Solvent-assisted mechanochemical crystallization of the metal-free perovskite solid solution (H 2 dabco, H 2 hmta)NH 4 (BF 4 ) 3 .

All-proportional solid solutions of the metal-free perovskite (H 2 dabco 1- y , H 2 hmta y )(NH 4 )(BF 4 ) 3 ((d,h)-BF 4 ) were crystallized via a mechanochemical method. Their molecular dynamics depend on the ratio y with a compositional boundary at y = 0.43, where H 2 dabco 2+ was deduced to be at a dynamic disorder state, even below phase transition temperature to a plastic crystalline phase seen at y = 0.