Pressure‐Induced Perovskite‐to‐non‐Perovskite Phase Transition in CsPbBr3

The expanding range of optoelectronic applications of lead‐halide perovskites requires their production in diverse forms (single crystals, thin‐ and thick‐films or even nanocrystals), motivating the development of diverse materials processing and deposition routes that are specifically suited for these structurally soft, low‐melting semiconductors. Pressure‐assisted deposition of compact pellets or thick‐films are gaining popularity, necessitating studies on the pressure effects on the atomic structure and properties of the resulting material. Herein we report the phase transformation in bulk polycrystalline cesium lead bromide from its three‐dimensional perovskite phase (γ‐CsPbBr3) into the one‐dimensional polymorph (δ‐CsPbBr3) upon application of hydrostatic pressure (0.35 GPa). δ‐CsPbBr3 is characterized by a wide bandgap of 2.9 eV and broadband yellow luminescence at 585 nm (2.1 eV) originating from self‐trapped excitons. The formation of δ‐CsPbBr3 was confirmed and characterized by Raman spectroscopy, 207Pb and 133Cs solid‐state nuclear magnetic resonance, X‐ray diffraction, absorption spectroscopy, and temperature‐dependent and time‐resolved photoluminescence spectroscopy. No such phase transition was observed in colloidal CsPbBr3 nanocrystals.ISSN:0018-019XISSN:1522-267

Bright Blue and Green Luminescence of Sb(III) in Double Perovskite Cs2MInCl6 (M = Na, K) Matrices

The vast structural and compositional space of metal halides has recently become a major research focus for designing inexpensive and versatile light sources; in particular, for applications in displays, solid-state lighting, lasing, etc. Compounds with isolated ns2-metal halide centers often exhibit bright broadband emission that stems from self-trapped excitons (STEs). The Sb(III) halides are attractive STE emitters due to their low toxicity and oxidative stability; however, coupling these features with an appropriately robust, fully inorganic material containing Sb3+ in an octahedral halide environment has proven to be a challenge. Here, we investigate Sb3+ as a dopant in a solution-grown metal halide double perovskite (DP) matrix, namely Cs2MInCl6:xSb (M = Na, K, x = 0–100%). Cs2KInCl6 is found to crystallize in the tetragonal DP phase, unlike Cs2NaInCl6 that adopts the traditional cubic DP structure. This structural difference results in distinct emission colors, as Cs2NaInCl6:xSb and Cs2KInCl6:xSb compounds exhibit broadband blue and green emissions, respectively, with photoluminescence quantum yields (PLQYs) of up to 93%. Spectroscopic and computational investigations confirm that this efficient emission originates from Sb(III)-hosted STEs. These fully inorganic DP compounds demonstrate that Sb(III) can be incorporated as a bright emissive center for stable lighting applications.ISSN:0897-475