Influence of sensitizers on charge recombination in dye-sensitized solar cells

本研究的目的是阐明染料结构对染料敏化太阳能电池（DSC）中电荷复合的影响，并提出新的敏化剂的设计指导。电子寿命的DSC测量与染料的结构是系统地变化。结果发现，在测量寿命的观察到的趋势解释了三个因素：（1）阻塞效应，（2）部分电荷，和（3）色散力。染料分子的大小和吸附染料的密度决定了染料的封闭效果。部分电荷意味着有多少电荷位于特定原子上，例如，氧原子和金属原子。色散力由敏化剂的极化率决定。以前，色散力的影响并不明显。这是因为它的影响比其他人要小。在阻塞效应和部分电荷影响较小的情况下，色散力的影响出现。基于这些结果，染料延迟复合的设计指导是增加吸附密度，具有很少的部分电荷或离开那些远离表面的TiO 2，并添加障碍部分的敏化剂的框架。采用大体积的氧化还原对来增强阻断效果也是有效的。

The objectives of this study are to elucidate the effect of dye structures on the charge recombination in dye-sensitized solar cells (DSCs) and to propose the design guide for new sensitizers. The electron lifetime was measured for DSCs with dyes whose structures were systematically varied. It was found that the observed trends in the measured lifetime were explained by three factors : (1) blocking effect, (2) partial charges, and (3) dispersion forces. The blocking effect was controlled by the molecular size of the dyes and the density of adsorbed dyes. The partial charges mean how much charges are localized on particular atoms, e.g., oxygen and metal atoms. The dispersion force is determined by polarizability of sensitizers. Previously the effect of the dispersion force was not evident. This was because the effect was smaller than the others. Under the conditions that the effects of blocking effect and partial charges were little, the effect of dispersion force appeared. Based on the results, design guide for the dyes to retard recombination is to increase the adsorption density, to have little partial charges or leave those far from the surface of the TiO2, and to add obstacle moiety to the framework of the sensitizers. It was also effective to employ bulky redox couples to enhance the blocking effect.