Green-Emitting Lead-Free Cs₄SnBr₆ Zero-Dimensional Perovskite Nanocrystals with Improved Air Stability

Abstract

We report the synthesis and characterization of nanocrystals of a novel fully inorganic lead-free zero-dimensional perovskite, Cs 4 SnBr 6 . Samples are made of crystals with an average size of ∼20 nm with green emission centered around 530 nm. Interestingly, both colloidal suspensions and thin films show an enhanced air stability with respect to that of any other previous tin-based nanocrystalline system, with emission persisting for tens of hours under laboratory air.

Continuous‐Flow Synthesis of Orange Emitting Sn(II)‐Doped CsBr Materials

“…These materials transform to Cs 2 SnBr 6 in presence of air, subsequently lose the emission. [28] Cs 2 SnX 6 , vacancy ordered double perovskites are a class of materials, where the Sn atom has a +4-oxidation state and hence they possess higher stability in the open air. [18] Their optical performances enable many application segments including photovoltaics and light-emitting materials.…”

“…The former material is well-studied in accordance to their STE emission, A-site doping, and thermographic applications. [28][29][30][31]41] We found Cs 4 SnBr 6 is unstable and it degrades in open air over time and eventually transforms to Cs 2 SnBr 6 . However, the other material, Sn(II)-doped CsBr was prepared for the first time, which exhibits broadrange STE emission (PLQY = 21.5%, FWHM ≈180 nm) and highly stable in the open air over 7 months as per laboratory report.…”

“…[23] Recently, several reports on 0D Cs 4 SnBr 6 published portraying a self-trapped excitonic (STE) emission originated from the isolated [SnBr 6 ] 4octahedra. [27][28][29][30][31] Typical characteristics of STE emissions are i) broad emission and ii) large stokes shift. [32] Hence, the generation of white light due to covering a broad optical window and the reabsorption-related An ongoing demand toward lead-free all-inorganic cesium metal halide perovskites has presented Sn(II) as an ideal substitute of Pb(II) for applications in optoelectronic devices.…”

ASnX3—Better than Pb‐based Perovskite

“…first synthesized all‐inorganic 0D Cs 4 SnBr 6 nanocrystals (Figure 20), with average size of ∼20 nm and green emission centered around 530 nm. [ 169 ] The Cs 4 SnBr 6 0D nanocrystals showed impressive stability under humid air with a quenching of emission occurring after tens of hours and highest PLQYs ∼0.8%, in contrast to the typical performance reported for CsSnX nanocrystals of only for few minutes emission and ∼0.1‐0.2% PLQYs. Li et al.…”

Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

“…remains in the early stages; there are many reports of moderate PLQY from lead-free perovskite or double perovskite nanomaterials. [132][133][134][135][136] Some of these were synthesized at room temperature; for example, Zhang et al prepared Cs 3 Sb 2 Br 9 NCs that emit at 410 nm with PLQY = 46% (Figure 17a), [137] while Leng et al similarly synthesized Cs 3 Bi 2 Br 9 NCs with PLQY up to 19.4% at the same wavelength. [138] Yang et al reported that indium-doping of Cs 2 AgBiCl 6 NCs changed the bandgap from indirect to direct, increasing the PLQY from 6.7% to 36.6% for emission around 570 nm (Figure 17b).…”