Lead Mixed Oxyhalides Satisfying All Fundamental Requirements for High‐Performance Mid‐Infrared Nonlinear Optical Materials

Abstract

To design high-performance mid-infrared (mid-IR) nonlinear optical (NLO) materials,w eh ave focused on the combination of aheavy metal lone pair cation, Pb 2+ and mixed oxyhalides.Asystematic investigation in PbO-PbCl 2 -PbBr 2 system led us to discover the first examples of NLO lead mixed oxyhalides,n amely,P b 13 O 6 Cl 4 Br 10 ,P b 13 O 6 Cl 7 Br 7 ,a nd Pb 13 O 6 Cl 9 Br 5 .A ll the reported materials have remarkably comprehensive properties including broad IR transparency (up to 14.0 mm), qualified second harmonic generation (SHG) responses (0.6-0.9 AgGaS 2 ), wide band gaps (3.05-3.21 eV), and ease of crystal growth. Interestingly,acentimeter-sized single crystal (2.9 1.3 0.5 cm 3 )o fP b 13 O 6 Cl 9 Br 5 revealing aw ide transparent range (0.384-14.0 mm) and high laser damage threshold (LDT) (14.6 AgGaS 2 )h as been successfully grown in an open system. The study suggests that all the reported mixed oxyhalides are outstanding candidates for mid-IR NLO materials.

Cs3Pb2(CH3COO)2X5 (X=I, Br): Halides with Strong Second‐Harmonic Generation Response Induced by Acetate Groups

“…It is well‐known that the SHG contributions of cations and halogen anions usually follow the following trends, Pb 2+ > M 2+ (M=Be, Mg, Ca, Sr, Ba) for cations and I − > Br − > Cl − for halogen anions [4] . Therefore, some non‐centrosymmetric (NCS) cystals with Pb 2+ cation and halogen anions (I − and Br − ) display strong SHG response, such as Pb 2 B 5 O 9 X and Pb 2 BO 3 X (X=I, Br, Cl), and Pb 13 O 6 Cl 7 Br 7 [5–11] . Unfortunately, many lead halide perovskites, like NH 4 PbI 3 , [12] RbPbI 3 , [13] and CsPbX 3 (X=I, Br, Cl), [13–15] all crystallize in the centrosymmetric (CS) groups, resulting in no SHG response.…”

Recent Advances in Oxide‐based Nonlinear Optical Materials with Wide Infrared Transparency Beyond 6 μm

“…Although Pb 17 O 8 Cl 18 was identified as a promising mid‐IR NLO material in 2015, there was no NLO crystal in the related system (lead oxychlorides or other lead oxyhalides) for years until our work on lead mixed oxyhalides in PbO−PbCl 2 −PbBr 2 system reported [42d] . Compared to lead oxyhalides with a single halogen anion (F − , Cl − , Br − or I − ), the diversity of lead mixed oxyhalides incorporating multiple halogen anions would significantly increase.…”

“…Therefore, we firstly proposed lead mixed oxyhalides as a new promising source for mid‐IR NLO materials. Subsequently, the systematic investigation in PbO−PbCl 2 −PbBr 2 system led to the discovery of Pb 13 O 6 Cl 4 Br 10 , Pb 13 O 6 Cl 7 Br 7 , and Pb 13 O 6 Cl 9 Br 5 [42d] . Polycrystalline samples of the three compounds were synthesized via solid‐state reactions.…”

Pb18O8Cl15I5: A Polar Lead Mixed Oxyhalide with Unprecedented Architecture and Excellent Infrared Nonlinear Optical Properties

“…The asymmetric unit contains eighteen crystallographic Pb, eight O, thirteen Cl, three I, and four mixed Cl/I sites, and all the crystallographic sites are fully occupied (Table S2 and Figure S4). Noticeably, Pb 2+ cations exhibit diverse coordination geometries with asymmetric features: Pb(1)-Pb (16) have mixed ligand coordination with x O 2À + m Cl À + n I À (x = 1-3), while Pb(17)-Pb (18) are only coordinated by halogen anions (Figure S5). Typically, the structure of Pb 18 O 8 Cl 15 I 5 can be illuminated from the viewpoint of anion-centered tetrahedra.…”

“…[24] (Figures 1 a and b). Besides, every four O(5)Pb 4 -O(8)Pb 4 tetrahedra are edge-shared with each other to produce zero-dimensional (0D) isolated [O 4 Pb 8 ] 8+ tetramers (Figure 1 c) (18) occupy the channels along the a-axis and complete the final structure (Figure 1 d).…”