
[0033]
(4) Adsorption of pigment on metal oxide
When the dye is adsorbed to the metal oxide, a method of immersing a well-dried composite electrode in a dye solution or a method of applying a dye solution to the composite electrode can be used. In the case of the former method, a dipping method, a dip method, a roller method, an air knife method, etc. can be used. When the immersion method is used, the dye adsorption may be performed at room temperature, or may be performed by heating and refluxing as described in JP-A-7-249790. In the case of the latter method, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method, or the like can be used. In addition, a dye can be applied in an image form by an inkjet method or the like, and the image itself can be used as a photoelectric conversion element. When the semiconductor fine particle layer is formed on the composite electrode, the dye can be adsorbed to the formed semiconductor fine particle layer by the above method.
[0034]
Solvents used for the dye solution (adsorption solution) are preferably alcohols (methanol, ethanol, t-butyl alcohol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane Halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, - butanone, cyclohexanone), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) or a mixed solvent thereof.
[0035]
The amount of dye adsorbed is the unit area of the composite electrode (1 m²) Is preferably 0.01 to 100 mmol. Moreover, it is preferable that the adsorption amount with respect to the metal oxide of a pigment | dye is 0.01-1 mmol per 1g of metal oxides. By using such an amount of adsorbed dye, the sensitizing effect of the metal oxide can be sufficiently obtained. If the amount of dye adsorbed is too small, the sensitizing effect will be insufficient, and if the amount of dye adsorbed is too large, the dye not attached to the semiconductor will float and the sensitizing effect will be reduced. In order to increase the amount of dye adsorbed, it is preferable to heat the composite electrode before adsorption. In order to avoid water adsorbing on the surface of the composite electrode, it is preferable to quickly adsorb the dye when the temperature of the composite electrode is between 60 to 150 ° C. without returning to room temperature after the heat treatment.
[0036]
In order to reduce the interaction such as aggregation between the dyes, a colorless compound having properties as a surfactant may be added to the dye adsorption liquid and co-adsorbed to the metal oxide. Examples of such colorless compounds include steroid compounds having a carboxyl group or a sulfo group (cholic acid, deoxycholic acid, chenodeoxycholic acid, taurodeoxycholic acid, etc.), sulfonates as described below, and the like. .
[0037]
[Chemical 2]

[0038]
It is preferable to remove the unadsorbed dye by washing immediately after the adsorption step. Cleaning is preferably performed in a wet cleaning tank using an organic solvent such as acetonitrile or an alcohol solvent.
[0039]
After adsorbing the dye, a composite electrode using amines, quaternary ammonium salts, ureido compounds having at least one ureido group, silyl compounds having at least one silyl group, alkali metal salts, alkaline earth metal salts, etc. The surface may be treated. Examples of preferable amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Examples of preferable quaternary ammonium salts include tetrabutylammonium iodide and tetrahexylammonium iodide. These may be used by dissolving in an organic solvent, or may be used as they are in the case of a liquid.
[0040]
(B) Charge transport layer
The charge transport layer contains a charge transport material having a function of replenishing electrons to the oxidant of the dye. The charge transport material used in the present invention may be (i) a charge transport material related to ions, or (ii) a charge transport material related to carrier movement in a solid. (I) As a charge transport material in which ions are involved, a molten salt electrolyte composition containing a redox counter ion, a solution (electrolytic solution) in which redox pair ions are dissolved, and a redox couple solution into a polymer matrix gel Examples include so-called gel electrolyte compositions and solid electrolyte compositions impregnated, and (ii) charge transport materials that involve carrier movement in solids include electron transport materials and hole transport materials. A plurality of these charge transport materials may be used in combination. In the present invention, it is preferable to use a molten salt electrolyte composition or a gel electrolyte composition for the charge transport layer.
[0041]
(1) Molten salt electrolyte composition
The molten salt electrolyte composition includes a molten salt. The molten salt electrolyte composition is preferably liquid at room temperature. The molten salt as the main component is a liquid at room temperature or is an electrolyte having a low melting point, and general examples thereof include WO95 / 18456, JP-A-8-259543, “Electrochemistry”. 1997, Vol. 65, No. 11, p. Pyridinium salts, imidazolium salts, triazolium salts described in 923, and the like. The melting point of the molten salt is preferably 50 ° C. or less, and particularly preferably 25 ° C. or less. Specific examples of the molten salt are described in detail in paragraph numbers 0066 to 0082 of JP-A No. 2001-320068.
[0042]
The molten salt may be used alone or in combination of two or more. Also, LiI, NaI, KI, LiBF₄, CF₃COOLi, CF₃Alkali metal salts such as COONa, LiSCN, and NaSCN can also be used in combination. The addition amount of the alkali metal salt is preferably 2% by mass or less, more preferably 1% by mass or less, based on the entire composition. Moreover, it is preferable that 50 mol% or more of the anions contained in the molten salt electrolyte composition is iodide ions.
[0043]
Usually, the molten salt electrolyte composition contains iodine. The content of iodine is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass with respect to the entire molten salt electrolyte composition.
[0044]
The molten salt electrolyte composition preferably has low volatility and preferably does not contain a solvent. Even when a solvent is added, the amount of the solvent added is preferably 30% by mass or less with respect to the entire molten salt electrolyte composition. The molten salt electrolyte composition may be used after gelation as described below.
[0045]
(2) Electrolyte
The electrolytic solution is preferably composed of an electrolyte, a solvent, and an additive. Examples of electrolytes used in the electrolyte include I₂And iodide (LiI, NaI, KI, CsI, CaI₂A combination of metal iodides such as tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, etc.₂And bromide (LiBr, NaBr, KBr, CsBr, CaBr₂A combination of metal bromides such as tetraalkylammonium bromide, pyridinium bromide, etc., metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ion, sodium polysulfide, alkyl Examples thereof include sulfur compounds such as thiol-alkyl disulfides, viologen dyes, hydroquinone-quinones, and the like. Above all, I₂An electrolyte in which LiI or a quaternary ammonium compound iodine salt such as pyridinium iodide or imidazolium iodide is combined is preferable. The electrolyte may be used as a mixture.
[0046]
The electrolyte concentration in the electrolytic solution is preferably 0.1 to 10 M, and more preferably 0.2 to 4M. Moreover, the preferable addition density | concentration of an iodine in the case of adding an iodine to electrolyte solution is 0.01-0.5M.
[0047]
The solvent used in the electrolytic solution is preferably a compound that has low viscosity and improved ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ion conductivity. Examples of such solvents include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether , Chain ethers such as polyethylene glycol dialkyl ether and polypropylene glycol dialkyl ether, alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether and polypropylene glycol monoalkyl ether, ethylene Glycol, propylene glycol, polyethylene glycol, polypropylene Glycol, polyhydric alcohols such as glycerin, acetonitrile, glutarodinitrile, methoxy acetonitrile, propionitrile, nitrile compounds such as benzonitrile, dimethyl sulfoxide, aprotic polar substances such as sulfolane, water and the like. These solvents can also be used as a mixture.
[0048]
Also, “Journal of the American Ceramic Society”, 1997, Vol. 80, No. 12, p. It is preferable to add a basic compound such as tert-butylpyridine, 2-picoline, or 2,6-lutidine as described in 3157-3171 to the aforementioned molten salt electrolyte composition or electrolytic solution. A preferable concentration range when adding the basic compound to the electrolytic solution is 0.05 to 2M. When added to the molten salt electrolyte composition, the basic compound preferably has an ionic group. The mass ratio of the basic compound to the entire molten salt electrolyte composition is preferably 1 to 40% by mass, more preferably 5 to 30% by mass.
[0049]
(3) Gel electrolyte composition
In the present invention, the molten salt electrolyte composition or the electrolytic solution is gelated (solidified) by a method such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. You can also. In the case of gelation by adding a polymer, it is described in “Polymer Electrolite Reviews-1 and 2” (J.R. MacCallum and C.A. Vincent co-edit, ELSEVILER APPLIED SCIENCE). Although a compound can be used, especially polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by adding an oil gelling agent, “Industrial Science Magazine (Journal of the Chemical Society of Japan, Industrial Chemistry Sections)”, 1943, Vol. 46, p. 779, “Journal of the American Chemical Society”, 1989, Vol. 111, p. 5542, “Journal of the Chemical Society, Chemical Communications,” 1993, p. 390, “Angewandte Chemie International Edition in England”, 1996, Vol. 35, p. 1949, “Chemistry Letters”, 1996, p. 885, and "Journal of the Chemical Society, Journal of the Chemical Society", 1997, p. Although the compound described in 545 can be used, it is preferable to use a compound having an amide structure. An example of gelling the electrolytic solution is described in JP-A No. 11-185863, and an example of gelling the molten salt electrolyte is also described in JP-A No. 2000-58140, which can also be applied to the present invention.
[0050]
Moreover, when making it gelatinize by the crosslinking reaction of a polymer, it is desirable to use together the polymer and crosslinking agent containing the reactive group which can be bridge | crosslinked. In this case, preferred crosslinkable reactive groups are amino groups and nitrogen-containing heterocyclic rings (pyridine ring, imidazole ring, thiazole ring, oxazole ring, triazole ring, morpholine ring, piperidine ring, piperazine ring, etc.), and preferred bridges. The agent is a bifunctional or higher functional reagent capable of electrophilic reaction with nitrogen atom (halogenated alkyls, halogenated aralkyls, sulfonic acid esters, acid anhydrides, acid chlorides, isocyanate compounds, α, β-inactive Saturated sulfonyl compounds, α, β-unsaturated carbonyl compounds, α, β-unsaturated nitrile compounds, etc.). The cross-linking techniques described in JP 2000-17076 A and 2000-86724 can also be applied.
[0051]
(4) Hole transport material
In the present invention, instead of an ion conductive electrolyte such as a molten salt, an organic solid hole transport material, an inorganic solid hole transport material, or a material in which both are combined can be used.
[0052]
(A) Organic hole transport material
Examples of organic hole transport materials that can be preferably used in the present invention include those described by J. Hagen et al., “Synthetic Metal”, 1997, Vol. 89, p. 215-220, “Nature”, 1998, Vol. 395, No. 8 Oct. , P583-585, pamphlet of International Publication No. 97/10617, JP-A-59-194393, JP-A-5-234681, US Pat. No. 4,923,774, JP-A-4-308688. U.S. Pat. No. 4,764,625, JP-A-3-2699084, 4-129271, 4-175395, 4-264189, 4-290851, No. 4-364153, No. 5-25473, No. 5-239455, No. 5-320634, No. 6-1972, No. 7-138562, No. 7-252474, No. 11 Aromatic amines described in JP-A Nos. 1441473, etc., JP-A Nos. 11-149821, 11-148067, and 11-17. Etc. triphenylene derivatives described in 489 JP like. Also, “Advanced Materials”, 1997, Vol. 9, No. 7, p. 557, “Angewandte Chemie International Edition in England”, 1995, Vol. 34, No. 3, p. 303-307, “Journal of the American Chemical Society”, 1998, Vol. 120, No. 4, p. Oligothiophene compounds described in 664-672 and the like; Murakoshi, et al. , “Chemistry Letters”, 1997, p. Polypyrrole described in 471, described in NALWA, “Handbook of Organic Conductors and Polymers”, Volumes 1, 2, 3, and 4, WILEY Conductives such as derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof, polythiophene and derivatives thereof, polyaniline and derivatives thereof, polytoluidine and derivatives thereof Can also be preferably used.
[0053]
“Nature”, 1998, Vol. 395, No. 8 Oct. , P. 583-585, compounds containing cation radicals such as tris (4-bromophenyl) aminium hexachloroantimonate may be added to the hole transport material to control the dopant level. . In addition, in order to perform potential control (space charge layer compensation) of the oxide semiconductor surface, Li [(CF₃SO₂)₂N] may be added.
[0054]
(B) Inorganic hole transport material
A p-type inorganic compound semiconductor can be used as the inorganic hole transport material, and the band gap is preferably 2 eV or more, more preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye adsorption electrode in order to reduce the holes of the dye. Although the preferable range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 to 5.5 eV, more preferably 4.7 to 5.3 eV. A preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, and examples thereof include CuI, CuSCN, and CuInSe.₂, Cu (In, Ga) Se₂, CuGaSe₂, Cu2O, CuS, CuGaS₂, CuInS₂, CuAlSe₂Etc. Among these, CuI and CuSCN are preferable, and CuI is most preferable. Examples of other p-type inorganic compound semiconductors include GaP, NiO, CoO, FeO, Bi₂O₃, MoO₂, Cr₂O₃Etc.
[0055]
(5) Formation of charge transport layer
The charge transport layer can be formed by one of two methods. One is a method in which a counter electrode is first bonded onto the photosensitive layer, and a liquid charge transport layer is sandwiched between the gaps. The other is a method in which a charge transport layer is directly provided on the photosensitive layer, and the counter electrode is subsequently provided.
[0056]
In the case of the former method, when the charge transport layer is sandwiched, a normal pressure process using capillary action due to immersion or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used.
[0057]
In the latter method, when a wet charge transport layer is used, a counter electrode is usually applied in an undried state to prevent liquid leakage at the edge. Moreover, when using a gel electrolyte composition, you may solidify by methods, such as superposition | polymerization, after apply | coating this with a wet process. Solidification may be performed before or after applying the counter electrode. In the case of forming a charge transport layer made of an electrolytic solution, a wet organic hole transport material, a gel electrolyte composition, etc., the same method as the method for forming the semiconductor fine particle layer described above can be used.
[0058]
When a solid electrolyte composition or a solid hole transport material is used, a charge transport layer can be formed by a dry film forming process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided. The organic hole transport material can be introduced into the electrode by a vacuum deposition method, a casting method, a coating method, a spin coating method, a dipping method, an electrolytic polymerization method, a photoelectrolytic polymerization method, or the like. The inorganic solid compound can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, an electrolytic deposition method, an electroless plating method, or the like.
[0059]
(C) Counter electrode
The counter electrode may have a single layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. In the present invention, since the dye-sensitized photoelectric conversion element emits light from the counter electrode side, a highly transparent metal oxide (indium-tin composite oxide, fluorine-doped tin oxide, etc.) is used for the counter electrode conductive layer. A small amount of metal (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, etc. may be used in combination. The substrate used for the counter electrode is preferably a glass substrate or a plastic substrate, and can be used by applying or vapor-depositing the above-mentioned conductive agent. The thickness of the counter electrode conductive layer is limited by the light transmittance. The light transmittance is preferably 30% or more, and more preferably 50% or more. The surface resistance of the counter electrode conductive layer is preferably as low as possible, preferably 50Ω / □ or less, more preferably 20Ω / □ or less.
[0060]
The counter electrode may be installed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive agent on the charge transport layer, or by attaching the conductive layer side of the substrate having the conductive layer. A metal lead may be used for the purpose of reducing the resistance of the counter electrode. The metal lead is preferably made of a metal such as platinum, gold, nickel, titanium, aluminum, copper, or silver, and particularly preferably made of aluminum or silver. It is preferable that a metal lead is disposed on the transparent substrate by vapor deposition, sputtering, or the like, and a transparent counter electrode conductive layer made of fluorine-doped tin oxide, ITO film or the like is disposed thereon. It is also preferable that a metal lead is provided on the transparent counter electrode conductive layer after the transparent counter electrode conductive layer is provided on the transparent substrate. The decrease in the amount of incident light due to the installation of the metal lead is preferably within 10%, more preferably 1 to 5%.
[0061]
(D) Specific example of internal structure of photoelectric conversion element
As described above, the internal structure of the photoelectric conversion element can take various forms depending on the purpose. When the internal structure of the photoelectric conversion element is roughly divided into two, there are a structure in which light can be incident from both sides and a structure in which light can be incident only from one side. Examples of a preferable internal structure of the photoelectric conversion element are shown in FIGS. 1 and 2 to 4 described above. In the structure shown in FIG. 2, the charge transport layer 30 and the transparent counter electrode conductive layer 40a are provided on the conductive layer 10 and the photosensitive layer 20, and the transparent substrate 50a in which the metal lead 11 is partially provided thereon is provided on the metal lead 11 side. It is arranged with the inside. In the structure shown in FIG. 3, the photosensitive layer 20, the charge transport layer 30, and the transparent counter electrode conductive layer 40a are provided on both surfaces of the conductive layer 10, and the transparent substrate 50a is disposed thereon. In the structure shown in FIG. 4, a solid charge transport layer 30 is provided on the conductive layer 10 and the photosensitive layer 20, and a part of the counter electrode conductive layer 40 or the metal lead 11 is provided thereon.
[0062]
[3] Photocell
The photovoltaic cell of the present invention is one in which the photoelectric conversion element of the present invention is caused to work with an external load. Among photocells, the case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and the case where the main purpose is power generation by sunlight is called a solar cell.
[0063]
The side surface of the photovoltaic cell is preferably sealed with a polymer, an adhesive or the like in order to prevent deterioration of the constituents and volatilization of the contents. The external circuit itself connected to the conductive support and the counter electrode via a lead may be a known one.
[0064]
Even when the photoelectric conversion element of the present invention is applied to a solar cell, the structure inside the cell is basically the same as the structure of the photoelectric conversion element described above. Moreover, the dye-sensitized solar cell using the photoelectric conversion element of the present invention can basically have the same module structure as a conventional solar cell module. The solar cell module generally has a structure in which a cell is formed on a support substrate such as metal or ceramic, and the cell is covered with a filling resin or protective glass, and light is taken in from the opposite side of the support substrate. It is also possible to use a transparent material such as tempered glass for the support substrate, configure a cell thereon, and take in light from the transparent support substrate side. Specifically, module structures called super straight type, substrate type, potting type, and substrate integrated module structures used in amorphous silicon solar cells, etc. are known, and dye sensitization using the photoelectric conversion element of the present invention is known. As for the type solar cell, the module structure can be appropriately selected according to the purpose of use, the place of use and the environment. Specifically, it is preferable to adopt the structure and aspect described in Japanese Patent Application No. 11-8457, Japanese Patent Application Laid-Open No. 2000-268892, and the like.
[0065]
【Example】
Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
[0066]
Example 1
(1) TiO₂Preparation of fine particle coated electrode (Comparative electrode A)
TiO in a stainless steel container coated with Teflon (registered trademark) on the inside₂Put 15 g of fine particles (Nippon Aerosil Co., Ltd., P-25), 45 g of water, 1 g of Triton X-100 (manufactured by Aldrich), and 30 g of zirconia beads having a diameter of 0.5 mm (manufactured by Nikkato Co., Ltd.) The mixture was dispersed at 1500 rpm for 2 hours using a sand grinder mill (manufactured by IMEX Co., Ltd.). Filtration of zirconia beads from the dispersion and TiO₂A fine particle coating solution was obtained.
[0067]
Transparent conductive glass coated with tin oxide doped with fluorine (Nippon Sheet Glass Co., Ltd., surface resistance of about 10 Ω / cm²Using a doctor blade on the conductive surface side with a length of 100 mm, a width of 19 mm, and a thickness of 1.1 mm, the above TiO₂A fine particle coating solution was applied. After drying at 25 ° C. for 30 minutes, it was baked at 450 ° C. for 30 minutes using an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.), and TiO₂A fine particle-coated electrode (Comparative electrode A) was obtained. From the mass change before and after coating and firing, the TiO of the comparative electrode A₂The amount of coating was determined to be 9 g / m²Met.
[0068]
(2) Production of titanium-titanium oxide composite electrodes E-1 and E-2
Titanium-aluminum alloy (length 20 mm, width 10 mm, thickness 5 mm)(Co., Ltd., manufactured by High Purity Chemical Research Laboratory, titanium content 70 mass% and aluminum content 30 mass%) was immersed in 7.0 mmol sodium hydroxide aqueous solution at 80 ° C. for 20 hours, and then washed with neutral water. Then, the ratio of titanium to aluminum was measured by X-ray surface analysis (XPS). This operation was repeated several times, and when the ratio of aluminum to titanium became 5% by mass or less, this operation was finished to obtain a porous metal titanium electrode. The upper end of the obtained titanium electrode in the longitudinal direction was connected to the + terminal of the source measure unit 238 type (manufactured by Keithley), and the bottom electrode was immersed in 2M dilute sulfuric acid in a quartz cell up to 14 mm. A platinum wire immersed in the same cell was connected to the negative terminal of the source measure unit and electrolytically oxidized at a voltage of 5 V to obtain a composite electrode E-1. In addition, the same upper end of the same titanium-aluminum alloy in the longitudinal direction as above was connected to the + terminal of the source measure unit 238 type (manufactured by Keithley), and the bottom of 14 mm was placed in a quartz cell at 7.0 mol / L. The composite electrode E-2 was immersed in an aqueous solution of sodium hydroxide, and the platinum wire immersed in the same cell was connected to the negative terminal of the source measure unit and electrolytically oxidized while removing aluminum at a voltage of 35V. Obtained. When X-ray diffraction (XRD) of these composite electrodes was measured, both of them were anatase TiO in addition to titanium metal.₂Was detected.
[0069]
(3) TiO₂Evaluation of mechanical strength of membrane
The comparative electrode A was cut into a size of 10 mm × 19 mm, Mylar tape (manufactured by Nitto Denko Co., Ltd.) was applied to the coated surface side, and the surface was rubbed well with the belly of the finger and pressed. Next, when this tape was peeled off, a considerable amount of TiO₂Was peeled off and adhered to the adhesive surface of the tape. On the other hand, when a similar experiment was performed on the composite electrodes E-1 and E-2, TiO 2 was applied to the adhesive surface of the tape.₂Did not adhere at all. Therefore, the composite electrodes E-1 and E-2 are TiO.₂TiO 2 than electrode coated and fired₂It can be seen that the mechanical strength of the layer is high.
[0070]
Example 2
(1) Preparation of comparative titanium-titanium oxide composite electrode B
Connect the upper end in the longitudinal direction of a 20 mm long, 10 mm wide, 0.25 mm thick titanium plate (manufactured by Aldrich) to the + terminal of the source measure unit type 238 (manufactured by Keithley), and 14 mm from below Were immersed in 2M dilute sulfuric acid in a quartz cell. A platinum wire immersed in the same cell was connected to the negative terminal of the source measure unit and electrolytically oxidized at a voltage of 5V. Initially, after an electrolysis current exceeding 10 mA flowed, it rapidly decayed and became 50 μA or less after 5 minutes. Thereafter, current was further applied for 3 hours at an applied voltage of 5V. The obtained electrode was baked at 450 ° C. for 30 minutes to obtain a comparative electrode B.
[0071]
(2) Dye adsorption
Immediately after firing, the electrodes (comparative electrode B, composite electrodes E-1 and E-2) were immersed in a solution (adsorbed liquid) containing 0.3 mmol / liter of the following dye (D-1) for 16 hours. The adsorption temperature was 25 ° C., and a solvent in which ethanol, t-butanol, and acetonitrile were mixed at 1: 1: 2 (volume ratio) was used as the solvent for the adsorbed liquid. The comparative electrode B dyed and the composite electrodes E-1 and E-2 were sequentially washed with ethanol and acetonitrile to obtain dye-sensitized electrodes DB, DE-1 and DE-2, respectively.
[0072]
[Chemical 3]

[0073]
(3) Production of counter electrode
Transparent conductive glass coated with tin oxide doped with fluorine (Nippon Sheet Glass Co., Ltd., surface resistance of about 10 Ω / cm²) Was cut into a length of 20 mm and a width of 12 mm, and platinum was deposited using a JEE-4C type vacuum deposition apparatus (manufactured by JEOL Ltd.) to such an extent that the transparency of the conductive glass was not lost. The transmittance of this platinum-deposited conductive glass was 70% with respect to 550 nm light.
[0074]
(4) Production of photoelectric conversion element
As shown in FIG. 5, the produced dye-sensitized electrode 101, polyethylene spacer film (thickness: 25 μm) 103, and platinum-deposited conductive glass 102 are stacked, and an electrolyte solution (1,3-dimethylimidazo iodide) is placed in the gap between the two glasses. Acetonitrile solution of 0.65 mol / liter of lithium, 0.05 mol / liter of iodine, and 0.1 mol / liter of t-butylpyridine) was added. Excessive overflowing electrolyte solution was wiped off with paper, and the two electrodes were fixed with clips to obtain photoelectric conversion elements CB, CE-1 and CE-2 shown in Table 1.
[0075]
[Table 1]

[0076]
(5) Measurement of photoelectric conversion efficiency
Simulated sunlight was generated by passing light from a 500 W xenon lamp (manufactured by Ushio Corporation) through a spectral filter (manufactured by Oriel, AM1.5D). The light intensity is 87 mW / cm on the vertical surface.²Met. A silver paste was applied to the end of the platinum-deposited conductive glass of the photoelectric conversion element to form a positive electrode, and the positive electrode and the dye-sensitized electrode (negative electrode) were connected to a current-voltage measuring device (Keutley SMU238 type). The generated photocurrent was measured while vertically irradiating simulated sunlight. Table 2 shows the photocurrent values of the photoelectric conversion elements CE-1 and CE-2 and the comparative photoelectric conversion element CB of the present invention.
[0077]
(6) Measurement of dye adsorption amount
The dye that was eluted by immersing the active region of the dye-sensitized electrode (10 mm × 10 mm, the region used for photocurrent measurement) in a 0.1N aqueous sodium hydroxide solution was quantified by spectroscopy. At this time, other regions including the back surface were masked by applying a Mylar tape so that they would not be eluted even if the dye was adsorbed.
[0078]
[Table 2]

[0079]
From the results of Table 2, the photoelectric conversion element CE-1 of the present invention using the titanium-titanium oxide composite electrode E-1 obtained by electrolytically oxidizing a titanium electrode obtained by dissolving and removing aluminum from the titanium-aluminum alloy is simply It can be seen that the photocurrent is larger than that of the photoelectric conversion element CB using the comparative electrode B obtained by electrolytic oxidation of the titanium plate, and is an excellent photoelectric conversion element. The dye-sensitized electrodes DE-1 and DE-2 using the titanium-titanium oxide composite electrodes E-1 and E-2 have a larger amount of dye adsorption than the comparative dye-sensitized electrode DB. This is considered to be due to the high surface roughness, and can be presumed to be a cause of a large photocurrent.
[0080]
Example 3
Composite electrodes E-3 to E-8 were prepared in the same manner as E-2 of Example 1 except that the alloy type and the content of metal A in the alloy (A content: mass%) were changed as shown in Table 3. Produced. When these electrodes were examined for mechanical strength by the same method as in Example 1, TiO 2 was obtained.₂It was found that the electrode had high mechanical strength. Next, photoelectric conversion elements (CE-3 to CE-8) were produced in the same manner as in Example 2, and the photocurrent and the dye adsorption amount were measured. Table 3 shows the measurement results of CE-3 to CE-8 and CE-2 as a control.
[0081]
[Table 3]

[0082]
Table 3 shows that titanium is preferable as the metal A used for the composite electrode, and aluminum is preferable as the metal B to be removed contained in the alloy.
[0083]
【The invention's effect】
As described above in detail, according to the method of the present invention, mechanical strength is improved by removing other than one kind of metal from an alloy containing at least two kinds of metals and oxidizing the remaining one kind of metal. A metal-metal oxide composite electrode having a high surface roughness is obtained. By using this metal-metal oxide composite electrode, a dye-sensitized photoelectric conversion element having a high mechanical strength of the oxide semiconductor film and a large photocurrent can be obtained.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing the structure of a photoelectric conversion device according to a preferred embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing the structure of a photoelectric conversion device according to another preferred embodiment of the present invention.
FIG. 3 is a partial cross-sectional view showing the structure of a photoelectric conversion element according to still another preferred embodiment of the present invention.
FIG. 4 is a partial cross-sectional view showing the structure of a photoelectric conversion device according to still another preferred embodiment of the present invention.
5 is an exploded view showing a configuration of a photoelectric conversion element manufactured in Example 2. FIG.
[Explanation of symbols]
10 ... conductive layer
11 ... Metal lead
20 ... Photosensitive layer
21 ... Semiconductor fine particles
22 ... Dye
23 ... Charge transport material
30 ... Charge transport layer
40a ... Transparent counter electrode conductive layer
50a ... Transparent substrate
101 ... Dye-sensitized electrode
102 ... Platinum-deposited conductive glass
103 ... Polyethylene spacer film

Claims (9)

What is claimed is: 1. A metal-metal oxide composite electrode comprising: an alloy containing at least two kinds of metals, wherein one kind of metal is left and other metals are substantially removed and the remaining kind of metal is oxidized. Manufacturing method. 2. The method for producing a metal-metal oxide composite electrode according to claim 1, wherein the one kind of metal left in the alloy is titanium, niobium or tungsten. Manufacturing method. The method for producing a metal-metal oxide composite electrode according to claim 1 or 2, wherein the alloy is selected from the group consisting of metal A selected from the group consisting of titanium, niobium and tungsten, and a group consisting of aluminum, zinc, tin and indium. A method for producing a metal-metal oxide composite electrode, comprising: a selected metal B, wherein a metal other than the metal A is substantially removed, and then the metal A is oxidized. The method for producing a metal-metal oxide composite electrode according to any one of claims 1 to 3, wherein the alloy comprises only two kinds of metals. 5. The method for producing a metal-metal oxide composite electrode according to claim 1, wherein a metal containing aluminum is removed from the alloy. 6. The method for producing a metal-metal oxide composite electrode according to claim 1, wherein a metal other than the one kind of metal contained in the alloy is removed by immersing in a basic solution. A method for producing a metal-metal oxide composite electrode. 7. The method for producing a metal-metal oxide composite electrode according to claim 1, wherein the one kind of metal remaining in the alloy is oxidized by electrolytic oxidation. A method for producing a composite electrode. A dye-sensitized photoelectric conversion element comprising a metal-metal oxide composite electrode produced by the method according to claim 1, a dye, and a charge transport material. A photovoltaic cell using the dye-sensitized photoelectric conversion element according to claim 8.

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