Cs₂AgBiBr_6−xCl_x solid solutions – band gap engineering with halide double perovskites

Abstract

The halide double perovskite solid solution Cs2AgBiBr6−xClx has been investigated and found to exhibit a band gap that increases from 2.2 eV to 2.8 eV as the Cl− content increases, with an upward deviation from Vegard's law when x > 5.

Halide Mixing and Phase Segregation in Cs2AgBiX6 (X = Cl, Br, and I) Double Perovskites from Cesium-133 Solid-State NMR and Optical Spectroscopy

“…This result is in perfect agreement with a recent computational study of Cs 2 AgBiCl 6– x Br x double perovskites. 28 We note that the 133 Cs shift is not a linear function of the Cl/Br ratio ( Figure S4 ). Similar nonlinearity caused by the nonadditive effect of the nearest and next-nearest neighbors on the chemical shift has been previously observed for 89 Y and 119 Sn in solid solutions of mixed-metal pyrochlores and for 13 C in mixed-halide hybrid tin(II) halide perovskites.…”

“… 13 Very recently, mixed-halides Cs 2 AgBiCl 6- x Br x have been investigated both theoretically 26 , 27 and experimentally. 27 , 28 However, very little is known about halide miscibility and phase segregation phenomena in this class of materials. For example, optical properties have been previously calculated for Cs 2 AgInX 6 (X = Cl, Br, and I) double perovskites, assuming that halides can be mixed in any ratio, leading to pure-phase materials.…”

High-efficiency blue photoluminescence in the Cs2NaInCl6:Sb3+ double perovskite phosphor

“…To this end, Sb 3+ was doped into Cs 2 NaBiCl 6 and Cs 2 AgInCl 6 hosts using modifications of previously reported synthesis methods. 5,24,25 The samples were each irradiated with light from a broadband Ultra-Violet Products UVSL-25 Mineralight Lamp (365 longwave, 254 shortwave) excitation source to test for luminescence. However, no luminescence is observed at room temperature in Cs 2 NaBiCl 6 samples doped with Sb 3+ .…”

Mixed‐Halide Double Perovskite Cs2AgBiX6 (X=Br, I) with Tunable Optical Properties via Anion Exchange

“…Compositional engineering in lead‐halide perovskites, which creates advantageous optical and electrical properties, has been investigated widely, leading to optoelectronic devices with advanced performances [9] . In lead‐free double perovskites, mixed compositions have been explored by trivalent or monovalent metal alloying, [4b,10] as well as changing Br/Cl ratios [11] . However, Br/I mixed double perovskites have not previously been obtained.…”

“…[9] In lead‐free double perovskites, mixed compositions have been explored by trivalent or monovalent metal alloying,[ 4b , 10 ] as well as changing Br/Cl ratios. [11] However, Br/I mixed double perovskites have not previously been obtained. The direct fabrication of Cs 2 AgBiI 6 or Cs 2 AgBi(Br/I) 6 thin‐films from corresponding precursors followed by annealing always failed, resulting in Cs 3 Bi 2 I 9 product (Figure S1), due to the either negative or slightly positive enthalpies.…”