Narrowband Clusteroluminescence with 100% Quantum Yield Enabled by Through-Space Conjugation of Asymmetric Conformation

Different from traditional organic luminescent materials based on covalent delocalization, clusteroluminescence (CL) from nonconjugated luminogens relies on noncovalent through-space conjugation (TSC) of electrons. However, such spatial electron delocalization is usually weak, resulting in low luminescent efficiency and board emission peak due to multiple vibrational energy levels. Herein, several nonconjugated luminogens are constructed by employing biphenyl as the building unit to reveal the structure-property relationship and solve current challenges. The intramolecular TSC could be gradually strengthened by introducing building units and stabilized by rigid molecular skeleton and multiple intermolecular interactions. Surprisingly, narrowband CL with full width at half-maximum of 40 nm and 100% efficiency is successfully achieved via an asymmetric conformation, exhibiting comparable performance to the traditional conjugated luminogens. This work realizes highly efficient and narrowband CL from nonconjugated luminogens and highlights the essential role of structural conformation in manipulating the photophysical properties of unconventional luminescent materials.