Optical properties of a new luminescent hybrid material [C6N2H5]3BiCl6 involving a resonance energy transfer (RET)

This paper reports on the optical properties of new organic metal halide material [C6N2H5]3BiCl6. The crystal structure is built up from the packing of distorted [BiCl6]3- octahedra surrounded by organic cation [C6N2H5]+. Unlike the classical metal halide materials in which organic molecules are optically inactive, both organic and inorganic components in this structure are chromospheres. At ambient temperature, photoluminescence measurements show and intense emission in the yellow green region. This emission is believed to be due to π– π* electronic transition within the organic cation [C6N2H5]+. Optical absorption (OA) and photoluminescence (PL) spectra of this compound were analyzed and interpreted by comparison with those of the homologous hybrids on one hand and those of the organic molecules on the other hand. In addition, photoluminescence excitation (PLE) have shown that the intense emission is governed by a resonance energy and charge transfer process in which [BiCl6]3- ions is assumed as a donor and organic cation plays the role of an acceptor. Moreover, photoluminescence study as function of temperature using the Arrhenius model, reveals the behavior a quasi-localized exciton with a binding energy of 73 meV, substantially lower than those found for homologous compounds but it reflects the localized character of the exciton and it may explain the stability of the exciton at ambient temperature.