Localization of triplet excitons and biexcitons in the two-dimensional semiconductor (CH3C6H4CH2NH3)2PbBr4

We have measured emission spectra under selective excitation and time resolved photoluminescence spectra of a single crystal with a perovskite type structure (CH3C6H4CH2NH3)(2)PbBr4 at low temperature, and clarified that triplet excitons generated in the PbBr monolayer are recombined after localization in a random potential. The localized triplet exciton has a lifetime below 2.3 ns. From emission spectra under selective excitation of a strong nanosecond pulsed light, it is suggested that free and localized biexcitons are generated by inelastic collision of two free and localized triplet excitons, respectively. Moreover, it is concluded that the localized biexciton is annihilated radiatively leaving a localized triplet exciton.