Department of Physics, University of Basel, Klingelbergstrasse 82 CH4056, Switzerland ; School of Electrical Engineering, Faculty of Engineering, Tel-Aviv University, Ramat-Aviv 69978, Israel.
Beilstein J Nanotechnol. 2013 Jul 1;4:418-28. doi: 10.3762/bjnano.4.49. Print 2013.
Dye-sensitized solar cells (DSCs) provide a promising third-generation photovoltaic concept based on the spectral sensitization of a wide-bandgap metal oxide. Although the nanocrystalline TiO2 photoelectrode of a DSC consists of sintered nanoparticles, there are few studies on the nanoscale properties. We focus on the microscopic work function and surface photovoltage (SPV) determination of TiO2 photoelectrodes using Kelvin probe force microscopy in combination with a tunable illumination system. A comparison of the surface potentials for TiO2 photoelectrodes sensitized with two different dyes, i.e., the standard dye N719 and a copper(I) bis(imine) complex, reveals an inverse orientation of the surface dipole. A higher surface potential was determined for an N719 photoelectrode. The surface potential increase due to the surface dipole correlates with a higher DSC performance. Concluding from this, microscopic surface potential variations, attributed to the complex nanostructure of the photoelectrode, influence the DSC performance. For both bare and sensitized TiO2 photoelectrodes, the measurements reveal microscopic inhomogeneities of more than 100 mV in the work function and show recombination time differences at different locations. The bandgap of 3.2 eV, determined by SPV spectroscopy, remained constant throughout the TiO2 layer. The effect of the built-in potential on the DSC performance at the TiO2/SnO2:F interface, investigated on a nanometer scale by KPFM measurements under visible light illumination, has not been resolved so far.
染料敏化太阳能电池（DSC）提供了一种有前途的第三代光伏概念，基于宽能带隙金属氧化物的光谱敏化。尽管 DSC 的纳米晶 TiO2 光电 极由烧结的纳米颗粒组成，但对其纳米级性质的研究很少。我们专注于使用 Kelvin 探针力显微镜结合可调谐照明系统对 TiO2 光电 极的微观功函数和表面光电压（SPV）进行测定。对比两种不同染料敏化的 TiO2 光电 极的表面电位，即标准染料 N719 和铜（I）双亚胺配合物，揭示了表面偶极的反向取向。N719 光电 极的表面电位更高。由于表面偶极引起的表面电位增加与更高的 DSC 性能相关。由此得出结论，归因于光电 极的复杂纳米结构的微观表面电位变化会影响 DSC 的性能。对于裸态和敏化的 TiO2 光电 极，测量结果显示功函数的微观不均匀性超过 100 mV，并显示出不同位置的复合时间差异。通过 SPV 光谱法确定的 3.2 eV 带隙在整个 TiO2 层中保持不变。迄今为止，尚未在可见光照射下通过 KPFM 测量在纳米尺度上研究 TiO2/SnO2:F 界面上内置电势对 DSC 性能的影响。
