(C2H5NH3)2BiCl5−xBrx perovskites containing 1D chains: effect of Br substitution on their structural and optical properties

The observed high dielectric constant of pristine chlorine in (C 2 H 5 NH 3 ) 2 BiCl 5− x Br x is attributed to the high polarization of the [BiCl 5 ] 2− unit as a result of its high tilting angle.