Influence of the TiCl4 treatment on nanocrystalline TiO2 films in dye-sensitized solar cells.: 2.: Charge density, band edge shifts, and quantification of recombination losses at short circuit
Influence of the TiCl4 treatment on nanocrystalline TiO2 films in dye-sensitized solar cells.: 2.: Charge density, band edge shifts, and quantification of recombination losses at short circuit
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DOI：
10.1021/jp073056p
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发表时间：
2007-09-20
影响因子：
3.7
通讯作者：
Bakker, Nicolaas J.
中科院分区：
文献类型：
--
作者：
O'Regan, Brian C.;Durrant, James R.;Bakker, Nicolaas J.
从TiCl 4化学浴沉积TiO 2是一种常用的处理方法，可提高染料敏化TiO 2太阳能电池的光电流。在本文中，电荷密度和动力学数据显示，这种治疗的主要影响是一个80 mV的向下移动的TiO 2导带边缘电位和20倍的电子/电解质复合速率常数下降。总之，这些变化增加了界面处电荷分离的量子效率，从而提供了所观察到的光电流的增加。复合速率常数的减小允许更大浓度的电子在V1处累积，从而抵消否则从导带边缘偏移预期的V1，c损失。光电流瞬态和电荷提取数据表明，TiCl 4处理对短路时的电子输运几乎没有影响。用恒流瞬态光电压（CCTPV）技术测量了短路时电子/电解质复合速率常数。结果进一步证实，运输的任何改善都不会导致TiCl 4处理的有益效果。验证的CCTPV技术进行比较瞬态吸收和模型的技术。染料敏化电池中的电荷分离涉及两个步骤，电荷注入和染料再生。瞬态光学实验，以确定哪一个过程是由TiCl 4处理改善进行了讨论。
Chemical bath deposition of TiO2 from TiCl4 is an often used treatment that improves the photocurrent from dye-sensitized TiO2 solar cells. In this paper, charge density and kinetic data are used to show that the main effects of this treatment are an 80 mV downward shift in the TiO2 conduction band edge potential and a 20-fold decrease in the electron/electrolyte recombination rate constant. Together, these changes increase the quantum efficiency of charge separation at the interface, thus providing the observed increase in the photocurrent. The reduction in the recombination rate constant allows a greater concentration of electrons to accumulate at V,, thus offsetting the V,,c loss otherwise expected from the conduction band edge shift. Photocurrent transients and charge extraction data are used to show that the TiCl4 treatment has little effect on the transport of electrons at short circuit. The electron/electrolyte recombination rate constant at short circuit has been measured with the CCTPV (Constant Current Transient PhotoVoltage) technique. The results further confirm that any improvements in transport could not cause the beneficial effect of the TiCl4 treatment. Verification of the CCTPV technique is undertaken by comparison to transient absorption and by a model of the technique. Charge separation in dye-sensitized cells concerns two steps, charge injection and dye regeneration. Transient optical experiments to determine which process is improved by the TiCl4 treatment are discussed.