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Author Greenham, N. C. ♦ Peng, X. ♦ Alivisatos, A. P.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword MATERIALS SCIENCE ♦ COMPOSITE MATERIALS ♦ PHOTOLUMINESCENCE ♦ ALKYLATING AGENTS ♦ CADMIUM SELENIDES ♦ CADMIUM SULFIDES ♦ POLYMERS ♦ QUENCHING ♦ PHOTOCONDUCTIVITY ♦ ELECTRON MICROSCOPY ♦ RECOMBINATION ♦ CHARGE CARRIERS ♦ ELECTRONIC STRUCTURE ♦ AC ♦ QUANTUM DOTS
Abstract We study the processes of charge separation and transport in composite materials formed by mixing cadmium selenide or cadmium sulfide nanocrystals with the conjugated polymer poly(2-methoxy,5-(2{prime}-ethyl)-hexyloxy-{ital p}-phenylenevinylene) (MEH-PPV). When the surface of the nanocrystals is treated so as to remove the surface ligand, we find that the polymer photoluminescence is quenched, consistent with rapid charge separation at the polymer/nanocrystal interface. Transmission electron microscopy of these quantum-dot/conjugated-polymer composites shows clear evidence for phase segregation with length scales in the range 10{endash}200 nm, providing a large area of interface for charge separation to occur. Thin-film photovoltaic devices using the composite materials show quantum efficiencies that are significantly improved over those for pure polymer devices, consistent with improved charge separation. At high concentrations of nanocrystals, where both the nanocrystal and polymer components provide continuous pathways to the electrodes, we find quantum efficiencies of up to 12{percent}. We describe a simple model to explain the recombination in these devices, and show how the absorption, charge separation, and transport properties of the composites can be controlled by changing the size, material, and surface ligands of the nanocrystals. {copyright} {ital 1996 The American Physical Society.}
ISSN 01631829
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-12-01
Publisher Department Lawrence Berkeley National Laboratory
Publisher Place United States
Journal Physical Review, B: Condensed Matter
Volume Number 54
Issue Number 24
Organization Lawrence Berkeley National Laboratory


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