Doping of charge-transfer molecules in cocrystals for the design of materials with novel piezo-activated luminescence.

A novel piezo-activated luminescent material with wide range modulation of the luminescence wavelength and a giant intensity enhancement upon compression was prepared using a strategy of molecular doping. The doping of THT molecules into TCNB-perylene cocrystals results in the formation of a weak but pressure-enhanced emission center in the material at ambient pressure. Upon compression, the emissive band from the undoped component TCNB-perylene undergoes a normal red shift and emission quenching, while the weak emission center shows an anomalous blue shift from 615 nm to 574 nm and a giant luminescence enhancement up to 16 GPa. Further theoretical calculations show that doping by THT could modify intermolecular interactions, promote molecular deformation, and importantly, inject electrons into the host TCNB-perylene upon compression, which contributes to the novel piezochromic luminescence behavior. Based on this finding, we further propose a universal approach to design and regulate the piezo-activated luminescence of materials by using other similar dopants.