Temperature-Dependent Excitonic Behavior of Mechanically Exfoliated 2D Tetracene Crystals

Investigating the behavior and characteristics of molecular excitons in low-dimensional molecular solids is crucial for advancing our understanding of fundamental chemical principles and photonic applications. However, research into this phenomenon remains in its early stages, with a comprehensive understanding yet to be fully developed. Herein, we report the temperature-dependent excitonic behaviors of two-dimensional Tetracene (Tc) crystals, fabricated through mechanical exfoliation, as investigated by absorption and photoluminescence spectroscopies. The orientation of tetracene's transition dipole moment along its short molecular axis is identified through polarization-resolved spectroscopy. We found that the Davydov splitting energy exhibits an increasing trend as the temperature decreased. In contrast to the rising Davydov splitting energy, the Stokes shift exhibited a decreasing trend. Our findings of an enlarged exciton bandwidth with decreasing temperature provides deeper insights into the excitonic behavior of 2D molecular crystals.