Photoluminescence of excitons and biexcitons in (C4H9NH3)2PbBr4 crystals under high excitation density

Optical properties in (C4H9NH3)2PbBr4 single crystals under high density excitation have been investigated by photoluminescence (PL) spectroscopy. The PL bands associated with the Γ1, Γ2 and Γ5 excitons and the biexcitons have been observed. While the Γ2 exciton and biexciton PL intensities are proportional to the 0.9 and 1.7 power of the excitation density, respectively, the Γ5 exciton PL intensity shows the nonlinear dependence on the excitation density. The excitation‐density dependence of the PL bands is calculated by taking account of the dynamical change of the exciton and biexciton populations in an exciton‐biexciton system consisting of two exciton states and a biexciton state. The calculated results well explain the nonlinear dependence of the Γ5 exciton PL intensity on the excitation density. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)