title: Efficient exciton funneling in cascaded PbS quantum dot superstructures.
abstract: 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.
authors.affiliation: Department of Electrical & Computer Engineering, University of Delaware, 140 Evans Hall, Newark, Delaware, United States.
authors.forename: Fan
authors.initials: F
authors.lastname: Xu
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
authors.forename: Chelsea R
authors.initials: CR
authors.lastname: Haughn
authors.forename: Jamie
authors.initials: J
authors.lastname: Benavides
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Doty
authors.forename: Sylvain G
authors.initials: SG
authors.lastname: Cloutier
mesh_terms: D004735:Energy Transfer; D007854:Lead / Q000737:chemistry*; D008422:Materials Testing; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*
chemical_list: D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead