Boschloo Gerrit, Hagfeldt Anders
Department of Physical Chemistry, Uppsala University, P.O. Box 579, SE-751 23 Uppsala, Sweden.
J Phys Chem B. 2005 Jun 23;109(24):12093-8. doi: 10.1021/jp0513770.
Various characteristics of dye-sensitized nanostructured TiO2 solar cells, such as electron transport and electron lifetime, were studied in detail using monochromatic illumination conditions. The electron transport was found to be a thermally activated process with activation energies in the range of 0.10-0.15 eV for light intensities that varied 2 orders of magnitude. Electron lifetimes were determined using a new method and found to be significantly larger (>1 s) than previously determined. An average potential was determined for electrons in the nanostructured TiO2 under illumination in short-circuit conditions. This potential is about 0.2 V lower than the open-circuit potential at the same light intensity. The electron transport time varies exponentially with the internal potential at short-circuit conditions, indicating that the gradient in the electrochemical potential is the driving force for electron transport in the nanostructured TiO2 film. The applicability of the conventionally used trapping/detrapping model is critically analyzed. Although experimental results can be fitted using a trapping/detrapping model with an exponential distribution of traps, the distribution parameters differ significantly between different types of experiment. Furthermore, the experimental activation energies for electron transport are smaller than those expected in a trapping/detrapping model.
利用单色光照条件，对染料敏化纳米结构二氧化钛太阳能电池的各种特性，如电子传输和电子寿命进行了详细研究。对于强度变化2个数量级的光，发现电子传输是一个热激活过程，其激活能在0.10 - 0.15 eV范围内。使用一种新方法测定了电子寿命，发现其比先前测定的结果显著更长（>1 s）。在短路条件下光照时，测定了纳米结构二氧化钛中电子的平均电势。该电势比相同光强下的开路电势低约0.2 V。在短路条件下，电子传输时间随内部电势呈指数变化，这表明电化学势梯度是纳米结构二氧化钛薄膜中电子传输的驱动力。对传统使用的俘获/脱俘获模型的适用性进行了严格分析。虽然实验结果可以用具有指数分布陷阱的俘获/脱俘获模型拟合，但不同类型实验的分布参数差异显著。此外，电子传输的实验激活能小于俘获/脱俘获模型中预期的值。
