Towards optimization of functionalized single-walled carbon nanotubes adhering with poly(3-hexylthiophene) for highly efficient polymer solar cells

• We optimized SWCNTs by acid-treatment, solution ultrasonication time and dispersion in photoactive layer for solar cells.
• Two methods of acid-treated SWCNTs were compared and an optimum method was chosen to keep SWCNTs not to be destroyed.
• An optimum concentration of 0.3 wt% SWCNTs in P3HT:PCBM:SWCNTs nanocomposites was found.
• PCE can be increased by 10.3% with a JSC = 11.46 mA/cm2 as compared with that of the control device with no SWCNTs.
• The optimum ultrasonication duration time of 60 minutes was found for functionalized SWCNTs in DCB and it can last 144 h.

In this paper, we present the optimization of single-walled carbon nanotubes (SWCNTs) by acid-treatment, solution ultrasonication time and dispersion in photoactive layer for efficient organic solar cells. After non-covalently adhering with poly(3-hexylthiophene) (P3HT), pre-functionalized SWCNTs were blended into the composites of P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as photoactive layer, and a maximum power conversion efficiency (PCE) of 3.02% with a short-circuit current density of 11.46 mA/cm2 was obtained from photovoltaic cell indium-tin oxide (ITO)/poly(ethylene-dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)/P3HT:PCBM:SWCNTs/Al with an optimum 0.3 wt% SWCNTs in P3HT:PCBM:SWCNTs nanocomposite, the PCE can be enhanced by more than 10% as compared to the control device ITO/PEDOT:PSS/P3HT:PCBM/Al. The performance improvement by incorporating with functionalized SWCNTs is mainly attributed to the extension of excitons dissociation area and fastening charge carriers transfer across the active layer.