A blend of (poly[(9,9-bis((6’-(N,N,N-trimethylammonium)hexyl)-2,7-fluorene)-alt-(9,9-bis (2-(2-(2-methoxyethoxy) ethoxy)ethyl)-9-fluorene)) dibromide (WPF-6-oxy-F) and graphene oxide (GO) is investigated as a hole transporting layer for low-cost poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-fl uoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl]] (PTB7) : phenyl-C-71-butyric acid methyl ester (PC71BM) organic solar cells (OSCs). The conductivity of the WPF-6-oxy-F and GO composite material is higher than pristine GO by about 2 orders of magnitude due to efficient packing and p-doping between WPF-6-oxy-F and GO. The WPF-6-oxy-F-GO composite is inserted between the indium tin-oxide (ITO) and the active layer as a hole transporting layer by spin-coating. The resulting Voc, FF, and power conversion efficiency (PCE) of photovoltaic cells are significantly enhanced. The efficiency of devices with only GO and WPF-6-oxy-F-GO as a hole-transporting layer are 3.14 and 6.59 %, respectively