Manipulating Emission Enhancement and Piezochromism in Two-Dimensional Organic-Inorganic Halide Perovskite [(HO)(CH2)(2)NH3)](2)PbI4 by High Pressure

Two-dimensional (2D) organic-inorganic halide perovskites present remarkable stability and diversity and are promising alternatives to their three-dimensional (3D) counterparts. The 2D halide perovskite [(HO)(CH2)(2)NH3](2)PbI4 (ETA(2)PbI(4)) is regarded as a superior moisture-stabile smooth perovskite because of distinct hydrogen-bond networks that connect adjacent organic-inorganic layers. However, effectively engineering the optical properties of ETA(2)PbI(4) for practical applications still represents considerable challenges. Herein, we studied the effect of pressure on the optical characteristics and crystalline structure of ETA(2)PbI(4) through a diamond anvil cell. The emission was enhanced four times at 1.5 GPa and was accompanied by a photoluminescence (PL) peak that became more symmetric, which was attributed to pressure-suppression nonradiative recombination and an increase in exciton binding energy. Moreover, the red shift of the PL peak from 542 to 674 nm was continuous at a rate of 14.4 nm/GPa with pressure up to 9.2 GPa. Meanwhile, the optical micrographs showed visualized piezochromism. High-pressure in situ synchrotron X-ray diffraction (XRD), Raman measurements, and first-principles calculations indicated a distortion of the [PbI6](4-) inorganic octahedron with a decrease the Pb-I-Pb bond angle and the Pb-I bond length leading to this series of transformations. Our findings demonstrate that 2D halide ETA(2)PbI(4) is a prospective candidate for pressure sensors. [GRAPHICS] .

Automated summary

Pressure was found to enhance the emission of ETA(2)PbI(4) by four times at 1.5 GPa, resulting in a red shift of the photoluminescence peak to 674 nm, accompanied by visualized piezochromism. This study demonstrates the potential of 2D halide ETA(2)PbI(4) as a candidate material for pressure sensors.