Hybrid lead halide [(CH3)2NH2]PbX3 (X = Cl- and Br-) hexagonal perovskites with multiple functional properties
J. Mater. Chem. C 2019, 7, 10008-10018.
A. García-Fernández, E. J. Juarez-Perez, J. M. Bermúdez-García, A. L. Llamas-Saiz, R. Artiaga, J. J. López-Beceiro, M. A. Señarís-Rodríguez, M. Sánchez-Andújar, S. Castro-García
We have been able to prepare two new lead halides with the formula DMAPbX3 (where DMA is
dimethylammonium and X is Cl- or Br-), which display a 4H-hexagonal perovskite polytype, an unusual
crystal structure in hybrid organic–inorganic perovskites. Both compounds experience a first-order
phase transition, the chloride at B320 K and the bromide at B250 K, which involves two cooperative
processes: an off-center shift of the lead cations and an order–disorder process of the DMA cations.
Additionally, a sharp dielectric transition is associated with this structural transition in both hybrids. Both
compounds are semiconductors with band gap values of 3.5 eV (X: Cl-) and 3.0 eV (X: Br-). Also, the
LT-phase of the Br compound displays a broad red light photoluminescence (PL) emission (620 nm)
and PLE excitation with the maximum at a soft UV wavelength (360 nm). This broadband emission and
large Stokes-shifted PL seem to be related to a self-trapped exciton mechanism. Therefore, the
uncommon 4H-hexagonal perovskite is a promising crystal structure for understanding and designing
new hybrid materials with broad photoluminescent emission and dielectric properties.
We have been able to prepare two new lead halides with the formula DMAPbX3 (where DMA is
dimethylammonium and X is Cl- or Br-), which display a 4H-hexagonal perovskite polytype, an unusual
crystal structure in hybrid organic–inorganic perovskites. Both compounds experience a first-order
phase transition, the chloride at B320 K and the bromide at B250 K, which involves two cooperative
processes: an off-center shift of the lead cations and an order–disorder process of the DMA cations.
Additionally, a sharp dielectric transition is associated with this structural transition in both hybrids. Both
compounds are semiconductors with band gap values of 3.5 eV (X: Cl-) and 3.0 eV (X: Br-). Also, the
LT-phase of the Br compound displays a broad red light photoluminescence (PL) emission (620 nm)
and PLE excitation with the maximum at a soft UV wavelength (360 nm). This broadband emission and
large Stokes-shifted PL seem to be related to a self-trapped exciton mechanism. Therefore, the
uncommon 4H-hexagonal perovskite is a promising crystal structure for understanding and designing
new hybrid materials with broad photoluminescent emission and dielectric properties.