Charge Recombination and Band-Edge Shift in the Dye-Sensitized Mg2+-Doped TiO2 Solar Cells

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• 作者：Changneng Zhang ; Shuanghong Chen ; Li鈥檈 Mo ; Yang Huang ; Huajun Tian ; Linhua Hu ; Zhipeng Huo ; Songyuan Dai ; Fantai Kong ; Xu Pan
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：August 25, 2011
• 年：2011
• 卷：115
• 期：33
• 页码：16418-16424
• 全文大小：971K
• 年卷期：v.115,no.33(August 25, 2011)
• ISSN：1932-7455

文摘

The effect of Mg²⁺ ions substituted into the anatase lattice on the charge recombination and band-edge movement in dye-sensitized solar cells was investigated in this study. The HRTEM results indicated that Mg²⁺ ions incorporation into the TiO₂ lattice led to the increased lattice spacing of the (101) plane of the anatase phase. Mg²⁺-doped TiO₂ could produce a blue shift in the optical absorption edge compared with that of the untreated samples. Detailed analysis of the open-circuit photovoltage (V_oc) under different surface charge densities showed that the Mg²⁺-doped TiO₂ samples resulted in the negative shift of the TiO₂ conduction band about 70 mV in comparison with the untreated samples. From Raman spectra and light intensity-dependent variation of the short-circuit current density (J_sc) of the solar cells, it could be concluded that the decreased efficiency of electron injection for DSCs with Mg²⁺-doped TiO₂ was attributed to the negative shift of the band edge in the Mg²⁺-doped TiO₂ electrode to obtain a decreased J_sc. The electron diffusion coefficient in Mg²⁺-doped TiO₂ was found to be higher than that in TiO₂ at the same photoelectron density. We present evidence that the increase of trap states in Mg²⁺-doped TiO₂ as recombination channels to decrease the electron lifetime could compensate for the effect of band-gap widening to obtain a slightly increased V_oc for DSCs with Mg²⁺-doped TiO₂. It is suggested that the recombination channels should be suppressed to enhance the performance of dye-sensitized Mg²⁺-doped TiO₂ solar cells.