Mn Doping in Centimeter-Sized Layered 2D Butylammonium Lead Bromide (BA2PbBr4) Single Crystals and Their Optical Properties

Layered lead halide perovskites such as butylammonium lead bromide (BA2PbBr4) possess a multiple-quantum-well structure, which is expected to enhance the interaction between the excitons and Mn dopants. Therefore, doping Mn in large single crystals of layered perovskites may induce interesting magneto-optic and magneto-electric properties, with minimal contributions from the detrimental grain boundary effects. Furthermore, these single crystals show stark differences in excitonic absorption and emission (dual emission) compared with the measurements done on the ensemble of corresponding microcrystals. Therefore, exploring the exciton–Mn interactions by performing measurements on one large crystal is important. We report the one-pot synthesis of centimeter-sized Mn-doped BA2PbBr4 single crystals to study the exciton–Mn interaction measured on a single crystal. Mn-doped BA2PbBr4 single crystal shows dual excitonic emission, and both of the excitonic features transfer their energies nonradiatively to Mn dopants, yielding Mn d–d emission with quantum yield ∼26%. The Mn emission, in these single crystals, shows a strong excitation energy dependence, which is related to the penetration depth of the excitation light into the single crystals. We also exfoliate the BA2PbBr4 single crystals using a Scotch-tape method. The differences in the optical properties of the exfoliated sample and the single crystal provide insights into both Mn doping and exciton–Mn interactions.

以丁胺溴化铅（BA₂PbBr₄）为代表的层状卤化铅钙钛矿（layered lead halide perovskites）具有多量子阱（multiple-quantum-well）结构，有望增强激子（exciton）与锰掺杂剂（Mn dopants）之间的相互作用。因此，在层状钙钛矿大单晶中掺杂锰，有望诱导出极具研究价值的磁光（magneto-optic）与磁电（magneto-electric）性质，且有害晶界效应（detrimental grain boundary effects）带来的不利影响极小。此外，与对应微晶集合体的测试结果相比，这类单晶在激子吸收与发射（双发射，dual emission）方面呈现出显著差异。因此，通过单颗大单晶的测试来探究激子-锰相互作用（exciton–Mn interactions）具有重要意义。本工作报道了厘米级尺寸锰掺杂BA₂PbBr₄单晶的一锅法合成（one-pot synthesis），用于开展单颗单晶上的激子-锰相互作用研究。锰掺杂BA₂PbBr₄单晶表现出双激子发射特性，且两种激子特征均以非辐射方式将能量转移给锰掺杂剂，最终得到量子产率约为26%的锰d-d跃迁发射（d–d emission）。该类单晶中的锰发射表现出强烈的激发能量依赖性，这与激发光在单晶中的穿透深度（penetration depth）密切相关。本研究还采用透明胶带剥离法（Scotch-tape method）对BA₂PbBr₄单晶进行剥离处理，剥离样品与原始单晶的光学性质差异，可为锰掺杂及激子-锰相互作用的相关研究提供重要见解。