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 [PbI 6 ] 4− octahedron ( n ) and [C 6 H 5 (CH 2 ) 2 NH 3 ] 2 (CH 3 NH 3 ) n ‐1 Pb n I 3 n +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 [PbI 6 ] 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 [C 6 H 5 (CH 2 ) 2 NH 3 ] 2 (CH 3 NH 3 ) n ‐1 Pb n I 3 n +1 , which is essential for the development of highly efficient photoelectronic devices.