Rational Molecular Design for Boosting Afterglow Efficiency in Nonplanar Carbazolocarbazoles

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Carbazolocarbazole (CCz) is a novel heterocyclic compound with unique properties.
• Previous synthesis challenges limited the study and application of CCz compounds.
• Solid-state afterglow materials are crucial for advanced optoelectronic applications.

Purpose of the Study:

• To develop a reproducible method for synthesizing gram-sized helical CCz.
• To investigate the photophysical properties, including afterglow, of CCz and its derivatives.
• To establish a strategy for enhancing the photoluminescence quantum yield (PLQY) of organic ultralong room-temperature phosphorescence (URTP) emitters.

Main Methods:

• Developed a gram-scale synthesis for helical carbazolocarbazole (CCz).
• Functionalized CCz to create six derivatives with diverse substituents.
• Investigated photoluminescence properties, including ultralong room-temperature phosphorescence (URTP) lifetimes and quantum yields.

Main Results:

• Successfully synthesized helical CCz and six derivatives.
• CCz compounds exhibit solid-state afterglow with URTP lifetimes of 0.52–0.72 s.
• The SpiroCCz derivative achieved a high PLQY of 79.9%, demonstrating efficient intersystem crossing (ISC) and spin-orbit coupling (SOC).

Conclusions:

• Helical CCz derivatives are promising for solid-state afterglow applications.
• The study provides a strategy to enhance PLQY in organic URTP emitters.
• These CCz compounds show potential for optoelectronic devices, bioimaging, and security printing.