Electronic and surface properties of PbS nanoparticles exhibiting efficient multiple exciton generation

Samantha J. O. Hardman; Darren M. Graham; Stuart K. Stubbs; Ben F. Spencer; Elaine A. Seddon; Ho-Ting Fung; Sandra Gardonio; Fausto Sirotti; Mathieu G. Silly; Javeed Akhtar; Paul O'Brien; David J. Binks; Wendy R. Flavell

doi:10.1039/C1CP22330E

Electronic and surface properties of PbS nanoparticles exhibiting efficient multiple exciton generation†

Samantha J. O. Hardman,*^a Darren M. Graham,^a Stuart K. Stubbs,^a Ben F. Spencer,^ab Elaine A. Seddon,^a Ho-Ting Fung,^a Sandra Gardonio,^c Fausto Sirotti,^d Mathieu G. Silly,^d Javeed Akhtar,‡^e Paul O'Brien,^e David J. Binks^a and Wendy R. Flavell^a

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* Corresponding authors

^a School of Physics and Astronomy and the Photon Science Institute, University of Manchester, Oxford Road, Manchester M13 9PL, UK
E-mail: samantha.hardman@manchester.ac.uk

^b Cockcroft Institute, Daresbury Science and Innovation Campus, Warrington, Cheshire WA4 4AD, UK

^c University of Nova Gorica Vipavska 11c, 5270 Ajdovscina, Slovenia

^d TEMPO beamline, Société civile Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin–BP 48, 91192 Gif-sur-Yvette, France

^e School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK

Abstract

Ultrafast transient absorption measurements have been used to study multiple exciton generation in solutions of PbS nanoparticles vigorously stirred to avoid the effects of photocharging. The threshold and slope efficiency of multiple exciton generation are found to be 2.5 ± 0.2 × E_g and 0.34 ± 0.08, respectively. Photoemission measurements as a function of nanoparticle size and ageing show that the position of the valence band maximum is pinned by surface effects, and that a thick layer of surface oxide is rapidly formed at the nanoparticle surfaces on exposure to air.

This article is part of the themed collection: In memory of Paul O’Brien

Physical Chemistry Chemical Physics

Electronic and surface properties of PbS nanoparticles exhibiting efficient multiple exciton generation†

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