Role of surface state on the electron flow in modified TiO2 film incorporating carbon powder for a dye-sensitized solar cell
Role of surface state on the electron flow in modified TiO2 film incorporating carbon powder for a dye-sensitized solar cell
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DOI：
10.1016/j.electacta.2007.02.038
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发表时间：
2007-04
影响因子：
6.6
通讯作者：
S. Kang;Jae-Yup Kim;Y. Sung
中科院分区：
文献类型：
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作者：
S. Kang;Jae-Yup Kim;Y. Sung
用电势阶跃计时电流法研究了碳粉掺杂修饰的纳米二氧化钛薄膜中的表面陷阱。为了改善纳米二氧化钛电极的形貌和表面状态，在白色二氧化钛粉末中实现了碳的掺杂。在计时安培数据中，所有的瞬变都表现出一个初始的快相(<；1s)，然后是一个与陷阱填充过程有关的较慢的相。随着外加负势的增大，含碳二氧化钛薄膜的陷阱填充周期变长，这是由于增加的比表面积引起的陷阱分布广泛。此外，通过积分计时安培数据的电流-时间曲线，得到了作为施加偏压的函数的薄膜电容。含碳二氧化钛薄膜的累积电荷在两个区域都有显著增加。平带电势在正区(−0.7V~−0.9V vs.Ag/AgCl13)的显著增加意味着表面相关陷阱中的电子占有率增加。在较负的电位下(低于−1.2V vs.Ag/AgCl.)，来自TiO2薄膜导带的电子对总电流有很大影响，从而导致电流的指数增加。因此，由于纳米结构二氧化钛薄膜的费米能级在−为1.14V，而在pH为13时为Ag/AgCl.因此，大多数陷阱位于平带电势的正区.在染料敏化太阳能电池运行中，二氧化钛薄膜亚能带区的陷阱位置在染料分子注入电子的电子传输和与氧化还原电解液的部分电荷复合中起重要作用.通过光伏和光电流暂态测量，研究了表面态增加形成的电荷陷阱对电子输运和电子转移的影响。
An investigation of surface-related traps in nanostructured TiO2films modified by the incorporation of carbon powder was conducted by the potential-step chronoamperometric method. For the modification of the morphology and surface state of the nanoporous TiO2electrode, the incorporation of carbon into the white TiO2powder was accomplished. In the chronoamperometric data, all of the transients showed an initial fast phase (<1s) followed by a slower phase which is related to the trap filling process. The trap-filling period of the carbon incorporated TiO2film becomes longer, as the applied negative potential increases, due to the widely distributed traps induced by the increased surface area. Furthermore, the film capacitance was derived as a function of the applied bias by integrating the current to time curves of the chronoamperometric data. The accumulated charge of the carbon incorporated TiO2film increases prominently in two regions. The dominant increase shown in the positive region (−0.7 to −0.9V vs. Ag/AgCl at pH 13) of the flat band potential implies that the electron occupancy in the surface-related traps is increased. At a more negative potential (below −1.2V vs. Ag/AgCl), electrons from the conduction band of the TiO2film substantially influence the total current, thereby inducing an exponential increase in the current. Therefore, it is found that most of the traps are located in the positive region of the flat band potential, since the Fermi level of the nanostructured TiO2film is positioned at −1.14V vs. Ag/AgCl at pH 13. The trap sites in the sub-bandgap region of the TiO2film are important in the electron transport of photoinjected electrons from dye molecules and partially charge recombination with redox electrolyte in operating dye-sensitized solar cell. The influence of charge trap formed by increased surface states on the electron transport and electron transfer was investigated by photovoltage and photocurrent transient measurements.