Effect of ZnO nanoparticle morphology and post-treatment with zinc acetate on buffer layer in inverted organic photovoltaic cells

Spherical and rod-shaped ZnO nanoparticles were synthesized through modified sol gel method to investigate the morphological effect in the buffer layer of inverted organic photovoltaic cells (OPVs). Also the buffer layers fabricated with ZnO nanoparticles were post-treated by using zinc acetate dihydrate in methanol (zinc acetate post-treatment) to survey the influence of surface state on buffer layer. After the zinc acetate post-treatment on ZnO buffer layer, the low series resistance (R-s) and high shunt resistance (R-sh) were obtained due to the enhancement of the electric contiguity at the interface (buffer layer/active layer) and interconnectivity between ZnO nanoparticles. By improving the resistance, the current density (J(sc)) and fill factor (FF) of devices were increased. The performance of device fabricated with rod-shaped ZnO particles was higher than that of cell fabricated with spherical ZnO particles because the 1-dimensional rod particles acted as an appropriate bridge to promote the electron mobility. The best power conversion efficiency (2.68%) could be achieved through the facile and effective zinc acetate post-treatment. (C) 2015 Elsevier Ltd. All rights reserved.