Ghadiri Elham, Zakeeruddin Shaik M, Hagfeldt Anders, Grätzel Michael, Moser Jacques-E
Photochemical Dynamics Group , Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Lausanne Centre for Ultrafast Science (LACUS), Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Sci Rep. 2016 Apr 20;6:24465. doi: 10.1038/srep24465.
Efficient dye-sensitized solar cells are based on highly diffusive mesoscopic layers that render these devices opaque and unsuitable for ultrafast transient absorption spectroscopy measurements in transmission mode. We developed a novel sub-200 femtosecond time-resolved diffuse reflectance spectroscopy scheme combined with potentiostatic control to study various solar cells in fully operational condition. We studied performance optimized devices based on liquid redox electrolytes and opaque TiO2 films, as well as other morphologies, such as TiO2 fibers and nanotubes. Charge injection from the Z907 dye in all TiO2 morphologies was observed to take place in the sub-200 fs time scale. The kinetics of electron-hole back recombination has features in the picosecond to nanosecond time scale. This observation is significantly different from what was reported in the literature where the electron-hole back recombination for transparent films of small particles is generally accepted to occur on a longer time scale of microseconds. The kinetics of the ultrafast electron injection remained unchanged for voltages between +500 mV and -690 mV, where the injection yield eventually drops steeply. The primary charge separation in Y123 organic dye based devices was clearly slower occurring in two picoseconds and no kinetic component on the shorter femtosecond time scale was recorded.
高效染料敏化太阳能电池基于高度扩散的介观层，这使得这些器件不透明，不适用于透射模式下的超快瞬态吸收光谱测量。我们开发了一种结合恒电位控制的新型亚200飞秒时间分辨漫反射光谱方案，以研究处于完全工作状态的各种太阳能电池。我们研究了基于液体氧化还原电解质和不透明TiO₂薄膜的性能优化器件，以及其他形态，如TiO₂纤维和纳米管。在所有TiO₂形态中，观察到Z907染料的电荷注入在亚200飞秒时间尺度内发生。电子 - 空穴反向复合动力学在皮秒到纳秒时间尺度内具有特征。这一观察结果与文献报道有显著不同，在文献中，小颗粒透明薄膜的电子 - 空穴反向复合通常被认为发生在更长的微秒时间尺度上。对于 +500 mV至 -690 mV之间的电压，超快电子注入动力学保持不变，在此电压范围内注入产率最终急剧下降。基于Y123有机染料的器件中的初级电荷分离明显较慢，发生在两个皮秒内，并且在较短的飞秒时间尺度上未记录到动力学成分。
