We have fabricated the bulk hetero-junction organic solar cells consisting of PCBM and P3HT blend on flat, and dense, low-temperature (<150 degrees C) processed anatase titanium oxide film obtained by sol-gel process. The photovoltaic properties were markedly improved by the insertion of MoO(3) layer between active layer and Au (or Ag). The photovoltaic properties of solar cell on non-treated low-temperature titanium oxide, however, markedly decreases compared with the cell on high-temperature processed titanium dioxide probably due to the dense surface defects on the low-temperature titanium oxide. Therefore, we have treated the surface of titanium oxide by fullerene based self-assembled monolayer (C(60)-SAM) using aminopropyl-ethoxysilane and C(60). The photovoltaic properties of polymer BHJ cells on surface treated low-temperature titanium oxide was improved markedly probably due to the passivation of surface defects on low-temperature processed titanium oxide films, such as -OH etc. and improved electron transfer between titanium oxide and active layer.