Semiconductor quantum dots driven by radiative and nonradiative energy transfer for high-efficiency hybrid LEDs and photovoltaics

Abstract

Today the world energy demand has overtaken unprecedented consumption levels, which have never been reached before in the history of the world. The current trends indicate that the increasing demand for energy will tend to continue at an increasing pace in the coming decades due to worldwide globalization and industrialization. Scientific community is challenged to devise and develop fundamentally new technologies to cope with the energy problem of the world. To this end, optoelectronics can offer several solutions for energy efficiency both in light harvesting and generation. In this thesis, we propose and demonstrate enhanced light generation and harvesting by utilizing both radiative and nonradiative energy transfer capabilities of semiconductor nanocrystal quantum dots, which are profited for the development of novel hybrid devices combining superior properties of the constituent material systems. One of our proposals in this thesis relies on grafting nanostructured light emitting diodes with nanocrystal quantum dots to realize highly efficient color conversion. To the best of our knowledge, we report the highest nonradiative energy transfer efficiency of 83% obtained at room temperature for this type of colorconversion light emitting diodes owing to the architectural superiorities of their nanostructure. In another proposal, we addressed charge injection problems of electrically pumped nanocrystal-based light emitting diodes. We proposed and demonstrated the utilization of novel excitonic injection scheme to drive such LEDs of nanocrystals, which may become prominent especially for the display technology. Finally, we proposed and implemented quantum dot downconversion layers in nanostructured silicon solar cells to benefit the advantages of their nanostructured architecture. We have shown that nanostructured silicon solar cells lead to stronger enhancements compared to the planar counterparts.