Harvesting incoming light by means of optical nanoantennas and concentrating it into defined hotspots with nanoscale precision, where it is either converted into electricity or reemitted at a tailored frequency, has become a key approach to improving the performance of solar cells, light-emitting diodes or photodetectors. This interdisciplinary project synergistically combines wet-chemical synthesis of semiconductor quantum dots (QD) and physically tailored optical properties of top-down engineered metal nanostructures. The metal acts as an antenna with the capability to collect light of tunable frequencies and to focus it onto nanoscale features where an extreme enhancement of the electromagnetic field is induced. Numerical simulations will be used to predict these hotspots and the antenna resonance frequencies in dependence of the material, shape, size and dielectric environment of the nanostructured metal. We will position solution-processible QDs within the volume of such hotspots, which serve as bright emitters of the collected light. By utilizing the quantum size effect, controlled doping and the unique optical properties that occur in QDs of ultra-small sizes, we will study the prospects of maximizing light transfer from the antenna onto the emitter but simultaneously blocking the reverse pathway by minimizing the spectral overlap of the QD excitation and emission. The results of this study are intended as a preliminary study to facilitate the application of nanostructured antennas to enhance the efficiency of QD-based lighting devices.
April 2015 - March 2016
Monika Fleischer (University of Tuebingen)