Extremely large binding energy of biexcitons in an organic–inorganic quantum-well material (C4H9NH3)2PbBr4

We have confirmed biexciton formation in an organic–inorganic hybrid quantum-well material (C4H9NH3)2PbBr4 by photoluminescence and two-photon absorption measurements. The biexciton has extremely large binding energy, 60 meV, which to our knowledge is the largest value ever reported for a semiconductor. By analyzing the spectrum of biexciton luminescence, the biexciton gas temperature was found to be much higher than the bath temperature due to a higher local temperature arising from the large biexciton binding energy.