New Low-Dimensional Lead-Free Perovskite (2-AMP)₂BiX₇·H₂O (X = Cl, Br) Crystals: Synthesis, Stability, and Nonlinear Optical Properties

Abstract

Organic–inorganic hybrid Pb-halide perovskites have attracted tremendous interest due to their potential application in photovoltaic and optoelectronic fields. However, the toxicity and poor stability of Pb-halide perovskites have become key bottlenecks toward their future commercialization and industrialization. Therefore, in this work, two novel hybrid lead-free perovskite nonlinear optical (NLO) crystals (2-AMP)2BiX7·H2O (X = Cl, Br) with high stability were successfully synthesized. Both the crystals belong to the orthorhombic P212121 space group, displaying a zero-dimensional perovskite structure. The thermal, environmental, and solvent atmospheric stabilities were comprehensively investigated, with high thermal stability up to 170 °C and high environmental and high solvent atmospheric stability observed for (2-AMP)2BiBr7·H2O. First-principles calculations were carried out to study the relationship of the structure and properties. A large birefringence of 0.1368@1064 nm was determined for (2-AMP)2BiBr7·H2O, which was derived from the strong aeolotropic conjugated π-electron distribution of planar 2-aminomethylpyridium. A second-harmonic generation (SHG) effect that was 0.25 and 0.32 times that of KH2PO4 (KDP) was measured for (2-AMP)2BiCl7·H2O and (2-AMP)2BiBr7·H2O, respectively, and the stronger SHG response of bromide was attributed to the larger distortions of {BiBr6} octahedrons. This work may offer new guidance for exploration of low toxicity and high stability of perovskite NLO materials.

(C4H10NO)PbX3 (X = Cl, Br): Design of Two Lead Halide Perovskite Crystals with Moderate Nonlinear Optical Properties

“…The second-order nonlinear optical (NLO) crystals that can broaden output wavelengths play a significant function in modern optical techniques, such as precise micromanufacturing, electro-optical amplitude modulation, photoetching, biological tissue imaging, and optical data storage. − The majority of the commercial NLO materials are inorganic crystals, such as KBe 2 BO 3 F 2 (KBBF), β-BaB 2 O 4 (β-BBO), LiB 3 O 5 (LBO), KH 2 PO 4 (KDP), and AgGaS 2 (AGS), etc. However, because of the enormous cost and time-consuming preparation of some NLO inorganic crystals, they cannot fill the fast-growing requirements of laser techniques, and continuous endeavors have been made to design and seek novel crystals with noncentrosymmetric (NCS) structuresa fundamental requirement for the SHG effect for the development of fundamental research as well as practical applications. − …”

High stability and moderate second-order nonlinear optical properties of hybrid lead-free perovskite [(CH3)3NCH2Cl]CdCl3 bulk crystals

“…An SHG conversion efficiency of 0.73 times of KH 2 PO 4 was detected in the particle size of 150–200 μm, and a higher SHG effect may be obtained using a larger size of (TMCM)CdCl 3 . Of particular note is that most of the reported NCS organically templated cadmium chlorides are non-perovskite structures, such as [C 3 H 8 N]CdCl 3 , C 12 H 20 N 6 O 4 Cd 2 Cl 5 , Cd(C 3 H 7 NO 3 )Cl 2 ·H 2 O, [C 5 H 14 NO]CdCl 3 , CdCl 2 (C 5 H 9 NO 3 ) and (C 4 H 10 NO) 2 Cd 2 Cl 6 , 13,40–44 which presented SHG responses of 0.1 to 0.73 times KDP, whereas reports on cadmium chloride perovskites with NCS structures are limited, [C 4 H 10 N]CdCl 3 and [C 6 H 11 NH 3 ] 2 CdCl 4 presented SHG intensity of 0.4 and 0.6 times KDP, respectively. 45,46…”

“…9,10 However, they still endure two main disadvantages, the environmental and biological toxicities of heavy-metal Pb, as well as poor temperature and chemistry stability under exposure to moisture, heat, and light. [11][12][13] Therefore, it is very urgent to develop OIMHPs with environment-friendly, high stability, and outstanding performances.…”

“…The distorted octahedrons of perovskite functional materials may lead to NCS structures as well as SHG characteristics. 8,13 Thus, it is a great crucial task and academic interest to discover and exploit the NLO performances of perovskite functional materials with NCS structures, especially those with potential applications in solar-blind UV ranges.…”

“…Secondly, low-dimensional OIMHPs usually demonstrate higher stability when compared with their 3D counterparts. 13,30 Thirdly, the piezoelectric property is often accompanied by second-order NLO characteristics, because both properties require the noncentralsymmetric structure. Furthermore, the combination of stereochemically active lone-pair d 10 metal cations (SCALP, such as Cd 2+ , Zn 2+ , and Hg 2+ ) that exhibited second-order Jahn-Teller (SOJT) distortion with halogen anions proved to be an effective method to enhance the SHG effect.…”