Controlled Photoluminescence Lifetimes and Quantum Efficiencies in Mn-Doped Two-Dimensional Perovskite via A-Site Cation Engineering

Low-dimensional metal halide perovskites are widely studied due to their excellent optoelectronic properties and environmental stability. Recently, transition metal Mn2+ ions were introduced into two-dimensional (2D) perovskite to modify their photophysical properties. However, the Mn luminescence mechanism still needs further exploration, which includes the role played by the A-site cation engineering. Herein, we prepared 2D perovskite microcrystals with four A-site cations: butylamine (BA), phenethylamine (PEA), octylamine (OCA) and oleylamine (OAM) by hot-injection method, namely Mn2+:BA2PbBr4, Mn2+:PEA2PbBr4, Mn2+:OCA2PbBr4, and Mn2+:OAM2PbBr4. The Mn PL lifetime is tuned from 0.12 to 0.75 ms, achieving a maximum PL QY of 83% in BA-based 2D perovskite. The obtained perovskite samples exhibited micrometer-sized morphology, and the periodic arrangement of X-ray diffraction demonstrated the formation of a single-layer 2D structure. The temperature-dependent PL spectra revealed that the enhancement mechanism of Mn emission was related to short-chain ligand surface passivation (BA and PEA) and improvement of the exciton-to-Mn2+ energy transfer. The experimental results indicate that A-site cation engineering enriches the diversity of Mn-doped low-dimensional perovskites, which provides a new approach to regulate Mn luminescence kinetics.