title: Multiple exciton generation in films of electronically coupled PbSe quantum dots.
abstract: We study multiple exciton generation (MEG) in electronically coupled films of PbSe quantum dots (QDs) employing ultrafast time-resolved transient absorption spectroscopy. We demonstrate that the MEG efficiency in PbSe does not decrease when the QDs are treated with hydrazine, which has been shown to greatly enhance carrier transport in PbSe QD films by decreasing the interdot distance. The quantum yield is measured and compared to previously reported values for electronically isolated QDs suspended in organic solvents at approximately 4 and 4.5 times the effective band gap. A slightly modified analysis is applied to extract the MEG efficiency and the absorption cross section of each sample at the pump wavelength. We compare the absorption cross sections of our samples to that of bulk PbSe. We find that both the biexciton lifetime and the absorption cross section increase in films relative to isolated QDs in solution.
authors.affiliation: Chemical and Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA. joseph_luther@nrel.gov
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Luther
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Beard
authors.forename: Qing
authors.initials: Q
authors.lastname: Song
authors.forename: Matt
authors.initials: M
authors.lastname: Law
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Ellingson
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Nozik
mesh_terms: D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D004579:Electron Transport; D004735:Energy Transfer; D007854:Lead / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008567:Membranes, Artificial; D008956:Models, Chemical; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D046911:Macromolecular Substances; D008567:Membranes, Artificial; D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead