Suppressing molecular motions: A pathway to enhanced organic room temperature phosphorescence

Organic room-temperature phosphorescence (RTP) emitters have emerged as a compelling research field with broad applications in optoelectronics, anti-counterfeiting, and biomedical imaging. This interest stems from the efficient utilization of the radiative relaxation of the triplet excited state. An efficient intersystem crossing (ISC) process alone is not sufficient for efficient and long-lived RTP emission. It is also crucial to suppress molecular motion, including rotation, vibration, and translation. By rigidifying molecular structures to suppress these motions, triplet excitons are effectively stabilized, and non-radiative transitions are reduced, presenting a viable strategy for developing a variety of efficient and long-lived RTP materials. This review focuses on the current rational engineering efforts to suppress molecular motion for efficient and long-lived RTP generation, enhancing understanding of the interplay between molecular motion and RTP emission, and emphasizing the critical role of restricting molecular motion in the development of efficient and long-lived RTP materials.