Superior ferroelectricity and nonlinear optical response in a hybrid germanium iodide hexagonal perovskite

Abstract

Abundant chemical diversity and structural tunability make organic–inorganic hybrid perovskites (OIHPs) a rich ore for ferroelectrics. However, compared with their inorganic counterparts such as BaTiO3, their ferroelectric key properties, including large spontaneous polarization (Ps), low coercive field (Ec), and strong second harmonic generation (SHG) response, have long been great challenges, which hinder their commercial applications. Here, a quasi-one-dimensional OIHP DMAGeI3 (DMA = Dimethylamine) is reported, with notable ferroelectric attributes at room temperature: a large Ps of 24.14 μC/cm2 (on a par with BaTiO3), a low Ec below 2.2 kV/cm, and the strongest SHG intensity in OIHP family (about 12 times of KH2PO4 (KDP)). Revealed by the first-principles calculations, its large Ps originates from the synergistic effects of the stereochemically active 4s2 lone pair of Ge2+ and the ordering of organic cations, and its low kinetic energy barrier of small DMA cations results in a low Ec. Our work brings the comprehensive ferroelectric performances of OIHPs to a comparable level with commercial inorganic ferroelectric perovskites.

Targeted regulation and optimization of multifunctional phase transition materials by novel void occupancy engineering

“…Normally, the SHG response is exclusively observed in noncentrosymmetric materials or interfaces. [47][48][49] Due to the noncentrosymmetric structure in the RTP and centrosymmetric structure in the HTP (Fig. S11 †), [TEA][Cd(SCN) 3 ] is anticipated to become a solid NLO (nonlinear optical) switching material.…”

Dielectric/SHG/PL triple-channel properties in chiral spirocyclic organic–inorganic hybrids

“…Meanwhile, it also confirms that the crystal structure of ( R / S -HASD) 2 MnBr 4 is destroyed and the crystal symmetry of ( R / S -HASD) 2 MnBr 4 is obviously enhanced in HTP. 53 During the phase transition process, the increased molecular thermal motion due to the disorder of high-temperature organic cations will lead to the weakening of the SHG signal, and this change indicates that ( R / S -HASD) 2 MnBr 4 is potential SHG switchable material. In addition, the SHG signal of ( R / S -HASD) 2 MnBr 4 at different particle sizes was measured for phase matching analysis.…”

Remarkable enhancement of optical and electric properties by temperature-controlled solid-phase molecular motion

“…34 In general, materials crystallized in polar structures can have inherent piezoelectric and nonlinear optical properties. 35–39 However, obtaining a polar crown-ether-based polar molecular rotator still remains challenging.…”