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Colloidal semiconductor nanocrystals have attracted attention for cost-effective, solution-based deposition of quantum-confined thin films for optoelectronics. However, two significant challenges must be addressed before practical nanocrystal-based devices can be realized. The first is coping with the ligands that terminate the nanocrystal surfaces. Though ligands provide the colloidal stability needed to cast thin films from solution, these ligands dramatically hinder charge carrier transport in the resulting film. Second, after a conductive film is achieved, doping has proven difficult for further control of the optoelectronic properties of the film. Here we report the ability to confront both of these challenges by exploiting the ability of silicon to engage in hypervalent interactions with hard donor molecules. For the first time, we demonstrate the significant potential of applying the interaction to the nanocrystal surface. In this study, hypervalent interactions are shown to provide colloidal stability as well as doping of silicon nanocrystals.
Bibliographical noteFunding Information:
The work of L.M.W., U.R.K. and N.R.N. was supported by the DOE Energy Frontier Research Center for Advanced Solar Photophysics. Part of this work was carried out in the College of Science and Engineering Characterization Facility, University of Minnesota, which has received capital equipment funding from the NSF through the UMN MRSEC program. The work of T.C. was supported primarily by the National Science Foundation through the University of Minnesota MRSEC under Award Number DMR-0819885. We acknowledge the Chemistry NMR lab and thank Letitia Yao and Karen Beckman for NMR measurements. We also thank Greg Haugstad for scanning probe microscopy characterization, Bo Zhang and Professor Tianhong Cui for their assistance with z-potential measurements, and David Rowe and David Barton for their helpful discussion. We would also like to thank Vincent Wheeler for lengthy discussion and manuscript editing.