Synthesis and luminescence properties of lead-halide based organic–inorganic layered perovskite compounds (CnH2n+1NH3)2PbI4 (n=4, 5, 7, 8 and 9)

This paper describes the synthesis and characterization of organic–inorganic layered perovskite compounds, (CnH2n+1NH3)2PbI4 (n=4, 5, 7, 8 and 9). The effect of the number of carbon atoms on luminescence properties has been examined. Thin films of microcrystalline (CnH2n+1NH3)2PbI4 fabricated by spin-coating are highly oriented, with the c-axis perpendicular to the substrate surface. Temperature-dependent optical absorption spectra reveal that (CnH2n+1NH3)2PbI4 films (n=4, 7, 8 and 9) show the structural phase transitions. The excitonic structures of (CnH2n+1NH3)2PbI4 vary with the number of carbon atoms of the alkyl chain length. At low temperatures below 100 K, the lowest-energy free-exciton band of (CnH2n+1NH3)2PbI4 (n=7, 8 and 9) split into three fine-structure levels. In contrast to (CnH2n+1NH3)2PbBr4 films, (CnH2n+1NH3)2PbI4 (n=7, 8 and 9) shows no triplet exciton emission, but it shows the Stokes-shifted emission from bound excitons.

► Self-organized organic–inorganic layered perovskites as novel luminescent compounds.
► Excitons in (CnH2n+1NH3)2PbI4 are influenced by the number of carbon atoms.
► In contrast to (CnH2n+1NH3)2PbBr4, (CnH2n+1NH3)2PbI4 shows no phosphorescence.
► Stokes-shifted emission with short lifetime can be considered bound excitons.