Laminated Carbon Nanotubes for the Facile Fabrication of Cost-Effective Polymer Solar Cells

In this study, we fabricate a metal- and vacuum-free electrode composed of aligned multiwall carbon nanotubes (MWCNTs) as top electrode in inverted type polymer solar cells. Simply drawn MWCNT sheets from vertically grown arrays were directly transferred over the top layer (PEDOT:PSS) of the device as an anode material. Without any post treatment, devices exhibited a short-circuit current density (J(sc)) of 7.53 mA cm(-2), which is 78% of that of devices employing a thermally deposited silver-based anode (J(sc) = 9.69 mA cm(-2)). Scanning electron microscopy images of the device (top and cross-sectional views) show the successful incorporation of MWCNT sheets over the surface of the device without any damage. The thickness of the MWCNT sheets as top electrode is also investigated, and it has been demonstrated that when the sheets' thickness increased, the conductance of the electrode increased, which showed improvement for the device performance. The attributes of being flexible, vacuum-free, and stable with regard to environmental factors may lead this idea to become a versatile approach toward cost-effective roll-to-roll production of environmentally friendly polymer solar cells.