Separate Control Model for Tailoring Ultralong Organic Room‐Temperature Phosphorescence with Highly Efficient Energy Transfer to Rhodamine B

Abstract Organic room‐temperature phosphorescence (RTP) materials have attracted significant attention for their promising applications, yet achieving high‐efficiency RTP molecules remains challenging. To address this, a comprehensive dataset of donor–acceptor (D–A) structured molecules is developed using D and A fragment pools. Promising phosphorescent candidates can be efficiently identified through high‐throughput screening that combines density functional theory (DFT) with high‐precision multireference perturbation theory calculations. A key innovation is the introduction of the “separate control model”, which independently optimizes both spin–orbit coupling (SOC) and the singlet‐triplet energy gap (Δ E ST ). Using this method, the phosphorescent unit 5,5‐dioxido‐10‐(phenanthren‐9‐yl)‐10H‐phenothiazin‐3‐yl)(phenyl) methanone (PPTZO‐CO), exhibits an exceptionally high intersystem crossing (ISC) rate constant of 10¹¹ s⁻¹, representing the highest value reported in organic systems to date. Remarkably, the RTP lifetime of PPTZO‐CO reaches up to 700 ms when doped into polymethyl methacrylate (PMMA). Co‐doping PPTZO‐CO with rhodamine B (RB) in PMMA yields red afterglow emission with near 100% energy transfer efficiency, the highest reported for co‐doped polymer systems. The PPTZO‐CO@PMMA system demonstrates promise in dynamic anti‐counterfeiting, showcasing its potential for practical use.