Abstract
The effects of incorporating functionalized multiwall carbon nanotubes with polystyrene (PSMWCNTs) in organic polymer solar cells were studied. Different concentrations of carbon nanotubes in poly(2-methoxy-5-(2-ethyhexyl-oxy)-p-phenylenevinylene) [MEH-PPV] were investigated via absorption spectroscopy, photoluminescence (PL) and current voltage measurements under illumination, in order to determine the photovoltaic effect of the elaborated organic solar cells. The decrease in PL intensity with the progressive addition of PSMWCNTs is a signature of an effective charge transfer at MEH-PPV/ PSMWCNTs heterojunction. Moreover, the addition of carbon nanotubes (CNTs) to the polymer increases the power conversion efficiency compared with the device with pristine polymer. A critical concentration value of 0.15 wt% of PSMWCNTs is found to achieve the best performance of devices. Direct current conductivity of the composite film was found to increase rapidly with the increase in PSMWCNTs concentration. The enhancement in conductivity is explained in terms of percolation theory with an estimated percolation threshold of 0.092 wf%,. (C) 2014 Elsevier Ltd. All rights reserved.