Bright Blue and Green Luminescence of Sb(III) in Double Perovskite CsMInCl (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 ns-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 Sb in an octahedral halide environment has proven to be a challenge. Here, we investigate Sb as a dopant in a solution-grown metal halide double perovskite (DP) matrix, namely CsMInCl:Sb (M = Na, K, = 0-100%). CsKInCl is found to crystallize in the tetragonal DP phase, unlike CsNaInCl that adopts the traditional cubic DP structure. This structural difference results in distinct emission colors, as CsNaInCl:Sb and CsKInCl:Sb 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.