Enhanced phosphorescence from nanocrystalline/microcrystalline materials based on (CH3NH3)(1-naphthylmethyl ammonium)2Pb2Cl7 and similar compounds

A broad phosphorescence band, with three main maxima at ca 500, 536 and 577 nm, was observed at room temperature, either from a mixture of (1-naphthylmethyl ammonium)2PbCl4 and CH3NH3PbCl3, or from (CH3NH3)(1-naphthylmethyl ammonium)2Pb2Cl7, or some Cl–Br analogues, in the form of suspensions in toluene or in the form of grinding deposits on quartz plates. It was attributed to supermigration of energy from the Wannier excitons of PbCl3 component to the triplet state of organic component (i.e., 1-naphthylmethyl group) of particulate material. This new effect seems to be a consequence of excitonic superradiance of particulate PbCl3.