CsPbBr₃@Cs₄PbBr₆ Emitter-in-Host Composite: Fluorescence Origin and Interphase Energy Transfer

Abstract

Although the superior halide perovskite (HP) nanocrystals (NCs) have garnered considerable research passion in recent years, their practical use is still dauntingly plagued by the instability issue. The so-called “zero-dimensional” (0D) cesium lead HP, equipped with similar fluorescent attributes as those of HP NCs but greatly enhanced stability, has emerged as a promising alternative. Nevertheless, a long-lasting debate over the microstructure and emissive mechanism was ignited then. The research community has been demarcated into two sides holding vastly different opinions, which are known as the earlier Br vacancy scenario and the later CsPbBr3 impurity scenario. The inadequate understanding hinders further fundamental investigations as well as potential applications of the 0D HP. Lately, some highly persuasive experimental evidence, the lack of which was the main cause of the earlier turn to Br vacancy theory, for the CsPbBr3 impurity theory was demonstrated. This Review tries to, with these reports, reproduce a CsPbBr3@­Cs4PbBr6 model of 0D HP and present how the CsPbBr3 impurity theory reasonably outcompetes the Br vacancy counterpart regarding shared experimental phenomena. Importantly, energy transfer within the diphase 0D HP, which has been overlooked but determines the optoelectronic/optical performance, is comprehensively discussed. Finally, potential fluorescent applications of 0D HP and corresponding challenges are prospected.

Scintillation Response Enhancement in Nanocrystalline Lead Halide Perovskite Thin Films on Scintillating Wafers

“…XRPD analysis in Figure 1 shows that synthesized nanocrystals were pure orthorhombic CsPbBr 3 phase with the mean crystallite size of (13.8 ± 0.6) nm, which is consistent with the value obtained by XRPD and TEM analysis in our previous paper [22]. The phase purity is further confirmed by the PLE spectrum in Figure 1b lacking the dip at 310 nm, and absorption spectrum lacking the peak at the same wavelength, which are both characteristic of the Cs 4 PbBr 6 impurity [22,25,26]. The PL spectrum shows a single excitonic peak at 515 nm.…”

Cs4PbBr6–xClx Single Crystals with Tunable Emission for X-ray Detection and Imaging

“…Finally, the PL peaks show a blue shift with the increase of Cl – in our Br 6– x Cl x SCs, and this blue shift might be caused by the bandgap widening of CsPbCl x Br 3– x NCs, , which is also indicative of the existence of the CsPbX 3 phase. These results might strengthen the CsPbX 3 impurity emission viewpoint in the debate. ,,, In addition, the core–shell composite structure of our Br 6– x Cl x SCs would potentially facilitate the efficient absorption of X-ray energy and then the energy transfer to a CsPbBr 3 NCs emitter, ,,− thus possibly leading to highly efficient X-ray detection.…”

“…Recently the solution-grown Cs 4 PbBr 6 microcrystals and SCs were reported. ,,,, Their emission has been confirmed to come from the CsPbBr 3 NCs embedded in the crystalline Cs 4 PbBr 6 matrix. ,, To decipher the optical properties of our SCs, we collected their UV–vis absorption spectra, PL spectra, time-resolved PL (TRPL) curves, and PLQY data, as shown in Figure and Table . As shown in Figure a, the absorption edge of Br 6 SCs locates at 524 nm (2.36 eV), which agrees well with the literature report .…”

Revisiting the origin of green emission in Cs4PbBr6

“…41 There are many more experimental reports that indicate or support CsPbBr 3 inclusions in Cs 4 PbBr 6 . 42–50…”