Long Persistent Luminescence of Melt‐Grown Bulk‐Sized Doped Organic Crystals

Host–guest systems constitute a primary subclass of long persistent luminescent (LPL) materials. Doped organic crystals serve as model platforms to clarify the intricate effect of chromophores embedded in an ordered lattice background. However, construction of doped organic crystals through traditional solution method is restricted by drawbacks such as inhomogeneity and imprecise quantification. In this report, a series of doped organic crystals is grown by a melt growth technique with centimeter-scale size and precisely controlled concentration and homogeneity. Although the host crystals are neutral with neither heavy atoms nor any functional groups, they show enhanced long persistent luminescence with lifetimes of nearly three orders longer than those of the pure guest molecules. Moreover, the LPL wavelength, lifetime, and quantum yield can be tuned by different host–guest combination and doping concentration. Theoretical optimizations reveal that the guest molecules are substitutively rather than interstitially embedded in the host crystal lattice. The results prove melt growth to be an effective way to build and to finely control host–guest long persistent luminescent systems.