Exciton-phonon coupling in two-dimensional layered (BA)2PbI4 perovskite microplates

Two-dimensional layered (BA)(2)PbI4 (BA = C4H9NH3) perovskites are emerging as a new class of layered materials and show great potential in optoelectronic applications. Elucidating how exciton-phonon interaction affects the excitonic emission is of great importance for a better knowledge of their optoelectronic properties. In this letter, we synthesized high-quality (BA)(2)PbI4 microplates via solution methods, and dual-excitonic emission peaks (surface-emission and interior-emission) were detected from the as-grown samples at low temperatures. Furthermore, we determine the energies for the longitudinal optical phonon modes to be similar to 27 and similar to 18 meV, and the exciton-phonon coupling strengths to be similar to 177 and similar to 21 meV for the surface-emission and interior-emission bands, respectively. Compared to the interior-emission band, the stronger exciton-phonon interaction results in a considerable degree of spectral broadening and red-shift for the surface-emission with increasing temperature. In contrast, the (OA)(2)PbI4 (OA = C8H17NH2) microplates with longer alkyl chains between Pb-I layers, exhibit only one excitonic emission peak, as well as a large exciton-phonon coupling strength. Our work clarifies the influence of exciton-phonon coupling on the excitonic emission of (BA)(2)PbI4 microplates, and also suggests the intrinsic relationship between the exciton-phonon coupling and the length of organic carbon chain ligands.