• fluorescence;
  • organic solids;
  • polymorphism;
  • solid-state structures;
  • switchable materials


Organic fluorescent materials have been an integral part of recently emerged optoelectronic device technologies owing to their good photophysical properties such as high quantum yields and significant photostability. In particular, switchable and tunable solid-state fluorescence has attracted increasing attention in recent years both in the field of fundamental research and industrial applications. Unlike in solution, fluorescence in the solid state is a collective phenomenon of molecules that are commonly modulated through controlling molecular packing and the electronic conjugation of fluorophores. Several strategies, including chemical modification, have been developed to alter the fluorophore molecular arrangement in the solid state. This Review article describes the various strategies that have been effectively utilised to achieve switchable and tunable fluorescence in the organic solid state.