Characterization of the ultrafast spectral diffusion and vibronic coherence of TIPS-pentacene using 2D electronic spectroscopy

Duc Viet Le; Jessica M de la Perrelle; Thanh Nhut Do; Xuan Leng; Patrick C Tapping; Gregory D Scholes; Tak W Kee; Howe-Siang Tan

doi:10.1063/5.0055528

Characterization of the ultrafast spectral diffusion and vibronic coherence of TIPS-pentacene using 2D electronic spectroscopy

J Chem Phys. 2021 Jul 7;155(1):014302. doi: 10.1063/5.0055528.

Authors

Duc Viet Le¹, Jessica M de la Perrelle², Thanh Nhut Do¹, Xuan Leng¹, Patrick C Tapping², Gregory D Scholes³, Tak W Kee², Howe-Siang Tan¹

Affiliations

¹ Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371.
² Department of Chemistry, University of Adelaide, Adelaide SA 5005, Australia.
³ Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.

PMID: 34241376
DOI: 10.1063/5.0055528

Abstract

TIPS-pentacene is a small-molecule organic semiconductor that is widely used in optoelectronic devices. It has been studied intensely owing to its ability to undergo singlet fission. In this study, we aim to develop further understanding of the coupling between the electronic and nuclear degrees of freedom of TIPS-pentacene (TIPS-Pn). We measured and analyzed the 2D electronic spectra of TIPS-Pn in solutions. Using center line slope (CLS) analysis, we characterized the frequency-fluctuation correlation function of the 0-0 vibronic transition. Strong oscillations in the CLS values were observed for up to 5 ps with a frequency of 264 cm^-1, which are attributable to a large vibronic coupling with the TIPS-Pn ring-breathing vibrational mode. In addition, detailed analysis of the CLS values allowed us to retrieve two spectral diffusion lifetimes, which are attributed to the inertial and diffusive dynamics of solvent molecules. Amplitude beating analysis also uncovered couplings with another vibrational mode at 1173 cm^-1. The experimental results can be described using the displaced harmonic oscillator model. By comparing the CLS values of the simulated data with the experimental CLS values, we estimated a Huang-Rhys factor of 0.1 for the ring-breathing vibrational mode. The results demonstrated how CLS analysis can be a useful method for characterizing the strength of vibronic coupling.