Evidence for Ferroelectricity of All-Inorganic Perovskite CsPbBr₃ Quantum Dots

Abstract

The combination of ferroelectric–optical properties in halide perovskites has attracted tremendous interess because of its potential for optoelectronic and energy applications. However, very few reports focus on the ferroelectricity of all-inorganic halide perovskites quantum dots. Herein, we report a excellent ferroelectricity in CsPbBr3 quantum dots (QDs) with a saturation polarization of 0.25 μC/cm2. Differential scanning calorimetry, X-ray diffraction, and transmission electronic microscopy revealed that the mechanism of ferroelectric–paraelectric switching of CsPbBr3 QDs can be attributed to the phase transition from cubic phase (Pm3̅m) to the orthorhombic phase (Pna2 1). In the orthorhombic CsPbBr3, the distortion of octahedral [PbBr6]4– structural units and the off-center Cs+ generated the slightly separated centers of positive charge and negative charge, resulting in the ferroelectric properties. The variable-temperature emission spectrum from 328 to 78 K exhibits green luminescence and a gradual red shift due to the phase transition. This finding opens up an avenue to explore the ferroelectric–optical properties of inorganolead halide perovskites for high-performance multifunctional materials.

Polarizable High‐Index Nanoparticles Used for Light‐Induced Crystal‐Silicon Passivation and Dielectric Antenna for High‐Efficiency Solar Cell

“…[ 18 ] Ferroelectric cesium lead tribromide (CsPbBr 3 ) NPs also show saturation polarization at room temperature, which is ascribed to the slightly mismatched centers of ferroelectric properties and positive charge due to orthorhombic CsPbBr 3 distortion units and off‐center cesium ions. [ 19 ] Here, CsPbBr 3 perovskite NPs were utilized to act as a polarizing layer, which was synthesized via a typical hot‐injection method according to a previously report. [ 20 ] To obtain stable and high‐photoluminescence (PL) CsPbBr 3 perovskite NPs, the thicknesses and lateral dimensions can be controlled by different ratios of short‐ and long‐chain ligands.…”

“…Figure a shows the UV–vis absorption and PL spectra of CsPbBr 3 NPs, which show the first exciton peak of 515 nm and PL peak of 520 nm, and they are lined well with the previous report. [ 19 ] The morphology and structure of CsPbBr 3 NPs were investigated by transmission electron microscopy (TEM). As shown in the inset of Figure 1b, the cubic‐shaped NPs exhibit an average size of ≈10 nm, and the size of the NPs is uniform, which means the diameter can be well controlled with suitable synthesis parameters.…”

Ferroic Halide Perovskite Optoelectronics

“…The ferroelectricity in halide perovskite quantum dots was also investigated. [ 123 ] It was demonstrated that a spontaneous polarization can emerge in CsPbBr 3 quantum dots due to phase change from cubic to orthorhombic structure. [ 123 ] In the orthorhombic phase, the [PbBr 6 ] [ 4 ]− octahedral distortion and the Cs + off‐centering are responsible for the spontaneous polarization, which lead to separated centers of positive and negative charges, resulting in ferroelectric polarization in CsPbBr 3 quantum dots.…”

“…[ 123 ] In the orthorhombic phase, the [PbBr 6 ] [ 4 ]− octahedral distortion and the Cs + off‐centering are responsible for the spontaneous polarization, which lead to separated centers of positive and negative charges, resulting in ferroelectric polarization in CsPbBr 3 quantum dots. [ 123 ]…”

“…The polarization of the chiral hybrid halide nanowire is around 0.03 µC cm −2 , which can reach 1.2 µC cm −2 for the corresponding single‐crystal sample. [ 122 ] The experimentally measured polarization of CsPbBr 3 quantum dot is 0.25 µC cm −2 at 77 K and 0.018 µC cm −2 at 293 K. [ 123 ] It was seen that these polarization values are smaller than those reported in LHHs (as discussed above). However, it is still unclear if this is a general trend; and if so, why the polarization of chiral halide nanowires and MHP quantum dots is smaller than LHHs.…”