Optical Memory Media Based on Excitation-Time Dependent Luminescence from a Thin Film of Semiconductor Nanocrystals

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Abstract
We describe the increase of photoluminescence intensity from densely packed semiconductor nanocrystals (quantum dots) with excitation time, which is clearly observed by the naked eye under ambient conditions. This enabled the invention of the first luminescence-based optical memory media feasible for practical applications. Bright luminescent images are stored and then read out by exciting the medium, a thin film of cadmium selenide nanocrystals, with blue or UV light. The increase in emission intensity is attributed to the trapping and accumulation of photo-generated electrons in the matrix of organic molecules capping the nanocrystals.