Abstract
Singlet fission generates multiple excitons from a single photon, which in theory can result in solar cell efficiencies with values above the Shockley-Queisser limit. Understanding the molecular structural dynamics during singlet fission will help to fabricate efficient organic photovoltaic devices. Here we use femtosecond stimulated Raman spectroscopy to reveal the structural evolution during the triplet separation in rubrene. We observe vibrational signatures of the correlated triplet pair, as well as shifting of the vibrational frequencies of the 1430 and 1542 cm-1 excited state modes, which increase by more than 25 cm-1 in 5 ps. Our results indicate that the correlated pair separation into two individual triplets occurs concurrently with the loss of electron density from the tetracene backbone in rubrene. This study provides new insights into the triplet separation process and proves the utility of structurally sensitive ultrafast vibrational techniques to understand the mechanism of singlet fission.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 5929-5934 |
| Number of pages | 6 |
| Journal | Journal of Physical Chemistry Letters |
| Volume | 8 |
| Issue number | 23 |
| DOIs | |
| State | Published - Dec 7 2017 |
Bibliographical note
Funding Information:This work is supported by the National Science Foundation, CHE-1552849 and DMR-1006566. The authors thank Professor James Johns for use of the furnace for rubrene crystal growth, Billy Ogden and Zhuoran Zhang for the F20 rubrene sample, and Soumen Ghosh and Dr. Ruchira Silva for helpful discussions on calculations. The authors also acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research reported in this paper.
Funding Information:
This work is supported by the National Science Foundation CHE-1552849 and DMR-1006566. The authors thank Professor James Johns for use of the furnace for rubrene crystal growth, Billy Ogden and Zhuoran Zhang for the F20 rubrene sample, and Soumen Ghosh and Dr. Ruchira Silva for helpful discussions on calculations. The authors also acknowledge the Minnesota Supercomputing Institute (MSI) at the University of Minnesota for providing resources that contributed to the research reported in this paper.
