Tunable phase transition temperature and nonlinear optical properties of organic–inorganic hybrid perovskites enabled by dimensional engineering

Abstract

Organic–inorganic hybrid materials have received extensive interest due to their easily adjustable structures, environmentally friendly features and excellent properties. Recently, plenty of organic–inorganic hybrids have been reported. However, low phase transition temperature and limited properties restrict their applications. Therefore, improving the phase transition temperature and enriching optoelectronics properties have become the top priorities. Herein, we have successfully synthesized two bilayer (2D/3D) perovskites, (MACH)₂·CsPb₂Br₇ (Prv-2) and (BMACH)·CsPb₂Br₇ (Prv-3), based on a single layer perovskite, (MACH)₂·PbBr₄ (Prv-1), (MACH = cyclohexanemethylaminium and BMACH = 1,3-cyclohexanedimethanaminium). The experimental results show that the phase transition temperature (385–415 K) of bilayer perovskites has been significantly improved by increasing the thickness of the inorganic framework. Meanwhile, the offset of the mineralizer (Cs⁺, (0.5, 0.5, 0.5) → (0.5, 0.76, 0.47)) in the Prv-3 makes it crystallize in the polar space group (Pmc2₁). Therefore, the SHG (second harmonic generation) measurement indicates that it possesses 0.5 times the signal intensity compared to KDP. Finally, optical characterization and theoretical calculation synergistically verify that all three perovskites belong to direct bandgap semiconductors. Consequentially, the strategies in this work might pave the way for the design and construction of multifunctional materials with a narrow band gap, non-linear optics and ferroelectricity.