The reversible photoluminescence enhancement of a CdSe/ZnS nanocrystal thin film

We report that the storage and clearing of multi-digital data, that is, the photoluminescence (PL) intensity of CdSe/ZnS core/shell nanocrystal (NC) thin film, can be operated by a single excitation wavelength. First, a 7.4 µm-square area on the NC film was irradiated by strong light ranging in intensity from 2.64 to 1370 nW. Then, a 60 µm-square area including the pre-irradiated region was scanned with weak light (about 0.6 nW) to visualize the PL intensity difference between pre- and non-irradiated regions ( I and I 0 , respectively). The normalized PL intensity, I / I 0 , increased with total pre-irradiation energy, until reaching saturation. The level of I / I 0 at which the PL intensity becomes saturated reversibly increased with decreasing light intensity at pre-irradiation. The results imply that Auger ionization becomes dominant and suppresses the enhancement of the emission efficiency with higher irradiation intensities.