Quantitative Intramolecular Singlet Fission in Bipentacenes

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• 作者：Samuel N. Sanders ; Elango Kumarasamy ; Andrew B. Pun ; M. Tuan Trinh ; Bonnie Choi ; Jianlong Xia ; Elliot J. Taffet ; Jonathan Z. Low ; John R. Miller ; Xavier Roy ; X.-Y. Zhu ; Michael L. Steigerwald ; Matthew Y. Sfeir ; Luis M. Campos
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：July 22, 2015
• 年：2015
• 卷：137
• 期：28
• 页码：8965-8972
• 全文大小：477K
• ISSN：1520-5126

文摘

Singlet fission (SF) has the potential to significantly enhance the photocurrent in single-junction solar cells and thus raise the power conversion efficiency from the Shockley鈥換ueisser limit of 33% to 44%. Until now, quantitative SF yield at room temperature has been observed only in crystalline solids or aggregates of oligoacenes. Here, we employ transient absorption spectroscopy, ultrafast photoluminescence spectroscopy, and triplet photosensitization to demonstrate intramolecular singlet fission (iSF) with triplet yields approaching 200% per absorbed photon in a series of bipentacenes. Crucially, in dilute solution of these systems, SF does not depend on intermolecular interactions. Instead, SF is an intrinsic property of the molecules, with both the fission rate and resulting triplet lifetime determined by the degree of electronic coupling between covalently linked pentacene molecules. We found that the triplet pair lifetime can be as short as 0.5 ns but can be extended up to 270 ns.