Excellent Persistent Near‐Infrared Room Temperature Phosphorescence from Highly Efficient Host–Guest Systems

Organic near‐infrared (NIR) room temperature phosphorescence (RTP) materials become a hot topic in bioimaging and biosensing for the large penetration depth and high signal‐to‐background ratio (SBR). However, it is challenging to achieve persistent NIR phosphorescence for severe nonradiative transitions by energy‐gap law. Herein, a universal system with persistent NIR RTP is built by visible (host) and NIR phosphorescence (guest) materials, which can efficiently suppress the nonradiative transitions by rigid environment of crystalline host materials with good matching, and further promote phosphorescence emission by the additional phosphorescence resonance energy transfer (≈100%) between them. The persistent NIR phosphorescence with ten‐folds enhancement of RTP lifetimes, compared to those of guest luminogens, can be achieved by modulation of aggregated structures of host–guest systems. This work provides a convenient way to largely prolong the phosphorescence lifetimes of various NIR luminogens, promoting their application in afterglow imaging with deeper penetration and higher SBRs. The persistent near‐infrared (NIR) room temperature phosphorescence (RTP) is achieved by doping NIR phosphors (guest) into visible RTP materials (host) as a new type of host–guest system, with ten‐folds increase of RTP lifetimes. The spatial matching of hosts and guests is proven as the crucial factor for the first time, which can efficiently suppress nonradiative transitions by space restriction, promoting RTP emission.