Structural, Optical, and Electrical Properties of Self-Assembled Films of PbSe Nanocrystals Treated with 1,2-Ethanedithiol

• Published in: ACS nano 2008-02, Vol.2 (2), p.271-280
• Main Authors: Luther, Joseph M, Law, Matt, Song, Qing, Perkins, Craig L, Beard, Matthew C, Nozik, Arthur J
• Format: Article
• Language: English
• Subjects: Crystallization - methods; Electric Conductivity; Electrochemistry - methods; Lead - chemistry; Light; Macromolecular Substances - chemistry; Materials Testing; Membranes, Artificial; Mercaptoethanol - analogs & derivatives; Mercaptoethanol - chemistry; Molecular Conformation; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanotechnology - methods; Particle Size; Photochemistry - methods; Refractometry; Scattering, Radiation; Selenium Compounds - chemistry; Surface Properties
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn7003348

We describe the structural, optical, and electrical properties of high-quality films of PbSe nanocrystals fabricated by a layer-by-layer (LbL) dip-coating method that utilizes 1,2-ethanedithiol (EDT) as an insolubilizing agent. Comparative characterization of nanocrystal films made by spin-coating and by the LbL process shows that EDT quantitatively displaces oleic acid on the PbSe surface, causing a large volume loss that electronically couples the nanocrystals while severely degrading their positional and crystallographic order of the films. Field-effect transistors based on EDT-treated films are moderately conductive and ambipolar in the dark, becoming p-type and 30–60 times more conductive under 300 mW cm−2 broadband illumination. The nanocrystal films oxidize rapidly in air to yield, after short air exposures, highly conductive p-type solids. The LbL process described here is a general strategy for producing uniform, conductive nanocrystal films for applications in optoelectronics and solar energy conversion.