Dopant‐Tailored Matrices: A Crystal Engineering Strategy for Organic Room‐Temperature Phosphorescent Host–Guest Systems and Beyond

Host–guest doping of molecular crystals is a powerful strategy to tune optoelectronic properties, yet achieving precise host–dopant compatibility and beneficial synergy without introducing detrimental effects caused by dopant‐induced disorders remains challenging. Here, a new crystal engineering strategy is introduced in which host matrices are rationally designed to accommodate a predefined class of dopants and promote favorable host–guest interactions. This tailored‐dopant matrix concept is demonstrated for dopant‐induced organic room‐temperature phosphorescence (RTP) using carbazole‐based matrices and benzoindole‐based dopants, a prototypical RTP system. Guided by the hypothesis that a herringbone packing of carbazole units promotes synergistic structural interactions with the dopant, a multiscale theoretical methodology is first developed to elucidate the intermolecular interactions stabilizing this motif in pristine carbazole‐based crystals. These insights enable the design and synthesis of new host architectures exhibiting the targeted packing arrangement. Ultimately, the resulting single‐crystalline host–guest materials exhibit long‐lived organic RTP, with phosphorescence lifetimes of several hundred milliseconds. This work could establish dopant‐tailored crystal engineering as a potential new paradigm for designing functional doped organic semiconductor crystals with tailored optoelectronic properties.