Eu Seunghun, Katoh Takashi, Umeyama Tomokazu, Matano Yoshihiro, Imahori Hiroshi
Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
Dalton Trans. 2008 Oct 28(40):5476-83. doi: 10.1039/b803272f. Epub 2008 Jun 30.
Phthalocyanines with high peripheral substitutions and free from potential contamination by regioisomers have been synthesized and evaluated as photosensitizers for dye-sensitized solar cell applications. Each of the sterically hindered precursor compounds was accomplished by Suzuki-Miyaura cross-coupling reactions with the arylchloride and corresponding boronic acids. Metal free phthalocyanine-sensitized solar cells showed no photocurrent generation due to its low excited singlet state (LUMO) compared with the conduction band of TiO(2). Upon zinc metalation, the LUMO level of the phthalocyanine was pushed up, and this variation afforded an exergonic free energy change for electron injection. The zinc phthalocyanine-sensitized solar cell displayed 0.57% power conversion efficiency (eta) and 4.9% maximal IPCE in the near infrared region. More importantly, the cell prepared with and without the presence of chenodeoxycholic acid revealed no difference in the power conversion efficiency. This implies that the well-known aggregation tendency of phthalocyanines that is considered to enhance the self-quenching of the phthalocyanine excited singlet state is effectively suppressed by the high degree of substitutions. The significance of the driving force for electron injection and the distance between the dye core and the TiO(2) surface is also highlighted for devising high performance phthalocyanine photosensitizers.
已合成了具有高周边取代且无区域异构体潜在污染的酞菁，并将其作为染料敏化太阳能电池应用的光敏剂进行了评估。每种空间位阻前体化合物均通过芳基氯与相应硼酸的铃木-宫浦交叉偶联反应制备而成。无金属酞菁敏化太阳能电池由于其激发单重态（最低未占分子轨道，LUMO）与二氧化钛导带相比很低，因而未产生光电流。金属锌化后，酞菁的最低未占分子轨道能级升高，这种变化为电子注入提供了一个放能的自由能变化。锌酞菁敏化太阳能电池在近红外区域显示出0.57%的功率转换效率（η）和4.9%的最大入射光子-电流转换效率（IPCE）。更重要的是，在有无鹅去氧胆酸存在的情况下制备的电池，其功率转换效率没有差异。这意味着酞菁众所周知的聚集倾向（被认为会增强酞菁激发单重态的自猝灭）被高度取代有效地抑制了。对于设计高性能酞菁光敏剂而言，电子注入驱动力以及染料核心与二氧化钛表面之间距离的重要性也得到了强调。
