Crown Ether-Substituted Carbazole Dye for Dye-Sensitized Solar Cells: Controlling the Local Ion Concentration at the TiO2/Dye/Electrolyte Interface

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• 作者：Yu Uemura ; Takurou N. Murakami ; Nagatoshi Koumura
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：July 31, 2014
• 年：2014
• 卷：118
• 期：30
• 页码：16749-16759
• 全文大小：652K
• ISSN：1932-7455

文摘

The conduction band edge potentials (E_CB) and electron lifetimes (蟿) of the TiO₂ electrodes in dye-sensitized solar cells (DSSCs) are affected by ion concentrations (e.g., Li⁺ and I^{鈥?/sup>/I₃鈥?/sup>) at the TiO₂/dye/electrolyte interface. To control the local concentrations of these ions in the vicinity of the TiO₂ surface, a novel carbazole-based dye incorporating a 12-crown-4 ether on the carbazole donor (MK-70) was synthesized as a DSSC sensitizer. The interactions between Li+/I鈥?/sup>/I₃鈥?/sup> and MK-70 were compared with those between Li+/I鈥?/sup>/I₃鈥?/sup> and MK-1, an analogue lacking the crown ether. The crown ether did not affect the E_CB level of TiO₂, but it did decrease 蟿 at a high electrolytic Li+ concentration. Results suggest that localized Li+ ions associated with the crown ethers electrostatically attract surplus I₃鈥?/sup> from the bulk electrolyte even though the crown ethers are located far from the TiO₂ surface. After the cells were aged, negative shifts in the E_CB levels of the TiO₂ electrode and blueshifts of the MK-70 absorption spectra were observed with electrolytes that included I鈥?/sup>/I₃鈥?/sup> and Li+. The aging behavior may be determined by the balance between two attractive forces, K₁ (I鈥?/sup>/I₃鈥?/sup> and Li+ at the TiO₂ surface) and K₂ (dye interactions with I鈥?/sup>/I₃鈥?/sup> and Li+).}