Hybrid Double Perovskite Derived Halides Based on Bi and Alkali Metals (K, Rb): Diverse Structures, Tunable Optical Properties and Second Harmonic Generation Responses

Abstract

Double perovskites (DP) have attracted extensive attention due to their rich structures and wide application prospects in the field of optoelectronics. Here, we report 15 new Bi‐based double perovskite derived halides with the general formula of A2BBiX6 (A=organic cationic ligand, B=K or Rb, X=Br or I). These materials are synthesized using organic ligands to coordinate with metal ions with a sp3 oxygen, and diverse structure types have been obtained with distinct dimensionalities and connectivity modes. The optical band gaps of these phases can be tuned by changing the halide, the organic ligand and the alkali metal, varying from 2.0 to 2.9 eV. The bromide phases exhibit increasing photoluminescence (PL) intensity with decreasing temperature, while the PL intensity of iodide phases changes nonmonotonically with temperature. Because the majority of these phases are non‐centrosymmetric, second harmonic generation (SHG) responses are also measured for selected non‐centrosymmetric materials, showing different particle‐size‐dependent trends. Our findings give rise to a series of new structural types to the DP family, and provide a powerful synthetic handle for symmetry breaking.

Pb2Ga3F6(SeO3)2X3·2H2O (X = Cl, Br): two new HTO-type members exhibiting large NLO effects mediated by ionic mixing and substitution strategies

“…[3][4][5] The SHG coefficient is a key parameter of NLO materials that concerns their frequency doubling conversion efficiency. The general strategy to enhance the SHG coefficient is to introduce asymmetric structural units such as stereochemically active lone pair (SCALP) electrons (Pb 2+ , Bi 3+ , Se 4+ , and I 5+ ), [6][7][8][9][10][11][12] and a distorted polyhedron constructed using d 10 (Zn 2+ , Cd 2+ ) or d 0 cations (Ti 4+ , Nb 5+ , V 5+ , and Mo 6+ ). [13][14][15][16][17] However, most of these atoms undergo d-d or f-f electron transition which is heavily against the effectiveness of transparency of related materials.…”