Time-resolved luminescence study of biexcitons in CuCl quantum dots

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Abstract
Population dynamics of excitons and biexcitons in nanometer-sized CuCl microcrystallites (nanocrystals) was studied with a time-resolved luminescence measurement. A recurring process between excitons and biexcitons was clearly observed as a function of the second decay component of the biexciton luminescence and with an increase of the exciton luminescence. They become prominent with an increase in the excitation intensity. The biexciton luminescence is broadened asymmetrically to higher energy with an increase in the biexciton density. These temporal as well as spectral characteristics of biexciton luminescence are inherent to CuCl nanocrystals but are not observed in a CuCl bulk crystal, which shows that biexcitons are much more efficiently formed from excitons in a CuCl nanocrystal than in a CuCl bulk crystal.