A lead bromide organic-inorganic hybrid perovskite material showing reversible dual phase transition and robust SHG switching.

A one-dimensional organic-inorganic hybrid perovskite material [3.3.0-dabco]PbBr 3 (1) was synthesized by the reaction of 1,5-diazabicyclo[3.3.0]octane (3.3.0-dabco) with PbBr 2 in concentrated HBr aqueous solution. Differential scanning calorimetry, dielectric measurements, and variable-temperature structural analyses revealed that compound 1 exhibits two successive structural phase transitions from P 2 1 2 1 2 1 to Pbcm at 387 K ( T 1 ) and then to P 6/ mmc at 436 K ( T 2 ), accompanied by two pairs of dielectric anomalies with a clear one at T 1 and an unobvious one at T 2 . In addition, compound 1 shows a robust second harmonic generation (SHG) effect between SHG-OFF and SHG-ON states during its centrosymmetric to non-centrosymmetric symmetry breaking phase transition at T 1 .