Femtosecond Time-Resolved Fluorescence Study of TiO2-Coated ZnO Nanorods/P3HT Photovoltaic Films

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• 作者：Yong Li ; Peifen Lu ; Minlin Jiang ; Rabin Dhakal ; Prem Thapaliya ; Zhonghua Peng ; Binay Jha ; Xingzhong Yan
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：December 6, 2012
• 年：2012
• 卷：116
• 期：48
• 页码：25248-25256
• 全文大小：479K
• 年卷期：v.116,no.48(December 6, 2012)
• ISSN：1932-7455

文摘

The photovoltaic performance of organic鈥搃norganic hybrid films based on regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) and ZnO nanorods depends strongly on the quality of the interfaces between the organic polymer and the inorganic nanostructures. A thin, solution-processed TiO₂ interlayer was introduced on the surface of ZnO nanorods to improve the interface between ZnO and P3HT. In order to understand the effects of the TiO₂ interlayer on the initial photophysical processes after photoexcitation, femtosecond time-resolved fluorescence dynamics of the hybrid ZnO nanorods/P3HT (ZnO/P3HT) films with or without TiO₂ interlayer coating were comparatively studied using a fluorescence up-conversion technique. Because of the well-aligned P3HT nanodomains in these annealed hybrid films, energetically downhill excitation energy transfer was found to be the dominant process in the subps time scale with an excitation at 400 nm. The fluorescence decay times for the ZnO鈥揟iO₂/P3HT film were significantly extended, which is likely due to the improved interface quality with fewer traps and defects when TiO₂ interlayer was introduced. Moreover, ultrafast anisotropy decay and a dramatic decrease in residual anisotropy at the emission of 660 nm were observed for the ZnO鈥揟iO₂/P3HT film in comparison to both P3HT pristine film and the ZnO/P3HT film. This suggests a change in the disorder of energy, the local field, and an efficient energy-transfer process, resulting in a faster exciton reaction (dissociation) within the ZnO鈥揟iO₂/P3HT film. Solar cells fabricated using TiO₂-coated ZnO nanorods and P3HT showed efficiencies of up to 0.76%, a 58% improvement over the TiO₂-free equivalent devices.