Hydrostatic findings reveal new features of 2-D hybrid organic-inorganic perovskites

When extending in only two dimensions, hybrid organic-inorganic perovskites (HOIPs) have shown greater promise than three-dimensional structures for solar cells, field effect transistors and light-emitting devices. Knowing how these materials react to stress is crucial for understanding how they can be used in technology. While the mechanical properties of other 2-D materials have been studied extensively, little is known about such features in 2-D HOIPS. New work on how these materials change under pressure looks to uncover secrets for how to process 2-D HOIPs more appropriately for future applications.

Feng et al. characterized the hydrostatic behavior of one 2-D hybrid perovskite semiconductor, benzylammonium lead bromide, (BA)2PbBr4, under high pressures. Studying the material with synchrotron powder X-ray diffraction over a pressure range up to 14.22 GPa, the authors discovered that (BA)2PbBr4 is softer than most 3-D hybrid perovskites and 2-D inorganic crystals, and showed anisotropic compressibility.

A layered BX42- perovskite motif in the studied substance leads to a material which resembles a multiple quantum well structure that allows for outstanding optoelectronic properties. It shows improved stability that could overcome drawbacks of 3-D systems during device fabrication processes.

Density functional theory calculations revealed that the structural changes of (BA)2PbBr4 under compression are attributed to the configurational alterations of benzylammonium organic cations and synergistic distortion of the (PbBr4)2- inorganic layer. Further extensive theoretical calculations of elastic tensors confirmed (BA)2PbBr4’s anisotropic elasticity. (BA)2PbBr4 exhibited a significant red shift and decrease in photoluminescence in response to hydrostatic stress.

The authors hope their findings will inspire more work on the lesser-understood 2-D hybrid perovskite and are looking to explore the influences of the organic cations and halides on the mechanical properties of these materials.

Source: “Structural evolution and photoluminescence properties of a 2D hybrid perovskite under pressure,” by Guoqiang Feng, Yan Qin, Cheng Ran, Lijun Ji, Liyuan Dong, and Wei Li, APL Materials (2018). The article can be accessed at https://doi.org/10.1063/1.5042645 .