Rigid Boron‐Fused Frameworks for Efficient Near‐Infrared Emission and Optical Gain Beyond 900 nm

ABSTRACT

Organic near‐infrared (NIR) luminophores are attractive for a wide range of applications owing to the unique advantages of organic materials. However, the development of efficient NIR emitters remains challenging because nonradiative decay rate constant ( k _nr ) increases rapidly with decreasing excited‐state energy according to the energy‐gap law. In this work, we developed a molecular design strategy that integrates rigid boron‐fused polycyclic framework derived from multiple‐resonance (MR) chemistry into a narrow‐gap molecular framework to suppress electron–vibration coupling and structural relaxation in the excited state. The resulting emitters exhibited reduced k _nr s, enhanced photoluminescence quantum yields, and higher external electroluminescence quantum efficiencies in NIR organic light‐emitting diodes relative to a conventional donor‐based analogue. Furthermore, these materials showed amplified spontaneous emission at wavelengths above 900 nm with significantly low thresholds, despite the difficulty of achieving efficient organic gain media in this spectral region. These results demonstrate that the incorporation of rigid MR‐derived framework is a promising strategy for controlling nonradiative losses and improving both efficient spontaneous and stimulated emission characteristics, providing a basis for the development of organic NIR materials.