High-rate unidirectional energy transfer in directly assembled CdTe nanocrystal bilayers

The direct layer-by-layer assembly of water-soluble CdTe nanocrystals (NCs) carrying oppositely charged stabilizer molecules without the need for supporting polymer linkers in between was investigated. The CdTe NCs used were synthesized in water by employing either thioglycolic acid (TGA) or 2-mercaptoethylamine (MEA) as the stabilizer. A polymer underlayer was deposited on a glass substrate to improve the adhesion of the NC bilayer grown on top of it. The electronic transitions of both the NC sizes were distinguished in the spectrum of the bilayer sample although the contribution of the acceptor NCs is reduced in comparison to the monolayer sample. Streak camera data binned by wavelengths rather than time were analyzed to figure out the energy transfer rate. The results show that directly assembled NC layers with fast and efficient unidirectional energy flow might contribute to the development of artificial photosynthetic systems and thin-film optoelectronic and photovoltaic devices.