title: Optimal Shell Thickness of Metal@Insulator Nanoparticles for Net Enhancement of Photogenerated Polarons in P3HT Films.
abstract: Embedding metal nanoparticles in the active layer of organic solar cells has been explored as a route for improving charge carrier generation, with localized field enhancement as a proposed mechanism. However, embedded metal nanoparticles can also act as charge recombination sites. To suppress such recombination, the metal nanoparticles are commonly coated with a thin insulating shell. At the same time, this insulating shell limits the extent that the localized enhanced electric field influences charge generation in the organic medium. It is presumed that there is an optimal thickness which maximizes field enhancement effects while suppressing recombination. Atomic Layer Deposition (ALD) was used to deposit Al2O3 layers of different thicknesses onto silver nanoparticles (Ag NPs), in a thin film of P3HT. Photoinduced absorption (PIA) spectroscopy was used to study the dependence of the photogenerated P3HT(+) polaron population on the Al2O3 thickness. The optimal thickness was found to be 3-5 nm. This knowledge can be further applied in the design of metal nanoparticle-enhanced solar cells.
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore.|Division of Materials Technology, School of Materials Science and Engineering, Nanyang Technological University , Block N4.1 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Goh
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore.
authors.forename: Evan L
authors.initials: EL
authors.lastname: Williams
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore.
authors.forename: Ren-Bin
authors.initials: RB
authors.lastname: Yang
authors.affiliation: Institute of High Performance Computing, A*STAR (Agency for Science, Technology and Research) , 1 Fusionopolis Way, #16-16 Connexis North, Singapore 138632, Singapore.
authors.forename: Wee-Shing
authors.initials: WS
authors.lastname: Koh
authors.affiliation: Division of Materials Technology, School of Materials Science and Engineering, Nanyang Technological University , Block N4.1 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Subodh
authors.initials: S
authors.lastname: Mhaisalkar
authors.affiliation: Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research) , 2 Fusionopolis Way, Innovis #08-03, Singapore 138634, Singapore.
authors.forename: Zi-En
authors.initials: ZE
authors.lastname: Ooi
keywords: insulating oxide; localized field enhancements; localized surface plasmons; metallic nanoparticles; optical scattering; photoinduced absorption spectroscopy; plasmon enhanced organic photovoltaic cell; polaron generation