Analysis of electrical parameters in heterojunctions based on poly 3-octylthiophene and cadmium sulfide thin films

Planar hybrid heterojunctions were built with poly 3-octylthiophene (P3OT) and chemical bath-deposited cadmium sulfide (CdS) thin films on a conductive glass substrate. The organic material, P3OT, acts as a light absorber and the inorganic one, CdS, as the electron acceptor. Two types of CdS films had been used: one is as-deposited and the other doped with HgCl2. Heterojunctions were formed by casting a chemically synthesized P3OT solution onto CdS films. The P3OT film thickness was also varied for heterojunction studies. Current vs. potential (I–V) characterizations under dark and illumination conditions were performed for the P3OT/CdS heterojunctions under 88 mW/cm2 irradiance level, which show photovoltaic effect with different open circuit voltage (VOC) levels, being as high as 1 V for some devices. A parametric analysis of I–V curves details the effect of CdS resistivity and P3OT film thickness on series and shunt resistance of the heterojunctions.