[K2PbX][Ga7S12] (X = Cl, Br, I): The First Lead‐Containing Cationic Moieties with Ultrahigh Second‐Harmonic Generation and Band Gaps Exceeding the Criterion of 2.33 eV

• Published in: Advanced science Vol. 10; no. 13; pp. e2207630 - n/a
• Main Authors: Chen, Wen‐Fa, Liu, Bin‐Wen, Pei, Shao‐Min, Jiang, Xiao‐Ming, Guo, Guo‐Cong
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.05.2023; John Wiley and Sons Inc; Wiley
• Subjects: chalcogenides; Crystals; Lasers; nonlinear optical materials; Pb element; second‐harmonic generation; Spectrum analysis; structure–property relationship; Pb element; chalcogenides; second-harmonic generation; nonlinear optical materials; structure-property relationship
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202207630

In contrast to anionic group theory of nonlinear optical (NLO) materials that second‐harmonic generation (SHG) responses mainly originate from anionic groups, structural regulation on the cationic groups of salt‐inclusion chalcogenides (SICs) is performed to make them also contribute to the NLO effects. Herein, the stereochemically active lone–electron‐pair Pb2+ cation is first introduced to the cationic groups of NLO SICs, and the resultant [K2PbX][Ga7S12] (X = Cl, Br, I) are isolated via solid‐state method. The features of their three‐dimensional structures comprise highly oriented [Ga7S12]3− and [K2PbX]3+ frameworks derived from AgGaS2, which display the largest phase‐matching SHG intensities (2.5−2.7 × AgGaS2 @1800 nm) among all SICs. Concurrently, three compounds manifest band gap values of 2.54, 2.49, and 2.41 eV (exceeding the criterion of 2.33 eV), which can avoid two‐photon absorption under the fundamental laser of 1064 nm, along with the relatively low anisotropy of thermal expansion coefficients, leading to improved laser‐induced damage thresholds (LIDTs) values of 2.3, 3.8, and 4.0 times that of AgGaS2. In addition, the density of states and SHG coefficient calculations demonstrate that the Pb2+ cations narrow the band gaps and benefit SHG responses. By introducing stereochemically active lone–electron‐pair cations in the cationic groups of salt‐inclusion chalcogenides (SICs), three compounds [K2PbX][Ga7S12] (X = Cl, Br, I) are successfully obtained, which display the highest phase‐matching nonlinear optical (NLO) responses in reported SICs and suitable band gaps exceeding 2.33 eV to avoid two‐photon absorption at 1064 nm.