JP2004014370A - Oxide semiconductor electrode and photoelectric conversion element - Google Patents

Abstract

｛一般式（Ｉ）中、Ｒ^１〜Ｒ^６及びＲ^７〜Ｒ^９は、Ｈ、Ｃ_１〜Ｃ_５のアルキル基、アルコキシ基、チオアルキル基、ハロゲン原子、シアノ基、ニトロ基、（置換）アミノ基、カルボキシル基、カルボン酸エステル基、水酸基、５〜７員環の炭化水素基、または複素環基を表す。｝。
【選択図】なしAn oxide semiconductor electrode having a perimidine dye having a sensitizing effect adsorbed thereon and a photoelectric conversion element having the electrode are provided.
An organic dye-sensitized porous oxide semiconductor electrode formed by adsorbing a perimidine dye represented by the following general formula (I), and a photoelectric conversion element using the electrode.

In the general formula (I), R ^{1 to} R ⁶ and R ^{7 to} R ⁹ are H, C _{1 to} C ₅ alkyl, alkoxy, thioalkyl, halogen, cyano, nitro, (substituted) It represents an amino group, a carboxyl group, a carboxylic ester group, a hydroxyl group, a 5- to 7-membered hydrocarbon group, or a heterocyclic group. ｝.
[Selection diagram] None

Description

【０００９】
｛一般式（Ｉ）中、Ｒ^１〜Ｒ^６及びＲ^７〜Ｒ^９は、互いに独立して水素原子、炭素数１〜５のアルキル基、炭素数１〜５のアルコキシ基、炭素数１〜５のチオアルキル基、ハロゲン原子、シアノ基、ニトロ基、−ＮＲ^１１Ｒ^１２（式中、Ｒ^１１，Ｒ^１２は、水素原子、炭素数１〜３のアルキル基、またはフェニル基を表す。）、カルボキシル基、−ＣＯＯＲ^１３（式中、Ｒ^１３は炭素数１〜３のアルキル基を表す。）、水酸基、５〜７員環の飽和若しくは不飽和の炭化水素基、または５〜７員環の飽和若しくは不飽和の複素環基を表す。当該アルキル基、アルコキシ基、チオアルキル基、フェニル基、５〜７員環の炭化水素基及び複素環基は、更にハロゲン原子、炭素数１〜３のアルコキシ基、またはシアノ基で置換されていてもよい。｝。
【００１０】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明の有機色素増感型多孔質酸化物半導体電極は、有機色素を多孔質酸化物半導体の表面に吸着させて形成させてなるものであり、有機色素は前記一般式（Ｉ）で表される色素である。
前記一般式（Ｉ）において、Ｒ^１〜Ｒ^６及びＲ^７〜Ｒ^９は、互いに独立して水素原子、炭素数１〜５のアルキル基、炭素数１〜５のアルコキシ基、炭素数１〜５のチオアルキル基、ハロゲン原子、シアノ基、ニトロ基、−ＮＲ^１１Ｒ^１２（式中、Ｒ^１１，Ｒ^１２は、水素原子、炭素数１〜３のアルキル基、またはフェニル基を表す。）、カルボキシル基、−ＣＯＯＲ^１３（式中、Ｒ^１３は炭素数１〜３のアルキル基を表す。）、水酸基、５〜７員環の飽和若しくは不飽和の炭化水素基、または５〜７員環の飽和若しくは不飽和の複素環基を表す。これらのアルキル基、アルコキシ基、チオアルキル基、フェニル基、５〜７員環の炭化水素基及び複素環基は、更にハロゲン原子、炭素数１〜３のアルコキシ基、またはシアノ基で置換されていてもよい。
【００１１】
炭素数１〜５のアルキル基、炭素数１〜５のアルコキシ基、および炭素数１〜５のチオアルキル基におけるアルキルとしては、メチル、エチル、ｎ−プロピル、イソプロピル、ｎ−ブチル、イソブチル、ｔ−ブチル、アミル等が挙げられるが、これらの中メチル、エチル、ｎ−プロピル、イソプロピル等の炭素数１〜３のアルキルが好ましく、特にメチルが好ましい。
ハロゲン原子としては、塩素原子、臭素原子、フッ素原子、ヨウ素原子が挙げられるが、塩素原子および臭素原子が好ましい。
【００１２】
式−ＮＲ^１１Ｒ^１２で示されるアミノ基における置換基Ｒ^１１，Ｒ^１２は、水素原子、炭素数１〜３のアルキル基、またはフェニル基を表すが、アルキル基としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基が挙げられ、メチル基が好ましい。具体的には、アミノ基、メチルアミノ基、ジメチルアミノ基等が挙げられる。
式−ＣＯＯＲ^１３で示されるカルボン酸エステル基のＲ^１３は、炭素数１〜３のアルキル基であり、メチル基、エチル基、ｎ−プロピル基、イソプロピル基が挙げられるが、メチル基が好ましい。
【００１３】
５〜７員環の飽和若しくは不飽和の炭化水素基としては、シクロペンチル、シクロペンテニル、シクロヘキシル、シクロヘキセニル、シクロヘキサジエニル、フェニル、シクロヘプチル、シクロヘプテニル等が挙げられる。また、５〜７員環の飽和若しくは不飽和の複素環基に含まれる異原子としては、窒素、酸素、硫黄原子が挙げられる。複素環基として具体的には、ピロリニル、ピロリジニル、ピリジニル、ピペリジニル、フラニル、テトラヒドロフラニル、ピラニル、チオフェニル、チアニル等が挙げられる。これらの炭化水素基および複素環基の環が不飽和である場合、芳香族性有していなくても良い。
更に、これらの環は、ハロゲン原子、メトキシ基、エトキシ基，ｎ−プロポキシ基、イソプロポキシ基等の炭素数１〜３のアルコキシ基、またはシアノ基で置換されていてもよい。
【００１４】
本発明で使用する色素は、上記一般式（Ｉ）において、Ｒ^１〜Ｒ^６が水素原子、炭素数１〜５のアルキル基、炭素数１〜５のアルコキシ基、ハロゲン原子、シアノ基、またはカルボキシル基であり、Ｒ^７〜Ｒ^９が水素原子であるものが好ましい。更にＲ^１〜Ｒ^６のうち、特にＲ^１、Ｒ^３及びＲ^４がメチル基、メトキシ基、塩素原子、臭素原子、シアノ基、またはカルボキシル基でるのが好ましく、Ｒ^３およびＲ^４が同種であっても良い。Ｒ^７〜Ｒ^９は、好ましくは水素原子である。
【００１５】
本発明の一般式（Ｉ）で表される色素の具体例を以下に示す。
【化３】

【００１６】
【化４】

【００１７】
本発明の有機色素増感型多孔質酸化物半導体電極は、所定の多孔質酸化物半導体に、特定の有機色素を吸着させることによって製造される。増感色素の吸着点を増やすという観点から、酸化物半導体の表面積は高い方が好ましい。さらに、酸化物半導体の一次粒子径が小さいことが好ましい。酸化物半導体の一次粒子径の下限は１ｎｍ以上であり、上限は２００ｎｍ以下、好ましくは５０ｎｍ以下である。その比表面積は５〜１００ｍ^２／ｇ程度である。　酸化物半導体を電極とするにはその粉末だけでペレット化して焼結してもよいが、導電性基板上に酸化物半導体の焼成物膜を形成し、基板上に固定して用いるのが好ましい。この場合基板としては、導電性を有する基板で、例えばガラス上にＩｎ_２Ｏ_３やＳｎＯ_２等の導電性金属酸化物薄膜を形成した導電性ガラスやカーボンなどでもよい。この導電性表面を有する基板は、透明又は不透明であってもよい。
基板上の酸化物半導体の厚さは通常、２００ｎｍ以上、好ましくは１０００ｎｍ以上であり、２００００ｎｍ以下である。この範囲以下であると電極が薄いために光が透過してしまうため好ましくない。
【００１８】
酸化物半導体としては公知のものを用いることができる。このようなものには、酸化チタン、酸化亜鉛、酸化すず、酸化インジウム、酸化ニオブなどがあげられる。
酸化物半導体粒子は、純粋な金属前駆体の分解によって調製する。金属前駆体としては、出来るだけ不純物の少ない上記金属の水酸化物、硝酸塩、塩化物、アルコキシド等を充分精製してから加水分解して純粋な水酸化物を調製し、用いても良い。また不純物が少なく表面積の大きな酸化物半導体微粒子が市販であるときはそれを利用しても良い。多孔質酸化物半導体電極が充分に機能するためには、金属酸化物又は低温で加水分解した金属酸化物は前焼成するのが望ましい。この前焼成は、金属酸化物を空気中で通常３００℃以上、好ましくは５００℃以上で、９００℃以下、好ましくは８００℃以下の温度にゆっくり昇温し、その温度に約１時間保ち、またゆっくり温度を下げることによって実施される。
【００１９】
前焼成して形成した酸化物は、上記の導電性基板に所定の厚さで固定される。そのためには酸化物の懸濁液に基板をディッピングしてもいいし、酸化物のスラリーを基板上に塗布してもよい。酸化物スラリー（塗布液）は水又は有機溶媒中に酸化物微粒子を分散させて調製されるが、必要に応じ界面活性剤やポリエチレングリコールなどの粘度調節剤を添加して粘性を高めてもよい。その後基板上の塗布液はゆっくり乾燥させる。次に基板ごと空気中又は不活性雰囲気下で焼成を行い、基板上により強く固定した焼成物膜を形成する。焼成温度は、通常３００℃以上、好ましくは４００℃以上で、９００℃以下、好ましくは８００℃以下の温度で１時間程度行う。ただし、焼成は、基板に損傷を与えない温度で行なうことが必要である。
【００２０】
本発明の有機色素増感型多孔質酸化物半導体電極は、多孔質酸化物半導体電極に特定の有機色素、即ち前記一般式（１）で示されるペリミジン系色素を単分子吸着させることにより形成される。このためには、まず、有機色素を有機溶媒に溶解させ、有機色素溶液を調製する。有機溶媒の種類は、有機色素に対しある程度の溶解度を持ち、かつ有機色素の半導体への吸着を阻害しないものが好ましい。具体的には、メタノール、エタノール、ｔｅｒｔ−ブタノール、アセトニトリル、ジメチルホルムアミドなどの溶媒が挙げられる。有機色素溶液中の色素濃度は、色素及び溶媒の種類により適宜決められるが、通常、溶液１００ｍｌ中、１ｍｇ以上、好ましくは１０ｍｇ以上で、１００００ｍｇ以下、好ましくは５００ｍｇ以下程度である。
【００２１】
次に、酸化物半導体電極をこの色素溶液に浸すが、上記のようにして調製した基板上の酸化物半導体膜の場合は、基板とともに浸漬すればよい。色素溶液の温度は室温〜色素の分解温度または溶媒の沸点のいずれか低い温度まであげられる。温度を上昇するのは色素溶液を多孔質な電極の内部までしみ込ませるためであり、又、その為には電極を色素溶液に浸漬するに先立ち、減圧処理または加温処理温することにより電極内部の気泡を除去しておくのが好ましい。温度は溶媒の沸点または色素の分解温度のいずれか低い温度以下にあわせる。浸漬時間（吸着時間）は３０分を基準にするが、数分から１昼夜（２４時間）行っても良い。色素濃度は１００ｍｇ／１００ｍｌを基準にするが、その１００倍程度濃度が高くても問題ない。色素の溶解度が低い場合は、浸漬処理を繰り返して行っても良い。又、色素の吸着がうまくいかないときは、促進剤を添加する。例えば、色素を半導体表面とエステル結合させるには脱水剤を入れると良い。浸漬処理後の色素を吸着した酸化物半導体電極は、通常、室温〜８０℃程度で乾燥する。
【００２２】
本発明においては、酸化物半導体に吸着させる色素は１種である必要はなく、好ましくは光吸収領域の異なる複数の有機色素を吸着させる。これによって、光を効率よく利用することができる。複数の有機色素を酸化物半導体膜に吸着させるには、複数の有機色素を含む溶液中に酸化物半導体膜を浸漬する方法や、有機色素溶液を複数用意し、これらの溶液に酸化物半導体膜を順次浸漬する方法等が挙げられる。
【００２３】
本発明の光電変換素子は、少なくとも上記の有機色素増感型多孔質酸化物半導体電極、その対向電極及び該電極間に挟持される導電層を有するものである。電極間に挟持される導電層としては、公知の導電性材料から構成され、電子、ホール、イオンを輸送できるものを用いることができる。具体的には、例えば、ポリビニルカルバゾール等のホール輸送材料、電子輸送材料、ポリピロール等の導電性ポリマー、液体電解質、高分子固体電解質等のイオン導電体を用いることができる。
【００２４】
本発明において、液体電解質に、Ｉ⁻／Ｉ^３−系や、Ｂｒ⁻／Ｂｒ^３−系、Ｆｅ^２＋／Ｆｅ^３＋系、キノン／ハイドロキノン系等の酸化還元種を含有させてもよい。このような酸化還元種は、従来公知の方法によって得ることができ、例えば、Ｉ⁻／Ｉ^３−酸化還元種は、ヨウ素のリチウム塩とヨウ素を混合することによって得ることができる。液体電解質において、その溶媒としては、電気化学的に不活性なものが用いられ、例えば、アセトニトリル、炭酸プロピレン、エチレンカーボネート等が用いられる。
【００２５】
次に、固体電解質としては、酸化還元種を溶解あるいは酸化還元種を構成する少なくとも１つの物質と結合することができる固体状の物質であり、たとえば、ポリエチレンオキシド、ポリプロピレンオキシド、ポリエチレンサクシネート、ポリ−β−プロピオラクトン、ポリエチレンイミン、ポリアルキレンスルフィドなどの高分子化合物またはそれらの架橋体、ポリフォスファゼン、ポリシロキサン、ポリビニルアルコール、ポリアクリル酸、ポリアルキレンオキサイドなどの高分子官能基に、ポリエーテルセグメントまたはオリゴアルキレンオキサイド構造を側鎖として付加したもの、またはそれらの共重合体などが挙げられ、その中でも特にオリゴアルキレンオキサイド構造を側鎖として有するものやポリエーテルセグメントを側鎖として有するものが好ましい。
【００２６】
前記の固体中に酸化還元種を含有させるには、たとえば、高分子化合物となるモノマーと酸化還元種との共存下で重合する方法、高分子化合物などの固体を必要に応じて溶媒に溶解し、次いで、前記の酸化還元種を加えてもよい。酸化還元種の含有量は、必要とするイオン伝導性能に応じて、適宜選定することができる。
【００２７】
対向電極としては、通常の電極として使用されるものから適宜選択して使用することが出来、例えば、白金電極、導電材料表面に白金めっきや白金蒸着を施したもの、ロジウム金属、ルテニウム金属、酸化ルテニウム、カーボン等が挙げられる。
【００２８】
本発明による光電変換素子は、太陽電池、光スイッチング装置、センサー等のデバイスに適用される。本発明の光電変換素子を用いた太陽電池に太陽光を照射すると、太陽電池における色素は光を吸収して励起する。この励起によって発生する電子とホールはそれぞれ半導体層に移動し、次いで、透明導電性電極を通って対電極に移動する。一方、太陽電池内部において、色素に残る電子は電解質中の酸化還元種を通して、対極の色素に戻る。このようなプロセスによって電流が流れ、光エネルギーは連続的に電気エネルギーに変換される。
【００２９】
本発明による光電変換素子の応用例としては、従来より太陽電池やそれを用いた電源装置を利用している機器であれば、いずれのものでも可能であり、例えば、電子卓上計算機、腕時計用の太陽電池に用いることも可能であるが、上述した本発明の光電変換素子の特徴を有利に活用する例としては、例えば、携帯電話、携帯ラジオ、携帯オーディオ機器、カーアクセサリー、日照時間の短い地域で使用される道路標識などがあげられる。また、充電式や乾電池式の電気機器の連続使用時間を長くするための補助電源として用いることもでき、特に二次電池充電用の電源装置として用いることが有効である。
【００３０】
【実施例】
次に、本発明を実施例により更に詳細に説明するが、本発明はその要旨を越えない限り以下の実施例に限定されるものではない。
実施例１
（ａ）酸化物半導体電極の作成
酸化チタン（日本アエロジル（株）製；「Ｐ−２５」）６．０ｇ、アセチルアセトン０．２ｍｌ、純水８ｍｌ、および界面活性剤（ナカライテクス（株）製；商品名「トリトン　Ｘ−１００」）０．２ｍｌを混合してスラリーを作成した。
作成したスラリーを、フッ素ドープした酸化スズ電極を設けた透明ガラス上に塗布し、膜を作成した。４５０℃、３０分焼成後、放冷して酸化チタン膜の電極を得た。膜厚は７μｍである。
【００３１】
（ｂ）色素の吸着
下記構造式で表される有機色素（有本化学工業（株）製；色素「ＳｃａｒｌｅｔＲ−１」）を、
【化５】

ブタノール／アセトニトリル＝１／１（容量比）の混合溶液に溶解し、これに先に（ａ）で作成した酸化チタン電極を一昼夜（２４時間）漬けた。電極を引き上げエタノールで洗浄後、色素が吸着した電極を得た。
【００３２】
（ｃ）光電変換素子作成
Ｐｔ電極を対極に用い、レドックス電解液としては、ヨウ化リチウム（０．１Ｍ）、１，２−ジメチル−３−プロピルイミダゾリウムヨウ素（０．６Ｍ）、ヨウ素（０．０５Ｍ）、および４−ｔ−ブチルピリジン（１Ｍ）のメトキシアセトニトリル溶液を用いた。
上記（ｂ）で作製した色素を吸着した酸化チタン電極とＰｔ電極の間に、レドックス電解液を入れて光電変換素子を作成した。
該素子の分光感度を、定光量分光感度測定装置（日本分光（株）製「ＹＱ−２５０」）を用いて測定したところ、波長４６０ｎｍ（使用した有機色素「ＳｃａｒｌｅｔＲ−１」の、エタノール中における最大吸収波長）における光電変換の量子効率（ＩＰＣＥ；Ｉｎｃｉｄｅｎｔ　Ｐｈｏｔｏｎ−ｔｏ−Ｃｕｒｒｅｎｔ　Ｃｏｎｖｅｒｓｉｏｎ　Ｅｆｆｉｃｉｅｎｃｙ）は１０％であり、光電変換能を示した。
【００３３】
【発明の効果】
本発明のペリミジン系色素は、増感作用を有するので、該色素を吸着させた酸化物半導体電極を用いた光電変換素子は光電変換効率に優れた性能を有する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an organic dye-sensitized porous oxide semiconductor electrode using a specific perimidine dye, and a photoelectric conversion element using the same, such as a solar cell.
[0002]
[Prior art]
Attention has been paid to solar cells using sunlight as an energy source instead of fossil fuels, and various studies have been made. Currently, the mainstream of solar cells that are put into practical use is to use polycrystalline or amorphous silicon cells.However, economical costs and energy costs in the manufacturing process are high, and highly toxic materials such as gallium and arsenic are used. Seems to have a problem.
[0003]
As a new type of solar cell, Japanese Unexamined Patent Publication Nos. 5-50402, 7-500630, and WO 94/05025 disclose wet solar cells to which photoinduced electron transfer of a metal complex is applied. I have.
The wet solar cell has two electrodes, at least one of which is substantially transparent, separated by an electrolytic solution, and the transparent electrode comprises a porous titanium dioxide layer on which a photosensitizing dye is adsorbed. Have.
[0004]
The principle of this wet solar cell is that titanium dioxide as a semiconductor is made to adsorb a photosensitizing dye having the lowest unoccupied orbital of electrons at a higher position, and the highest occupied orbital of the photosensitizing dye from an electron donor. By applying a fast electron transfer to the anode, the anode current flows due to the quick electron transfer of the excited electrons. This wet type solar cell has advantages such as low cost, high efficiency, simple structure and easy manufacture.
[0005]
In Japanese Patent Application Laid-Open Nos. Hei 5-502043, Hei 7-500630 and WO 94/05025, iodine is used as an electron donor, and titanium dioxide is used as an electron acceptor (semiconductor). As the sensitizing dye, a ruthenium complex of a polypyridyl compound is used. In WO 94/05025, a phthalocyanine compound having a carboxyl group, a naphthalocyanine compound, or the like is also used as a photosensitizing dye.
[0006]
However, the ruthenium complex of the polypyridyl compound used as the photosensitizing dye has problems such as insufficient light fastness, a complicated production method, and an expensive ruthenium. Research on wet-type solar cells using an organic dye having an excellent sensitizing effect instead of the ruthenium complex has been advanced.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide an oxide semiconductor electrode using an organic dye having a high sensitizing effect. By using the electrode, a photoelectric conversion element having high photoelectric conversion ability can be provided.
[0008]
[Means for Solving the Problems]
The gist of the present invention is to provide an organic dye-sensitized porous oxide semiconductor electrode formed by adsorbing an organic dye represented by the following general formula (I) on the surface of a porous oxide semiconductor, and the electrode: There is a photoelectric conversion element using.
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[0009]
中 In the general formula (I), R ^{1 to} R ⁶ and R ^{7 to} R ⁹ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, 5, a thioalkyl group, a halogen atom, a cyano group, a nitro group, -NR ¹¹ R ¹² (wherein R ¹¹ and R ¹² represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group), A carboxyl group, —COOR ¹³ (wherein, R ¹³ represents an alkyl group having 1 to 3 carbon atoms), a hydroxyl group, a 5- to 7-membered saturated or unsaturated hydrocarbon group, or a 5- to 7-membered ring. Represents a saturated or unsaturated heterocyclic group. The alkyl group, alkoxy group, thioalkyl group, phenyl group, 5- to 7-membered hydrocarbon group and heterocyclic group may be further substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or a cyano group. Good. ｝.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The organic dye-sensitized porous oxide semiconductor electrode of the present invention is formed by adsorbing an organic dye on the surface of a porous oxide semiconductor, and the organic dye is represented by the general formula (I). Dye.
In the general formula (I), R ^{1 to} R ⁶ and R ^{7 to} R ⁹ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, 5, a thioalkyl group, a halogen atom, a cyano group, a nitro group, -NR ¹¹ R ¹² (wherein R ¹¹ and R ¹² represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group), A carboxyl group, —COOR ¹³ (wherein, R ¹³ represents an alkyl group having 1 to 3 carbon atoms), a hydroxyl group, a 5- to 7-membered saturated or unsaturated hydrocarbon group, or a 5- to 7-membered ring. Represents a saturated or unsaturated heterocyclic group. These alkyl group, alkoxy group, thioalkyl group, phenyl group, 5- to 7-membered hydrocarbon group and heterocyclic group may be further substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or a cyano group. Is also good.
[0011]
Examples of the alkyl in the alkyl group having 1 to 5 carbon atoms, the alkoxy group having 1 to 5 carbon atoms, and the thioalkyl group having 1 to 5 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t- Examples thereof include butyl and amyl. Among them, alkyl having 1 to 3 carbon atoms such as methyl, ethyl, n-propyl and isopropyl is preferable, and methyl is particularly preferable.
Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom, and a chlorine atom and a bromine atom are preferable.
[0012]
The substituents R ¹¹ and R ¹² in the amino group represented by the formula —NR ¹¹ R ¹² represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group, and examples of the alkyl group include a methyl group and an ethyl group. , N-propyl group and isopropyl group, and a methyl group is preferable. Specific examples include an amino group, a methylamino group, and a dimethylamino group.
R ¹³ of the carboxylic acid ester group represented by the formula —COOR ¹³ is an alkyl group having 1 to 3 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, and an isopropyl group, and a methyl group is preferable.
[0013]
Examples of the 5- to 7-membered saturated or unsaturated hydrocarbon group include cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, phenyl, cycloheptyl, cycloheptenyl and the like. Further, examples of the heteroatom contained in the 5- to 7-membered saturated or unsaturated heterocyclic group include nitrogen, oxygen and sulfur atoms. Specific examples of the heterocyclic group include pyrrolinyl, pyrrolidinyl, pyridinyl, piperidinyl, furanyl, tetrahydrofuranyl, pyranyl, thiophenyl, and thianyl. When the rings of these hydrocarbon groups and heterocyclic groups are unsaturated, they do not need to have aromaticity.
Furthermore, these rings may be substituted with a halogen atom, a methoxy group, an ethoxy group, an n-propoxy group, an alkoxy group having 1 to 3 carbon atoms such as an isopropoxy group, or a cyano group.
[0014]
In the dye used in the present invention, in the general formula (I), R ^{1 to} R ⁶ are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogen atom, a cyano group, or Preferred is a carboxyl group, wherein R ^{7 to} R ⁹ are hydrogen atoms. Further, among R ^{1 to} R ⁶ , R ¹ , R ³ and R ⁴ are particularly preferably a methyl group, a methoxy group, a chlorine atom, a bromine atom, a cyano group or a carboxyl group, and R ³ and R ⁴ are the same. There may be. R ^{7 to} R ⁹ are preferably a hydrogen atom.
[0015]
Specific examples of the dye represented by formula (I) of the present invention are shown below.
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[0016]
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[0017]
The organic dye-sensitized porous oxide semiconductor electrode of the present invention is manufactured by adsorbing a specific organic dye on a predetermined porous oxide semiconductor. From the viewpoint of increasing the adsorption point of the sensitizing dye, the surface area of the oxide semiconductor is preferably higher. Further, the oxide semiconductor preferably has a small primary particle diameter. The lower limit of the primary particle diameter of the oxide semiconductor is 1 nm or more, and the upper limit is 200 nm or less, preferably 50 nm or less. Its specific surface area is about 5 to 100 m ² / g. In order to use an oxide semiconductor as an electrode, it may be pelletized and sintered only with the powder, but it is preferable to form a fired product film of the oxide semiconductor on a conductive substrate and fix it on the substrate for use. . In this case, the substrate may be a conductive substrate, for example, conductive glass or carbon formed by forming a conductive metal oxide thin film such as In ₂ O ₃ or SnO _{2 on} glass. The substrate having this conductive surface may be transparent or opaque.
The thickness of the oxide semiconductor on the substrate is usually greater than or equal to 200 nm, preferably greater than or equal to 1000 nm, and less than or equal to 20000 nm. If the thickness is less than this range, light is transmitted because the electrode is thin, which is not preferable.
[0018]
A known oxide semiconductor can be used. Such materials include titanium oxide, zinc oxide, tin oxide, indium oxide, niobium oxide and the like.
Oxide semiconductor particles are prepared by decomposition of a pure metal precursor. As the metal precursor, a pure hydroxide may be prepared by sufficiently purifying a hydroxide, a nitrate, a chloride, an alkoxide, or the like of the above-mentioned metal having as few impurities as possible, and then hydrolyzing it to prepare a pure hydroxide. When oxide semiconductor particles having a small amount of impurities and a large surface area are commercially available, they may be used. In order for the porous oxide semiconductor electrode to function sufficiently, it is desirable that the metal oxide or the metal oxide hydrolyzed at a low temperature be pre-baked. In this pre-baking, the metal oxide is slowly heated to a temperature of usually 300 ° C. or higher, preferably 500 ° C. or higher, and 900 ° C. or lower, preferably 800 ° C. or lower in air, and kept at that temperature for about 1 hour; This is done by slowly lowering the temperature.
[0019]
The oxide formed by pre-baking is fixed to the conductive substrate with a predetermined thickness. For this purpose, the substrate may be dipped in an oxide suspension, or an oxide slurry may be applied on the substrate. The oxide slurry (coating solution) is prepared by dispersing oxide fine particles in water or an organic solvent, and may be added with a viscosity modifier such as a surfactant or polyethylene glycol as needed to increase the viscosity. . Thereafter, the coating liquid on the substrate is slowly dried. Next, the whole substrate is fired in air or under an inert atmosphere to form a fired product film which is more firmly fixed on the substrate. The firing temperature is usually 300 ° C. or higher, preferably 400 ° C. or higher, and 900 ° C. or lower, preferably 800 ° C. or lower for about 1 hour. However, baking must be performed at a temperature that does not damage the substrate.
[0020]
The organic dye-sensitized porous oxide semiconductor electrode of the present invention is formed by adsorbing a single molecule of a specific organic dye, that is, a perimidine-based dye represented by the general formula (1), on the porous oxide semiconductor electrode. You. For this purpose, first, an organic dye is dissolved in an organic solvent to prepare an organic dye solution. The type of the organic solvent is preferably one having a certain degree of solubility in the organic dye and not inhibiting the adsorption of the organic dye to the semiconductor. Specifically, solvents such as methanol, ethanol, tert-butanol, acetonitrile, dimethylformamide and the like can be mentioned. The dye concentration in the organic dye solution is appropriately determined depending on the types of the dye and the solvent, but is usually about 1 mg or more, preferably 10 mg or more, and 10,000 mg or less, preferably about 500 mg or less in 100 ml of the solution.
[0021]
Next, the oxide semiconductor electrode is immersed in the dye solution. In the case of an oxide semiconductor film on a substrate prepared as described above, it may be immersed together with the substrate. The temperature of the dye solution is from room temperature to a temperature at which the decomposition temperature of the dye or the boiling point of the solvent is lower. The temperature is increased to allow the dye solution to penetrate into the porous electrode, and for this purpose, before the electrode is immersed in the dye solution, the electrode is subjected to a decompression treatment or a heating treatment to increase the temperature inside the electrode. It is preferable to remove air bubbles. The temperature is adjusted to a temperature lower than the lower of the boiling point of the solvent or the decomposition temperature of the dye. The immersion time (adsorption time) is based on 30 minutes, but may be several minutes to one day and night (24 hours). The dye concentration is based on 100 mg / 100 ml, but there is no problem if the concentration is about 100 times higher. When the solubility of the dye is low, the immersion treatment may be repeated. If the dye does not adsorb properly, an accelerator is added. For example, a dehydrating agent may be added to form a dye into an ester bond with the semiconductor surface. The oxide semiconductor electrode that has absorbed the dye after the immersion treatment is usually dried at room temperature to about 80 ° C.
[0022]
In the present invention, the dye adsorbed on the oxide semiconductor does not need to be one kind, and preferably, a plurality of organic dyes having different light absorption regions are adsorbed. Thus, light can be used efficiently. In order to adsorb a plurality of organic dyes to the oxide semiconductor film, a method of immersing the oxide semiconductor film in a solution containing a plurality of organic dyes, or a method of preparing a plurality of organic dye solutions, and adding the oxide semiconductor film to these solutions Are sequentially immersed.
[0023]
The photoelectric conversion element of the present invention has at least the organic dye-sensitized porous oxide semiconductor electrode described above, a counter electrode thereof, and a conductive layer sandwiched between the electrodes. As the conductive layer sandwiched between the electrodes, a layer formed of a known conductive material and capable of transporting electrons, holes, and ions can be used. Specifically, for example, hole transport materials such as polyvinyl carbazole, electron transport materials, conductive polymers such as polypyrrole, and ionic conductors such as liquid electrolytes and solid polymer electrolytes can be used.
[0024]
In the present invention, the liquid electrolyte may contain a redox species such as an I ⁻ / I ³⁻ system, a Br ⁻ / Br ³⁻ system, an Fe ²⁺ / Fe ³⁺ system, and a quinone / hydroquinone system. Such a redox species can be obtained by a conventionally known method. For example, an I ⁻ / I ^{3 −} redox species can be obtained by mixing a lithium salt of iodine with iodine. In the liquid electrolyte, an electrochemically inert solvent is used as the solvent, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like.
[0025]
Next, the solid electrolyte is a solid substance capable of dissolving the redox species or combining with at least one substance constituting the redox species, such as polyethylene oxide, polypropylene oxide, polyethylene succinate, Polymer compounds such as -β-propiolactone, polyethyleneimine, polyalkylene sulfide or cross-linked products thereof, polyphosphazene, polysiloxane, polyvinyl alcohol, polyacrylic acid, polyalkylene oxide; Those having an ether segment or an oligoalkylene oxide structure added as a side chain, or copolymers thereof, and the like, among which those having an oligoalkylene oxide structure as a side chain and a polyether segment as a side chain As it has been it is preferable.
[0026]
In order to contain the redox species in the solid, for example, a method of polymerizing in the coexistence of a monomer to be a polymer compound and the redox species, a solid such as a polymer compound is dissolved in a solvent as necessary Then, the redox species described above may be added. The content of the redox species can be appropriately selected according to the required ion conduction performance.
[0027]
The counter electrode can be appropriately selected from those used as a normal electrode and used, for example, a platinum electrode, a platinum-plated or platinum-deposited conductive material surface, rhodium metal, ruthenium metal, oxide Ruthenium, carbon and the like can be mentioned.
[0028]
The photoelectric conversion element according to the present invention is applied to devices such as solar cells, optical switching devices, and sensors. When sunlight is irradiated on a solar cell using the photoelectric conversion element of the present invention, the dye in the solar cell absorbs light and is excited. The electrons and holes generated by this excitation move to the semiconductor layer, and then move to the counter electrode through the transparent conductive electrode. On the other hand, inside the solar cell, the electrons remaining in the dye return to the counter electrode through the redox species in the electrolyte. Through such a process, current flows and light energy is continuously converted to electrical energy.
[0029]
As an application example of the photoelectric conversion element according to the present invention, any device that conventionally uses a solar cell or a power supply device using the same can be used, such as an electronic desk calculator and a wristwatch. Although it is possible to use it for a solar cell, examples of advantageous use of the characteristics of the above-described photoelectric conversion element of the present invention include, for example, a mobile phone, a mobile radio, a mobile audio device, a car accessory, and an area with a short sunshine time. Road signs and the like. Further, it can be used as an auxiliary power supply for extending the continuous use time of a rechargeable or dry battery type electric device, and it is particularly effective to use it as a power supply device for charging a secondary battery.
[0030]
【Example】
Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.
Example 1
(A) Preparation of an oxide semiconductor electrode 6.0 g of titanium oxide (manufactured by Nippon Aerosil Co., Ltd .; "P-25"), 0.2 ml of acetylacetone, 8 ml of pure water, and a surfactant (manufactured by Nakarai Tex Corp .; 0.2 ml of trade name "Triton X-100") was mixed to prepare a slurry.
The prepared slurry was applied on a transparent glass provided with a fluorine-doped tin oxide electrode to form a film. After firing at 450 ° C. for 30 minutes, the mixture was allowed to cool to obtain a titanium oxide film electrode. The thickness is 7 μm.
[0031]
(B) Adsorption of dye An organic dye represented by the following structural formula (manufactured by Arimoto Chemical Co., Ltd .;
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It was dissolved in a mixed solution of butanol / acetonitrile = 1/1 (volume ratio), and the titanium oxide electrode previously prepared in (a) was immersed in it for 24 hours. After the electrode was lifted and washed with ethanol, an electrode having a dye adsorbed thereon was obtained.
[0032]
(C) Preparation of photoelectric conversion element A Pt electrode was used as a counter electrode, and as a redox electrolyte, lithium iodide (0.1 M), 1,2-dimethyl-3-propylimidazolium iodine (0.6 M), iodine (0 M) was used. 0.05M), and a solution of 4-t-butylpyridine (1M) in methoxyacetonitrile.
A redox electrolytic solution was inserted between the titanium oxide electrode adsorbing the dye prepared in (b) and the Pt electrode to prepare a photoelectric conversion element.
When the spectral sensitivity of the element was measured using a constant light intensity spectral sensitivity measuring device (“YQ-250” manufactured by JASCO Corporation), the wavelength of 460 nm (the used organic dye “ScarletR-1”) in ethanol The quantum efficiency (IPCE; Incident Photon-to-Current Conversion Efficiency) of the photoelectric conversion at the maximum absorption wavelength was 10%, indicating a photoelectric conversion ability.
[0033]
【The invention's effect】
Since the perimidine-based dye of the present invention has a sensitizing effect, a photoelectric conversion element using an oxide semiconductor electrode to which the dye is adsorbed has excellent performance in photoelectric conversion efficiency.

Claims (3)

An organic dye-sensitized porous oxide semiconductor electrode formed by adsorbing an organic dye represented by the following general formula (I) on the surface of a porous oxide semiconductor.

中 In the general formula (I), R ^{1 to} R ⁶ and R ^{7 to} R ⁹ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, 5, a thioalkyl group, a halogen atom, a cyano group, a nitro group, -NR ¹¹ R ¹² (wherein R ¹¹ and R ¹² represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group), A carboxyl group, —COOR ¹³ (wherein, R ¹³ represents an alkyl group having 1 to 3 carbon atoms), a hydroxyl group, a 5- to 7-membered saturated or unsaturated hydrocarbon group, or a 5- to 7-membered ring. Represents a saturated or unsaturated heterocyclic group. The alkyl group, alkoxy group, thioalkyl group, phenyl group, 5- to 7-membered hydrocarbon group and heterocyclic group may be further substituted with a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or a cyano group. Good. ｝. In the general formula ^(I), R 1 ~R ⁶ is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a halogen atom, a cyano group or a carboxyl group,, ^{R 7} organic dye-sensitized porous oxide semiconductor electrode according to claim 1, characterized in that to R ⁹ is a hydrogen atom. In a photoelectric conversion element having an oxide semiconductor electrode, a counter electrode and a conductive layer sandwiched between the electrodes, the oxide semiconductor electrode is the organic dye-sensitized porous oxide semiconductor electrode according to claim 1 or 2. A photoelectric conversion element characterized by the above-mentioned.