JP2004103420A - Manufacturing method of metal-metal oxide composite electrode, photoelectric conversion element, and photocell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a metal-metal oxide composite electrode suitable for a photoelectric conversion element, and a dye-sensitized photoelectric conversion element with an oxide layer having high mechanical strength and heavy photoelectric current. <P>SOLUTION: In this manufacturing method of the metal-metal oxide composite electrode, electrolytic oxidation is applied to a metal selected from a group composed of titanium, niobium and tungsten, or to an alloy containing the metal selected from the group composed of titanium, niobium, and tungsten while irradiating it with ultraviolet rays. The metal-metal oxide composite electrode obtained by this method is used for the photoelectric transfer element. <P>COPYRIGHT: (C)2004,JPO

Description

【００２９】
（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年刊）、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）」、第１８章、第１４節、第４ｐ．８２〜５１５、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年刊）、「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）」、２ｎｄ．　Ｅｄ．、ｖｏｌ．ＩＶ、ｐａｒｔ　Ｂ、第１５章、ｐ．３６９−４２２、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刊）、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。
【００３０】
（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、或い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。
【００３１】
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。
【００３２】
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、加熱処理後に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。
【００３３】
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。
【００３４】
【化２】

【００３５】
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。
【００３６】
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。
【００３７】
（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。
【００３８】
（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，　第６５巻，　１１号，　ｐ．９２３　（１９９７年）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。
【００３９】
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。
【００４０】
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。
【００４１】
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。
【００４２】
（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。
【００４３】
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。
【００４４】
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。
【００４５】
また、Ｊ．　Ａｍ．　Ｃｅｒａｍ．　Ｓｏｃ．，　８０　（１２）　３１５７−３１７１　（１９９７）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。
【００４６】
（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、”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（Ｊ．　Ｃｈｅｍ．Ｓｏｃ．　Ｊａｐａｎ，　Ｉｎｄ．　Ｃｈｅｍ．　Ｓｅｃ．），　４６，　７７９　（１９４３）、Ｊ．　Ａｍ．　Ｃｈｅｍ．　Ｓｏｃ．，　１１１，　５５４２　（１９８９）、Ｊ．　Ｃｈｅｍ．　Ｓｏｃ．，　Ｃｈｅｍ．　Ｃｏｍｍｕｎ．，　１９９３，　３９０、Ａｎｇｅｗ．　Ｃｈｅｍ．　Ｉｎｔ．　Ｅｄ．　Ｅｎｇｌ．，　３５，　１９４９　（１９９６）、Ｃｈｅｍ．　Ｌｅｔｔ．，　１９９６，　８８５、及びＪ．　Ｃｈｅｍ．　Ｓｏｃ．，　Ｃｈｅｍ．　Ｃｏｍｍｕｎ．，　１９９７，　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。
【００４７】
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。
【００４８】
（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。
【００４９】
（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、Ｊ．　Ｈａｇｅｎ，　ｅｔ　ａｌ．，　Ｓｙｎｔｈｅｔｉｃ　Ｍｅｔａｌ，　８９，　２１５−２２０　（１９９７）、Ｎａｔｕｒｅ，　Ｖｏｌ．３９５，　８　Ｏｃｔ．，　ｐ５８３−５８５　（１９９８）、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、Ａｄｖ．　Ｍａｔｅｒ．，　９，　Ｎｏ．７，　ｐ５５７　（１９９７）、Ａｎｇｅｗ．　Ｃｈｅｍ．　Ｉｎｔ．　Ｅｄ．　Ｅｎｇｌ．，　３４，　Ｎｏ．３，　ｐ．３０３−３０７　（１９９５）、ＪＡＣＳ，　Ｖｏｌ．１２０，　Ｎｏ．４，　ｐ．６６４−６７２　（１９９８）等に記載のオリゴチオフェン化合物、Ｋ．　Ｍｕｒａｋｏｓｈｉ，　ｅｔ　ａｌ．，　Ｃｈｅｍ．　Ｌｅｔｔ．　ｐ．４７１　（１９９７）に記載のポリピロール、”Ｈａｎｄｂｏｏｋ　ｏｆ　Ｏｒｇａｎｉｃ　Ｃｏｎｄｕｃｔｉｖｅ　Ｍｏｌｅｃｕｌｅｓ　ａｎｄ　Ｐｏｌｙｍｅｒｓ，　Ｖｏｌ．　１，２，３，４”（ＮＡＬＷＡ著、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。
【００５０】
Ｎａｔｕｒｅ，　Ｖｏｌ．３９５，　８　Ｏｃｔ．，　ｐ．５８３−５８５　（１９９８）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。
【００５１】
（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。
【００５２】
（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。
【００５３】
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。
【００５４】
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。
【００５５】
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。
【００５６】
（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。
【００５７】
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。
【００５８】
（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。
【００５９】
［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。
【００６０】
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。
【００６１】
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。
【００６２】
【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。
【００６３】
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ベッセルに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時間分散した。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。
【００６４】
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１０Ω／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、焼成前後の重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。
【００６５】
（２）　チタン−酸化チタン複合電極Ｅ−１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の＋端子に接続し、下から１４　ｍｍまでを石英セルの中に入った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、石英セルの外側からＬＡ−３００ＵＶ紫外線照射器（林時計工業（株）製）で直径１２　ｍｍの円形に紫外線を照射しながら、５Ｖの電圧で電解酸化した。はじめ、１０　ｍＡを越える電流が流れたが、直ちに減衰し、５分後には２　ｍＡとなって安定した。この条件でさらに３時間電解酸化を続けた。得られた電極を４５０℃で３０分間焼成し、複合電極Ｅ−１を得た。この電極のＸ線回折（ＸＲＤ）を測定したところ、金属チタンの他にアナターゼ型ＴｉＯ_２が検出された。
【００６６】
（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。
【００６７】
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った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。
【００６８】
（２）　色素の吸着
焼成直後の電極（比較用電極Ｂ及び複合電極Ｅ−１）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）で混合した混合溶媒を用いた。色素の染着した比較用電極Ｂ及び複合電極Ｅ−１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及びＤＥ−１を得た。
【００６９】
【化３】

【００７０】
（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、日本電子製ＪＥＥ−４Ｃ型真空蒸着装置を用いて、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。
【００７１】
（４）　光電変換素子の作製
上述のようにして作製した色素増感電極、ポリエチレンスペーサーフィルム（厚さ：２５μｍ）、白金蒸着導電ガラスを図５のように重ね、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及びＣＥ−１を得た。
【００７２】
【表１】

【００７３】
（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８７ｍＷ／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及び比較用光電変換素子ＣＢの光電流の値を示す。
【００７４】
（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。
【００７５】
【表２】

【００７６】
表２の結果から、紫外線を照射しながら電解酸化した本発明の方法によるチタン−酸化チタン複合電極Ｅ−１を用いた光電変換素子は、紫外線を照射しないで電解酸化した比較電極Ｂを用いた光電変換素子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を用いた色素増感電極ＤＥ−１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、これが、光電流の大きい原因であると推定できる。
【００７７】
実施例３
次に電解電圧を表３に示すように変えた以外実施例１と同様の方法で複合電極Ｅ−２〜５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−２〜ＣＥ−５）を作製し、光電流及び色素吸着量を測定した。ＣＥ−２〜ＣＥ−５及び対照としてＣＥ−１の測定結果を表３に示す。
【００７８】
【表３】

【００７９】
本発明の方法による複合電極は光電解酸化の際の電解電圧が高いほど、電極への色素吸着量が多くなり、光電変換素子にしたときの光電流の値が大きいことがわかる。
【００８０】
【発明の効果】
以上詳述したように、本発明では、チタン、ニオブ又はタングステンの金属又は合金に紫外線を照射しながら電解酸化することにより、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り、実施例２で作製した光電変換素子の構成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. Photoelectric conversion elements include those using metals, those using semiconductors, those using organic pigments and dyes, and combinations of these, and various systems have been put into practical use.
[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, patent documents). 1-9 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 a dye having high mechanical strength and high photocurrent. It is to provide a 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-mentioned object, the present inventors have developed a metal-metal oxide composite electrode having a high mechanical strength and a high surface roughness according to the following (1) to (6), and a dye increase with a high photocurrent. The inventors have found that a photoelectric conversion element and a photovoltaic cell can be obtained, and have arrived at the present invention.
(1) A metal characterized by electrolytic oxidation while irradiating ultraviolet light onto a metal selected from the group consisting of titanium, niobium and tungsten, or an alloy containing a metal selected from the group consisting of titanium, niobium and tungsten A method for producing a metal oxide composite electrode.
(2) The production method according to (1), wherein a titanium-titanium oxide composite electrode is produced by electrolytic oxidation while irradiating titanium or an alloy containing titanium with ultraviolet rays.
(3) The production method according to (1) or (2), wherein the electrolytic voltage is 20 V or more.
(4) The production method according to any one of (1) to (3), wherein a strong acid is used as the electrolyte.
(5) A dye-sensitized photoelectric conversion element comprising a metal-metal oxide composite electrode produced by the method according to any one of (1) to (4), a dye, and a charge transport material.
(6) A photovoltaic cell using the dye-sensitized photoelectric conversion element of (5).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The main point of the present invention is that a metal-metal oxide composite having a large surface roughness is obtained by irradiating ultraviolet rays when an oxide film is formed on titanium, niobium or tungsten through an electric current in an electrolyte solution using titanium, niobium or tungsten as an anode. It is to obtain an electrode. The method will be described in detail below.
[0009]
[1] Method for producing metal-metal oxide composite electrode
The metals used for the metal-metal oxide composite electrode (hereinafter abbreviated as “composite electrode”) are titanium, niobium and tungsten. These may be a single metal or an alloy. An alloy is used when the composite electrode to be produced is made porous. Elements other than titanium, niobium, and tungsten contained in the alloy are elements that are mostly eluted under electrolytic oxidation conditions. The proportion of titanium, niobium and tungsten in the alloy in the entire alloy is preferably 30% by mass or more, and more preferably 50% by mass or more. When the composite electrode is used for a dye-sensitized photoelectric conversion element, titanium is particularly preferable as a metal, and an alloy containing titanium is particularly preferable as an alloy. In this case, the shape of the metal or alloy is preferably a plate shape.
[0010]
The ultraviolet rays used in the method of the present invention are light having a wavelength of 400 nm or less, and are usually 100 to 400 nm, preferably 180 to 380 nm. In addition to ultraviolet light, visible light, infrared light, or the like may be mixed. UV intensity is usually 0.1-500 mW / cm²1-100 mW / cm²Is preferred. As the ultraviolet ray generator, a high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp or the like is usually used. Further, an ultraviolet laser may be used. Ultraviolet rays may be applied to only one surface of a metal or alloy, or may be applied to both surfaces.
[0011]
Next, conditions for electrolytic oxidation will be described. First, a metal electrode to be electrolytically oxidized is connected to a power source as an anode. The electrolysis voltage is usually 0.1 to 200 V, preferably 5 to 100 V, and 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. The higher the electrolysis voltage, the higher the surface roughness of the composite electrode produced, so that the photocurrent can be increased. 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 (gold, platinum, etc.) having low reactivity, carbon or the like.
[0012]
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.). Of these, acids, particularly strong acids (sulfuric acid, nitric acid, perchloric acid, methanesulfonic acid, trifluoromethanesulfonic acid, etc.) are preferred.
[0013]
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 ultraviolet irradiation and the voltage application may be performed simultaneously, or the voltage application time may be longer than the ultraviolet irradiation time. For example, electrolytic oxidation may be started before ultraviolet irradiation, or electrolytic oxidation may be continued after ultraviolet irradiation. Moreover, you may intermittently irradiate an ultraviolet-ray, performing electrolytic oxidation continuously. However, it is necessary that there is at least a time during which ultraviolet irradiation and voltage application are performed simultaneously.
[0014]
[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.
[0015]
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.
[0016]
(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.
[0017]
(1) Semiconductor
A dispersion or colloidal solution containing semiconductor fine particles may be applied on the composite electrode as long as the film strength is not lowered. In this case, the coated semiconductor fine particles also carry a dye and act as a photoreceptor. The thickness of the semiconductor fine particle film to be applied 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.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
A pressure treatment may be performed instead of the heat treatment. The method of pressure treatment is described by Lindstrom et al., Journal of Photochemistry and Photobiology, Vol. 145, p. 107-112 (2001, Elsevier). When the pressure treatment is performed, a binder such as a polymer is not used in the semiconductor fine particle coating solution.
[0022]
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.
[0023]
(2) Processing
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 selected from the group consisting of scandium, yttrium, lanthanoid, zirconium, hafnium, niobium, tantalum, gallium, indium, germanium, and tin, a halide, and the like 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.
[0024]
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.
[0025]
(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.
[0026]
The dye preferably has an appropriate interlocking group having an adsorption ability with respect to the surface of the semiconductor fine particles. 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.
[0027]
(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.
[0028]
[Chemical 1]

[0029]
(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”, Cyanine Compounds and Relatives, “Heterocyclic Compounds-Special Topics in Hetero” by John Wiley & Sons, New York, London (1964), D.M. Cyclic Chemistry (Heterocyclic Compounds-Special Topics in Hetero yclic Chemistry) ", Chapter 18, Section 14, second 4p. 82-515, John Wiley & Sons, New York, London (published in 1977), "Rods' Chemistry of Carbon Compounds", 2nd. Ed. , Vol. IV, part B, Chapter 15, p. 369-422, Elsevier Science Public Publishing Inc., New York (published in 1977), UK Patent No. 1,077,611, Ukrainski Kimichskii, Vol. 40 3, p. 253-258, “Dies and Pigments”, Vol. 21, p. 227-234, these references, etc.
[0030]
(4) Adsorption of pigment on metal oxide
When the dye is adsorbed on 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 adsorption of the dye 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.
[0031]
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.
[0032]
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 ° C. and 150 ° C. without returning to room temperature after the heat treatment.
[0033]
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. .
[0034]
[Chemical 2]

[0035]
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.
[0036]
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.
[0037]
(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.
[0038]
(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 a main component is a liquid at room temperature or is an electrolyte having a low melting point, and general examples thereof include International Publication No. 95/18456, JP-A-8-259543, Electrochemistry, No. 65, No. 11, p. Pyridinium salts, imidazolium salts, triazolium salts described in 923 (1997) 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.
[0039]
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.
[0040]
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.
[0041]
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.
[0042]
(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.
[0043]
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.
[0044]
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.
[0045]
In addition, J.H. Am. Ceram. Soc. , 80 (12) 3157-3171 (1997), basic compounds such as tert-butylpyridine, 2-picoline, and 2,6-lutidine are added to the aforementioned molten salt electrolyte composition and electrolyte. It is preferable to add. 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.
[0046]
(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, compounds described in “Polymer Electrolyte Reviews-1 and 2” (J.R. MacCallum and C.A. Vincent co-edit, ELSEVIER APPLIED SCIENCE) can be used. In particular, polyacrylonitrile and polyvinylidene fluoride can be preferably used. In the case of gelation by adding an oil gelling agent, an industrial scientific journal (J. Chem. Soc. Japan, Ind. Chem. Sec.), 46, 779 (1943), J. Chem. Am. Chem. Soc. 111, 5542 (1989); Chem. Soc. , Chem. Commun. , 1993, 390, Angew. Chem. Int. Ed. Engl. , 35, 1949 (1996), Chem. Lett. , 1996, 885, and J.A. Chem. Soc. , Chem. Commun. , 1997, 545 can be used, but 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.
[0047]
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.
[0048]
(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.
[0049]
(A) Organic hole transport material
Examples of organic hole transport materials that can be preferably used in the present invention include those described in J. Org. Hagen, et al. , Synthetic Metal, 89, 215-220 (1997), Nature, Vol. 395, 8 Oct. , P583-585 (1998), pamphlet of International Publication No. 97/10617, JP 59-194393 A, JP 5-234861 A, US Pat. No. 4,923,774, JP No. 308688, U.S. Pat. No. 4,764,625, JP-A-3-269084, JP-A-4-129271, JP-A-4-175395, JP-A-4-264189, JP-A-4290851 Gazette, 4-364153, 5-25473, 5-239455, 5-320634, 6-1972, 7-138562, 7-252474 Aromatic amines described in JP-A-11-144773, JP-A-11-149821, JP-A-11-148067 Etc. triphenylene derivatives described in the same 11-176489 JP, and the like. Also, Adv. Mater. , 9, No. 7, p557 (1997), Angew. Chem. Int. Ed. Engl. , 34, No. 3, p. 303-307 (1995), JACS, Vol. 120, No. 4, p. 664-672 (1998), etc. Murakoshi, et al. , Chem. Lett. P. 471 (1997), polyacetylene and derivatives thereof described in “Handbook of Organic Conductives and Polymers, Vol. 1, 2, 3, 4” (by NALWA, published by WILEY), and poly (p-phenylene). Conductive polymers such as 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. .
[0050]
Nature, Vol. 395, 8 Oct. , P. 583-585 (1998), a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate is added to the hole transport material to control the dopant level. May be. In addition, in order to perform potential control (space charge layer compensation) of the oxide semiconductor surface, Li [(CF₃SO₂)₂N] may be added.
[0051]
(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.
[0052]
(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.
[0053]
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.
[0054]
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.
[0055]
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.
[0056]
(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.
[0057]
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%.
[0058]
(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.
[0059]
[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.
[0060]
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.
[0061]
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.
[0062]
【Example】
Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
[0063]
Example 1
(1) TiO₂Preparation of fine particle coated electrode (Comparative electrode A)
TiO on a stainless steel vessel 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.) Dispersion was performed 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.
[0064]
Transparent conductive glass coated with tin oxide doped with fluorine (manufactured by Nippon Sheet Glass Co., Ltd., surface resistance of about 10Ω / cm)²Using 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 weight change before and after coating and firing, the TiO of the comparative electrode A₂The amount of coating was determined to be 9 g / m²Met.
[0065]
(2) Production of titanium-titanium oxide composite electrode E-1
Connect the upper end in the longitudinal direction of a 20 mm long, 10 mm wide, 0.25 mm thick titanium plate (Aldrich) to the + terminal of the source measure unit, and the bottom 14 mm in the quartz cell It was immersed in 2M dilute sulfuric acid. Connect a platinum wire immersed in the same cell to the negative terminal of the source measure unit, and irradiate a 12 mm diameter circle with UV light from the outside of the quartz cell with an LA-300 UV UV irradiator (manufactured by Hayashi Watch Industry Co., Ltd.). However, electrolytic oxidation was performed at a voltage of 5V. Initially, a current exceeding 10 mA flowed, but immediately decayed and became stable at 2 mA after 5 minutes. Under these conditions, the electrolytic oxidation was further continued for 3 hours. The obtained electrode was baked at 450 ° C. for 30 minutes to obtain a composite electrode E-1. When X-ray diffraction (XRD) of this electrode was measured, anatase TiO in addition to titanium metal₂Was detected.
[0066]
(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 the same experiment was conducted on the composite electrode E-1, TiO was applied to the adhesive surface of the tape.₂Did not adhere at all. Therefore, the composite electrode E-1 is TiO₂TiO 2 than electrode coated and fired₂It can be seen that the mechanical strength of the layer is high.
[0067]
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 the bottom. 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.
[0068]
(2) Dye adsorption
Immediately after firing, the electrodes (comparative electrode B and composite electrode E-1) were immersed in a solution (adsorbed solution) containing 0.3 mmol / L of the following dye (D-1) for 16 hours. The adsorption temperature was 25 ° C., and a mixed solvent in which ethanol, t-butanol, and acetonitrile were mixed at 1: 1: 2 (volume ratio) was used as the solvent of the adsorbing liquid. The comparative electrode B and the composite electrode E-1 stained with the dye were sequentially washed with ethanol and acetonitrile to obtain dye-sensitized electrodes DB and DE-1, respectively.
[0069]
[Chemical 3]

[0070]
(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 vapor-deposited to such an extent that the transparency of the conductive glass was not lost using a JEE-4C vacuum vapor deposition apparatus manufactured by JEOL. The transmittance of this platinum-deposited conductive glass was 70% with respect to 550 nm light.
[0071]
(4) Production of photoelectric conversion element
The dye-sensitized electrode, the polyethylene spacer film (thickness: 25 μm), and the platinum-deposited conductive glass prepared as described above are stacked as shown in FIG. 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 and CE-1 shown in Table 1.
[0072]
[Table 1]

[0073]
(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 plane.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 values of photocurrents of the photoelectric conversion element CE-1 and the comparative photoelectric conversion element CB of the present invention.
[0074]
(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.
[0075]
[Table 2]

[0076]
From the result of Table 2, the photoelectric conversion element using the titanium-titanium oxide composite electrode E-1 by the method of the present invention that was electrolytically oxidized while irradiating ultraviolet rays used the comparative electrode B that was electrolytically oxidized without irradiating ultraviolet rays. It can be seen that the photocurrent is larger than that of the photoelectric conversion element, and the photoelectric conversion element is excellent. Further, the dye-sensitized electrode DE-1 using the titanium-titanium oxide composite electrode E-1 has a larger amount of dye adsorption than the comparative dye-sensitized electrode DB. This is considered to be because the surface roughness is high, and it can be estimated that this is a cause of a large photocurrent.
[0077]
Example 3
Next, composite electrodes E-2 to 5 were produced in the same manner as in Example 1 except that the electrolytic voltage was changed as shown in Table 3. When these electrodes were examined for mechanical strength in the same manner as in Example 1, TiO 2 was obtained.₂It was found that the electrode had high mechanical strength. Next, photoelectric conversion elements (CE-2 to CE-5) were produced by the same method as in Example 2, and the photocurrent and the dye adsorption amount were measured. Table 3 shows the measurement results of CE-2 to CE-5 and CE-1 as a control.
[0078]
[Table 3]

[0079]
It can be seen that the composite electrode obtained by the method of the present invention has a higher amount of dye adsorbed to the electrode as the electrolysis voltage at the time of photoelectrolytic oxidation is higher, and the value of the photocurrent when the photoelectric conversion element is made larger.
[0080]
【The invention's effect】
As described above in detail, in the present invention, the oxide semiconductor film having high mechanical strength and high photocurrent is obtained by electrolytic oxidation while irradiating titanium, niobium, or tungsten metal or alloy with ultraviolet rays. A photoelectric conversion element is obtained.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a structure of a photoelectric conversion element according to a preferred embodiment of the present invention, and a partial cross-sectional view showing a configuration of a photoelectric conversion element manufactured in Example 2. FIG.
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 (3)

A metal-metal oxide characterized by electrolytically oxidizing a metal selected from the group consisting of titanium, niobium and tungsten or an alloy containing a metal selected from the group consisting of titanium, niobium and tungsten while irradiating with ultraviolet rays. 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 2.

Images