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.