This letter reports efficiency improvements in single-heterojunction organic photovoltaic (OPV) cells exploiting different wide-bandgap electron-blocking layer (EBL) materials of N,N,NO',N' tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), Tris(phenypyrazole)iridium (Ir(ppz)3), or 4,4,4 ''-tris-(3-methyl-phenylphenylamino)triphenylamine (m-MTDATA), respectively. The OPV structure consists of an indium-tin-oxide (ITO) anode, 4 nm m-MTDATA, 30 nm copper phthalocyanine (CuPc), 40 nm fullerene (C60), 10 nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and a 100 nm Al cathode. Optimum device performances by insertion the EBL of m-MTDATA have been achieved, including short-circuit current density (J(SC)) of 7.26 mA/cm(2), open-circuit voltage (V-oc) of 0.5 V. fill-factor (FF) 01 43%, and power conversion efficiency (PCE) of 1.56% at an illumination intensity of 100 mW/cm(2). (C) 2012 Elsevier Ltd. All rights reserved.