Ferroelectricity of the Orthorhombic and Tetragonal MAPbBr₃ Single Crystal

Abstract

Hybrid organic−inorganic halide perovskites (HOIPs) MAPbBr 3 and their ramifications have emerged because of the photovoltaic, optical, and other fascinating performances of HOIPs in recent years. However, many intrinsic properties, such as crystal structure and ferroelectricity, are still controversial. In this work, the ferroelectricity of the orthorhombic and tetragonal MAPbBr 3 single crystal was confirmed through the dielectric behavior versus bias electric field ε(E), the temperature-dependent pyroelectric current with positive/negative poling, and the positive-up-negative-down (PUND) measurements. The electric field dependence of dielectric constant curves shows a butterfly type shape in the orthorhombic and tetragonal phase. The pyroelectric current shows two maxima at 155 and 245 K, corresponding to ferroelectric−ferroelectric and ferroelectric−paraelectric phase transitions, respectively. In particular, the direction of the pyroelectric current can be reversed by a positive or negative poling electric field, which is the assertive evidence of ferroelectricity. The PUND measurements act as the most convincing proof of the ferroelectricity of the MAPbBr 3 single crystal. This work reports new evidence of the ferroelectric properties of the MAPbBr 3 single crystal, which provides the intrinsic property when considering their high power conversion efficiencies.

Temperature-Dependent Optical Band Gap in CsPbBr3, MAPbBr3, and FAPbBr3 Single Crystals

“…Although the trend of the E gap versus T and its value near 0 K are often fitted with the Bose–Einstein equation to account for electron–phonon interactions, 27 − 30 MAPbBr 3 and FAPbBr 3 are still in the tetragonal phase within the investigated T -range while in CsPbBr 3 the transition to orthorhombic is not linear (see also Figure SI-3 ). 39 , 40 A linear fit in this region would overestimate E gap (0) and would contradict what was reported in ref ( 22 ) (see Figure 3 ). To properly apply the Bose–Einstein equation, the sample should be cooled down near 0 K. 21 , 22 , 41 Under these circumstances, the relative weight of thermal expansion and electron–phonon coupling could be evaluated, as in the case of MAPbI 3 .…”

Structural Phase Transitions of Hybrid Perovskites CH3NH3PbX3 (X = Br, Cl) from Synchrotron and Neutron Diffraction Data

“…On the other hand, CH 3 NH 3 PbCl 3 is also an alternative material that presents a wider band gap (3.1 eV), being also sensitive to the UV region. Furthermore, this compound exhibits a fast photoresponse and long-term photostability, having a charge carrier concentration, mobility, and diffusion length comparable with the best-developed crystal structures of CH 3 NH 3 PbI 3 and CH 3 NH 3 PbBr 3 [28][29][30]. However, both CH 3 NH 3 PbCl 3 and the mixed anion CH 3 NH 3 Pb(Br 1−x Cl x ) 3 have been less investigated [31].…”

Giant Bulk Photostriction and Accurate Photomechanical Actuation in Hybrid Perovskites

“…It is known that a PZT ceramic actuator commonly shows a ≈0.1–0.3% strain driven by an electric field as high as 20 kV cm −1 , which implies that a 3.0 mm thick PZT ceramic plate may be elongated for ≈3–9 µm with a driving voltage over 6 kV. [ 1,54 ] Currently, the multilayer actuator composed of thousands of ≈50 μm thick piezoelectric slices and inner electrodes is developed, but the driving voltage of about ≈100 V still requires a heavy external power source. Third, the as‐grown MAPbI 3 single crystals are usually millimeters in size, and they are light‐driven actuators with pm‐scale accuracy.…”