The effect of organic salt, tetrabutylammonium hexafluorophosphate (TBAPF(6)) doping on the performance of single layer bulk heterojunction organic solar cell with ITO/MEHPPV:PCBM/Al structure was investigated where indium tin oxide (ITO) was used as anode, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV) as donor, (6,6)-phenyl-C61 butyric acid methyl ester (PCBM) as acceptor and aluminium (Al) as cathode. In contrast to the undoped device, the electric field-treated device doped with TBAPF(6) exhibited better solar cell performance under illumination with a halogen projector lamp at 100 mW/cm(2). The short circuit current density and the open circuit voltage of the doped device increased from 0.54 mu A/cm(2) to 6.41 mu A/cm(2) and from 0.24 V to 0.50 V, respectively as compared to those of the undoped device. The significant improvement was attributed to the increase of built-in electric field caused by accumulation of ionic species at the active layer/electrode interfaces. (C) 2010 Elsevier Ltd. All rights reserved.