Application of cobalt-sulphide to suppress charge recombinations in polymer solar cell

Abstract

Cobalt-sulphide nano-particles were synthesized and employed in absorber layer of thin film organic solar cells (TFOSCs). The incorporation of nano-particles was designed to assist exciton dissociation processes and boost the collection photo-generated currents in TFOSC. Solar cells were fabricated from polymers blend photo-active layer consisting of Poly[[4,8- bis[(2-ethylhexyl) oxy] benzo[1,2-b:4,5-b] dithiophene2,6-diyl] [3 -fluoro-2-[(2- ethylhexyl)carbonyl]thieno[3,4- b] thiophenediyl]] (PTB7)and [6,6]-phenyl C 71 -butyric acid methyl ester (PC 71 BM) with/without the incorporation CoS. The optical and electrical properties of the active layers are found to be highly impacted by the inclusion of CoS NPs in the medium. Consequently, significant improvement on the collection of photo-currents was recorded that led to high power conversion efficiency of the devices compared to the reference cell. The influence of CoS nano-particles is found to be dependent on its concentration in the medium where the best solar cell performance recorded, in this experiment, was at 1wt% CoS, which brings about an increase in efficiency by 37%.