Controlling photo-induced spectral changes in CdSe/ZnS quantum dots by tuning inter-dot energy transfer

We study photo-induced spectral changes in films containing two sizes of chemically synthesized CdSe/ZnS quantum dots (QDs) using static and time-resolved spectroscopies. As the concentration of the smaller (donor) QDs is varied over two orders of magnitude relative to the larger (acceptor) dots, we find that with decreasing proportion of donors, the photo-oxidation rate increases in acceptors but slows down in donors. We conclude that these differences originate from the variations in the amount of inter-dot energy transfer from donors to acceptors, and this tunability can be used to enhance the shelf-life of QD based opto-electronic and photovoltaic devices.