Nonlinear luminescence from an inorganic–organic layered semiconductor

Excitation intensity dependence of the photoluminescence (PL) from an inorganic–organic layered semiconductor, (C6H5C2H4NH3)2PbI4, has been investigated at 10 K. When the excitation intensity exceeds 2×1013 photons/cm2 per pulse which is more than that necessary for observing the PL from the excitonic molecule, two novel PL lines are observed at 2.295 and 2.28 eV. The former is most likely assigned to the amplified spontaneous emission of the transition between the exciton and the excitonic molecule. The latter is tentatively assigned to the emission from the tri-exciton complex leaving two excitons behind.