Efficient and Ultralong Room Temperature Phosphorescence from Isolated Molecules under Visible Light Excitation.

Abstract

Visible-light-excited ultralong organic phosphorescence (UOP) materials hold significant potential for various practical applications. Red-shifted excitation wavelength can be achieved by introducing large π-conjugation structures into organic molecules, thereby increasing intermolecular interactions and coupling. However, generating visible-light-excited UOP from isolated molecules poses a great challenge. Herein, we pioneered a strategy to achieve visible-light-excited UOP by doping organic molecules into a rigid polymer. The resulting materials exhibit an ultralong lifetime of up to 2.226 s and a high phosphorescence efficiency of 42.6% under ambient conditions. Impressively, poly(vinyl alcohol) films doped with 1 wt % different guests demonstrate blue and green visible-light-excited UOP. Moreover, they show long-persistent luminescence, lasting over 30 min at room temperature. Through control experiments and theoretical calculations, we discovered that hydrogen bonding between the guests and PVA confines the molecular motion, promoting efficient UOP. The intramolecular charge transfer within the single molecular state contributes to the low energy level, thus leading to the red-shifted absorption. This work will open a new way for developing visible-light-excited UOP based on amorphous polymers, offering highly efficient UOP and long-persistent luminescence under ambient conditions.