Although research on organic–inorganic
hybrid perovskites
(OIHPs) has grown exponentially in the past two decades, the high
phase transition temperature of OIHP materials is still one of the
insurmountable difficulties. Herein, a series of A2BX4 type OIHP materials [(2,n-DFBA)2PbCl4] (n = 3, for 1; n = 4, for 2; n = 5, for 3; n = 6, for 4) have been prepared
by reactions of double-substituted difluorobenzylamine (difluorobenzylamine
= DFBA) with lead chloride in concentrated HCl aqueous solution. It
was found the OIHP compounds 1–3 proceed
a switchable phase transition with phase transition temperatures (T
c) at 449 K (1), 462 K (2) and 500 K (3), higher than that of the parent compound
[(BA)2PbCl4] (BA = benzylammonium) at 438 K,
but compound 4 exhibits no phase transition. A crystal
structure analysis elucidated that the organic template ligands DFBA
lead in the inorganic part in compounds 1–3 to a two-dimensional (2D) perovskite structure, while that
in compound 4 leads to a one-dimensional (1D) chain structure.
The different double-substituted positions of fluorine atoms on benzylamine
have important influences on the phase transition in compounds 1–4.