The Formation of Ti–H Species at Interface Is Lethal to the Efficiency of TiO2-Based Dye-Sensitized Devices

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• 作者：Yan Yan ; Weidong Shi ; Zhen Yuan ; Shenggui HeDongmei Li ; Qingbo Meng ; Hongwei Ji ; Chuncheng Chen ; Wanhong MaJincai Zhao
• 刊名：Journal of the American Chemical Society
• 出版年：2017
• 出版时间：February 8, 2017
• 年：2017
• 卷：139
• 期：5
• 页码：2083-2089
• 全文大小：499K
• ISSN：1520-5126

文摘

TiO₂-based dye-sensitization cycle is one of the basic strategies for the development of solar energy applications. Although the power conversion efficiency (PCE) of dye-sensitized devices has been improved through constant attempts, the intrinsically fatal factor that leads to the complete failure of the PCE of TiO₂-mediated dye-sensitized devices has not yet been determined. Here, by using isotopically labeled MAS–¹H NMR, ATR-FTIR spectroscopy (separate H/D and ⁴⁸Ti/⁴⁹Ti experiments), and ESR, we revealed that the accumulative formation of Ti–H species on the TiO₂ surface is the intrinsic cause of the PCE failure of TiO₂-based dye-sensitization devices. Such a Ti–H species is generated from the reduction of hydrogen ions (mostly released from dye carboxyl groups or organic electrolyte) accompanied by electron injection on the surface of TiO₂, which deteriorates the PCE mainly by reducing the electrical conductivity of the TiO₂ (by a maximum of ∼80%) and the hydrophilic nature of the TiO₂ surface (contact angle increased).