JP4638973B2 - Photoelectric conversion element and photovoltaic cell - Google Patents

Description

【００３７】
（ただし、R_aは水素原子または置換基を表し、置換基としてはたとえば、ハロゲン原子、炭素原子数１〜12の置換または無置換のアルキル基、炭素原子数７〜12の置換または無置換のアラルキル基、あるいは炭素原子数６〜12の置換または無置換のアリール基、カルボン酸基、リン酸基（これらの酸基は塩を形成していてもよい）が挙げられ、アルキル基およびアラルキル基のアルキル部分は直鎖状でも分岐状でもよく、またアリール基およびアラルキル基のアリール部分は単環でも多環（縮合環、環集合）でもよい。）により表される化合物から選ばれた有機配位子を表す。B-a、B-bおよびB-cは同一でも異なっていてもよく、いずれか１つまたは２つであってもよい。
【００３８】
錯体色素の好ましい具体例を以下に示すが、本発明はこれらに限定されるものではない。
【００３９】
【化２】

【００４０】
【化３】

【００４１】
【化４】

【００４２】
（b）メチン色素
本発明で好ましく用いられるメチン色素は、特開平１１−３５８３６号、特開平１１−１５８３９５号、特開平１１−１６３３７８号、特開平１１−２１４７３０号、特開平１１−２１４７３１号、欧州特許８９２４１１号および同９１１８４１号の各明細書に記載の色素である。これらの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「ヘテロ素サイクリック・コンパウンズースペシャル・トピックス・イン・複素 サイクリック・ケミストリー(Heterocyclic Compounds-Special topics in heterocyclic chemistry)」、第１８章、第１４節、第４８２から５１５頁、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,１９７７刊、第１５章、第３６９から４２２頁、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.)社刊、ニューヨーク、英国特許第1,077,611号、Ukrainskii Khimicheskii Zhurnal, 第４０巻、第３号、２５３〜２５８頁、Dyes and Pigments, 第２１巻、２２７〜２３４頁およびこれらの文献に引用された文献になどに記載されている。
【００４３】
（４）半導体への色素の吸着
半導体微粒子に色素を吸着させるには、色素の溶液中に良く乾燥した半導体微粒子層を有する導電性支持体を浸漬するか、色素の溶液を半導体微粒子層に塗布する方法を用いることができる。前者の場合、浸漬法、ディップ法、ローラ法、エアーナイフ法等が使用可能である。なお浸漬法の場合、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。また後者の塗布方法としては、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、スプレー法等があり、印刷方法としては、凸版、オフセット、グラビア、スクリーン印刷等がある。溶媒は、色素の溶解性に応じて適宜選択できる。例えば、アルコール類（メタノール、エタノール、t-ブタノール、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）やこれらの混合溶媒が挙げられる。
【００４４】
色素の溶液の粘度についても、半導体微粒子層の形成時と同様に、高粘度液（例えば0.01〜500Poise）ではエクストルージョン法の他に各種印刷法が適当であり、また低粘度液（例えば0.1Poise以下）ではスライドホッパー法、ワイヤーバー法またはスピン法が適当であり、いずれも均一な膜にすることが可能である。
【００４５】
このように色素の塗布液の粘度、塗布量、導電性支持体、塗布速度等に応じて、適宜色素の吸着方法を選択すればよい。塗布後の色素吸着に要する時間は、量産化を考えた場合、なるべく短い方がよい。
【００４６】
未吸着の色素の存在は素子性能の外乱になるため、吸着後速やかに洗浄により除去するのが好ましい。湿式洗浄槽を使い、アセトニトリル等の極性溶剤、アルコール系溶剤のような有機溶媒で洗浄を行うのが好ましい。また色素の吸着量を増大させるため、吸着前に加熱処理を行うのが好ましい。加熱処理後、半導体微粒子表面に水が吸着するのを避けるため、常温に戻さずに40〜80℃の間で素早く色素を吸着させるのが好ましい。
【００４７】
色素の全使用量は、導電性支持体の単位表面積（１m²）当たり0.01〜100mmolが好ましい。また色素の半導体微粒子に対する吸着量は、半導体微粒子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、半導体における増感効果が十分に得られる。これに対し、色素が少なすぎると増感効果が不十分となり、また色素が多すぎると、半導体に付着していない色素が浮遊し、増感効果を低減させる原因となる。
【００４８】
会合のような色素同士の相互作用を低減する目的で、無色の化合物を半導体微粒子に共吸着させてもよい。共吸着させる疎水性化合物としてはカルボキシル基を有するステロイド化合物（例えばケノデオキシコール酸）等が挙げられる。また紫外線吸収剤を併用することもできる。
【００４９】
余分な色素の除去を促進する目的で、色素を吸着した後にアミン類を用いて半導体微粒子の表面を処理してもよい。好ましいアミン類としてはピリジン、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。これらが液体の場合はそのまま用いてもよいし、有機溶媒に溶解して用いてもよい。
【００５０】
（C）電荷移動層
電荷移動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層である。本発明で用いることのできる代表的な電荷輸送材料の例としては、▲１▼イオン輸送材料として、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、酸化還元対イオンを含有する溶融塩電解質、さらには固体電解質が挙げられる。また、イオンがかかわる電荷輸送材料のほかに、▲２▼固体中のキャリアー移動が電気伝導にかかわる材料として、電子輸送材料や正孔（ホール）輸送材料、を用いることもできる。これらは、併用することができる。
【００５１】
（１）溶融塩電解質
溶融塩電解質は、光電変換効率と耐久性の両立という観点から好ましい。本発明の光電変換素子に溶融塩電解質を用いる場合は、例えばWO95/18456号、特開平8-259543号、電気化学，第65巻，11号，923頁（1997年）等に記載されているピリジニウム塩、イミダゾリウム塩、トリアゾリウム塩等の既知のヨウ素塩を用いることができる。
【００５２】
好ましく用いることのできる溶融塩としては、下記一般式（Y-a）、（Y-b）及び（Y-c）のいずれかにより表されるものが挙げられる。
【００５３】
【化５】

【００５４】
一般式（Y-a）中、Q_y1は窒素原子と共に５又は６員環の芳香族カチオンを形成しうる原子団を表す。Q_y1は炭素原子、水素原子、窒素原子、酸素原子及び硫黄原子からなる群から選ばれる１種以上の原子により構成されるのが好ましい。
【００５５】
Q_y1により形成される５員環は、オキサゾール環、チアゾール環、イミダゾール環、ピラゾール環、イソオキサゾール環、チアジアゾール環、オキサジアゾール環又はトリアゾール環であるのが好ましく、オキサゾール環、チアゾール環又はイミダゾール環であるのがより好ましく、オキサゾール環又はイミダゾール環であるのが特に好ましい。Q_y1により形成される６員環は、ピリジン環、ピリミジン環、ピリダジン環、ピラジン環又はトリアジン環であるのが好ましく、ピリジン環であるのがより好ましい。
【００５６】
一般式（Y-b）中、A_y1は窒素原子又はリン原子を表す。
【００５７】
一般式（Y-a）、（Y-b）及び（Y-c）中のR_y1〜R_y6はそれぞれ独立に置換又は無置換のアルキル基（好ましくは炭素原子数１〜24、直鎖状であっても分岐状であっても、また環式であってもよく、例えばメチル基、エチル基、プロピル基、イソプロピル基、ペンチル基、ヘキシル基、オクチル基、2-エチルヘキシル基、t-オクチル基、デシル基、ドデシル基、テトラデシル基、2-ヘキシルデシル基、オクタデシル基、シクロヘキシル基、シクロペンチル基等）、或いは置換又は無置換のアルケニル基（好ましくは炭素原子数２〜24、直鎖状であっても分岐状であってもよく、例えばビニル基、アリル基等）を表し、より好ましくは炭素原子数２〜18のアルキル基又は炭素原子数２〜18のアルケニル基であり、特に好ましくは炭素原子数２〜６のアルキル基である。
【００５８】
また、一般式（Y-b）中のR_y1〜R_y4のうち２つ以上が互いに連結してA_y1を含む非芳香族環を形成してもよく、一般式（Y-c）中のR_y1〜R_y6のうち２つ以上が互いに連結して環構造を形成してもよい。
【００５９】
一般式（Y-a）、（Y-b）及び（Y-c）中のQ_y1及びR_y1〜R_y6は置換基を有していてもよく、好ましい置換基の例としては、ハロゲン原子（F、Cl、Br、I等）、シアノ基、アルコキシ基（メトキシ基、エトキシ基等）、アリーロキシ基（フェノキシ基等）、アルキルチオ基（メチルチオ基、エチルチオ基等）、アルコキシカルボニル基（エトキシカルボニル基等）、炭酸エステル基（エトキシカルボニルオキシ基等）、アシル基（アセチル基、プロピオニル基、ベンゾイル基等）、スルホニル基（メタンスルホニル基、ベンゼンスルホニル基等）、アシルオキシ基（アセトキシ基、ベンゾイルオキシ基等）、スルホニルオキシ基（メタンスルホニルオキシ基、トルエンスルホニルオキシ基等）、ホスホニル基（ジエチルホスホニル基等）、アミド基（アセチルアミノ基、ベンゾイルアミノ基等）、カルバモイル基（N,N-ジメチルカルバモイル基等）、アルキル基（メチル基、エチル基、プロピル基、イソプロピル基、シクロプロピル基、ブチル基、2-カルボキシエチル基、ベンジル基等）、アリール基（フェニル基、トルイル基等）、複素環基（ピリジル基、イミダゾリル基、フラニル基等）、アルケニル基（ビニル基、1-プロペニル基等）等が挙げられる。
【００６０】
一般式（Y-a）、（Y-b）又は（Y-c）により表される化合物は、Q_y1又はR_y1〜R_y6を介して多量体を形成してもよい。
【００６１】
これらの溶融塩は、単独で使用しても、２種以上混合して使用してもよく、また、ヨウ素アニオンを他のアニオンで置き換えた溶融塩と併用することもできる。ヨウ素アニオンと置き換えるアニオンとしては、ハロゲン化物イオン（Cl^-、Br^-等）、NCS^-、BF₄ ^-、PF₆ ^-、ClO₄ ^-、(CF₃SO₂)₂N^-、(CF₃CF₂SO₂)₂N^-、CF₃SO₃ ^-、CF₃COO^-、Ph₄B^-、(CF₃SO₂)₃C^-等が好ましい例として挙げられ、(CF₃SO₂)₂N^-又はBF₄ ^-であるのがより好ましい。また、ＬｉＩなど他のヨウ素塩を添加することもできる。
【００６２】
上記溶融塩電解質には、溶媒を用いない方が好ましい。後述する溶媒を添加しても構わないが、溶融塩の含有量は電解質組成物全体に対して50質量％以上であるのが好ましい。また、塩のうち、50質量％以上がヨウ素塩であることが好ましく、70％以上であることがさらに好ましい。
【００６３】
電解質組成物にヨウ素を添加するのが好ましく、この場合、ヨウ素の含有量は、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。
【００６４】
（２）電解液
電荷移動層に電解液を使用する場合、電解液は電解質、溶媒、および添加物から構成されることが好ましい。本発明の電解質はＩ₂とヨウ化物の組み合わせ（ヨウ化物としてはＬｉＩ、ＮａＩ、ＫＩ、ＣｓＩ、ＣａＩ₂ などの金属ヨウ化物、あるいは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など４級アンモニウム化合物のヨウ素塩など）、Ｂｒ₂と臭化物の組み合わせ（臭化物としてはＬｉＢｒ、ＮａＢｒ、ＫＢｒ、ＣｓＢｒ、ＣａＢｒ₂ などの金属臭化物、あるいは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など４級アンモニウム化合物の臭素塩など）のほか、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などの金属錯体、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などのイオウ化合物、ビオロゲン色素、ヒドロキノン−キノンなどを用いることができる。この中でもI₂とＬｉＩやピリジニウムヨーダイド、イミダゾリウムヨーダイドなど４級アンモニウム化合物のヨウ素塩を組み合わせた電解質が本発明では好ましい。上述した電解質は混合して用いてもよい。
【００６５】
好ましい電解質濃度は０．１M以上１５M以下であり、さらに好ましくは0.2M以上１０M以下である。また、電解質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０．０１M以上０．５M以下である。
【００６６】
本発明で電解質に使用する溶媒は、粘度が低くイオン易動度を向上したり、も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などのカーボネート化合物、３−メチル−２−オキサゾリジノンなどの複素環化合物、ジオキサン、ジエチルエーテルなどのエーテル化合物、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などの鎖状エーテル類、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などのアルコール類、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、グリセリンなど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、ベンゾニトリルなどのニトリル化合物、ジメチルスルフォキシド、スルフォランなど非プロトン極性物質、水などを用いることができる。
【００６７】
また、本発明では、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添加することもできる。塩基性化合物を添加する場合の好ましい濃度範囲は0.05M以上2M以下である。
【００６８】
（３）ゲル電解質
本発明では、電解質はポリマー添加、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させる場合は、¨Polymer Electrolyte Revi ews-1および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、ポリフッ化ビニリデンを好ましく使用することができる。オイルゲル化剤添加によりゲル化させる場合はJ. Chem Soc. Japan, Ind. Chem.Sec., 46,779(1943), J. Am. Chem. Soc., 111,5542(1989), J. Chem. Soc., Chem. Com mun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35,1949(1996), Chem. Lett., 1996, 885, J. Chm. 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、好ましい化合物は分子構造中にアミド構造を有する化合物である。
【００６９】
また、ポリマーの架橋反応により電解質をゲル化させる場合、架橋可能な反応性基を含有するポリマーおよ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、含窒素複素環（例えば、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、ピペラジン環など）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（例えば、ハロゲン化アルキル、ハロゲン化アラルキル、スルホン酸エステル、酸無水物、酸クロライド、イソシアネートなど）である。
【００７０】
（４）正孔輸送材料
本発明では、電解質の替わりに有機または無機あるいはこの両者を組み合わせた正孔輸送材料を使用することができる。
【００７１】
（a）有機正孔輸送材料
本発明に適用可能な有機正孔輸送材料としては、N，N'-ジフエニル-N、N'-ビス（４-メトキシフェニル）-（1，1'-ビフェニル）-4，4'-ジアミン(J.Hagen et al.,Synthetic Metal 89(1997)215-220）、2,2',7,7'-テトラキス（N,N-ジ-p-メトキシフェニルアミン）9,9'-スピロビフルオレン（Nature,Vol.395, 8 Oct. 1998,p583-585およびWO97/10617）、1,1-ビス｛4-（ジ-ｐ-トリルアミノ）フェニル｝シクロヘキサンの3級芳香族アミンユニットを連結した芳香族ジアミン化合物（特開昭59−194393号公報）、4，4，‐ビス［（N-1-ナフチル）‐N-フェニルアミノ］ビフェニルで代表される２個以上の3級アミンを含み２個以上の縮合芳香族環が窒素原子に置換した芳香族アミン（特開平5−234681号公報）、トリフェニルベンゼンの誘導体でスターバースト構造を有する芳香族トリアミン（米国特許第4，923，774号、特開平4−308688号公報）、N，N'-ジフエニル-N、N'-ビス（3-メチルフェニル）-（1，1'-ビフェニル）-4，4'-ジアミン等の芳香族ジアミン（米国特許第4，764，625号）、α，α，α'，α'-テトラメチル-α，α'-ビス（4-ジ-p-トリルアミノフェニル）-p-キシレン（特開平3−269084号公報）、p-フェニレンジアミン誘導体、分子全体として立体的に非対称なトリフェニルアミン誘導体（特開平4−129271号公報）、ピレニル基に芳香族ジアミノ基が複数個置換した化合物（特開平4−175395号公報）、エチレン基で3級芳香族アミンユニツトを連結した芳香族ジアミン（特開平4−264189号公報）、スチリル構造を有する芳香族ジアミン（特開平4−290851号公報）、ベンジルフェニル化合物（特開平4−364153号公報）、フルオレン基で3級アミンを連結したもの（特開平5−25473号公報）、トリアミン化合物（特開平5−239455号公報）、ピスジピリジルアミノビフェニル（特開平5−320634号公報）、N，N，N−トリフェニルアミン誘導体（特開平6−1972号公報）、フェノキザジン構造を有する芳香族ジアミン（特開平7-138562号）、ジアミノフエニルフエナントリジン誘導体（特開平7-252474号）等に示される芳香族アミン類を好ましく用いることができる。
また、α-オクチルチオフェンおよびα,ω-ジヘキシル-α-オクチルチオフェン（Adv. Mater. 1997,9,N0.7,p557)、ヘキサドデシルドデシチオフェン(Angew. Chem. Int. Ed. Engl. 1995, 34, No.3,p303-307)、2,8-ジヘキシルアンスラ[2,3-b:6,7-b']ジチオフェン(JACS,Vol120, N0.4,1998,p664-672)等のオリゴチオフェン化合物、ポリピロール（K. Murakoshi et al.,;Chem. Lett. 1997, p471）、¨ Handbook of Organic Conductive Molecules and Polymers Vol.1,2,3,4¨ （NALWA著、WILEY出版）に記載されているポリアセチレンおよびその誘導体、ポリ(p-フェニレン) およびその誘導体、ポリ( p-フェニレンビニレン) およびその誘導体、ポリチエニレンビニレンおよびその誘導体、ポリチオフェンおよびその誘導体、ポリアニリンおよびその誘導体、ポリトルイジンおよびその誘導体等の導電性高分子を好ましく使用することができる。
正孔（ホール）輸送材料にはNature,Vol.395, 8 Oct. 1998,p583-585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添加したり、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[(CF₃SO₂)₂N]のような塩を添加しても構わない。
【００７２】
（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る。ｐ型無機化合物半導体のバンドギャップは色素吸収を妨げないため大きいことが好ましい。ｐ型無機化合物半導体のバンドギャップは、2eV以上であることが好ましく、さらに2.5eV以上であることが好ましい。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ホール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。本発明の光電変換素子に使用する色素によって電荷移動層に使用する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ってくるが、一般に4.5eV以上5.5eV以下であることが好ましく、さらに4.7eV以上5.3eV以下であることが好ましい。本発明に好ましく使用されるｐ型無機化合物半導体は一価の銅を含む化合物半導体であり、一価の銅を含む化合物半導体としてはCuI, CuSCN, CuInSe₂, Cu(In,Ga)Se₂, CuGaSe₂, Cu₂O, CuS, CuGaS₂, CuInS₂, CuAlSe₂などが挙げられる。この中でもCuIおよび CuSCNが好ましく、CuIが最も好ましい。銅を含む化合物以外に用いることができるｐ型無機化合物半導体としては、GaP、NiO、CoO、FeO、Bi₂O₃、MoO₂、Cr₂O₃等を挙げることができる。また、本発明のｐ型無機化合物半導体を含有する電荷移動層の好ましいホール移動度は10^-4cm²/V・sec以上10⁴cm²/V・sec以下であり、さらに好ましくは10^-3cm²/V・sec以上10³cm²/V・sec以下である。さらに、本発明の電荷移動層の好ましい導電率は10^-8S/cm以上10²S/cm以下であり、さらに好ましくは10^-6S/cm以上10S/cm以下である。
【００７３】
（５）電荷移動層の形成
電荷移動層の形成方法に関しては２通りの方法が考えられる。１つは増感色素を担持させた半導体微粒子含有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移動層を挟み込む方法である。もう１つは半導体微粒子含有層上に直接電荷移動層を付与する方法で、対極はその後付与することになる。
【００７４】
前者の場合の電荷移動層の挟み込み方法として、浸漬等による毛管現象を利用する常圧プロセスと常圧より低い圧力にして気相を液相に置換する真空プロセスが利用できる。
【００７５】
後者の場合、湿式の電荷移動層においては未乾燥のまま対極を付与し、エッジ部の液漏洩防止措置も施すことになる。またゲル電解質の場合には湿式で塗布して重合等の方法により固体化する方法もあり、その場合には乾燥、固定化した後に対極を付与することもできる。電解液のほか湿式有機正孔輸送材料やゲル電解質を付与する方法としては、半導体微粒子含有層や色素の付与と同様に、浸漬法、ローラ法、ディップ法、エアーナイフ法、エクストルージョン法、スライドホッパー法、ワーヤーバー法、スピン法、スプレー法、キャスト法、各種印刷法等が考えられる。
【００７６】
固体電解質や固体の正孔（ホール）輸送材料の場合には真空蒸着法やＣＶＤ法等のドライ成膜処理で電荷移動層を形成し、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、光電解重合法等の手法により電極内部に導入することができる。無機固体化合物の場合も、キャスト法，塗布法，スピンコート法、浸漬法、電解メッキ法等の手法により電極内部に導入することができる。
【００７７】
量産化を考える場合、固体化できない電解液や湿式の正孔輸送材料の場合には、塗設後速やかにエッジ部分を封止することで対応も可能であるが、固体化可能な正孔輸送材料の場合は湿式付与により正孔輸送層を膜形成した後、例えば光重合や熱ラジカル重合等の方法により固体化することがより好ましい。このように膜付与方式は液物性や工程条件により適宜選択すればよい。
【００７８】
感光層（半導体層）と対極との短絡が生じないように、電荷移動層は、ある程度の厚さを有するが、厚すぎると光電変換効率上好ましくない。電荷移動層の厚さは、好ましくは０．０５μｍ以上１００μｍ以下であり、より好ましくは０．１μｍ以上５０μｍ以下である。なお、電荷輸送材料は、半導体微粒子から形成された多孔質の感光層中にも存在することになる。
【００７９】
なお、電荷移動層中の水分としては１０，０００ｐｐｍ以下が好ましく、さらに好ましくは２，０００ｐｐｍ以下であり、特に好ましくは１００ｐｐｍ以下である。
【００８０】
（D）対極
発明の素子で用いる対極は、色素増感半導体層を担持する光電極が光アノードとしてはたらくとき、カソードとして電荷輸送層への電子移動をおこなう。本発明では、色素増感した半導体微粒子層を金属支持体上に設置するので、感光層に光が到達するためには、対極が実質的に透明である必要がある。光透過率は、４００〜９００ｎｍの波長域で50％以上であるのが好ましく、70％以上が特に好ましい。
本発明おいては、対極は透明導電性材料からなる対極透明導電層の単層構造でもよいし、対極透明導電層と透明支持体基板から構成されていてもよい。対極透明導電層に用いる導電性の材料としては金属(例えば、白金、金、銀、銅、アルミ二ウム、ロジウム、インジウム、マグネシウムなど)、導電性金属酸化物(インジウム−錫複合酸化物、酸化錫にフッ素をドープしたもの、インジウム−亜鉛複合酸化物等)があげられる。金属の中では、白金、金、銀、銅、アルミニウムまたはマグネシウムを対極透明導電層として好ましく使用することができるが、電池内での安定性から白金が特に好ましい。金属を用いる場合は、光透過性を確保するため、十分に薄層にするか、格子またはメッシュ状など光の透過する状態にする必要かある。光透過性からは、金属酸化物の透明導電層が好ましい。対極の好ましい透明支持基板の例は、ガラスまたは透明プラスチックであり、これに上記の導電剤を塗布、蒸着またはスパッタリングして用いることができる。金属酸化物の透明導電層上に導電性向上の目的から、金属薄膜層や金属超微粒子を付設するのも好ましい。対極導電層の厚さは特に制限されないが、３ｎｍ以上10μｍ以下が好ましい。対極層の表面抵抗は低い程よい。好ましい表面抵抗としては80Ω／□以下であり、さらに好ましくは２０Ω／□以下であり、もっとも好ましくは５Ω／□以下である。
【００８１】
対極は、電荷移動層上に直接導電剤を塗布、メッキまたは蒸着(ＰＶＤ、ＣＶＤ)するか、導電層を有する基板の導電層側を貼り付ければよい。また、対極透明導電層の抵抗を下げる目的で金属リードを用いるのが好ましい。金属リードの材質はアルミニウム、銅、銀、金、白金、ニッケル等の金属が好ましく、特にアルミニウムおよび銀が好ましい。金属リードは透明基板に蒸着、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、またはＩＴＯ膜からなる透明導電層を設けるのが好ましい。また透明導電層を透明基板に設けた後、透明導電層上に金属リードを設置するのも好ましい。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。
【００８２】
（E）その他の層
導電性支持体および対極の一方または両方に、保護層、反射防止層等の機能性層を設けても良い。このような機能性層を多層に形成する場合、同時多層塗布法や逐次塗布法を利用できるが、生産性の観点からは同時多層塗布法が好ましい。同時多層塗布法では、生産性および塗膜の均一性を考えた場合、スライドホッパー法やエクストルージョン法が適している。これらの機能性層の形成には、その材質に応じて蒸着法や貼り付け法等を用いることができる。
【００８３】
（F）光電変換素子の内部構造の具体例
色素増感型太陽電池のセル内部の構造は、基本的には上述した光電変換素子や光電気化学電池と同じであるが、目的に合わせ様々な形態が可能である。本発明における作用電極は光学的に不透明な金属支持体を使用するため、感光層に入射する光は対極側から入射する。代表的な構成例を図２（ａ）〜（ｃ）に示す。図２（ａ）は、金属支持体５０上に酸化物半導体膜１０を介して、感光層２０を設け、さらに電荷移動層３０および対極透明導電層４０を設け、この上に透明基板６０を配置した構造である。図２（ｂ）は、金属支持体５０上に酸化物半導体膜１０を介して、感光層（色素吸着半導体層）２０を設け、さらに電荷移動層３０と対極透明導電層４０を設け、一部に金属リード４１を設けた透明基板６０を金属リード４１を内側にして配置した構造である。図２（ｃ）は、金属支持体５０上に酸化物半導体膜１０を介して、感光層２０を設け、さらに固体の電荷移動層３１を設け、この上の一部に金属リード４１を有する構造である。
【００８４】
〔２〕光電池
本発明の光電池は、上記光電変換素子に外部回路で仕事をさせるようにしたものである。光電池は構成物の劣化や内容物の揮散を防止するために、側面をポリマーや接着剤等で密封するのが好ましい。導電性支持体および対極にリードを介して接続される外部回路自体は公知のもので良い。本発明の光電変換素子をいわゆる太陽電池に適用する場合、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。以下、本発明の光電変換素子を用いた太陽電池のモジュール構造について説明する。
【００８５】
本発明の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あるいはアモルファスシリコン太陽電池などで用いられる基板一体型などのモジュール構造が可能である。これらのモジュール構造は使用目的や使用場所（環境）により適宜選択できる。入射光の利用効率を高めるため、対極側から見たときの感光層の面積比率を大きくした方が好ましい。
【００８６】
スーパーストレートタイプやサブストレートタイプの代表的な構造は、片側または両側が透明で反射防止処理を施された支持基板の間に、一定間隔にセルが配置され、隣り合うセル間が金属リードまたはフレキシブル配線等によって接続されており、外縁部に集電電極を配置して、発生した電力を外部に取り出す構造になっている。基板とセルの間には、セルの保護や集電効率アップのため、目的に応じ、エチレンビニルアセテート（ＥＶＡ）等様々な種類のプラスチック材料をフイルムまたは充填樹脂の形で用いることができる。また、外部からの衝撃が少ないところなど表面を硬い素材で覆う必要のない場所に使う場合には、表面保護層を透明プラスチックフイルムで構成したり、または、上記充填・封止材料を硬化させることによって保護機能を付与し、片側の支持基板を無くすことも可能である。支持基板の周囲は、内部の密封およびモジュールの剛性確保のため、金属製のフレームでサンドイッチ状に固定し、支持基板とフレームの間は封止材で密封シールする。
【００８７】
モジュールは、導電性支持体上に感光層・電荷移動層・対極等が立体的かつ一定間隔で配列されるように、選択メッキ・選択エッチング・ＣＶＤ・ＰＶＤといった半導体プロセス技術、あるいはパターン塗布または広幅で塗布した後にレーザースクライビングやプラズマＣＶＭ（Solar Energy Materials and Solar Cells, 48, p373-381等に記載）または研削等の機械的手法などの方法でパターニングすることができ、これらにより所望のモジュール構造を得ることができる。
【００８８】
【実施例】
以下に具体例をあげ、本発明をさらに詳しく説明するが、発明の主旨を超えない限り、本発明は実施例に限定されるものではない。
尚、実施例−１及び実施例−３は参考例と読み替えるものとする。
【００８９】
１．酸化物半導体薄膜を付与した金属支持体の作製
（１）導電性支持体−Ａの作製
アルミニウム(材質JIS１０５０材、厚さ0.38ｍｍ)基板表面に付着した圧延オイルをアセトンにより除去し、その表面に400℃加熱下でチタニウムテトライソプロポキシド(ＴＴＩＰ)５．６８ｇ、アセチルアセトン４．０ｇ、エタノール８０ｍｌの混合溶液をスプレー法で塗布した後、電気炉で４５０℃、３０分焼成し、導電性支持体―Ａを得た。酸化チタンの膜厚は約５０ｎｍ、結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９０】
（２）導電性支持体−Ｂの作製 (導電性支持体の連続製造)
ロール状に巻回されたアルミニウムコイルから連続的に送り出したアルミニウムウェブをアセトン浴に通して圧延オイルを除去した後、乾燥し、次いで加熱ゾーンに搬送し、４００℃に加熱した状態でスプレー法により上記混合溶液(ＴＴＩＰ5.68ｇ，アセチルアセトン4.0ｇ、エタノール８０ｍｌ混合溶液)を塗布した後、４５０℃で加熱して作成した。すなわち圧延オイル除去から４５０℃加熱処理までアルミニムウエブの搬送により連続工程で作成した。酸化物半導体薄膜の膜厚は８０ｎｍ、結晶形はＸ線回折によりアアターゼ形酸化チタンであることを確認した、
【００９１】
（３）導電性支持体−Ｃの作製
圧延オイルをアセトンにより除去したアルミニウム(材質JIS１０５０材、厚さ0.38ｍｍ)基板表面にスパッタリング法により３００ｎｍの酸化チタン薄膜を付設し、導電性支持体−Ｃを得た。酸化チタンの結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９２】
（４）導電性支持体−Ｄの作製
圧延オイルをアセトンにより除去した圧延銅板(ＪＩＳ-１２２０、厚さ０．3ｍｍ)を用いた以外は導電性支持体−Ｃの作製と同様にして銅基板上に酸化チタンを付与した導電性支持体―Ｄを得た。酸化チタンの膜厚は３００ｎｍ、結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９３】
（５）導電性支持体−Ｅの作製
チタン板(ＪＩＳ−１種、厚さ０．３ｍｍ)を用いた以外は導電性支持体−Ａの作製と同様にしてチタン基板上に酸化チタンを付与した導電性支持体―Ｅを得た。酸化チタンの膜厚は約７５ｎｍ、結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９４】
（６）金属支持体−Ｆの作製
ニッケル板(Ｎｉ合金モネルメタル60〜70Ｎｉ-Ｃｕ、厚さ０．３ｍｍ)を用いた以外は導電性支持体-Ａの作製と同様にしてニッケル基板上に酸化チタンを付与した金属支持体−Ｆを得た。酸化チタンの膜厚は約５０ｎｍ、結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９５】
（７）導電性支持体−Ｇの作製
ステンレス鋼板(ＳＵＳ３０５、厚さ０．2ｍｍ)を用いた以外は導電性支持体−Ａの作製と同様にしてステンレス鋼板上に酸化チタンを付与した導電性支持体−Ｇを得た。酸化チタンの膜厚は約７５ｎｍ、結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９６】
（８）導電性支持体−Ｈの作製
ステンレス鋼鈑(ＳＵＳ３０５，厚さ０．２ｍｍ）表面に三塩化チタンの電解酸化により酸化チタン薄膜を付与した金属支持体-Ｈを得た。酸化チタンの膜厚は約５０ｎｍ，結晶形はＸ線回折によりアナターゼ形酸化チタンであることを確認した。
【００９７】
（９）比較用導電性支持体の作製
上記Ｃ〜Ｇと同じ金属支持体で酸化物半導体膜を付与しない比較用の導電性支持体Ｉ〜Ｍを作製した。また、フッ素をドープした二酸化スズをコーティングした透明導電性ガラス（日本板硝子製ＴＣＯガラス、サイズ２５ｍｍ ×１００ｍｍ）を比較用の導電性支持体Ｎとした。
【００９８】
以上の導電性支持体について、使用した金属支持体（その表面抵抗値）と酸化物半導体膜（その膜厚）を表１にまとめた。
【００９９】

【０１００】
［実施例−１］
２．二酸化チタン粒子含有塗布液の作製
Ｃ．Ｊ．ＢａｒｂｅらのＪ．Ａｍ．Ｃｅｒａｍｉｃ Ｓｏｃ．80巻，ｐ３１５７の論文に記載の製造方法に従い、チタン原料にチタニウムテトライソプロポキシドを用い、オートクレーブ中での重合反応の温度を２３０℃に設定して二酸化チタン濃度１１重量％の二酸化チタン分散物を合成した。得られた二酸化チタン粒子の平均サイズは約１０nmであった。
この分散物に二酸化チタンに対し３０重量％のポリエチレングリコール（分子量２０，０００、和光純薬製）を添加し、混合して塗布液を得た。
【０１０１】
３．色素を吸着した二酸化チタン電極の作製
上述のようにして作製した導電性支持体−Ａ (サイズ２５ｍｍ × １００ｍｍ)の酸化物半導体付与面側に２の塗布液をにドクターブレード法で６０μmの厚みで塗布し、室温で１時間風乾した後、電気炉で４５０℃にて３０分間焼成した。二酸化チタンの塗布量は９g/m²であり、膜厚は６μmであった。
この二酸化チタン電極を取出し冷却した後、前記の色素化合物Ｒ−１で示される色素の３×１０^-4モル／リットル濃度溶液(組成：色素３７５ｍｇをエタノール２５０ｍｌに超音波溶解し、t−ブタノール２５０ｍｌとアセト二トリル５００ｍｌ混合溶媒を添加して１リットルとする。軽く攪拌した後トリオキシエチレンノニルフェノキシブチルナトリウムスルフォネートエーテル１０００ｍｇ添加し溶解する)に４０℃で１．５時間浸漬した。色素の吸着した二酸化チタン電極をアセト二トリルで洗浄し、暗所にて自然乾燥させた。
【０１０２】
４．電解質の注入
色素増感された二酸化チタン電極（サイズ２ｃｍＸ１．５ｃｍ）の電極面に溶融塩系電解質(組成 ： １-エチル３-メチルイミダゾリウムテトラフルオロボレート０．３ｇ、１-ブチル３-メチルイミダゾリウムアイオダイド０．７ｇ、ヨウ素０．０２ｇ)を５μl滴下し、減圧下で１時間５０℃にて加熱して二酸化チタン電極細孔中に電解質を浸透させた。
【０１０３】
５．光電池の作製
対極はフッ素をドープした二酸化スズをＣＶＤ法でコーテイングした導電性ガラス(日本板硝子製ＴＣＯ）の導電層表面に塩化白金酸のイソプロピルアルコール溶液を塗布し、４２０℃２０分間空気中で焼成して作製した、透明性の高い白金付ＴＣＯ対極を使用した（白金層の平均厚さは約１ｎｍ、二酸化スズ層の厚さは約600ｎｍ）。上記４で作製した二酸化チタン電極と同じ大きさの対極を白金側が向き合うように、二酸化チタン電極と重ね合わせた。その際リード取出しの寸法分だけ位置をずらせて重ねあわせた。次いで二つの基板の周辺部を熱融解型の接着剤で封止し、本発明になる光電池１を作製した。
【０１０４】
６．光電池の出力（Ｐmax(ｍW)）の測定
本発明の光電変換素子の光電変換効率は次のようにして測定した。５００Ｗのキセノンランプ（ウシオ電気）に太陽光シミュレーション用補正フィルター（Ｏｒｉｅｌ社製ＡＭ１．５）とシャープカットフイルター(Ｋｅｎｋｏ Ｌ−４２)を通すことにより紫外線を含まない模擬太陽光を発生させた。電池への入射光強度が１００ｍＷ/ｃｍ²に調整された模擬太陽光を照射した。
作製した光電池の二酸化チタン電極側金属支持体と対極側導電性ガラスにそれぞれ、ワニロクリップを接続し、模擬太陽光を照射し発生した電気を電流電圧測定装置(ケースレー製ＳＭＵ２３８型)にて測定した。 これにより求められた光電池の出力（Ｐmax(ｍW)）を表２に記載した。
【０１０５】
［実施例−２］ （導電性支持体−Ｂを用いた色素吸着二酸化チタン電極の作製）
二酸化チタン粒子含有塗布液の作製は実施例−１と同様に行った。
色素を吸着した二酸化チタン電極の作製は、二酸化チタン半導体薄膜を付与したロール状に巻回された金属支持体−Ｂを連続的に送り出し、酸化物半導体薄膜表面にカーテンコート法で二酸化チタン粒子含有塗布液を約６０μｍの厚みで塗布した後、４５０℃の加熱ゾーンで焼成して多孔質酸化チタン膜を形成させ、次いで色素吸着ゾーンで実施例−１で使用したのと同じ色素化合物Ｒ−１で示される色素の３×１０^-4モル／リットル濃度溶液に浸漬した。色素吸着した二酸化チタン電極をアセトニトリルで洗浄し暗所にて自然乾燥した。
電解液の注入は、色素増感した二酸化チタン電極を（サイズ２cm ×1.5cm）に裁断した以外実施例−１と同様にして電解液を注入し、実施例−１と同様にして光電池２を作製した。光電池の評価も実施例−１と同様に行い、その結果を表２に示した。
【０１０６】
［実施例−３］
導電性支持体−Ａを表−１に記載の導電性支持体Ｃ〜Ｈに変えた以外は実施例−１と同様にして光電池３〜８を作製し、最大出力値を求め表２に一括して記載した。
【０１０７】
［比較例］
導電性支持体−Ａを表−２に記載の比較用導電性支持体Ｉ〜Ｎに変えた以外は実施例−１と同様にして比較用光電池９〜１４を作製し、最大出力値を求め表２に記載した。
【０１０８】

【０１０９】
本発明の酸化物半導体薄膜を付与した金属支持体を用いた光電池１〜８は、 比較例の透明導電性ガラス(ＴＣＯ)を用いた光電池１４に比べて電池の出力が高いことがわかる。また、比較例の酸化物半導体薄膜を付与しない金属支持体を用いた光電池９〜１３は出力がでていない、あるいは出力が低く酸化物半導体薄膜の付与効果が大きいことがわかる。
【０１１０】
【発明の効果】
本発明では作用電極用導電性支持体としてロール状に巻回された金属支持体を用ることができ、そのため巻回された金属コイルから連続的に金属ウエブを送り出しながら、その表面に酸化物半導体薄膜、色素増感二酸化チタン層等を連続的に作製することができるので製造コストダウン効果が大きく、光電池の低価格化ができる。本発明によって、高出力、低コストでエネルギー変換効率の優れた色素増感光電変換素子および光電池が提供できる。
【図面の簡単な説明】
【図１】 本発明の光電変換素子の好ましい構造を示す部分断面図である。
【図２】 本発明の光電変換素子の好ましい構造を示す部分断面図である。
【符号の説明】
10 酸化物半導体膜
20 感光層
21 半導体微粒子
22 色素
23 電荷輸送材料
30 電荷移動層
31 固体の電荷移動層
40 透明導電層
41 金属リード
50 金属支持体
60 透明基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric conversion element using a semiconductor sensitized with a dye. Furthermore, the present invention relates to a photovoltaic cell (particularly a solar cell) using the same.
[0002]
[Prior art]
At present, photovoltaic power generation is the main technology for practical application, improvement of compound solar cells such as single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, cadmium telluride and indium copper selenide, A power generation efficiency exceeding 10% is obtained as the solar energy conversion efficiency. However, in order to disseminate these for the future, it is necessary to overcome problems such as high energy costs for material production and a large environmental load for commercialization, and long energy payback time for users. For this reason, many solar cells that use organic materials that can be easily increased in size as photosensitive materials to replace silicon have been proposed so far, but the energy conversion efficiency is as low as 1% or less,
There was a problem of poor durability.
Under such circumstances, Nature (Vol. 353, pp. 737-740, 1991) and U.S. Pat. No. 4,927,721 and the like include photoelectric conversion elements and solar cells using semiconductor fine particles sensitized with a dye and an electrolyte, As well as the materials and manufacturing techniques required for this fabrication. The proposed battery is a wet solar cell using a titanium dioxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The first advantage of this method is that an inexpensive oxide semiconductor such as titanium dioxide can be used without the need to purify it to high purity, so that it can be provided as an inexpensive photoelectric conversion element, and it is used for the second. The absorption of the dye is broad, and sunlight can be converted into electricity over a wide wavelength range of visible light.
[0003]
[Problems to be solved by the invention]
In order to put the above dye-sensitized solar cell into practical use, higher output and lower cost are required. In order to increase the output, it is necessary to reduce the internal resistance of the battery as the photocurrent increases in the photosensitive layer. In order to reduce the cost, it is necessary to reduce the manufacturing cost by continuous coating using an inexpensive conductive support. However, a conventionally used conductive support, that is, a glass substrate with a transparent conductive film, has a large area resistance of the substrate and a large internal resistance of the battery. Therefore, it is difficult to increase the output, and it is expensive and photosensitive layer (semiconductor layer). ) Is difficult to continuously apply, resulting in an increase in manufacturing cost. In addition, when an inexpensive metal is used as a support, there is a problem that corrosion due to an electrolytic solution occurs and the battery does not function. For this reason, a photoelectrode using a metal support that has a low surface resistance, can increase the output of a battery, and prevents corrosion due to an electrolytic solution, which can be manufactured at low cost and can be manufactured at low cost by continuous application of a photosensitive layer. Technology development was desired. That is, an object of the present invention is to provide a dye-sensitized photoelectric conversion element and a photovoltaic cell that can be produced at high cost with high output and excellent energy conversion efficiency.
[0004]
[Means for Solving the Problems]
  The object of the present invention has been achieved by the following matters specifying the present invention and preferred embodiments thereof.
[1]
In a method for producing a conductive support, a photosensitive layer containing a semiconductor adsorbing a dye coated on the conductive support, a charge transfer layer, and a dye-sensitized photoelectric conversion element having a counter electrode, a rolled metal A photoelectric conversion comprising a step of continuously coating an oxide semiconductor film and a photosensitive semiconductor layer using a support, wherein the conductive support comprises a metal support and an oxide semiconductor film. Device manufacturing method.
[2]
The method for producing a photoelectric conversion element according to [1], wherein the metal support contains a metal selected from aluminum, copper, titanium, nickel, iron, stainless steel, zinc, and molybdenum.
[3]
The method for producing a photoelectric conversion element according to [1] or [2], wherein the metal support is a metal selected from aluminum, copper, titanium, nickel, and stainless steel.
[4]
The method for producing a photoelectric conversion element according to any one of [1] to [3], wherein the metal support is aluminum or copper.
[5]
The oxide semiconductor film contains at least one oxide selected from tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, niobium oxide, titanium oxide, and strontium titanate. The method for producing a photoelectric conversion element according to any one of [1] to [3], which is characterized.
[6]
The method for producing a photoelectric conversion element according to any one of [1] to [5], wherein the oxide semiconductor film has a thickness of 5 nm to 2 μm.
The present invention relates to the above [1] to [6], but other matters are also described.
(1) In a dye-sensitized photoelectric conversion element having a conductive support, a photosensitive layer containing a semiconductor adsorbing a dye coated on the conductive support, a charge transfer layer, and a counter electrode, the conductive support A photoelectric conversion element, wherein the body comprises a metal support and an oxide semiconductor film.
(2) The conductive support is provided with an oxide semiconductor film on the surface of the metal support.
(3) The metal support contains a metal selected from aluminum, copper, titanium, nickel, iron, stainless steel, zinc and molybdenum.
(4) The metal support is a metal selected from aluminum, copper, titanium, nickel and stainless steel.
(5) The metal support is aluminum or copper.
(6) The oxide semiconductor film contains at least one oxide selected from tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, niobium oxide, titanium oxide, and strontium titanate. To do.
(7) The metal support has a thickness of 10 μm to 2 mm.
(8) The oxide semiconductor film has a thickness of 5 nm to 2 μm.
(9) The semiconductor of the photosensitive layer is titanium dioxide.
(10) The method for producing a photoelectric conversion element, comprising a step of continuously coating an oxide semiconductor film and a semiconductor layer of a photosensitive layer using a roll-shaped metal support.
(11) A photovoltaic cell using the photoelectric conversion element according to any one of the above.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
[1] Photoelectric conversion element
The dye-sensitized photoelectric conversion element comprises a conductive support, a photosensitive layer disposed on the conductive layer and a semiconductor sensitized by the dye (a conductive electrode and a photosensitive layer constitute a photoelectrode), a charge transfer layer The basic configuration is a counter electrode. In the present invention, the conductive support is composed of a metal support and an oxide semiconductor film. As shown in FIG. 1, the photoelectric conversion element of the present invention is preferably formed by laminating a metal support 50, an oxide semiconductor film 10, a photosensitive layer 20, a charge transfer layer 30, and a counter transparent conductive layer 40 in this order. 20 is composed of the semiconductor fine particles 21 sensitized by the dye 22 and the charge transport material 23 that has penetrated into the gaps between the semiconductor fine particles 21. The charge transport material 23 is composed of the same components as the material used for the charge transfer layer 30. Further, a transparent substrate 60 may be provided outside the counter electrode transparent conductive layer 40 in order to impart strength to the photoelectric conversion element. Hereinafter, in the present invention, a layer made of the metal support 50 and the oxide semiconductor film 10 is called a “conductive support”, and a layer made of the counter electrode transparent conductive layer 40 and the transparent substrate 60 optionally provided is called a “counter electrode”. This photoelectric conversion element is connected to an external circuit for work, and is a photovoltaic cell, which includes a solar cell. When the charge transport layer is an ion conductive electrolyte, it is characterized as a photoelectrochemical cell. In the element and battery of the present invention, light is incident from the counter electrode side.
[0006]
In the photoelectric conversion element of the present invention shown in FIG. 1, the light incident on the photosensitive layer 20 containing the semiconductor fine particles 21 sensitized by the dye 22 excites the dye 22 and the like, and the high energy in the excited dye 22 and the like. Electrons are transferred to the conduction band of the semiconductor fine particles 21 and further reach the conductive layer 10 by diffusion. At this time, the molecule such as the dye 22 is an oxidant. In the photovoltaic cell, the electrons in the conductive layer 10 return to the oxidant such as the dye 22 through the counter electrode conductive layer 40 and the charge transfer layer 30 while working in the external circuit, and the dye 22 is regenerated. The conductive layer and the photosensitive layer both function as a negative electrode (photoanode), and the counter electrode transparent conductive layer 40 functions as a positive electrode. At the boundary of each layer (for example, the boundary between the oxide semiconductor film 10 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transfer layer 30, the boundary between the charge transfer layer 30 and the counter electrode conductive layer 40, etc.) The constituent components may be diffusively mixed with each other. Each layer will be described in detail below.
[0007]
(A) Conductive support
(1) Metal support
As a result of diligent examination of the conductive support used in the present invention, it is possible to obtain a high output battery because the metal support has a small surface resistance and the internal resistance of the battery can be reduced, and it can be obtained on an industrial scale and at a low cost. Further, it has been clarified that a dye-sensitized semiconductor layer and the like can be continuously applied while continuously feeding the wound metal support, and the manufacturing cost can be reduced.
In particular, any of aluminum, titanium, copper, iron, nickel, stainless steel, zinc and molybdenum can be preferably used as the metal support. These metals may be alloys as long as their properties are not impaired. Of these, aluminum, titanium, copper, nickel or stainless steel is more preferred, aluminum or copper is more preferred, and aluminum is most preferred. Examples of aluminum include pure aluminum, wrought aluminum alloy, 1000 series to 7000 series (Light Metal Association: Aluminum Handbook, Light Metal Association, (1978), 26), etc. as long as the characteristics of aluminum are not impaired. An alloy may be used. The lower the surface resistance of the metal support used in the present invention, the better. The range of the surface resistance is preferably 10Ω / □ or less, more preferably 1Ω / □ or less, and particularly preferably 0.1Ω / □ or less. The thickness of the metal support in the present invention is preferably 10 μm or more and 2000 μm or less, more preferably 10 μm or more and 1000 μm or less, and particularly preferably 50 μm or more and 500 μm or less.
In addition, as long as the said characteristic is satisfied, the support body which joined the said metal to the flexible polymer film can also be used as a support body of this invention. Polymer film materials include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate ( PAr), polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like.
[0008]
(2) Oxide semiconductor film
An oxide semiconductor film is applied to the surface of the metal support used in the present invention in order to prevent corrosion of the metal support by a charge transport material (particularly an electrolyte). The oxide semiconductor film preferably has a dense structure so that the charge transport material does not pass therethrough. In other words, the oxide semiconductor film may have voids, but the pore size is small enough that the charge transport material does not penetrate and contact the metal support, and the oxide semiconductor film has a small porosity. It is preferable to use a thick film.
The oxide semiconductor material contains, as a main component, at least one oxide selected from tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, niobium oxide, titanium oxide, and strontium titanate. It is preferable. Specifically, SnO₂, SnO₂-Sb, SnO₂-F, SnO₂-P, In₂O_Three, In₂O_Three-ZnO, In₂O_Three-Sn, In₂O_Three-SnO₂, In₂O_Three-F, In₂O_Three-Cd, Fe₂O_Three, Nb₂O_Five, ZnO, ZnO-Al, CdO, Sb₂O_Three, TiO₂, WO_Three, TiSrO_ThreeEtc. can be used. Of these, SnO is preferred.₂System (including the above dopant content), Nb₂O_Five, ZnO, TiO₂, WO_ThreeOr TiSrO_ThreeIt is.
The oxide semiconductor film can be formed on the metal support surface by coating methods (dip coating, roll coating, spray coating (including spray pyrolysis method), etc.), vacuum deposition methods (resistance heating evaporation, electron beam evaporation, etc.), Known methods such as chemical vapor deposition (CVD, thermal CVD, plasma CVD, MOCVD, etc.), high-frequency sputtering, and electrolytic oxidation can be employed. For example, when a titanium oxide semiconductor thin film is formed on the surface of an aluminum support, a titanium tetraisopropoxide (TTIP) solution (solvent: the aluminum web continuously fed from the wound aluminum coil is heated to 400 ° C. A continuous production method in which acetylacetone or ethanol) is applied by spraying and then heat-treated at 450 ° C. is possible.
The thickness of the oxide semiconductor thin film on the surface of the metal support is preferably 5 nm or more and 1000 nm or less, and more preferably 10 nm or more and 500 nm or less. If it is too thin, the metal support comes into contact with the charge transport material, and corrosion and short-circuiting easily occur. If it is too thick, the internal resistance increases and the photoelectric conversion efficiency decreases.
[0009]
In the photoelectric conversion element of the present invention, since light is incident from the counter electrode side, the conductive support preferably has a high light reflectance.
[0010]
(B) Photosensitive layer
In the photosensitive layer, the semiconductor acts as a so-called photoconductor, absorbs light, separates charges, and generates electrons and holes. In dye-sensitized semiconductors, light absorption and thus the generation of electrons and holes occurs primarily in the dye, and the semiconductor is responsible for receiving and transmitting these electrons. In an n-type semiconductor, conduction band electrons become carriers, and in a p-type semiconductor, holes become carriers and produce conductivity. 10 as carrier concentration¹⁴-10²⁰Piece / cm^ThreeThe semiconductor of the range is preferable. The semiconductor used in the present invention is preferably an n-type semiconductor in which conduction band electrons become carriers under photoexcitation and give an anode current.
[0011]
(1) Semiconductor
Semiconductors include simple semiconductors such as silicon and germanium, III-V compound semiconductors, metal chalcogenides (eg, oxides, sulfides, selenides, etc.), or compounds having a perovskite structure (eg, strontium titanate, titanate) Calcium, sodium titanate, barium titanate, potassium niobate, etc.) can be used.
[0012]
Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Examples of other compound semiconductors include phosphides such as zinc, gallium, indium, and cadmium, gallium-arsenic or copper-indium selenides, and copper-indium sulfides.
[0013]
Preferred specific examples of the semiconductor used in the present invention include Si and TiO.₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_Five, CdS, ZnS, PbS, Bi₂S_Three, CdSe, CdTe, GaP, InP, GaAs, CuInS₂, CuInSe₂And more preferably TiO₂, ZnO, SnO₂, Fe₂O_Three, WO_Three, Nb₂O_Five, CdS, PbS, CdSe, InP, GaAs, CuInS₂Or CuInSe₂And particularly preferably TiO₂Or Nb₂O_FiveAnd most preferably TiO₂It is.
[0014]
The semiconductor used in the present invention may be single crystal or polycrystalline. From the viewpoint of conversion efficiency, a single crystal is preferable, but from the viewpoint of manufacturing cost, securing raw materials, energy payback time, and the like, polycrystalline is preferable, and a porous film made of semiconductor fine particles is particularly preferable.
[0015]
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. preferable. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 100 μm.
[0016]
Two or more kinds of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 5 nm or less. For the purpose of improving the light capture rate by scattering incident light, semiconductor particles having a large particle size, for example, about 300 nm may be mixed.
[0017]
Semiconductor fine particles are prepared by Sakuo Sakuo's "Sol-gel Method Science" Agne Jofusha (1998), Technical Information Association "Sol-gel Method Thin Film Coating Technology" (1995), etc. The sol-gel method described, Tadao Sugimoto's "Synthesis of monodisperse particles by the new synthesis gel-sol method and size morphology control", Materia, Vol. 35, No. 9, pp. 1012-1018 (1996) The gel-sol method described in 1 is preferred. Also preferred is a method developed by Degussa to produce an oxide by high-temperature hydrolysis of chloride in an oxyhydrogen salt.
[0018]
When the semiconductor fine particles are titanium oxide, the sol-gel method, gel-sol method, and high-temperature hydrolysis method in oxyhydrogen salt of chloride are all preferred, but Kiyoshi Manabu's “Titanium oxide properties and applied technology” The sulfuric acid method and the chlorine method described in Gihodo Publishing (1997) can also be used. Furthermore, as a sol-gel method, the method described in Journal of American Ceramic Society of Barb et al., Vol. 80, No. 12, pp. 3157-3171 (1997), and the chemistry of Burnside et al. The method described in Materials, Vol. 10, No. 9, pages 2419-2425 is also preferable.
[0019]
Titanium oxide mainly has two types of crystal forms, anatase type and rutile type, and either type can be used depending on the production method and thermal history, and it is often obtained as a mixture of both. The titanium oxide of the present invention preferably has a high anatase content, and more preferably 80% or more. Anatase has a shorter wavelength of light absorption than rutile, and damage of photoelectric conversion elements due to ultraviolet rays is less. The anatase content can be determined by X-ray diffraction, and can be determined from the ratio of diffraction peak intensities derived from anatase and rutile.
[0020]
(2) Semiconductor fine particle layer
In order to apply the semiconductor fine particles on the conductive support, in addition to the method of applying a dispersion or colloidal solution of the semiconductor fine particles on the conductive support, the above-described sol-gel method or the like can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of conductive support, etc., a wet film forming method is relatively advantageous. As a wet film forming method, a coating method and a printing method are typical.
[0021]
In addition to the sol-gel method described above, a method for producing a dispersion of semiconductor fine particles includes a method of grinding with a mortar, a method of dispersing while grinding using a mill, or a fine particle in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned.
[0022]
Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like). At the time of dispersion, a polymer such as polyethylene glycol, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid as necessary. By changing the molecular weight of polyethylene glycol, a film that does not easily peel off can be formed, and the viscosity of the dispersion can be adjusted. Therefore, it is preferable to add polyethylene glycol.
[0023]
As application methods, roller method, dip method, etc. as application system, air knife method, blade method, etc. as metering system, and application and metering can be made the same part, disclosed in Japanese Patent Publication No. 58-4589 The wire bar method, the slide hopper method, the extrusion method, the curtain method, etc. described in US Pat. Nos. 2,681,294, 2761419, 2761791 and the like are preferable. 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. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
[0024]
The viscosity of the dispersion of semiconductor fine particles greatly depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as surfactants and binders. For a high viscosity liquid (for example, 0.01 to 500 Poise), an extrusion method, a casting method, a screen printing method, or the like is preferable. For low-viscosity liquids (for example, 0.1 Poise or less), the slide hopper method, wire bar method, or spin method is preferable, and a uniform film can be obtained. If there is a certain amount of coating, coating by the extrusion method is possible even in the case of a low viscosity liquid. Thus, a wet film forming method may be selected as appropriate according to the viscosity of the coating solution, the coating amount, the support, the coating speed, and the like.
[0025]
The semiconductor fine particle layer is not limited to a single layer, but a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a multi-layer coating of a coating layer containing different types of semiconductor fine particles (or different binders and additives) You can also Multi-layer coating is also effective when the film thickness is insufficient with a single coating. For multilayer coating, an extrusion method or a slide hopper method is suitable. In the case of applying multiple layers, the multiple layers may be applied at the same time, or may be successively applied several times to several dozen times. Further, screen printing can be preferably used as long as it is sequentially overcoated.
[0026]
In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) increases, the amount of supported dye increases per unit projected area, and thus the light capture rate increases. Loss due to coupling also increases. Therefore, the preferable thickness of the semiconductor fine particle layer is 0.1 to 100 μm. When used in a solar cell, the thickness of the semiconductor fine particle layer is preferably 0.5 to 30 μm, more preferably 1 to 25 μm. Semiconductor fine particle support 1m²The hit application amount is preferably 0.5 to 400 g, more preferably 1 to 100 g.
[0027]
After the semiconductor fine particles are applied on the conductive support, the semiconductor fine particles are preferably brought into contact with each other electronically, and heat treatment is preferably performed in order to improve the coating strength and the adhesion to the support. A preferable heating temperature range is 40 ° C. or more and 700 ° C. or less, and more preferably 100 ° C. or more and 600 ° C. or less. The heating time is about 10 minutes to 10 hours. When using a support 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 support. Moreover, it is preferable that it is as low as possible also from a viewpoint of cost. The temperature can be lowered by using a combination of small semiconductor fine particles of 5 nm or less as described above, heat treatment in the presence of a mineral acid, or the like.
[0028]
In order to increase the surface area of semiconductor fine particles after heat treatment, increase the purity near the semiconductor fine particles, and increase the efficiency of electron injection from the dye to the semiconductor fine particles, for example, chemical plating treatment using titanium tetrachloride aqueous solution or titanium trichloride aqueous solution You may perform the electrochemical plating process using.
[0029]
The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the support is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times.
[0030]
In the present invention, an oxide semiconductor film is provided on a metal support continuously fed from a wound metal support coil, and a semiconductor fine particle dispersion is applied to the surface of the oxide semiconductor film by, for example, a curtain coating method. After coating, heat treatment is performed, then electroplating treatment is performed as necessary, and the dye adsorption treatment can be performed continuously, so that a photoelectrode can be produced at a low production cost.
[0031]
(3) Dye
In the present invention, a dye-adsorbed semiconductor obtained by physically or chemically adsorbing a dye to the semiconductor is used for the photosensitive layer. The dye used in the photosensitive layer is preferably a metal complex dye, a phthalocyanine dye or a methine dye. 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 mixed. Further, the dye to be mixed and its ratio can be selected so as to match the wavelength range and intensity distribution of the target light source.
[0032]
Such a dye preferably has a suitable interlocking group for the surface of the semiconductor fine particles. Preferred linking groups include COOH groups, OH groups, SO_ThreeH group, cyano group, -P (O) (OH)₂Group, -OP (O) (OH)₂Groups or chelating groups with π-conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. Among them, COOH group, -P (O) (OH)₂Group, -OP (O) (OH)₂The group is particularly preferred. These 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.
[0033]
Hereinafter, preferred dyes used in the photosensitive layer will be specifically described.
[0034]
(A) Metal complex dye
When the dye is a metal complex dye, the metal atom is preferably ruthenium Ru. Examples of the ruthenium complex dye include, for example, U.S. Pat. Complex dyes described in No. and the like.
[0035]
Further, the ruthenium complex dye used in the present invention has the following general formula (I):
(A₁)_pRu (B-a) (B-b) (B-c) (I)
Is preferably represented by: In general formula (I), A₁Is Cl, SCN, H₂This represents a ligand selected from the group consisting of O, Br, I, CN, NCO and SeCN, and p is an integer of 0 to 3. B-a, B-b and B-c are each independently represented by the following formulas B-1 to B-10:
[0036]
[Chemical 1]

[0037]
(However, R_aRepresents a hydrogen atom or a substituent. Examples of the substituent include a halogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 12 carbon atoms, or carbon. Examples thereof include a substituted or unsubstituted aryl group having 6 to 12 atoms, a carboxylic acid group, and a phosphoric acid group (these acid groups may form a salt), and the alkyl part of the alkyl group and the aralkyl group is directly The aryl group and the aryl part of the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly). ) Represents an organic ligand selected from the compounds represented by: B-a, B-b and B-c may be the same or different, and may be any one or two.
[0038]
Although the preferable specific example of a complex dye is shown below, this invention is not limited to these.
[0039]
[Chemical formula 2]

[0040]
[Chemical 3]

[0041]
[Formula 4]

[0042]
(B) Methine dye
The methine dyes preferably used in the present invention include JP-A-11-35836, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730, JP-A-11-214731, European Patent 892411 and It is a dye described in each specification of JP-A-911841. For the synthesis of these dyes, see FM Hamer, `` Heterocyclic Compounds-Cyanine Dyes and Related Compounds '', John Willie. John Wiley & Sons-New York, London, 1964, DMSturmer, "Heterocyclic Compounds (Heterocyclic Compounds) Special Topics in Complex Cyclic Chemistry" -Special topics in cyclic chemistry), Chapter 18, Section 14, 482-515, John Wiley & Sons, New York, London, 1977, "Rods Chemistry." Rodd's Chemistry of Carbon Compounds '' 2nd Vol. IV, part B, 1977, Chapter 15, pages 369-422, published by Elsevier Science Publishing Company Inc., New York, UK Patent No. 1,077,611 Ukrainskii Khimicheskii Zhurnal, Vol. 40, No. 3, pp. 253-258, Dyes and Pigments, Vol. 21, pp. 227-234, and references cited in these documents.
[0043]
(4) Adsorption of dye to semiconductor
In order to adsorb the dye to the semiconductor fine particles, a method of immersing a conductive support having a well-dried semiconductor fine particle layer in the dye solution or applying a dye solution to the semiconductor fine particle layer can be used. In the former case, an immersion method, a dip method, a roller method, an air knife method or the like can be used. In the case of the immersion method, the dye may be adsorbed at room temperature, or may be carried out by heating and refluxing as described in JP-A-7-249790. Examples of the latter application method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method, and the like. Printing methods include letterpress, offset, gravure, and screen printing. The solvent can be appropriately selected according to the solubility of the dye. For example, alcohols (methanol, ethanol, t-butanol, 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, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane) , Petroleum ether, ben Zen, toluene, etc.) and mixed solvents thereof.
[0044]
As for the viscosity of the dye solution, as in the formation of the semiconductor fine particle layer, various printing methods other than the extrusion method are suitable for the high-viscosity liquid (for example, 0.01 to 500 poise), and the low-viscosity liquid (for example, 0.1 poise) In the following, a slide hopper method, a wire bar method, or a spin method is suitable, and any of them can form a uniform film.
[0045]
Thus, the dye adsorption method may be appropriately selected according to the viscosity of the dye coating solution, the coating amount, the conductive support, the coating speed, and the like. The time required for the dye adsorption after coating is preferably as short as possible when mass production is considered.
[0046]
Since the presence of unadsorbed dye causes disturbance in device performance, it is preferable to remove it by washing immediately after adsorption. It is preferable to use a wet cleaning tank and perform cleaning with a polar solvent such as acetonitrile or an organic solvent such as an alcohol solvent. In order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to quickly adsorb the dye between 40 to 80 ° C. without returning to normal temperature.
[0047]
The total amount of dye used is the unit surface area of the conductive support (1 m²) Is preferably from 0.01 to 100 mmol. The amount of the dye adsorbed on the semiconductor fine particles is preferably 0.01 to 1 mmol per 1 g of the semiconductor fine particles. By setting such an amount of dye adsorption, a sensitizing effect in a semiconductor can be sufficiently obtained. On the other hand, if the amount of the dye is too small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not attached to the semiconductor floats, which causes a reduction in the sensitizing effect.
[0048]
For the purpose of reducing the interaction between dyes such as association, a colorless compound may be co-adsorbed on the semiconductor fine particles. Examples of the hydrophobic compound to be co-adsorbed include steroid compounds having a carboxyl group (for example, chenodeoxycholic acid). An ultraviolet absorber can also be used in combination.
[0049]
For the purpose of promoting the removal of excess dye, the surface of the semiconductor fine particles may be treated with amines after adsorbing the dye. Preferable amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.
[0050]
(C) Charge transfer layer
The charge transfer layer is a layer containing a charge transport material having a function of replenishing electrons to the oxidant of the dye. Examples of typical charge transport materials that can be used in the present invention are as follows. (1) As an ion transport material, a solution (electrolyte) in which redox pair ions are dissolved, and a redox pair solution are polymer matrix gels. So-called gel electrolytes impregnated in the above, molten salt electrolytes containing redox counterions, and solid electrolytes. In addition to the charge transport material that involves ions, (2) an electron transport material or a hole transport material can also be used as a material that involves carrier transport in solids in electrical conduction. These can be used in combination.
[0051]
(1) Molten salt electrolyte
The molten salt electrolyte is preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. When a molten salt electrolyte is used for the photoelectric conversion element of the present invention, it is described in, for example, WO95 / 18456, JP-A-8-259543, Electrochemistry, Vol. 65, No. 11, page 923 (1997), etc. Known iodine salts such as pyridinium salts, imidazolium salts, and triazolium salts can be used.
[0052]
Examples of the molten salt that can be preferably used include those represented by any of the following general formulas (Y-a), (Y-b), and (Y-c).
[0053]
[Chemical formula 5]

[0054]
Q in general formula (Y-a)_y1Represents an atomic group capable of forming a 5- or 6-membered aromatic cation with a nitrogen atom. Q_y1Is preferably composed of at least one atom selected from the group consisting of carbon atom, hydrogen atom, nitrogen atom, oxygen atom and sulfur atom.
[0055]
Q_y1The five-membered ring formed by is preferably an oxazole ring, thiazole ring, imidazole ring, pyrazole ring, isoxazole ring, thiadiazole ring, oxadiazole ring or triazole ring, and is an oxazole ring, thiazole ring or imidazole ring. More preferably, it is particularly preferably an oxazole ring or an imidazole ring. Q_y1The 6-membered ring formed by is preferably a pyridine ring, pyrimidine ring, pyridazine ring, pyrazine ring or triazine ring, and more preferably a pyridine ring.
[0056]
In general formula (Y-b), A_y1Represents a nitrogen atom or a phosphorus atom.
[0057]
R in general formula (Y-a), (Y-b) and (Y-c)_y1~ R_y6Each independently represents a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, which may be linear or branched, or cyclic, such as a methyl group or an ethyl group Propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, t-octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, etc. ), Or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms, which may be linear or branched, such as vinyl group, allyl group, etc.), more preferably carbon An alkyl group having 2 to 18 atoms or an alkenyl group having 2 to 18 carbon atoms is preferable, and an alkyl group having 2 to 6 carbon atoms is particularly preferable.
[0058]
In addition, R in the general formula (Y-b)_y1~ R_y4Two or more of them connected to each other_y1May form a non-aromatic ring containing R in the general formula (Y-c)_y1~ R_y6Two or more of them may be connected to each other to form a ring structure.
[0059]
Q in general formulas (Y-a), (Y-b) and (Y-c)_y1And R_y1~ R_y6May have a substituent, and examples of preferred substituents include halogen atoms (F, Cl, Br, I, etc.), cyano groups, alkoxy groups (methoxy groups, ethoxy groups, etc.), aryloxy groups (phenoxy). Group), alkylthio group (methylthio group, ethylthio group etc.), alkoxycarbonyl group (ethoxycarbonyl group etc.), carbonate group (ethoxycarbonyloxy group etc.), acyl group (acetyl group, propionyl group, benzoyl group etc.), Sulfonyl group (methanesulfonyl group, benzenesulfonyl group etc.), acyloxy group (acetoxy group, benzoyloxy group etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group etc.), phosphonyl group (diethylphosphonyl group etc.) Amide group (acetylamino group, benzoylamino group, etc.), carbamo Group (N, N-dimethylcarbamoyl group, etc.), alkyl group (methyl group, ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc.), aryl group (phenyl) Group, toluyl group, etc.), heterocyclic group (pyridyl group, imidazolyl group, furanyl group, etc.), alkenyl group (vinyl group, 1-propenyl group, etc.) and the like.
[0060]
The compound represented by the general formula (Y-a), (Y-b) or (Y-c) is Q_y1Or R_y1~ R_y6A multimer may be formed via
[0061]
These molten salts may be used singly or as a mixture of two or more, and may be used in combination with a molten salt in which the iodine anion is replaced with another anion. Anions that replace iodine anions include halide ions (Cl^-, Br^-Etc.), NCS^-, BF_Four ^-, PF₆ ^-, ClO_Four ^-, (CF_ThreeSO₂)₂N^-, (CF_ThreeCF₂SO₂)₂N^-, CF_ThreeSO_Three ^-, CF_ThreeCOO^-, Ph_FourB^-, (CF_ThreeSO₂)_ThreeC^-Etc. are preferable examples, and (CF_ThreeSO₂)₂N^-Or BF_Four ^-It is more preferable that Also, other iodine salts such as LiI can be added.
[0062]
It is preferable not to use a solvent for the molten salt electrolyte. Although the solvent described later may be added, the content of the molten salt is preferably 50% by mass or more based on the entire electrolyte composition. In addition, 50% by mass or more of the salt is preferably an iodine salt, and more preferably 70% or more.
[0063]
It is preferable to add iodine to the electrolyte composition. In this case, 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 electrolyte composition. .
[0064]
(2) Electrolyte
When an electrolytic solution is used for the charge transfer layer, the electrolytic solution is preferably composed of an electrolyte, a solvent, and an additive. The electrolyte of the present invention is I₂And iodide (LiI, NaI, KI, CsI, CaI as iodides)₂ Metal iodides such as tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide and the like quaternary ammonium compounds such as iodine salts), Br₂And bromide combinations (LiBr, NaBr, KBr, CsBr, CaBr as bromides)₂ Metal bromide such as tetraalkylammonium bromide, pyridinium bromide, bromide salts of quaternary ammonium compounds), metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sodium polysulfide, Sulfur compounds such as alkylthiol-alkyldisulfides, viologen dyes, hydroquinone-quinones, and the like can be used. I among them₂In the present invention, an electrolyte obtained by combining iodine salt of a quaternary ammonium compound such as LiI, pyridinium iodide, imidazolium iodide and the like is preferable. The electrolytes described above may be used in combination.
[0065]
A preferable electrolyte concentration is 0.1 M or more and 15 M or less, and more preferably 0.2 M or more and 10 M or less. Moreover, the preferable addition concentration of iodine when adding iodine to the electrolyte is 0.01 M or more and 0.5 M or less.
[0066]
The solvent used for the electrolyte in the present invention is a compound that has low viscosity and improves ion mobility, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ionic conductivity. desirable. Examples of the solvent 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, and polyethylene. Chain ethers such as 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, polypropylene glycol monoalkyl ether, ethylene glycol, Propylene glycol, polyethylene glycol, polyp Polyhydric alcohols such as pyrene glycol and glycerol, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile, aprotic polar substances such as dimethyl sulfoxide and sulfolane, and water can be used. .
[0067]
In the present invention, bases such as tert-butylpyridine, 2-picoline, 2,6-lutidine and the like described in J. Am. Ceram. Soc., 80 (12) 3157-3171 (1997) are also used. Sexual compounds can also be added. A preferable concentration range when adding a basic compound is 0.05M or more and 2M or less.
[0068]
(3) Gel electrolyte
In the present invention, the electrolyte can be used after gelation (solidification) by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. In the case of gelation by addition of a polymer, compounds described in Polymer Electrolyte Reviews-1 and 2 (JR MacCallum and CA Vincent, edited by ELSEVIER APPLIED SCIENCE) can be used, but in particular, polyacrylonitrile and polyfluoride can be used. Vinylidene chloride can be preferably used. J. Chem Soc. Japan, Ind. Chem. Sec., 46,779 (1943), J. Am. Chem. Soc., 111,5542 (1989), J. Chem. Soc ., Chem. Com mun., 1993, 390, Angew. Chem. Int. Ed. Engl., 35, 1949 (1996), Chem. Lett., 1996, 885, J. Chm. Soc., Chem. Commun. , 1997, 545 can be used, but preferred compounds are those having an amide structure in the molecular structure.
[0069]
Further, when the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a crosslinkable reactive group and a crosslinking agent in combination. In this case, a preferable crosslinkable reactive group is a nitrogen-containing heterocyclic ring (for example, a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, a triazole ring, a morpholine ring, a piperidine ring, a piperazine ring), and a preferable crosslinking agent. Is a bifunctional or higher functional reagent (for example, alkyl halide, halogenated aralkyl, sulfonate ester, acid anhydride, acid chloride, isocyanate, etc.) capable of electrophilic reaction with a nitrogen atom.
[0070]
(4) Hole transport material
In the present invention, a hole transport material combining organic or inorganic or a combination of both can be used instead of the electrolyte.
[0071]
(A) Organic hole transport material
Organic hole transport materials applicable to the present invention include N, N′-diphenyl-N, N′-bis (4-methoxyphenyl)-(1,1′-biphenyl) -4,4′-diamine ( J. Hagen et al., Synthetic Metal 89 (1997) 215-220), 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene (Nature, Vol. 395, 8 Oct. 1998, p583-585 and WO97 / 10617), 1,1-bis {4- (di-p-tolylamino) phenyl} cyclohexane tertiary aromatic amine unit linked fragrance Group diamine compounds (Japanese Patent Laid-Open No. 59-194393), including 2,4, -bis [(N-1-naphthyl) -N-phenylamino] biphenyl and two or more tertiary amines An aromatic amine in which the above condensed aromatic ring is substituted with a nitrogen atom (Japanese Patent Laid-Open No. 5-234681), an aromatic triamine having a starburst structure with a derivative of triphenylbenzene (US Pat. No. 4, 923,774, JP-A-4-308688), N, N′-diphenyl-N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine, etc. Aromatic diamine (US Pat. No. 4,764,625), α, α, α ′, α′-tetramethyl-α, α′-bis (4-di-p-tolylaminophenyl) -p-xylene (Japanese Patent Laid-Open No. 3-269084), p-phenylenediamine derivatives, sterically asymmetric triphenylamine derivatives as a whole molecule (Japanese Patent Laid-Open No. 4-129271), and a pyrenyl group substituted with a plurality of aromatic diamino groups Compounds (Japanese Patent Laid-Open No. 4-175395), aromatic diamines having tertiary aromatic amine units linked by ethylene groups (Japanese Patent Laid-Open No. 4-264189), aromatic diamines having a styryl structure (Japanese Patent Laid-Open No. 4-290851) Publication), benzylphenyl compound (Japanese Patent Laid-Open No. 4-364153), and a tertiary amine linked by a fluorene group (Japanese Patent Laid-Open No. 4-364153) 5-25473), triamine compounds (JP-A-5-239455), pisdipyridylaminobiphenyl (JP-A-5-320634), N, N, N-triphenylamine derivatives (JP-A-6-1972) Aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine derivatives (JP-A-7-252474) and the like can be preferably used.
In addition, α-octylthiophene and α, ω-dihexyl-α-octylthiophene (Adv. Mater. 1997, 9, N0.7, p557), hexadodecyl dodecithiophene (Angew. Chem. Int. Ed. Engl. 1995) , 34, No. 3, p303-307), 2,8-dihexylanthra [2,3-b: 6,7-b '] dithiophene (JACS, Vol120, N0.4,1998, p664-672), etc. Oligothiophene compound, polypyrrole (K. Murakoshi et al.,; Chem. Lett. 1997, p471), ¨ Handbook of Organic Conductive Molecules and Polymers Vol. 1,2,3,4 (NALWA, published by WILEY) Polyacetylene and its derivatives, poly (p-phenylene) and its derivatives, poly (p-phenylenevinylene) and its derivatives, polythienylene vinylene and its derivatives, polythiophene and its derivatives, polyaniline and its derivatives, polytoluidine and Conductive polymers such as derivatives can be preferably used. .
Hole transport materials contain tris (4-bromophenyl) aminium hexachloroantimonate to control dopant levels as described in Nature, Vol. 395, 8 Oct. 1998, p583-585. Li [(CF to add compounds containing such cation radicals or to control the potential of oxide semiconductor surfaces (space charge layer compensation)_ThreeSO₂)₂A salt such as N] may be added.
[0072]
(B) Inorganic hole transport material
A p-type inorganic compound semiconductor can be used as the inorganic hole transport material. The band gap of the p-type inorganic compound semiconductor is preferably large because it does not hinder dye absorption. The band gap of the p-type inorganic compound semiconductor is preferably 2 eV or more, and more preferably 2.5 eV or more. Also, 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 dye holes. Although the preferred range of the ionization potential of the p-type inorganic compound semiconductor used in the charge transfer layer varies depending on the dye used in the photoelectric conversion device of the present invention, it is generally preferably 4.5 eV or more and 5.5 eV or less, and more preferably 4.7 eV. It is preferably 5.3 eV or less. The p-type inorganic compound semiconductor preferably used in the present invention is a compound semiconductor containing monovalent copper. Examples of the compound semiconductor containing monovalent copper 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 p-type inorganic compound semiconductors that can be used in addition to compounds containing copper include GaP, NiO, CoO, FeO, and Bi.₂O_Three, MoO₂, Cr₂O_ThreeEtc. Further, the preferred hole mobility of the charge transfer layer containing the p-type inorganic compound semiconductor of the present invention is 10^-Fourcm²/ V ・ sec or more 10^Fourcm²/ V · sec or less, more preferably 10^-3cm²/ V ・ sec or more 10^Threecm²/ V · sec or less. Furthermore, the preferred conductivity of the charge transfer layer of the present invention is 10^-8S / cm or more 10²S / cm or less, more preferably 10^-6S / cm or more and 10 S / cm or less.
[0073]
(5) Formation of charge transfer layer
There are two possible methods for forming the charge transfer layer. One is a method in which a counter electrode is first pasted on a semiconductor fine particle-containing layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched in the gap. The other is a method of directly providing a charge transfer layer on the semiconductor fine particle-containing layer, and the counter electrode is subsequently applied.
[0074]
As the sandwiching method of the charge transfer layer in the former case, a normal pressure process using a capillary phenomenon due to immersion or a vacuum process in which a gas phase is replaced with a liquid phase at a pressure lower than normal pressure can be used.
[0075]
In the latter case, in the wet charge transfer layer, a counter electrode is provided without being dried, and measures for preventing liquid leakage at the edge portion are also taken. In the case of a gel electrolyte, there is a method of applying it in a wet state and solidifying it by a method such as polymerization, in which case the counter electrode can be applied after drying and fixing. In addition to the electrolytic solution, wet organic hole transport materials and gel electrolytes can be applied in the same manner as semiconductor fine particle containing layers and pigments, as well as immersion, roller method, dipping method, air knife method, extrusion method, slide A hopper method, a Werber method, a spin method, a spray method, a casting method, various printing methods, and the like can be considered.
[0076]
In the case of a solid electrolyte or a solid hole transport material, a charge transfer layer can be formed by a dry film formation 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 techniques such as vacuum deposition, casting, coating, spin coating, dipping, electrolytic polymerization, and photoelectrolytic polymerization. In the case of an inorganic solid compound, it can also be introduced into the electrode by techniques such as casting, coating, spin coating, dipping, and electrolytic plating.
[0077]
When considering mass production, in the case of an electrolyte solution or a wet hole transport material that cannot be solidified, it is possible to respond by sealing the edge part immediately after coating, but hole transport that can be solidified In the case of materials, it is more preferable to form a hole transport layer by wet application and then solidify by a method such as photopolymerization or thermal radical polymerization. Thus, the film application method may be appropriately selected depending on the liquid physical properties and process conditions.
[0078]
The charge transfer layer has a certain thickness so that a short circuit between the photosensitive layer (semiconductor layer) and the counter electrode does not occur. However, if the thickness is too thick, it is not preferable in terms of photoelectric conversion efficiency. The thickness of the charge transfer layer is preferably 0.05 μm or more and 100 μm or less, and more preferably 0.1 μm or more and 50 μm or less. The charge transport material is also present in a porous photosensitive layer formed from semiconductor fine particles.
[0079]
The moisture in the charge transfer layer is preferably 10,000 ppm or less, more preferably 2,000 ppm or less, and particularly preferably 100 ppm or less.
[0080]
(D) Counter electrode
The counter electrode used in the device of the invention performs electron transfer to the charge transport layer as a cathode when the photoelectrode carrying the dye-sensitized semiconductor layer serves as a photoanode. In the present invention, since the dye-sensitized semiconductor fine particle layer is placed on the metal support, the counter electrode needs to be substantially transparent in order for light to reach the photosensitive layer. The light transmittance is preferably 50% or more in the wavelength region of 400 to 900 nm, particularly preferably 70% or more.
In the present invention, the counter electrode may be a single-layer structure of a counter electrode transparent conductive layer made of a transparent conductive material, or may be composed of a counter electrode transparent conductive layer and a transparent support substrate. As the conductive material used for the transparent transparent conductive layer, metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, magnesium, etc.), conductive metal oxide (indium-tin composite oxide, oxidation) And tin doped with fluorine, indium-zinc composite oxide, etc.). Among metals, platinum, gold, silver, copper, aluminum, or magnesium can be preferably used as the counter electrode transparent conductive layer, but platinum is particularly preferable in terms of stability in the battery. In the case of using a metal, it is necessary to make the layer sufficiently thin or to transmit light such as a lattice or mesh in order to ensure light transmittance. From the viewpoint of light transmittance, a metal oxide transparent conductive layer is preferred. An example of a preferable transparent support substrate for the counter electrode is glass or transparent plastic, and the above-mentioned conductive agent can be applied, vapor-deposited or sputtered to the glass or transparent plastic. For the purpose of improving conductivity, it is also preferable to attach a metal thin film layer or metal ultrafine particles on the metal oxide transparent conductive layer. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm or more and 10 μm or less. The lower the surface resistance of the counter electrode layer, the better. The surface resistance is preferably 80Ω / □ or less, more preferably 20Ω / □ or less, and most preferably 5Ω / □ or less.
[0081]
The counter electrode may be formed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive agent on the charge transfer layer or attaching the conductive layer side of the substrate having the conductive layer. Further, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode transparent conductive layer. The material of the metal lead is preferably a metal such as aluminum, copper, silver, gold, platinum, nickel, and particularly preferably aluminum and silver. The metal lead is preferably installed on a transparent substrate by vapor deposition, sputtering or the like, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is preferably provided thereon. Moreover, it is also preferable to install a metal lead on the transparent conductive layer after providing the transparent conductive layer 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%.
[0082]
(E) Other layers
A functional layer such as a protective layer or an antireflection layer may be provided on one or both of the conductive support and the counter electrode. When such a functional layer is formed in multiple layers, a simultaneous multilayer coating method or a sequential coating method can be used, but the simultaneous multilayer coating method is preferable from the viewpoint of productivity. In the simultaneous multilayer coating method, the slide hopper method and the extrusion method are suitable in view of productivity and coating film uniformity. For forming these functional layers, an evaporation method, a bonding method, or the like can be used depending on the material.
[0083]
(F) Specific example of internal structure of photoelectric conversion element
The structure inside the cell of the dye-sensitized solar cell is basically the same as that of the above-described photoelectric conversion element or photoelectrochemical cell, but various forms are possible depending on the purpose. Since the working electrode in the present invention uses an optically opaque metal support, light incident on the photosensitive layer enters from the counter electrode side. A typical configuration example is shown in FIGS. In FIG. 2A, the photosensitive layer 20 is provided on the metal support 50 via the oxide semiconductor film 10, the charge transfer layer 30 and the counter electrode transparent conductive layer 40 are further provided, and the transparent substrate 60 is disposed thereon. This is the structure. In FIG. 2B, a photosensitive layer (dye-adsorbing semiconductor layer) 20 is provided on a metal support 50 with an oxide semiconductor film 10 interposed therebetween, and a charge transfer layer 30 and a counter electrode transparent conductive layer 40 are provided. The transparent substrate 60 provided with the metal leads 41 is arranged with the metal leads 41 inside. FIG. 2C shows a structure in which a photosensitive layer 20 is provided on a metal support 50 with an oxide semiconductor film 10 interposed therebetween, a solid charge transfer layer 31 is further provided, and a metal lead 41 is provided on a part thereof. It is.
[0084]
[2] Photocell
The photovoltaic cell of the present invention is one in which the photoelectric conversion element is caused to work in an external circuit. In order to prevent deterioration of components and volatilization of the contents of the photovoltaic cell, it is preferable to seal the side surface with a polymer or an adhesive. The external circuit itself connected to the conductive support and the counter electrode via a lead may be a known one. When the photoelectric conversion element of the present invention is applied to a so-called solar battery, the structure inside the cell is basically the same as the structure of the photoelectric conversion element described above. Hereinafter, a module structure of a solar cell using the photoelectric conversion element of the present invention will be described.
[0085]
The dye-sensitized solar cell 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 cells are 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, a module structure such as a super straight type, a substrate type, or a potting type or a substrate integrated type used in an amorphous silicon solar cell or the like is possible. These module structures can be appropriately selected depending on the purpose of use and the place of use (environment). In order to increase the utilization efficiency of incident light, it is preferable to increase the area ratio of the photosensitive layer when viewed from the counter electrode side.
[0086]
The typical structure of the super straight type and the substrate type is such that cells are arranged at regular intervals between support substrates that are transparent on one or both sides and treated with antireflection, and metal leads or flexible wiring between adjacent cells. Are connected to each other, and a collecting electrode is arranged on the outer edge portion, and the generated electric power is taken out to the outside. Various types of plastic materials such as ethylene vinyl acetate (EVA) can be used between the substrate and the cell in the form of a film or a filled resin depending on the purpose in order to protect the cell and increase the current collection efficiency. In addition, when using it in a place where it is not necessary to cover the surface with a hard material, such as where there is little impact from the outside, the surface protective layer should be composed of a transparent plastic film, or the above filling and sealing material should be cured It is also possible to provide a protective function and eliminate the support substrate on one side. The periphery of the support substrate is fixed in a sandwich shape with a metal frame in order to seal the inside and secure the rigidity of the module, and the support substrate and the frame are hermetically sealed with a sealing material.
[0087]
The module is a semiconductor process technology such as selective plating, selective etching, CVD, PVD, or pattern coating or wide width so that the photosensitive layer, charge transfer layer, counter electrode, etc. are arranged three-dimensionally and at regular intervals on a conductive support. After coating, it can be patterned by laser scribing, plasma CVM (described in Solar Energy Materials and Solar Cells, 48, p373-381 etc.) or mechanical methods such as grinding. Obtainable.
[0088]
【Example】
  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples as long as the gist of the invention is not exceeded.
In addition, Example-1 and Example-3 shall be read as a reference example.
[0089]
1. Preparation of metal support with oxide semiconductor thin film
(1) Production of conductive support-A
Rolling oil adhering to the aluminum (material JIS1050 material, thickness 0.38 mm) substrate surface is removed with acetone, and titanium tetraisopropoxide (TTIP) 5.68 g, acetylacetone 4.0 g, ethanol on the surface under heating at 400 ° C., ethanol 80 ml of the mixed solution was applied by a spray method and then baked in an electric furnace at 450 ° C. for 30 minutes to obtain a conductive support-A. The film thickness of titanium oxide was about 50 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0090]
(2) Production of conductive support-B (Continuous production of conductive support)
The aluminum web continuously fed from the rolled aluminum coil is passed through an acetone bath to remove the rolling oil, then dried, then transported to a heating zone and heated to 400 ° C. by a spray method. After applying the above mixed solution (TTIP 5.68 g, acetylacetone 4.0 g, ethanol 80 ml mixed solution), it was heated at 450 ° C. to prepare. That is, it was produced in a continuous process by conveying an aluminum web from rolling oil removal to 450 ° C. heat treatment. The film thickness of the oxide semiconductor thin film was 80 nm, and the crystal form was confirmed to be atatase titanium oxide by X-ray diffraction.
[0091]
(3) Production of conductive support-C
A 300 nm titanium oxide thin film was attached to the surface of an aluminum (material JIS 1050 material, thickness 0.38 mm) substrate from which the rolling oil was removed with acetone by sputtering, to obtain a conductive support-C. The crystal form of titanium oxide was confirmed to be anatase titanium oxide by X-ray diffraction.
[0092]
(4) Preparation of conductive support-D
Conductive support provided with titanium oxide on a copper substrate in the same manner as the preparation of conductive support-C except that a rolled copper plate (JIS-1220, thickness 0.3 mm) from which the rolling oil was removed with acetone was used. -D was obtained. The film thickness of titanium oxide was 300 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0093]
(5) Production of conductive support-E
Except for using a titanium plate (JIS-1 type, thickness 0.3 mm), a conductive support-E in which titanium oxide was provided on a titanium substrate was obtained in the same manner as in the preparation of the conductive support-A. The film thickness of titanium oxide was about 75 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0094]
(6) Preparation of metal support-F
A metal support F obtained by applying titanium oxide on a nickel substrate was prepared in the same manner as the production of the conductive support A except that a nickel plate (Ni alloy monel metal 60 to 70 Ni-Cu, thickness 0.3 mm) was used. Obtained. The film thickness of titanium oxide was about 50 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0095]
(7) Production of conductive support-G
Except that a stainless steel plate (SUS305, thickness 0.2 mm) was used, a conductive support-G in which titanium oxide was provided on a stainless steel plate was obtained in the same manner as in the production of the conductive support-A. The film thickness of titanium oxide was about 75 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0096]
(8) Production of conductive support-H
A metal support-H having a titanium oxide thin film provided on the surface of a stainless steel plate (SUS305, thickness 0.2 mm) by electrolytic oxidation of titanium trichloride was obtained. The film thickness of titanium oxide was about 50 nm, and the crystal form was confirmed to be anatase titanium oxide by X-ray diffraction.
[0097]
(9) Preparation of conductive support for comparison
Comparative conductive supports I to M for which no oxide semiconductor film was provided using the same metal supports as C to G were prepared. Moreover, the transparent conductive glass (TCO glass by Nippon Sheet Glass, size 25 mm x 100 mm) coated with fluorine-doped tin dioxide was used as a conductive support N for comparison.
[0098]
About the above electroconductive support body, the metal support body (its surface resistance value) and oxide semiconductor film (its film thickness) which were used were put together in Table 1.
[0099]

[0100]
[Example-1]
2. Preparation of coating solution containing titanium dioxide particles
C. J. et al. Barbe et al. Am. Ceramic Soc. In accordance with the production method described in the 80th volume, p. 3157, titanium tetraisopropoxide is used as the titanium raw material, the temperature of the polymerization reaction in the autoclave is set to 230 ° C., and the titanium dioxide dispersion has a titanium dioxide concentration of 11% by weight. Was synthesized. The average size of the obtained titanium dioxide particles was about 10 nm.
To this dispersion, 30% by weight of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries, Ltd.) with respect to titanium dioxide was added and mixed to obtain a coating solution.
[0101]
3. Fabrication of dye-adsorbed titanium dioxide electrode
The coating liquid of 2 was applied to the surface of the conductive support-A (size 25 mm × 100 mm) provided with the conductive semiconductor-A by the doctor blade method to a thickness of 60 μm and air-dried at room temperature for 1 hour. Then, it baked for 30 minutes at 450 degreeC with the electric furnace. The amount of titanium dioxide applied is 9g / m²The film thickness was 6 μm.
After the titanium dioxide electrode was taken out and cooled, 3 × 10 3 of the dye represented by the dye compound R-1 was used.^-FourMole / liter concentration solution (Composition: 375 mg of the dye was ultrasonically dissolved in 250 ml of ethanol, and a mixed solvent of 250 ml of t-butanol and 500 ml of acetonitryl was added to make 1 liter. After lightly stirring, trioxyethylene nonylphenoxybutyl sodium It was immersed in 1000 mg of sulfonate ether for dissolution for 1.5 hours at 40 ° C. The dye-adsorbed titanium dioxide electrode was washed with acetonitrile and allowed to dry naturally in the dark.
[0102]
4). Electrolyte injection
Molten salt electrolyte (composition: 0.3 g of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl 3-methylimidazolium iodide) on the electrode surface of a dye-sensitized titanium dioxide electrode (size 2 cm × 1.5 cm) 0.7 g and 0.02 g of iodine) were added dropwise and heated at 50 ° C. for 1 hour under reduced pressure to infiltrate the electrolyte into the titanium dioxide electrode pores.
[0103]
5. Production of photovoltaic cells
The counter electrode is made by applying an isopropyl alcohol solution of chloroplatinic acid to the conductive layer surface of a conductive glass (TCO made by Nippon Sheet Glass) coated with fluorine-doped tin dioxide by the CVD method and firing in air at 420 ° C for 20 minutes. A highly transparent TCO counter electrode with platinum was used (the average thickness of the platinum layer was about 1 nm and the thickness of the tin dioxide layer was about 600 nm). The counter electrode having the same size as the titanium dioxide electrode produced in the above 4 was overlapped with the titanium dioxide electrode so that the platinum side faced. At that time, the positions were shifted by the amount corresponding to the lead extraction dimensions and overlapped. Next, the peripheral portions of the two substrates were sealed with a heat-melting adhesive to produce a photovoltaic cell 1 according to the present invention.
[0104]
6). Measurement of photovoltaic cell output (Pmax (mW))
The photoelectric conversion efficiency of the photoelectric conversion element of the present invention was measured as follows. Simulated sunlight containing no ultraviolet rays was generated by passing through a 500 W xenon lamp (USHIO ELECTRIC) through a correction filter for sunlight simulation (AM1.5 manufactured by Oriel) and a sharp cut filter (Kenko L-42). Incident light intensity to the battery is 100 mW / cm²Was irradiated with simulated sunlight adjusted to.
Connect the alligator clip to the titanium dioxide electrode side metal support and the counter electrode side conductive glass of the produced photovoltaic cell, and measure the electricity generated by irradiating simulated sunlight with a current-voltage measuring device (SMU238 model manufactured by Keithley). did. The output (Pmax (mW)) of the photovoltaic cell thus obtained is shown in Table 2.
[0105]
[Example-2] (Preparation of dye-adsorbed titanium dioxide electrode using conductive support-B)
Preparation of the coating solution containing titanium dioxide particles was performed in the same manner as in Example-1.
The production of the titanium dioxide electrode adsorbed with the dye was carried out by continuously feeding the metal support-B wound in a roll shape provided with a titanium dioxide semiconductor thin film, and containing titanium dioxide particles on the surface of the oxide semiconductor thin film by a curtain coating method. After coating the coating solution with a thickness of about 60 μm, it was baked in a heating zone at 450 ° C. to form a porous titanium oxide film, and then the same dye compound R-1 used in Example-1 in the dye adsorption zone 3 × 10 of the dye represented by^-FourIt was immersed in a mol / liter concentration solution. The dye-adsorbed titanium dioxide electrode was washed with acetonitrile and naturally dried in the dark.
The electrolytic solution was injected in the same manner as in Example 1 except that the dye-sensitized titanium dioxide electrode was cut into (size 2 cm × 1.5 cm), and the photovoltaic cell 2 was prepared in the same manner as in Example 1. Produced. Evaluation of the photovoltaic cell was performed in the same manner as in Example 1, and the results are shown in Table 2.
[0106]
[Example-3]
Photoelectric cells 3 to 8 were produced in the same manner as in Example 1 except that the conductive support-A was changed to the conductive supports C to H shown in Table 1, and the maximum output values were obtained and collectively shown in Table 2. And described.
[0107]
[Comparative example]
Comparative photovoltaic cells 9 to 14 were produced in the same manner as in Example 1 except that the conductive support-A was changed to the comparative conductive supports I to N described in Table 2, and the maximum output value was obtained. It described in Table 2.
[0108]

[0109]
It can be seen that the photovoltaic cells 1 to 8 using the metal support provided with the oxide semiconductor thin film of the present invention have higher battery output than the photovoltaic cell 14 using the transparent conductive glass (TCO) of the comparative example. Moreover, it turns out that the photovoltaic cells 9-13 using the metal support body which does not provide the oxide semiconductor thin film of a comparative example do not output, or the output is low and the provision effect of an oxide semiconductor thin film is large.
[0110]
【The invention's effect】
In the present invention, a metal support wound in a roll shape can be used as the conductive support for the working electrode. Therefore, while continuously feeding the metal web from the wound metal coil, an oxide is formed on the surface of the metal support. Since a semiconductor thin film, a dye-sensitized titanium dioxide layer, etc. can be produced continuously, the manufacturing cost reduction effect is great, and the cost of the photovoltaic cell can be reduced. According to the present invention, it is possible to provide a dye-sensitized photoelectric conversion element and a photovoltaic cell having high output, low cost and excellent energy conversion efficiency.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a preferred structure of a photoelectric conversion element of the present invention.
FIG. 2 is a partial cross-sectional view showing a preferred structure of the photoelectric conversion element of the present invention.
[Explanation of symbols]
10 Oxide semiconductor film
20 Photosensitive layer
21 Semiconductor fine particles
22 Dye
23 Charge transport materials
30 Charge transfer layer
31 Solid charge transfer layer
40 Transparent conductive layer
41 Metal lead
50 Metal support
60 Transparent substrate

Claims (6)

In a method for producing a conductive support, a photosensitive layer containing a semiconductor adsorbing a dye coated on the conductive support, a charge transfer layer, and a dye-sensitized photoelectric conversion element having a counter electrode, a rolled metal A photoelectric conversion comprising a step of continuously coating an oxide semiconductor film and a photosensitive semiconductor layer using a support, wherein the conductive support comprises a metal support and an oxide semiconductor film. Device manufacturing method. The method for producing a photoelectric conversion element according to claim 1, wherein the metal support contains a metal selected from aluminum, copper, titanium, nickel, iron, stainless steel, zinc, and molybdenum . The method for producing a photoelectric conversion element according to claim 1 , wherein the metal support is a metal selected from aluminum, copper, titanium, nickel, and stainless steel . The said metal support body is aluminum or copper, The manufacturing method of the photoelectric conversion element of any one of Claims 1-3 characterized by the above-mentioned . The oxide semiconductor film contains at least one oxide selected from tin oxide, indium oxide, zinc oxide, cadmium oxide, antimony oxide, iron oxide, tungsten oxide, niobium oxide, titanium oxide, and strontium titanate. The manufacturing method of the photoelectric conversion element of any one of Claims 1-3 characterized by the above-mentioned . The method for producing a photoelectric conversion element according to claim 1, wherein the oxide semiconductor film has a thickness of 5 nm to 2 μm .

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