Pure zero-dimensional Cs₄PbBr₆ single crystal rhombohedral microdisks with high luminescence and stability

Abstract

Zero-dimensional (0D) perovskite CsPbBr has been speculated to be an efficient solid-state emitter, exhibiting strong luminescense on achieving quantum confinement. Although several groups have reported strong green luminescence from CsPbBr powders and nanocrystals, doubts that the origin of luminescence comes from CsPbBr itself or CsPbBr impurities have been a point of controversy in recent investigations. Herein, we developed a facile one-step solution self-assembly method to synthesize pure zero-dimensional rhombohedral CsPbBr micro-disks (MDs) with a high PLQY of 52% ± 5% and photoluminescence full-width at half maximum (FWHM) of 16.8 nm. The obtained rhombohedral MDs were high quality single-crystalline as demonstrated by XRD and SAED patterns. We demonstrated that CsPbBr MDs and CsPbBr MDs were phase-separated from each other and the strong green emission comes from CsPbBr. Power and temperature dependence spectra evidenced that the observed strong green luminescence of pure CsPbBr MDs originated from direct exciton recombination in the isolated octahedra with a large binding energy of 303.9 meV. Significantly, isolated PbBr octahedra separated by a Cs ion insert in the crystal lattice is beneficial to maintaining the structural stability, depicting superior thermal and anion exchange stability. Our study provides an efficient approach to obtain high quality single-crystalline CsPbBr MDs with highly efficient luminescence and stability for further optoelectronic applications.

Zero-Dimensional Cesium Lead Halides: History, Properties, and Challenges

“…For instance, no CsPbBr 3 diffractions peaks were reported in various Cs 4 PbBr 6 samples, including powders, single crystals, and NCs. 11,14,17,18,20,21 For instance, De Bastiani et al were able to demonstrate that the presence of any CsPbBr 3 impurity phase down to 0.5% in weight could be detected by XRD (Figure 4a). 21 Nevertheless a similar experiment, in which nonluminescent Cs 4 PbBr 6 NCs were mixed with a small amount (2% molar, 0.5 wt %) of highly luminescent CsPbBr 3 NCs, indicated that this small amount of CsPbBr 3 did not result in any clear CsPbBr 3 features in the XRD pattern (Figure 4b).…”

“…For instance, unlike CsPbBr 3 and its hybrid perovskite counterpart, which are usually found to be bromine-deficient, 80−83 Cs 4 PbBr 6 is often reported to have a Br:Pb ratio that is usually higher than 6, thus implying that Cs 4 PbBr 6 are rather halide rich. 14,18,20,80 One could therefore expect a rather low density of V Br .…”

“…11,18,21,90 If the green PL were to originate from a midgap state or a trap state, then the absorption of the Cs 4 PbBr 6 host would remain unaltered, i.e., it would have no features in the visible range. Take, for example, the case of fluorescent, low-dimensional organic–inorganic lead or tin halides, 85,91−94 in which the dimensionality (whether 2D, 1D, or 0D) is tuned by using specially designed amines, like 2,2′-(ethylenedioxy)bis(ethylamine), C 4 N 2 H 14 2+ , or C 4 N 2 H 14 Br + .…”

A Single Nonblinking Cs4PbBr6 Nanoparticle as a Nanothermometer

“…The maximum of the emission spectrum peak locates at 519 nm. Based on the spectra, we can estimate the band gap of Cs 4 PbBr 6 nanoparticles to be 2.4 eV in good agreement with the reported values . We have to state that there was a big discussion about the origin of the PL for this material ,,,,,.…”

“…Both performance and fundamental understanding of Cs 4 PbBr 6 have been widely investigated. In addition, temperature dependence of PL of perovskite materials including Cs 4 PbBr 6 nanoparticles has also been reported ,,,. However, temperature‐dependence at single particle level has rarely been reported so far.…”