Magic-Angle Stacking and Strong Intermolecular π–π Interaction in a Perylene Bisimide Crystal: An Approach for Efficient Near-Infrared (NIR) Emission and High Electron Mobility

A single crystal of N,N'-bis(4-methoxybenzyl)perylene-3,4,9,10-bis(dicarboximide) (mb-PBI) that possesses novel magic-angle stacking (M-type stacking) and strong intermolecular π-π interaction is achieved by physical vapor transport (PVT), which shows attractive optoelectronic functions such as efficient NIR emission and high electron mobility. In this special M-type staking, the strong Frenkel/CT mixing state promotes fluorescence and, importantly, the elimination of long-distance Förster resonance energy transfer enables the minimization of the possible fluorescence quenching, which ensure the highly efficient emission. Moreover, the strong π-π interaction elongates the "supramolecular conjugation" to reduce the energy gap and also benefits the electron mobility of the crystal. The experimental results clearly indicate that M-type staking is a novel approach to optimize the optoelectronic functions of organic semiconducting materials.