Luminescent CsPbI3 and Cs4PbI6 Aggregates in Annealed CsI:Pb Crystals

Abstract

Luminescent aggregates of various types have been produced in quenched CsI : Pb single crystals by their annealing in vacuum at temperatures from 220 to 370 o C for 18 to 137 h. It has been found that the relative concentrations of different aggregates depend on thermal treatment conditions. Their optical characteristics obtained at 4.2-300 K have been compared with the corresponding characteristics of CsPbI 3 and Cs 4 PbI 6 single crystals as well as with the characteristics of CsPbI 3 and Cs 4 PbI 6 -type aggregates in CsI-PbI 2 thin films. The absorption band located near 411 nm and the emission bands peaking at 465, 535 and %600 nm have all been ascribed to the CsPbI 3 -type aggregates dispersed in a CsI single crystal matrix. The emission band peaking at 435 nm and the corresponding excitation bands at 362 and 288 nm have been ascribed to the Cs 4 PbI 6 -type aggregates. The mechanism of the creation of aggregates in a CsI : Pb crystal has been discussed.

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

“…Lead halide perovskite nanocrystals of the formula CsPbX 3 (X = Cl, Br, I) were first reported more than 20 years ago [1][2][3], but have only been studied thoroughly since 2015, when their colloidal synthesis was introduced [4]. There are a large body of papers published on this topic, but the majority of work focuses on their luminescent properties and applications such as LEDs, displays, photovoltaics, or lasers [5][6][7].…”

Fast Anion-Exchange in Highly Luminescent Nanocrystals of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I)

“…The direct synthesis of single- or mixed-halide CsPbX 3 at such low temperatures yields either exclusively large and polydisperse crystallites of poorly or nonluminescent, wider-bandgap orthorhombic phases or simply no crystalline products at all. CsPbI 3 , for example, is highly luminescent and red in its three-dimensional cubic phase, yet yellow and nonluminescent upon conversion into its orthorhombic polymorph. − …”

Lead Halide Perovskite Nanocrystals in the Research Spotlight: Stability and Defect Tolerance

“…3D polymorphs of CsPbI 3 and FAPbI 3 are thermodynamically metastable and undergo transitions to wide-bandgap 1D polymorphs. 13−16,61−65 Thin films and NCs of CsPbI 3 and FAPbI 3 exhibit extended but finite stability in their 3D polymorphs (days to several months), primarily due to surface effects. 35,53,66−69 Thermodynamic instability is caused by the Cs and FA ions being, respectively, slightly too small and too large for the A-site, as determined by the Goldschmidt TF and by the octahedral factor for the required dense packing in 3D perovskites.…”

“…The synthesis of bulk CsPbX 3 compounds was reported as early as 1893, whereas their perovskite crystal structure and photoconductive, and hence semiconductive, nature was only discerned later, in the 1950s . Since then and until the late 1990s, CsPbX 3 compounds were rather thoroughly characterized as to the details of their crystallography and phase diagrams, including direct structural characterization by X-ray and neutron scattering and by nuclear magnetic resonance. − Also, a number of lead-free halide perovskites were studied at that time; CsSnX 3 phase transitions were characterized, ,− and specific electrical conductivity was observed . CsGeCl 3 was reported to have dielectric constants comparable to BaTiO 3 while exhibiting ferroelectric characteristics as well .…”

“…Another form of structural instability comes from the polymorphism, which is especially pronounced for iodide-based LHPs (CsPbI 3 and FAPbI 3 ). 3D polymorphs of CsPbI 3 and FAPbI 3 are thermodynamically metastable and undergo transitions to wide-bandgap 1D polymorphs. − ,− Thin films and NCs of CsPbI 3 and FAPbI 3 exhibit extended but finite stability in their 3D polymorphs (days to several months), primarily due to surface effects. ,,− Thermodynamic instability is caused by the Cs and FA ions being, respectively, slightly too small and too large for the A-site, as determined by the Goldschmidt TF and by the octahedral factor for the required dense packing in 3D perovskites. ,− Combined with the chemical instability of the MAPbI 3 NC system, a “red wall” exists for LHP NCsa difficulty to obtain stable NCs with PL in red and near-infrared spectral regions.…”