The purpose of tlus study is to investigate the photovoltaic effect of the undopedrnpoly[3-( 4-octylphenyl)-2,2'-bithiophene 1 (PTOPT) by performing the current density-voltagern(J-V) measurements in the dark and under illumination. The Al/PTOPT junction forms arnSchottky barrier. The semiconductor property of PTOPT was confirmed from opticalrnabsorption spectroscopy. The electrical and photovoltaic properties of an Al/PTOPT/ITOrndevice were investigated by the J-V measurement in the dark and under illumination. FromrnJ-V in the dark, the reverse saturation current density, Jo = 6.7 x 1O-14Alcm2 was obtained.rnThe diode ideality factor n and the barrier height