Dendronized Encapsulation with Hierarchical Rigidification Enabling Robust Solution Room‐Temperature Phosphorescence, Efficient Electroluminescence and Ultralong Afterglow

Abstract Organic room‐temperature phosphorescence (RTP) materials face a fundamental challenge: their environment‐specific phosphorescent behavior fundamentally conflicts with the growing demand for multifunctional materials. To overcome this limitation, a multiscale confinement strategy is developed that integrates intramolecular flexible encapsulation with intermolecular rigid immobilization. Dendronized donor‐acceptor molecules are engineered with alkyl‐chain‐carbazole dendrons to achieve intramolecular encapsulation. This design enables abundant spatial interactions, balancing conformational flexibility (for solution processing) and emission rigidity. Multiscale confinement via molecular aggregation and poly(methyl methacrylate) (PMMA) doping further enhances rigidification. Together, these mechanisms suppress nonradiative transitions across four temporal orders of magnitude (10 −3 –10 0 s). The resulting material system exhibits unprecedented environment‐adaptive RTP properties: 1) ≈9 ms solution‐phase RTP lifetime under ambient conditions without deoxygenation, representing the longest lifetime among solution‐dissolved RTP systems; 2) 72% photoluminescence quantum yield in doped films and 17.2% external quantum efficiency in organic light‐emitting diodes (OLEDs), making them among the most efficient solution‐processed RTP‐OLEDs; 3) Ultralong afterglow with 1.16 s persistent RTP and 10 s naked‐eye‐detectable emission. Notably, this work represents the first demonstration of a single material simultaneously enabling solution‐phase RTP, high‐efficiency electroluminescence, and long afterglow. This intra/intermolecular engineering overcomes single‐environment limitations, establishing universal design principles for adaptive luminescent materials in various optoelectronic applications.