Effect of Molecular Structure Perturbations on the Performance of the D鈥揂鈭捪€鈥揂 Dye Sensitized Solar Cells

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• 作者：Xiongwu Kang ; Junxiang Zhang ; Daniel O鈥橬eil ; Anthony J. Rojas ; Wayne Chen ; Paul Szymanski ; Seth R. Marder ; Mostafa A. El-Sayed
• 刊名：Chemistry of Materials
• 出版年：2014
• 出版时间：August 12, 2014
• 年：2014
• 卷：26
• 期：15
• 页码：4486-4493
• 全文大小：436K
• ISSN：1520-5002

文摘

Three D鈥揂鈭捪€鈥揂 organic dyes based on 5,6-difluoro-2,1,3-benzothiadiazole (DFBTD) were synthesized by sequential direct arylation and characterized by spectroscopic and electrochemical techniques. Compared to 2,1,3-benzothiadiazole (BTD) analogue, the presence of two fluorine atoms on DFBTD results not only in a significant increase in the molar absorptivity but also in a blue shift of the onset of the absorption spectra. In the system of DFBTD-based sensitizers, replacing the thienyl unit bridge with disubstituted cyclopenta[1,2-b:5,4-b鈥瞉dithiophene (CPDT) further increases molar absorptivity and decreases the oxidation potential of the excited state E_(s+/s*). Similarly, changing the indoline donor to 4-butoxy-N-(4-butoxyphenyl)-N-phenylaniline increases the optical band gap and decreases the oxidation potential of the excited state E_(s+/s*) of the sensitizer. The correlation between the molecular structure of these sensitizers and the photovoltaic performance of the dye cells were examined using current鈥搗oltage scan, incident photon to electron conversion efficiency (IPCE), femtosecond transient absorption spectroscopy (TAS), and electrochemical impedance spectroscopy (EIS). The observed change of the photovoltage and photocurrent upon changing the molecular structure of the sensitizers are discussed in terms of the charge injection from the excited state to the interband gap states of TiO₂ and the charge recombination between injected electrons into TiO₂ film and electrolyte. In all, it is found that the most efficient D鈥揂鈭捪€鈥揂 dye achieved an open circuit voltage of 0.717 V, short circuit current density of 18.8 mA/cm², corresponding to an overall power conversion efficiency of 9.1%.