Exciton–exciton interaction in an inorganic–organic layered semiconductor, (C6H5C2H4NH3)2PbI4

We have investigated the exciton–exciton interaction in an inorganic–organic layered semiconductor, (C6H5C2H4NH3)2PbI4, by the pump–probe spectroscopy. The excitonic shift and the induced absorption due to the excitation of the exciton to the excitonic molecule are measured as functions of the delay time in the co-circular and opposite-circular polarization configurations. The contribution of the exciton–exciton interaction to exciton renormalization is distinguished by femtosecond resolution. Based on a rate-equation analysis for exciton-relaxation kinetics, it is found that the contribution of the interaction between excitons with opposite spins is ca. −5% of that of the interaction between excitons with the same spin. In order to explain this result, possible types of interactions, which originate solely from the Coulomb interaction without restriction from the Pauli exclusion principle, are examined.