Delayed Fluorescence and Room Temperature Phosphorescence from a Liquid Arene.

Area of Science:

• Materials Science
• Photophysics
• Organic Chemistry

Background:

• Delayed fluorescence (DF) is typically observed in solutions or crystalline solids.
• Intermolecular interactions in crystals significantly influence emission properties.
• Triplet-triplet annihilation (TTA) is a key mechanism for DF.

Purpose of the Study:

• To investigate TTA-induced DF in a room-temperature liquid homotruxene.
• To compare the emission behavior of a liquid derivative with its crystalline analog.
• To explore the impact of suppressing crystallization on DF characteristics.

Main Methods:

• Synthesis of trialkoxy-homotruxene derivatives.
• Spectroscopic analysis of emission properties in liquid and crystalline states.
• Temperature-dependent emission studies (down to 90 K).
• Measurement of phosphorescence lifetimes and photoluminescence quantum yield (PLQY).

Main Results:

• TTA-DF was observed in the liquid homotruxene at room temperature and low temperatures (90 K).
• The liquid phase exhibited a 4% increase in the singlet-triplet energy gap compared to the crystalline analog.
• Phosphorescence and DF lifetimes were slightly shorter in the liquid state.
• Neat films showed TTA-DF, phosphorescence up to 50 ms, and a PLQY of 24%.

Conclusions:

• Trialkoxy-homotruxene derivatives effectively suppress crystallization while retaining TTA-DF.
• TTA-DF is sustained in a single-component isotropic liquid phase, demonstrating both molecular and aggregate emissions.
• The absence of periodic molecular stacking has minimal impact on DF properties in this liquid system.