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Effect of Molecule–Surface Reaction Mechanism on the Electronic Characteristics and Photovoltaic Performance of Molecularly Modified Si

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      We report on the passivation properties of molecularly modified, oxide-free Si(111) surfaces. The reaction of 1-alcohol with the H-passivated Si(111) surface can follow two possible paths, nucleophilic substitution (S N) and radical chain reaction (RCR), depending on adsorption conditions. Moderate heating leads to the S N reaction, whereas with UV irradiation RCR dominates, with S N as a secondary path. We show that the site-sensitive S N reaction leads to better electrical passivation, as indicated by smaller surface band bending and a longer lifetime of minority carriers. However, the surface-insensitive RCR reaction leads to more dense monolayers and, therefore, to much better chemical stability, with lasting protection of the Si surface against oxidation. Thus, our study reveals an inherent dissonance between electrical and chemical passivation. Alkoxy monolayers, formed under UV irradiation, benefit, though, from both chemical and electronic passivation because under these conditions both S N and RCR occur. This is reflected in longer minority carrier lifetimes, lower reverse currents in the dark, and improved photovoltaic performance, over what is obtained if only one of the mechanisms operates. These results show how chemical kinetics and reaction paths impact electronic properties at the device level . It further suggests an approach for effective passivation of other semiconductors.

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          Wet chemical routes to the assembly of organic monolayers on silicon surfaces via the formation of Si-C bonds: surface preparation, passivation and functionalization.

          Organic functionalization of non-oxidized silicon surfaces, while allowing for robust chemical passivation of the inorganic substrate, is intended and expected to broaden the chemical, physical and electronic properties of the currently most relevant technological material. Numerous protocols are now available for the preparation of Si-C, Si-O and Si-N bound layers. In particular, the covalent attachment of 1-alkenes and 1-alkynes onto hydride-terminated Si(100) and Si(111) has seen a wealth of research activity starting from the pioneering work of Linford and Chidsey (Alkyl monolayers covalently bonded to silicon surfaces, J. Am. Chem. Soc., 1993, 115(26), 12631-12632). This critical review aims to bring together the available wet-chemical routes toward the formation of silicon-organic monolayers under ambient conditions. Particular emphasis is placed on discussing the reasons behind the need for novel chemical approaches that are straightforward, modular and of wide scope so as to allow the application of silicon electrodes in aqueous electrolytes. A general introduction to biomolecular recognition events at functionalized silicon surfaces is also presented (281 references).

            Author and article information

            []Department of Materials & Interfaces, Weizmann Institute of Science , Rehovoth 76100, Israel
            []Institute of Solid State Physics, Graz University of Technology , A-8010 Graz, Austria
            [§ ]National Renewable Energy Laboratory , Golden, Colorado 80401, United States
            []Department of Chemical Research Support, Weizmann Institute of Science , Rehovoth 76100, Israel
            Author notes
            [* ]David Cahen. Tel.: 972-8-934-2246. E-mail: david.cahen@ . Ayelet Vilan. Tel.: 972-8-934-3729. E-mail: ayelet.vilan@ . Leeor Kronik. Tel.: 972-8-934-4993. E-mail: leeor.kronik@ .
            J Phys Chem C Nanomater Interfaces
            J Phys Chem C Nanomater Interfaces
            The Journal of Physical Chemistry. C, Nanomaterials and Interfaces
            American Chemical Society
            03 June 2013
            31 October 2013
            : 117
            : 43 , Ron Naaman Festschrift
            : 22351-22361
            Copyright © 2013 American Chemical Society
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            Thin films & surfaces


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