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

Abstract

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.

Efficient Lone-Pair-Driven Luminescence: Structure–Property Relationships in Emissive 5s2 Metal Halides

“… 39 , 137 − 139 A new report found that undoped and Sb 3+ -doped Cs 2 InCl 5 ·H 2 O had essentially identical features and temperature-dependent intensities, 39 while recent work in our group showed that pure Cs 2 NaInCl 6 and Cs 2 InCl 5 ·H 2 O do not emit. 140 In our view, trace Sb 3+ dopants in the precursors may be responsible for these emissions, similar to the miniscule levels of Sn impurities that were found by Mitzi et al to generate STE emission in PEA 2 PbBr 4 . 141 Careful experimental work would be required to demonstrate this, perhaps utilizing InX monohalides as indium precursors that would be chemically less likely to contain trace Sb 3+ impurities.…”

Hybrid 0D Antimony Halides as Air‐Stable Luminophores for High‐Spatial‐Resolution Remote Thermography

“…[ 49 ] and the herein presented Sb‐based compounds, due to the more complex excited state structure in the latter, which arises from the nondegeneracy of the lowest unoccupied molecular orbital (LUMO) states in square pyramidal molecular geometry and exciton–phonon interactions. [ 47,68,77 ] TPP 2 SbBr 5 exhibits spectral variation in emission relaxation times (shorter relaxation times for shorter wavelengths and longer relaxation times for longer wavelengths, Figure S5a,c, Supporting Information) and non‐monoexponential behavior in the traces detected in narrow spectral windows (Figure S5b, Supporting Information), as previously demonstrated for other pnictogen halides. [ 78 ]…”

Lead‐Free Halide Double Perovskites: Structure, Luminescence, and Applications

“…[ 59 ] The doping ratio of Sb 3+ is less than 10% for efficient self‐trapped excitons (STEs). [ 60,61 ] In conclusion, the additive amounts of Bi 3+ and Sb 3+ are much smaller than that of CsPbX 3 . So, at least for luminescent applications, the environmental risk of Bi and Sb should not be a severe problem.…”