JP2004103404A - Ion conductive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet solar cell in which an open circuit voltage is not reduced even if the open circuit voltage is high and used for a long period of time. <P>SOLUTION: In the wet solar cell having a structure in which a charge transfer layer is installed between a negative electrode consisting of a photoelectric conversion element wherein a photosensitive layer including a semiconductor layer to which a pigment is adhered is retained on an electroconductive support and opposing electrode, as the charge transfer layer, an ionic conductive composition containing an amide compound having a group shown by a formula in Fig. in a molecule such as 3,4-dihydropyrrole 2-on, and an electrolyte such as 1,2-dimethylpropyl imidazolium iodide, 1-hexyl-3-methyl imidazolium iodide, 1-propyl-3-methyl imidazolium iodide, lithium iodide, and potassium iodide is used. However, hydrogen atom is not bound to nitrogen atom in the formula. <P>COPYRIGHT: (C)2004,JPO

Description

【００１０】
（但し、上記式で示される基の窒素原子に直接水素原子が結合することはない。）
で示される３価の基を有するアミド化合物及び電解質を含有してなることを特徴とするイオン導電性組成物である。
【００１１】
また、他の本発明は、上記イオン導電性組成物を用いた電荷移動層を具備する光化学電池である。
【００１２】
発明は理論に拘束されるものではないが、本発明の優れた効果が発現する機構は次のようなものであると考えられる。即ち、従来の湿式太陽電池においては、負極において半導体層に流れ込んだ電子の全てが導電性支持体に流れずにその一部が漏れ電流（暗電流ともいう）として電荷移動相中のＩ_２またはＩ_３ ⁻に流れて開放電圧が低下するのに対し、本発明のイオン導電性組成物を電荷移動層に用いた湿式太陽電池においては、本発明のイオン導電性組成物に含まれる前記アミド化合物が半導体の色素が吸着していない部分に吸着することにより上記のような漏れ電流の発生が抑制されて、開放電圧が向上するものと思われる。このような効果は４−ｔｅｒｔ−ブチルピリジン、２−ビニルピリジン、カルボン酸類等を用いた場合にも得られるが、これら化合物に比べて前記アミド化合物は化合物側の吸着サイト近傍の電子密度や立体構造が、半導体側の漏れ電流を発生させやすいサイトに吸着するのに適度であるため、このようなサイトが選択的にふさがれ、漏れ電流発生防止効果（別言すれば、開放電圧向上効果）が高くなっているものと推測される。また、アミド化合物自体或いは吸着した状態でのアミド化合物が安定であるため、開放電圧向上効果が長期間安定して持続すると考えられる。さらに、一般に半導体に化合物が吸着されると抵抗が上昇し、短絡電流が低下する傾向があるが、前記アミド化合物は特定の吸着サイトに選択的に吸着するため短絡電流低下率が他の化合物を用いたときよりも小さくなっているものと思われる。
【００１３】
【発明の実施の形態】
本発明のイオン導電性組成物は、分子内に下記式
【００１４】
【化６】

【００１５】
（但し、上記式で示される基の窒素原子に直接水素原子が結合することはない。）
で示される３価の基を有するアミド化合物及び電解質を含有してなる。上記アミド化合物が添加された電解質を含むイオン導電性組成物を電荷移動層として用いることにより、光電池の開放電圧を高くし、変換効率を高くすると共にその効果を長期間安定して持続することが可能となる。
【００１６】
本発明で使用するアミド化合物は、分子内に上記式で示される３価の基｛＝Ｎ−Ｃ（＝Ｏ）−基｝（但し、上記式で示される基の窒素原子に直接水素原子が結合することはない。）を有すること、即ち、Ｎ二置換アミド化合物であることを必須とする。同じアミド化合物であっても窒素原子に１または２個の水素原子が直接結合しているアミド化合物｛別言すれば、Ｈ_２Ｎ−Ｃ（＝Ｏ）−基または−ＨＮ−Ｃ（＝Ｏ）−基を有するアミド化合物｝を使用した場合には、恐らく窒素原子の電子密度が低下するため、あるいは、水素が障害となるために半導体への選択的な吸着が起こり難くなることが原因と思われるが、このような効果を得ることはできない。
【００１７】
本発明で使用するアミド化合物は、上記式で示される基を有するアミド化合物であれば特に限定されないが、開放電圧向上効果およびその効果の持続性の高さの観点から、上記式で示される基における窒素原子の半経験的分子軌道法ＰＭ３法で求められる電荷が−０．０９５〜−０．１７５（ｅ．ｕ．）であり、当該基における酸素原子の半経験的分子軌道法ＰＭ３法で求められる電荷が−０．２２５〜−０．２６５（ｅ．ｕ．）であるアミド化合物を使用するのが好適である。
【００１８】
なお、窒素原子および酸素原子の電子密度を求めるのに使用する半経験的分子軌道法ＰＭ３法とはＪ．Ｐ．Ｓｔｅｗａｒｔらが１９８９年に発表した分子軌道計算方法で、ＭＯＰＡＣとして広く利用されている分子軌道計算用プログラムで利用可能である。
【００１９】
本発明においては、上記したような効果が特に高いという理由から、下記式
【００２０】
【化７】

【００２１】
（式中、下記式
【００２２】
【化８】

【００２３】
で示される環は、環員数５或いは６の単環式へテロ環または炭素数５〜６の環が２〜５個縮合した縮合へテロ環であり、Ｒは、置換若しくは非置換のアルキル基または置換若しくは非置換のアリール基であり、ａは０〜４の整数であり、ａが２以上のときＲは互いに異なっていてもよい。）
で示されるアミド化合物を使用するのが特に好適である。
【００２４】
前記式における下記
【００２５】
【化９】

【００２６】
で示される環の内、好適な環を具体的に例示すると、次のような環を挙げることができる。
【００２７】
【化１０】

【００２８】
また、前記式における好適なＲを具体的に例示すると、非置換アルキル基としては、メチル基、エチル基、プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｔｅｒｔ−ブチル基、ペンチル基およびヘキシル基等の炭素数１〜８のアルキル基が、置換アルキル基としてはベンジル基が、非置換アリール基としてはフェニル基およびナフチル基が、置換アリール基としてはこれら非置換アリール基の１〜４個の水素原子がメチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔｅｒｔ−ブチル基等の炭素数１〜４のアルキル基またはフッ素、塩素等のハロゲン原子等で置換されたものを挙げることができる。これらの中でも、炭素数３〜５の直鎖或いは分岐の非置換アルキル基またはフェニル基が特に好適である。
前記式で示される３価の基を有するアミド化合物のうち、本発明で好適に使用できるものを具体的に示せば、下記構造の化合物を挙げることができる。
【００２９】
【化１１】

【００３０】
本発明のイオン導電性組成物で使用する電解質は、水その他の溶媒に溶解したときの溶液がイオン電導性を示すような物質であれば特に限定されず、湿式太陽電池等の光化学電池で従来使用されている電解質を使用が何ら制限なく使用できる。本発明においては、溶解度や高濃度における粘度上昇が少なく高イオン伝導性であるという理由から、リチウムヨウ化物、ナトリウムヨウ化物、カリウムヨウ化物などの金属ヨウ化物、アルキルアンモニウムヨウ化物、四級ピリジニウムヨウ化物又は四級イミダゾリウムヨウ化物を使用するのが特に好適である。これら電解質は単独で或いは異なった種類のものを混合して使用することができる。
本発明のイオン導電性組成物に含まれる前記アミド化合物と電解質との量比は特に限定されないが、湿式太陽電池の電荷移動層として使用する場合には、アミド化合物の添加量が少量では開放電圧の向上効果は十分でなく、添加量が多すぎると短絡電流量が小さくなり光電流変換効率の低下を招くという理由から、本発明のイオン導電性組成物に含まれる電解質の合計モル数に対する前記アミド化合物のモル数は、電解質の合計モル数を１としたときに０．００１〜０．１、特に０．００３〜０．００７となるモル数であるのが好適である。なお、上記アミド系化合物は、１種類の化合物を用いても異なる複数の化合物を混合して用いてもよい。
本発明のイオン導電性組成物は溶媒を含んでいてもよい。かかる溶媒としては、前記アミド化合物及び電解質と反応せずにこれらを溶解または分散させることができるものであれば特に限定されず、例えば従来の湿式太陽電池の電解移動層で用いられる溶媒が制限無く使用できる。このような溶媒を具体的に例示すれば、エチレンカーボネートやプロピレンカーボネートのカーボネート類、アセトニトリルやメトキシアセトニトリルやプロピオニトリルなどのニトリル類、及びこれらの混合物を挙げることができる。これら溶媒の使用量は特に限定されないが、湿式太陽電池等の光学電池の電荷移動層として使用する場合には、電解質１重量部に対して１〜３０重量部、特に５〜１５重量部使用するのが好適である。
さらに本発明のイオン導電性組成物は、上記のような溶媒を加えた上に、アクリロイル基やメタクリロイル基のような重合性基を持つ化合物、例えばアクリロニトリルやメタクリロニトリル等を加えて重合して架橋構造を有するてマトリックスを構成し、該マトリックスに本発明の導電性組成物（溶媒を含んでいてもよい）を保持させた形で使用することもできる。
本発明のイオン導電性組成物は、湿式太陽電池に代表される光化学電池の電荷移動層として好適に使用することができる。そして、本発明のイオン導電性組成物を電荷移動層として用いた本発明の光化学電池は、開放電圧が高く光電変換効率に優れ、高い耐久性を持つという特長を有する。
以下、図面を参照して本発明の光化学電池について更に詳しく説明する。図１に代表的な本発明の光化学電池１の模式図を示す。該光化学電池１は、基本的には従来の湿式太陽電池と同様の構造を有し、光電変換素子２と、電荷移動層３と、対向電極４とで構成されている。上記光電変換素子２は、負極として作用する。該光電変換素子２は、例えばガラスからなる基板５ａ上に例えばＩＴＯ等の導電性物質から成る導電層６が形成された導電性支持体７と、感光層８とから成る。また、上記対向電極４は、ガラス等の基板５ｂ上に金属膜９が積層された構造を有する。なお、上記感光層８は図２に示すように色素１０が吸着した半導体１１からなり、上記電荷移動層３は本発明のイオン導電性組成物で構成されている。
本発明の光化学電池で使用する各構成部材は、従来の光化学電池で使用されているものと特に変わることは無い。例えば、導電性支持体としては光透過性及び電気導電性を有するもの、具体的にはガラスもしくは透明プラスチック基板にＩＴＯや酸化亜鉛等の導電性の金属酸化物を塗布したものが好適に使用できる。
【００３１】
また、感光層を構成する半導体としては、ＴｉＯ_２、ＺｎＯ、ＳｎＯ_２、Ｆｅ_２Ｏ_３、ＷＯ_３、Ｎｂ_２Ｏ_５等が使用でき、中でも製造コストと原材料確保とエネルギー変換効率の点からＴｉＯ_２微粒子が特に好適に使用できる。また、色素としては、米国特許４９２７７２１号、同４６８４５３７号、同５０８４３６５号、同５３５０６４４号、同５４６３０５７号、同５５２５４４０号および、特開平７−２４９７９０号明細書等に記載された錯体色素、より具体的には、シス−ジシアネート−ビス−２、２’−ジピリジル−４、４’−ジカルボキシレート）ルテニウム（ＩＩ）等が使用できる。なお、上記感光層の形成は、例えば、ゾル−ゲル法等により作製した平均粒子径１〜１０００ｎｍの半導体微粒子に分散媒を加え調製した分散液を導電性支持体に塗布後、乾燥して焼結した後に含浸法当により色素を吸着させる方法等が挙げられる。用いる分散媒としては水、有機溶媒、あるいはその混合物などが特に制限無く用いることができる。また、必要に応じて界面活性剤などを分散液に添加しても良い。塗布する方法としては、ブレード法、印刷法、スプレー法などを用いることができる。焼成は空気中あるいは不活性ガス中で３００〜７００℃で行い感光層を形成する。膜厚は厚いほど半導体層中の色素の量が多くなり光の吸収が強くなるが、導電性支持体までの距離が増し電気抵抗が大きくなるために、感光層の厚みは０．１〜１００μｍ、好ましくは１〜５０μｍである。
【００３２】
また、対向電極としてはガラスもしくは透明プラスチック基板上に金属を蒸着またはスパッタリングによって金属薄膜を形成したものが好適に使用できる。このような部材を用いた場合には、感光層の支持体側から入射した光が対向電極で反射するので、光の利用効率が高くなる。
【００３３】
【実施例】
以下に実施例を挙げて本発明をより具体的に説明するが、本発明はこれに限定されるものではない。下記実施例及び比較例で使用したアミド化合物を以下に示す。
【００３４】
【化１２】

【００３５】
なお、上記各化合物の合成方法または入手先を以下に示す。
【００３６】
化合物Ａ（実施例１で使用）：Ｃｈｅｍｉｓｃｈｅ　Ｂｅｒｉｃｈｔｅ、ｖｏｌｕｍｅ　１０３　、１９７０、ｐａｇｅ　３７８３〜３７９０の記載に従って合成した。
【００３７】
化合物Ｂ（実施例２で使用）：Ｂｕｌｌｅｔｉｎ　ｏｆ　Ｓｏｃｉｅｔｅ　ｄｅ　Ｆｒａｎｃｅ、１９６４、ｐａｇｅ　７４８〜７５１の記載に従って合成した。
【００３８】
化合物Ｃ（実施例３で使用）：Ｊｏｕｒｎａｌ　ｏｆ　Ｃｈｅｍｉｃａｌ　Ｓｏｃｉｅｔｙ　ｐｅｒｋｉｎ　Ｔｒａｎｓａｃｔｉｏｎｓ　２、１９８６、ｐａｇｅ　１５８９〜１５９２の記載に従って合成した。
【００３９】
化合物Ｄ（比較例で使用）：Ａｌｄｒｉｃｈ社製。
【００４０】
これら化合物Ａ〜Ｄの窒素原子の電荷密度および酸素原子の電荷密度を表１に示す。なお、何れの電荷密度も半経験的分子軌道法ＰＭ３で求めた値である。
【００４１】
【表１】

【００４２】
実施例１〜３及び比較例１
電解液に添加するアミド化合物としてそれぞれ上記した化合物を用いて光化学電池を作成し、その評価を行った。その結果を表１に示す。なお、光化学電池の作製は、“色素増感太陽電池の最新技術”（シーエムシー社、２００１）の４４〜５３項に記載された方法、或いはインターネット上の東北大学多元物質科学研究所のホームページ（ｋｕｒｏｐｐｅ．ｉｃｒｓ．ｔｏｈｏｋｕ．ａｃ．ｊｐ／￣ｍａｓａｋｉ／ｗｅｔ＿ｃｅｌｌ／ｍａｉｎ−ｊ．ｈｔｍ）に掲載された方法等に基づき下記（１）〜（４）の手順で作製した。また、得られた光化学電池の光電変換効率は、下記（５）に示すようにして測定した。
【００４３】
（１）　半導体電極の作製
和光純薬工業株式会社から購入したチタンイソプロポキサイド１２５ｍｌを０．１Ｍの硝酸水溶液７５０ｍｌに攪拌しながらゆっくり滴下した。８０度８時間攪拌後室温まで放冷後、オートクレーブを用いて２２５℃で１２時間水熱処理を行い酸化チタンの含有量が１１重量％になるよう調整した。得られたコロイド溶液１重量部に和光純薬株式会社製Ｔｒｉｔｏｎ−Ｘを０．０２〜０．０５重量部加え均一な分散液とした。フッ素をドープした酸化スズ透明電極付ガラス基板にこの分散液をブレード法で塗布し１００℃で１時間乾燥した後、４５０℃で１時間焼成した。その後０．１Ｍの四塩化チタン水溶液を一滴滴下し一晩放置した。その後水洗し、再び１００℃で１時間乾燥した後、４５０℃で１時間焼成し作製した。
【００４４】
（２）　色素の固定
色素の固定はルテニウム増感色素（シス−ジシアネート−ビス−２、２‘−ジピリジル−４、４’−ジカルボキシレート）ルテニウム（ＩＩ）０．３ｍｍｏｌ含むエタノール溶液に上記チタニア板を一晩浸漬し固定した。
【００４５】
（３）　電解液の調整
電解液はアセトニトリルにヨウ化リチウム、１、２−ジメチル−３−プロピルイミダゾリウムヨウ化物、ヨウ素、及び各実施例及び比較例で使用する種芳香族へテロ環系化合物をアセトニトリルにヨウ化リチウム０．３Ｍ、１、２−ジメチル−３−プロピルイミダゾリウムヨウ化物０．５Ｍ、ヨウ素０．０５Ｍ、各種芳香族へテロ環系化合物０．５Ｍとなるように添加して調製した。
【００４６】
（４）　光化学電池の作製
前記（２）で作製したチタニア基板を光電変換素子とし、対向電極として白金をスパッタしたガラス基板を用いた。スペーサーをはさんで電極をはさみ、注入口２箇所を残しエポキシ系接着剤で周りを封止後、電解液を注入し、注入後注入口をエポキシ系接着剤で封止した。この後電極にリード線を取り付けて光化学電池とした。
【００４７】
（５）光電変換効率の測定
５００Ｗのキセノンランプの光をＡＭ１．５フィルターとＵＶカットフィルターを通した擬似太陽光を作製した光化学電池に照射し発電性能の測定を行った。また、寿命試験として２４０時間の照射前後の光電変換効率を測定した。これらによって得られた光電気化学電池の開放電圧、短絡電圧、変換効率をまとめて表２に示す。尚、劣化の度合いを表す数値として
変換効率低下度　＝（２４０時間後変換効率／初期変換効率）　Ｘ　１００を求め、どの程度低下したかの指標とした。
【００４８】
【表２】

【００４９】
表２に示されるように、比較例の光化学電池に比べて実施例の光化学電池は開放電圧が高く（その結果光電変換効率も高くなっている）、また２４０時間後においても変換効率も劣化が少なくなっている。
【００５０】
【発明の効果】
本発明により開放電圧および耐久性の向上に優れた光電気化学電池を提供することができる。
【図面の簡単な説明】
【図１】本図は、代表的な本発明の光化学電池の模式図である。
【図２】本図は、図１に示す光化学電池の感光層の構造を示す図である。
【符号の説明】
１・・・光化学電池
２・・・光電変換素子
３・・・電荷移動層
４・・・対向電極４
５ａ、５ｂ・・・基板
６・・・導電層
７・・・導電性支持体
８・・・感光層
９・・・金属膜
１０・・・色素
１１・・・半導体１１[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ionic conductive composition, and more particularly to an ionic conductive composition that can be suitably used as a charge transfer layer of a photovoltaic cell.
[0002]
[Prior art]
Photovoltaic power generation has attracted attention as an energy source that does not emit carbon dioxide or the like that causes global warming, and various solar cells have been researched and developed, and some of them have been put to practical use. As one of such solar cells, a wet solar cell using an oxide semiconductor by dye sensitization is known (see Non-Patent Document 1). This wet solar cell has a structure in which a charge transfer layer is provided between a negative electrode composed of a photoelectric conversion element in which a photosensitive layer including a semiconductor layer to which a dye is adsorbed is held on a conductive support and a counter electrode. Then, the electrons of the dye excited by the light irradiation flow through the semiconductor, the conductive support, and the external circuit to the counter electrode to generate a current. The wet type solar cell has a feature that a relatively high energy conversion efficiency can be obtained and can be manufactured at low cost, but the conversion efficiency is not sufficient.
[0003]
As a method for increasing the conversion efficiency of a wet solar cell, there is known a method for improving the conversion efficiency by adding 4-tert-butylpyridine or 2-vinylpyridine to an electrolyte to increase the open-circuit voltage (Non-Patent Document). 2). However, this method does not have sufficient sustaining effect of the open-circuit voltage improving effect, and it cannot be said that the conversion efficiency is sufficiently improved.
[0004]
Further, it has been reported that the stability can be significantly improved by adding a carboxylic acid to the electrolyte of a wet solar cell (see Non-Patent Document 3). Although it is low and the short-circuit current increases, it cannot be said that it is sufficient in terms of improving the conversion efficiency.
[0005]
[Non-patent document 1]
Nature, vol. 353, page 737, 1991
[Non-patent document 2]
J. phys. chem. B, vol. 101, page 2576 (1997)
[Non-Patent Document 3]
J. The Electrochem. Soc. , Vol. 147 (8), page 3049 (2000)
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a photoelectrochemical cell excellent in photoelectric conversion efficiency, particularly, open voltage and durability.
[0007]
[Means for Solving the Problems]
The present inventors have focused on aromatic heterocyclic compounds (the above-mentioned 4-tert-butylpyridine is also included in such compounds) in order to solve the above-mentioned problems, and have electrolyzed various aromatic heterocyclic compounds. When the wet solar cell performance when added to the liquid was evaluated, when a specific amide compound was added, the opening was higher than when 4-tert-butylpyridine and 2-vinylpyridine, and further, carboxylic acids were added. It showed a voltage and found that its durability was high, and completed the present invention.
[0008]
That is, the present invention provides the following formula in a molecule:
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[0010]
(However, a hydrogen atom is not directly bonded to a nitrogen atom of the group represented by the above formula.)
An ionic conductive composition comprising an amide compound having a trivalent group represented by formula (1) and an electrolyte.
[0011]
Another embodiment of the present invention is a photochemical cell including a charge transfer layer using the ionic conductive composition.
[0012]
The invention is not limited by theory, but the mechanism by which the excellent effects of the present invention are exhibited is considered to be as follows. That is, in the conventional wet solar cell, all of the electrons flowing into the semiconductor layer at the negative electrode (also referred to as a dark current) partially leak current does not flow in the conductive support I ₂ or charge transfer phase as While flowing to I ₃ ⁻ , the open-circuit voltage is reduced, whereas in a wet solar cell using the ionic conductive composition of the present invention for the charge transfer layer, the amide compound contained in the ionic conductive composition of the present invention is used. It is thought that the absorption of the above-mentioned in the portion of the semiconductor where the dye is not adsorbed suppresses the occurrence of the above-described leakage current and improves the open-circuit voltage. Such an effect can be obtained even when 4-tert-butylpyridine, 2-vinylpyridine, carboxylic acids, or the like is used. However, compared to these compounds, the amide compound has a higher electron density and higher stericity near the adsorption site on the compound side. Since the structure is appropriate to be attracted to a site on the semiconductor side where a leakage current is likely to be generated, such a site is selectively blocked, and a leakage current prevention effect (in other words, an open-circuit voltage improvement effect). Is estimated to be higher. Further, since the amide compound itself or the amide compound in the adsorbed state is stable, it is considered that the effect of improving the open-circuit voltage is stably maintained for a long time. Further, in general, when a compound is adsorbed on a semiconductor, the resistance increases and the short-circuit current tends to decrease.However, the amide compound selectively adsorbs to a specific adsorption site, so that the short-circuit current reduction rate is lower than that of other compounds. It seems to be smaller than when used.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
The ionic conductive composition of the present invention has the following formula in the molecule:
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[0015]
(However, a hydrogen atom is not directly bonded to a nitrogen atom of the group represented by the above formula.)
And an amide compound having a trivalent group and an electrolyte. By using an ion conductive composition containing an electrolyte to which the amide compound is added as a charge transfer layer, the open-circuit voltage of the photovoltaic cell can be increased, the conversion efficiency can be increased, and the effect can be stably maintained for a long time. It becomes possible.
[0016]
The amide compound used in the present invention has a trivalent group {= NC (= O)-group} represented by the above formula (where a hydrogen atom is directly attached to the nitrogen atom of the group represented by the above formula). That is, they are not bonded), that is, an N-disubstituted amide compound. An amide compound in which one or two hydrogen atoms are directly bonded to a nitrogen atom even in the same amide compound {in other words, an H ₂ N—C (＝ O) — group or —HN—C (＝ O )-Group-containing amide compound｝ is likely to be caused by a decrease in the electron density of the nitrogen atom or a difficulty in the selective adsorption to the semiconductor due to the hindrance of hydrogen. As you can imagine, such an effect cannot be obtained.
[0017]
The amide compound used in the present invention is not particularly limited as long as it is an amide compound having a group represented by the above formula. From the viewpoint of an open-circuit voltage improving effect and a high sustained effect, the amide compound represented by the above formula is used. Is -0.095 to -0.175 (eu), the charge of the nitrogen atom obtained by the semi-empirical molecular orbital method PM3 method is determined by the semi-empirical molecular orbital method PM3 method of the oxygen atom in the group. It is preferable to use an amide compound whose required charge is -0.225 to -0.265 (eu).
[0018]
The semi-empirical molecular orbital PM3 method used to determine the electron density of nitrogen and oxygen atoms is described in J. Am. P. The molecular orbital calculation method published by Stewart et al. In 1989 can be used in a molecular orbital calculation program widely used as MOPAC.
[0019]
In the present invention, since the effect as described above is particularly high, the following formula:
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[0021]
(Wherein the following formula:
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[0023]
Is a monocyclic hetero ring having 5 or 6 ring members or a condensed hetero ring obtained by condensing 2 to 5 rings having 5 to 6 carbon atoms, and R is a substituted or unsubstituted alkyl group. Or a substituted or unsubstituted aryl group, a is an integer of 0 to 4, and when a is 2 or more, Rs may be different from each other. )
It is particularly preferable to use an amide compound represented by
[0024]
In the above formula,
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[0026]
Specific examples of suitable rings among the rings represented by are the following rings.
[0027]
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[0028]
Specific examples of preferred R in the above formula include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, and unsubstituted alkyl groups. An alkyl group having 1 to 8 carbon atoms such as a hexyl group, a benzyl group as a substituted alkyl group, a phenyl group and a naphthyl group as an unsubstituted aryl group, and a substituted aryl group of 1 to 4 of these unsubstituted aryl groups. Hydrogen atoms were substituted with an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group and a tert-butyl group, or a halogen atom such as fluorine and chlorine. Things can be mentioned. Among these, a linear or branched unsubstituted alkyl group having 3 to 5 carbon atoms or a phenyl group is particularly preferred.
Among the amide compounds having a trivalent group represented by the above formula, those which can be suitably used in the present invention are specifically exemplified by compounds having the following structures.
[0029]
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[0030]
The electrolyte used in the ionic conductive composition of the present invention is not particularly limited as long as the solution when dissolved in water or another solvent exhibits ionic conductivity, and is conventionally used in photochemical cells such as wet solar cells. The electrolyte used can be used without any restrictions. In the present invention, lithium iodide, sodium iodide, metal iodide such as potassium iodide, alkyl ammonium iodide, quaternary pyridinium iodide It is particularly preferred to use iodides or quaternary imidazolium iodides. These electrolytes can be used alone or as a mixture of different types.
The amount ratio of the amide compound and the electrolyte contained in the ionic conductive composition of the present invention is not particularly limited, but when used as a charge transfer layer of a wet solar cell, the open voltage can be reduced with a small amount of the amide compound added. Is not sufficient, and if the addition amount is too large, the amount of short-circuit current is reduced and the photocurrent conversion efficiency is reduced, so that the above-mentioned amount relative to the total number of moles of the electrolyte contained in the ionic conductive composition of the present invention is considered. The number of moles of the amide compound is preferably 0.001 to 0.1, particularly 0.003 to 0.007 when the total number of moles of the electrolyte is 1. The amide compound may be a single compound or a mixture of a plurality of different compounds.
The ionic conductive composition of the present invention may contain a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the amide compound and the electrolyte without reacting with the electrolyte. For example, the solvent used in the electrolytic transfer layer of a conventional wet solar cell is not limited. Can be used. Specific examples of such a solvent include carbonates such as ethylene carbonate and propylene carbonate, nitriles such as acetonitrile, methoxyacetonitrile, and propionitrile, and mixtures thereof. The use amount of these solvents is not particularly limited, but when used as a charge transfer layer of an optical cell such as a wet solar cell, 1 to 30 parts by weight, particularly 5 to 15 parts by weight, is used per 1 part by weight of the electrolyte. Is preferred.
Furthermore, the ionic conductive composition of the present invention, after adding the solvent as described above, a compound having a polymerizable group such as an acryloyl group or a methacryloyl group, for example, acrylonitrile or methacrylonitrile, and polymerized. A matrix having a crosslinked structure may be used, and the matrix may be used in a state in which the conductive composition of the present invention (which may contain a solvent) is held.
The ionic conductive composition of the present invention can be suitably used as a charge transfer layer of a photochemical cell represented by a wet solar cell. The photochemical cell of the present invention using the ionic conductive composition of the present invention as a charge transfer layer has the features of high open voltage, excellent photoelectric conversion efficiency, and high durability.
Hereinafter, the photochemical cell of the present invention will be described in more detail with reference to the drawings. FIG. 1 shows a schematic diagram of a typical photochemical cell 1 of the present invention. The photochemical cell 1 has basically the same structure as a conventional wet solar cell, and includes a photoelectric conversion element 2, a charge transfer layer 3, and a counter electrode 4. The photoelectric conversion element 2 functions as a negative electrode. The photoelectric conversion element 2 includes a conductive support 7 in which a conductive layer 6 made of a conductive material such as ITO is formed on a substrate 5 a made of glass, for example, and a photosensitive layer 8. The counter electrode 4 has a structure in which a metal film 9 is laminated on a substrate 5b made of glass or the like. The photosensitive layer 8 is made of a semiconductor 11 to which a dye 10 is adsorbed as shown in FIG. 2, and the charge transfer layer 3 is made of the ionic conductive composition of the present invention.
Each component used in the photochemical cell of the present invention is not particularly different from that used in the conventional photochemical cell. For example, as the conductive support, those having optical transparency and electrical conductivity, specifically, those obtained by applying a conductive metal oxide such as ITO or zinc oxide to a glass or transparent plastic substrate can be suitably used. .
[0031]
Further, as the semiconductor constituting the photosensitive layer, TiO ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ , Nb ₂ O _{5 and the} like can be used. Among them, TiO 2 is preferable from the viewpoint of production cost, securing of raw materials and energy conversion efficiency. _Two fine particles can be particularly preferably used. Examples of the dye include complex dyes described in U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, and JP-A-7-249790. Specifically, cis-dicyanate-bis-2,2'-dipyridyl-4,4'-dicarboxylate) ruthenium (II) and the like can be used. The photosensitive layer is formed, for example, by applying a dispersion prepared by adding a dispersion medium to semiconductor fine particles having an average particle diameter of 1 to 1000 nm prepared by a sol-gel method or the like, applying the dispersion to a conductive support, and then drying and firing. After sintering, a method of adsorbing a dye by an impregnation method or the like may be used. As a dispersion medium to be used, water, an organic solvent, or a mixture thereof can be used without any particular limitation. Further, a surfactant or the like may be added to the dispersion as needed. As a coating method, a blade method, a printing method, a spray method, or the like can be used. The firing is performed at 300 to 700 ° C. in air or an inert gas to form a photosensitive layer. As the film thickness increases, the amount of dye in the semiconductor layer increases and light absorption increases, but the distance to the conductive support increases and the electrical resistance increases, so that the thickness of the photosensitive layer is 0.1 to 100 μm. , Preferably 1 to 50 μm.
[0032]
As the counter electrode, a metal thin film formed by vapor deposition or sputtering of a metal on a glass or transparent plastic substrate can be suitably used. When such a member is used, light incident from the support side of the photosensitive layer is reflected by the counter electrode, so that the light use efficiency increases.
[0033]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto. The amide compounds used in the following Examples and Comparative Examples are shown below.
[0034]
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[0035]
In addition, the synthesis method of each said compound or a source is shown below.
[0036]
Compound A (used in Example 1): synthesized according to the description of Chemische Berichte, volume 103, 1970, pages 3783-1790.
[0037]
Compound B (used in Example 2): synthesized according to Bulletin of Society de France, 1964, page 748-751.
[0038]
Compound C (used in Example 3): Synthesized according to the description of Journal of Chemical Society perkins Transactions 2, 1986, page 1589-1592.
[0039]
Compound D (used in Comparative Examples): manufactured by Aldrich.
[0040]
Table 1 shows the charge density of nitrogen atoms and the charge density of oxygen atoms of Compounds A to D. Each charge density is a value obtained by the semi-empirical molecular orbital method PM3.
[0041]
[Table 1]

[0042]
Examples 1 to 3 and Comparative Example 1
Photochemical cells were prepared using the above compounds as amide compounds to be added to the electrolytic solution, respectively, and evaluated. Table 1 shows the results. The fabrication of the photochemical cell is performed according to the method described in paragraphs 44 to 53 of “Latest Technology of Dye-Sensitized Solar Cells” (CMC, 2001), or the homepage of Tohoku University Institute of Multidisciplinary Materials Science on the Internet ( It was prepared by the following procedures (1) to (4) based on the method described in kuropup.icrs.tohoku.ac.jp/@masaki/wet_cell/main-j.htm. The photoelectric conversion efficiency of the obtained photochemical cell was measured as shown in the following (5).
[0043]
(1) Production of Semiconductor Electrode 125 ml of titanium isopropoxide purchased from Wako Pure Chemical Industries, Ltd. was slowly dropped into 750 ml of a 0.1 M nitric acid aqueous solution while stirring. After stirring at 80 ° C. for 8 hours, the mixture was allowed to cool to room temperature, and then subjected to hydrothermal treatment at 225 ° C. for 12 hours using an autoclave to adjust the content of titanium oxide to 11% by weight. To 1 part by weight of the obtained colloid solution, 0.02 to 0.05 parts by weight of Triton-X manufactured by Wako Pure Chemical Industries, Ltd. was added to obtain a uniform dispersion. This dispersion was applied to a fluorine-doped glass substrate with a tin oxide transparent electrode by a blade method, dried at 100 ° C. for 1 hour, and baked at 450 ° C. for 1 hour. Thereafter, one drop of a 0.1 M aqueous solution of titanium tetrachloride was dropped and left overnight. Thereafter, it was washed with water, dried again at 100 ° C. for 1 hour, and baked at 450 ° C. for 1 hour to produce.
[0044]
(2) Fixation of Dye The dye was fixed in an ethanol solution containing 0.3 mmol of ruthenium sensitizing dye (cis-dicyanate-bis-2,2′-dipyridyl-4,4′-dicarboxylate) ruthenium (II). The plate was immersed overnight and fixed.
[0045]
(3) Preparation of Electrolyte Solution The electrolyte solution was acetonitrile, lithium iodide, 1,2-dimethyl-3-propylimidazolium iodide, iodine, and a seed aromatic heterocyclic compound used in each of Examples and Comparative Examples. Was added to acetonitrile so as to obtain lithium iodide 0.3 M, 1,2-dimethyl-3-propylimidazolium iodide 0.5 M, iodine 0.05 M, and various aromatic heterocyclic compounds 0.5 M. Prepared.
[0046]
(4) Production of photochemical battery The titania substrate produced in the above (2) was used as a photoelectric conversion element, and a glass substrate on which platinum was sputtered was used as a counter electrode. The electrode was sandwiched between the spacers, the periphery was sealed with an epoxy adhesive except for two injection ports, and an electrolyte was injected. After the injection, the injection port was sealed with the epoxy adhesive. Thereafter, a lead wire was attached to the electrode to complete a photochemical battery.
[0047]
(5) Measurement of Photoelectric Conversion Efficiency A 500 W xenon lamp light was applied to a photochemical cell produced by simulating sunlight through an AM1.5 filter and a UV cut filter, and power generation performance was measured. Further, as a life test, photoelectric conversion efficiencies before and after irradiation for 240 hours were measured. Table 2 summarizes the open-circuit voltage, short-circuit voltage, and conversion efficiency of the photoelectrochemical cell obtained by these methods. In addition, conversion efficiency reduction degree = (conversion efficiency after 240 hours / initial conversion efficiency) × 100 was obtained as a numerical value indicating the degree of deterioration, and was used as an index of the degree of reduction.
[0048]
[Table 2]

[0049]
As shown in Table 2, the open-circuit voltage of the photochemical cell of the example was higher than that of the photochemical cell of the comparative example (the photoelectric conversion efficiency was higher), and the conversion efficiency deteriorated even after 240 hours. Is running low.
[0050]
【The invention's effect】
According to the present invention, it is possible to provide a photoelectrochemical cell excellent in the improvement of open voltage and durability.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a typical photochemical cell of the present invention.
FIG. 2 is a diagram showing a structure of a photosensitive layer of the photochemical cell shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photochemical cell 2 ... Photoelectric conversion element 3 ... Charge transfer layer 4 ... Counter electrode 4
5a, 5b ... substrate 6 ... conductive layer 7 ... conductive support 8 ... photosensitive layer 9 ... metal film 10 ... dye 11 ... semiconductor 11

Claims (4)

The following formula in the molecule

(However, a hydrogen atom is not directly bonded to a nitrogen atom of the group represented by the above formula.)
An ionic conductive composition comprising an amide compound having a trivalent group represented by the formula and an electrolyte. The following formula in the amide compound

The charge determined by the semi-empirical molecular orbital method PM3 method of the nitrogen atom in the trivalent group represented by is -0.095 to -0.175 (eu), and the half-experience of the oxygen atom in the group is The ion conductive composition according to claim 1, wherein the electric charge determined by the molecular orbital method PM3 is -0.225 to -0.265 (eu). The amide compound has the following formula:

(Where

Is a monocyclic hetero ring having 5 or 6 ring members or a condensed hetero ring obtained by condensing 2 to 5 rings having 5 to 6 carbon atoms, and R is a substituted or unsubstituted alkyl group. Or a substituted or unsubstituted aryl group, a is an integer of 0 to 4, and when a is 2 or more, Rs may be different from each other. )
The ionic conductive composition according to claim 1, which is a compound represented by the formula: A photochemical battery comprising a charge transfer layer using the ionic conductive composition according to claim 1.

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