Impacts of the Lattice Strain on Light Emission in Layered Perovskite Thin flakes

Strain engineering, as a non-chemical tuning knob, can enhance the performance of semiconductor devices. Here, an efficient manipulation of light emission is revealed in thin-layered 2D perovskite strongly correlated to layer numbers of [PbI₆]⁴⁻ octahedron (n) and [C₆H₅(CH₂)₂NH₃]₂(CH₃NH₃)_n-1Pb_nI_3n+1 (N) by applying uniaxial strains (ɛ) via bending the flexible substrate. As <n> increases from 1 to 3, an efficient light emission redshift (ɛ from −0.97% to 0.97%) is observed from bandgap shrinkage, and the shrinkage rate increases from 1.97 to 10.38 meV/%, which is attributed to the predominant uniaxial intralayer deformation due to the anisotropy of the [PbI₆]⁴⁻ octahedron lattice strain. Conversely, as <N> increases from 7 to 48 for n = 3, the deformation related to bandgap shrinkage rate is more prominent in small-N flakes (<N> ≈ 7, 15.2 meV/%) but is easily offset in large-N flakes (<N> ≈ 48, 7.7 meV/%). This anisotropic lattice deformation, meanwhile, inevitably modulates the carrier recombination dynamics of [C₆H₅(CH₂)₂NH₃]₂(CH₃NH₃)_n-1Pb_nI_3n+1, which is essential for the development of highly efficient photoelectronic devices.