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The structural and optical properties of single crystal [Zn.sub.1-x][Mg.sub.x]O nanorods (0

We report on the improvement of power conversion efficiency (PCE) of PTB7/PC70BM solar cells by the addition of small quantities (0.02%-0.04%) of pristine single-walled carbon nanotubes (SWNTs) in the active-layer. SWNTs and purified semiconducting SWNTs (S-SWNTs) were added in quantities, which is 2 orders of magnitude lower than previously reported value and resulted in a reduction in the series resistance of the solar cell with minor changes on the shunt resistance. On addition of purified S-SWNT, the PCE of air measured devices enhanced by 29% from 4.9% to 6.3%, with short-circuit current density (JSC) improving from 12.1mA/cm² to 14.4 mA/cm² and a fill factor improvement from 54% to 61%. In addition, the role of processing additive N-Methyl-2-pyrrolidone, which acts as a SWNT dispersant, is also investigated. A single diode model of a solar cell is used to extract the cell parameters and understand the effect of SWNTs. Based on experimental data and it's fitting to the single diode model, we propose that S-SWNT improve the transport and extraction of photogenerated charges within the solar cell device. [ABSTRACT FROM AUTHOR]

In this study, polarized-Raman scattering measurements of an individual ZnO nanorod were carried out by using a confocal microscope together with a high-resolution piezoelectric stage. A predominant A1 (TO) mode at 378 cm-1 in the parallel polarization (E∥) configuration and a predominant E2 (high) mode at 438 cm-1 in the perpendicular polarization (E⊥) configuration demonstrate the strong polarization dependent Raman scattering signals of an individual ZnO nanorod. The Raman intensity images of the individual ZnO nanorods with different orientation configurations can also be obtained, which reflect the interplay between the local phonon behavior and geometric anisotropy. [ABSTRACT FROM AUTHOR]