Butterfly‐Shaped Guest Molecules Enable Tunable Room‐Temperature Phosphorescence in Host‐Guest Doped Systems

Abstract Organic room‐temperature phosphorescence (RTP) materials have attracted significant interest due to their potential in optoelectronics and anti‐counterfeiting. However, achieving multicolor‐tunable and long‐lived RTP with simple, low‐cost systems remains challenging. Herein, a facile host‐guest doping strategy is developed to realize efficient and color‐tunable RTP by embedding butterfly‐shaped triphenylamine‐based guest molecules (TPA, DBD, and DBDBD) into various host matrices (e.g., TPP, BPP, or CA). The doped crystals exhibit distinct afterglow colors (green to yellow) and prolonged long‐persistent luminescence (LPL) (from 1 to 6 s of afterglow time) and phosphorescence lifetimes up to 763.33 ms, governed by host‐guest energy transfer and intersystem crossing enhancement. Density functional theory (DFT) calculations reveal that the guest's electron‐donating ability and the host's heavy‐atom effect (e.g., P in TPP) synergistically promote charge separation and suppress non‐radiative decay. Notably, DBDBD:TPP shows the longest LPL (6 s of afterglow time) due to optimal energy level alignment and strong intermolecular interactions. By leveraging the time‐ and color‐dependent afterglow, applications in multilevel information encryption and anti‐counterfeiting are demonstrated, where encrypted messages are dynamically revealed under UV excitation. This work provides a simple yet versatile approach to designing low‐cost, multicolor RTP materials for advanced photonic applications.