Extraordinary Photostability and Davydov Splitting in BN-Sandwiched Single-Layer Tetracene Molecular Crystals

TL;DR

This study demonstrates that sandwiching single-layer tetracene crystals between 2D inorganic materials like graphene or BN significantly enhances their photostability and excitonic properties, revealing new insights into 2D molecular crystal behavior.

Contribution

It provides the first systematic investigation of 2D tetracene crystals, showing enhanced photostability, Davydov splitting, and high crystallinity through experimental and theoretical analysis.

Findings

Enhanced photostability of 2D tetracene crystals.

Enlarged Davydov splitting observed in monolayer Tc.

High crystallinity and orientational registry confirmed.

Abstract

Two-dimensional molecular crystals have been beyond the reach of systematic investigation because of the lack or instability of their well-defined forms. Here, we demonstrate drastically enhanced photostability and Davydov splitting in single and few-layer tetracene (Tc) crystals sandwiched between inorganic 2D crystals of graphene or hexagonal BN. Molecular orientation and long-range order mapped with polarized wide-field photoluminescence imaging and optical second-harmonic generation revealed high crystallinity of the 2D Tc and its distinctive orientational registry with the 2D inorganic crystals, which were also verified with first-principles calculations. The reduced dielectric screening in 2D space was manifested by enlarged Davydov splitting and attenuated vibronic sidebands in the excitonic absorption and emission of monolayer Tc crystals. Photostable 2D molecular crystals and their size effects will lead to novel photophysical principles and photonic applications.