Alternation of Charge Injection and Recombination in Dye-Sensitized Solar Cells by the Addition of Nonconjugated Bridge to Organic Dyes

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• 作者：Xue-Hua Zhang ; Junichi Ogawa ; Kenji Sunahara ; Yan Cui ; Yu Uemura ; Tsutomu Miyasaka ; Akihiro Furube ; Nagatoshi Koumura ; Kohjiro Hara ; Shogo Mori
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：February 7, 2013
• 年：2013
• 卷：117
• 期：5
• 页码：2024-2031
• 全文大小：384K
• 年卷期：v.117,no.5(February 7, 2013)
• ISSN：1932-7455

文摘

Most metal-free organic dyes for dye-sensitized solar cells are designed by following a donor conjugated-bridge acceptor structure with a carboxyl acid as an anchoring unit. In this work, we examined the influence of a nonconjugated methylene unit between the cyano group and carboxyl acid by applying it to a previously reported carbazole dye, MK-2. Two dyes, MKZ-35 and -36, were synthesized with glycine and 尾-alanine, respectively. Dye-sensitized TiO₂ solar cells (DSSCs) with MKZ-35 and -36 showed smaller values in the short-circuit current (J_sc) and higher values in open-circuit voltage (V_oc) compared with the values with MK-2. The lower J_sc was due to less injection efficiency and fast geminate recombination while the higher V_oc was attributed to longer lifetime of the injected electrons in the DSSCs. DFT calculations showed that MKZ-35 dyes interact with each other. One possible explanation for the longer electron lifetime is that the interacted molecules may act as a 3D enlarged dimer molecule or form an induced quadrupole, reducing the interaction between the dyes and acceptor species. On the other hand, the longer electron lifetime with MKZ-36 than that with MK-2 seems to be due to the longer distance between the TiO₂ surface and conjugated framework of the dye.