A-Site-Mediated Lattice Strain and Phase Control for Spectrally Tunable and High-Quality Quasi-Two-Dimensional Blue Perovskite Films

Lattice strain and phase purity issues in blue perovskite materials severely limit the further improvement of device performance. As an important strategy to modulate the properties of perovskite materials, A-site cation engineering can effectively modulate lattice strain and phase distribution by selecting suitable cations. In this work, based on the Cs+/EA+ benchmark two-dimensional perovskite system, the divalent ion MDA2+ was introduced to partially replace EA+, and it was found that the appropriate amount of substitution led to the release of perovskite lattice strain, a reduction of the small n-phase, a reduction of unreacted PbBr2 and PbCl2, and a significant increase in luminescence efficiency. This study provides a novel A-site cation engineering strategy for perovskite lattice strain release, phase distribution regulation, and an important material design pathway for developing high-quality blue perovskite films.