Efficient exciton funneling in cascaded PbS quantum dot superstructures.

ACS Nano

Department of Electrical & Computer Engineering, University of Delaware, 140 Evans Hall, Newark, Delaware, United States.

Published: December 2011

Benzenedithiol (BDT) and ethanedithiol (EDT) ligand-exchange treatments can be used to cross-link colloidal PbS quantum dots into nanocrystalline film structures with distinct optoelectronic properties. Such structures can provide a unique platform to study the energy transfer between layers of quantum dots with different sizes. In this report, efficient exciton funneling and recycling of surface state-bound excitons is observed in cascaded PbS quantum dot-based multilayered superstructures, where the excitons transfer from the larger band gap or donor layers to the smallest band gap or acceptor layers. In this system, both the BDT- and EDT-treated cascaded structures exhibit dramatically enhanced photoluminescence from the acceptor layers. As we show, the energy transfer mechanisms involved and their efficiencies are significantly different depending on the ligand-exchange treatment. In the future, we believe these efficient exciton recycling and funneling mechanisms could be used to improve significantly the photocurrent, charge-transport, and conversion efficiencies in low-cost nanocrystalline and hybrid solar cells and the emission efficiencies in hybrid light-emitting devices.

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http://dx.doi.org/10.1021/nn203728tDOI Listing

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