Three-Dimensional Perovskite Methylhydrazinium Lead Chloride with Two Polar Phases and Unusual Second-Harmonic Generation Bistability above Room Temperature

Mirosław Ma̧czka (1) , Anna Gagor (2) , Jan Zaręba (3) , Dagmara Stefanska (2) , Marek Drozd (1) , Sergejus Balciunas (2) , Mantas Šimėnas (2) , Juras Banys (2) , Adam Sieradzki (3)

1 Institute of Low Temperature and Structure Research [Polish Academy of Sciences]
2 Vilnius University [Vilnius]
3 Wroclaw University of Science and Technology

Formation of noncentrosymmetric three-dimensional (3D) lead halide perovskites has been a widely sought after goal because the polar structure opens up new vistas to properties of these materials, e.g., improved charge separation for photovoltaics arising from ferroelectric order. Here, we report growth and unique properties of a new highly distorted 3D perovskite, methylhydrazinium lead chloride (CH3NH2NH2 PbCl3 , MHyPbCl3). This perovskite crystallizes in polar P21 structure at room temperature, which consists of two types of PbCl6 octahedra: one weakly and another strongly deformed. The unusual deformation of every second perovskite layer is forced by the large size of methylhydrazinium cations and the ability of NH2+ terminal groups of methylhydrazinium cations to form coordination bonds with Pb2+ metal centers. On heating, MHyPbCl3 undergoes a phase transition at 342 K into another polar Pb21m phase with ordered organic cations. Temperature-resolved second-harmonic generation (TR-SHG) measurements confirm acentricity of both phases and show that second-harmonic response is enhanced for the high-temperature Pb21m phase. This intriguing property of MHyPbCl3 has been employed to demonstrate an unprecedented kind of quadratic nonlinear optical switching in which a second-harmonic response is switched between a room-temperature, low-SHG state and a high-temperature, high-SHG state. X-ray diffraction shows that enhancement of polar properties is due to rearrangement of the perovskite's organic substructure. There is a clear pyrocurrent peak, but switching of the electric polarization could not be observed. Optical studies showed that MHyPbCl3 is a wide-bandgap material with a bandgap of 3.4 eV (365 nm). At low temperatures, it exhibits weak UV emissions at 362 and 369 nm as well as a strong broadband white emission.

Mots clés: perovskites; switching of SHG; second harmonic generation; second harmonic generation switching; dielectric measurements; pyroelectricity; optical studies; MHyPbCl3; methylhydrazinium; lead chloride perovskite

Domaines: Matériaux; Cristallographie

Mirosław Ma̧czka, Anna Gagor, Jan Zaręba, Dagmara Stefanska, Marek Drozd, et al.. Three-Dimensional Perovskite Methylhydrazinium Lead Chloride with Two Polar Phases and Unusual Second-Harmonic Generation Bistability above Room Temperature. Chemistry of Materials, 2020, 32 (9), pp.4072-4082. ⟨10.1021/acs.chemmater.0c00973⟩. ⟨hal-03526930⟩