RESONANT ENERGY TRANSFER WITHIN A COLLOIDAL NANOCRYSTAL POLYMER HOST SYSTEM
S. Kaufmann,1,2 T. Stöferle,1 N. Moll,1 R.F. Mahrt1
1IBM Research, Zurich Research Laboratory, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
2Quantum Optics Group, ETH Zürich, 8093 Zürich, Switzerland
There has been considerable interest in the optical and electronical properties of conjugated polymers and molecularly-doped polymers during recent years owing to their prospective applications in electronic and optoelectronic devices. At the same time, there has been much progress in the rapidly growing field of semiconductor nanocrystal quantum dots (QD) due to their promising applications such as display devices, lasers, biological fluorescent tagging materials and photodetectors. Favorably, the chemically synthesized colloidal QDs can easily be incorporated into conjugated polymer host systems allowing for novel organic/inorganic hybrid devices and combining the natural advantages from both organic as well as inorganic materials into one system. In order to optimize such hybrid systems in view of tailored optoelectronic properties a profound knowledge of the underlying electronic energy transfer processes between the inorganic and organic parts is necessary. We report on resonant energy transfer of non-equilibrium excitons in an amorphous polyﬂuorene donor CdSe/ZnS core-shell nanocrystal acceptor system. By time resolved photoluminescence (PL) spectroscopy we have investigated the PL decay behavior ofthe primarily excited polyﬂuorene as a function of the concentration of the nanocrystals. We are able to demonstrate that the finite rise time of the PL transient monitored at the spectral position of the acceptor PL directly reflects the PL decay of the donor. The results are promising in view of possible applications in light emitting diodes and lasers due to the broad tunability and the decoupling of transport properties from the emission. Furthermore, the fundamental question regarding transformation between small Frenkel excitons and more extended Mott-Wannier excitons will be addressed.