Activating Versatile Mechanoluminescence in Organic Host-Guest Crystals by Controlling Exciton Transfer

Mechanoluminescence (ML) materials are attracting increasing interest owing to promising applications in various areas. However, to date, it remains a major challenge to develop a precise and universal route to achieving organic ML materials. Herein, we show that ML can be easily realized in organic piezophotonic host-guest crystals, under conditions in which neither the host nor the guest is ML-active. The experimental and theoretical results reveal that excitons of the host generated by piezoelectricity can be harvested effectively by the guest for light emission, owing to the restraint of intersystem crossing process. Moreover, different host-guest crystals are constructed, wherein the emission color, intensity, color purity, and emission duration of ML can be manipulated. This work deepens our understanding of organic ML generation in piezophotonic host-guest crystals and provides an inspiring principle to design more organic ML materials.