Fig. 1
Characterizations of 2D perovskite single crystals. a Photograph of the as-synthesized perovskite single-crystal plates. From left to right: (BA)2(MA)n−1PbnBr3n+1 (denoted as PbnBr3n+1) and (BA)2(MA)n−1PbnI3n+1 (denoted as PbnI3n+1). b Absorption (dash line) and photoluminescence (solid line) spectra of the perovskite plates. c Powder XRD spectra of the perovskite crystal plates. The low angle part is magnified to clearly see the diffraction peaks for impurity phases. Black dot: (BA)2PbBr4 phase within (BA)2(MA)Pb2Br7; Navy rhombus: (BA)2(MA)3Pb4I13 phase within (BA)2(MA)2Pb3I10
