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Multi‐metallic halides of group IA and IB metals are emerged as a new class of color tunable emitters. While chalcogenides and perovskites are extensively studied, these families of materials are little explored. In comparison, herein, lead and cadmium free bimetallic Cs‐Ag‐X (X = Cl, Br, I) halides are reported where the larger ion Ag+ helped in incorporating all the halide ions which in turn tune their emission color in spanning from 397 nm (violet) to 820 nm (near infrared) as a function of their composition. The synthesis method adopted here is the solvent free ball milling of respective halides of Cs and Ag and took the record shortest time and in bulk scale. From decay lifetimes, emissions from these bimetallic halides are found as a result of fast recombination of self‐trapped excitons, which exhibited not only reasonably high quantum yield in the range of 17–68% but also excellent stability to air and moisture under ambient conditions. These also show wide Stokes shift with relatively longer decay lifetimes ranging above the exciton and below the surface trap or dopant induced emissions of inorganic semiconductors, indicating a new class of materials having unique identity of their optical behaviors.

Organic-inorganic metal-halide materials (OIMMs) with zero-dimensional (0D) structures offer useful optical properties with a wide range of applications. However, successful examples of 0D structural OIMMs with well-defined optical performance at the micro-/nanometer scale are limited. We prepared one-dimensional (1D) (DTA) 2 SbCl 5 •DTAC (DTAC = dodecyl trimethyl ammonium chloride) single-crystal microrods and 2D microplates with a 0D structure in which individual (SbCl 5 ) 2À quadrangular units are completely isolated and surrounded by the organic cation DTA + . The organic molecular unit with a long alkyl chain (C 12 ) and three methyl groups enables microrod and -plate formation. The singlecrystal microrods/-plates exhibit a broadband orange emission peak at 610 nm with a photoluminescence quantum yield (PLQY) of ca. 90 % and a large Stokes shift of 260 nm under photoexcitation. The broad emission originates from selftrapping excitons. Spatially resolved PL spectra confirm that these microrods exhibit an optical waveguide effect with a low loss coefficient (0.0019 dB mm À1 ) during propagation, and linear polarized photoemission with a polarization contrast (0.57).Organic-inorganic metal-halide materials (OIMMs), a bulk crystal with 0D structure at the molecular level, have attracted tremendous attentions due to their potential optoelectronic applications as light-emitting materials. [1] These materials though in bulk; but can have bright emission and also retain as high as near unity photoluminescence quantum yield (PLQY). [2] Among different applications these could also serve as a potential optical materials in micro-/ nanosized optical waveguides. [3] To date, research on optical

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