Manipulating P States of Organophosphine Polymers to Enhance Multi‐Channel Synergetic Room‐Temperature Phosphorescence

Abstract According to El‐Sayed's rule, nπ * component would facilitate intersystem crossing (ISC) and room‐temperature phosphorescence (RTP) of organic molecules. However, purposeful molecular design still faces big challenge due to insufficient understanding of inherent effect of nπ * states on RTP. Herein, phosphorus‐containing groups of triphenylphosphine, triphenylphosphine oxide, and tetraphenylphosphonium bromide are introduced in polyacrylamide matrix, corresponding to PAM‐TPP, PAM‐TPPO, and PAM‐TPP + . It shows that phosphorus (“P”) states determine excited‐state compositions of these polymers and, more importantly, result in different RTP processes. p – π conjugation between P atom and phenyls in PAM‐TPP integrates ISC acceleration and triplet convergence to stabilize triplet states (T n *). In contrast, P = O localized nπ * state of PAM‐TPPO competes with ππ * states of phenyls, while PAM‐TPP + has pure ππ * states. In contrast to RTP‐free PAM‐TPPO and PAM‐TPP + , with RTP dependent on 1 ππ * excitation, PAM‐TPP achieves the best RTP performance, including the longest lifetime beyond 250 ms, the highest efficiency reaching 10.8%, and the limited excitation dependence, owing to its more than fourfold larger ISC rate constants reaching 10 −7 s −1 and doubled RTP proportions. This work clarifies the importance of nπ *– ππ * synergy for developing high‐performance RTP materials.