Exciton localization and decomposition dynamics in cuprous halide nanocrystals

We report temporal changes of luminescence and absorption (differential transmission) of excitons in nanometer-size semiconductor crystals (nanocrystals) of CuCl embedded in NaCl or in glass, and CuBr nanocrystals embedded in glas. In CuCl nanocrystals in NaCl, an exciton relaxes nonradiatively to some localized state. In CuCl and CuBr nanocrystals in glass, the temporal changes of the differential transmission have a longer decay component in addition to the fast decay component which agrees with the luminescence decay. This result suggests exciton decomposition and the existence of an electron or a hole remainder in the nanocrystals. The decay time of the longer decay component increases by the accumulation of photoexcitation. This phenomenon indicates persistent trapping of carriers in the glass matrix, which is concerned with persistent spectral hole burning in nanocrystals.