Influence of sol-gel derived ZnO nano-ripples on the performance of inverted organic solar cells

Abstract

This study appraised the possibility of utilizing a sol-gel process technique for inverted organic solar cells (IOSCs). ZnO films were fabricated by a sol-gel processing technique. ZnO films were incorporated as an electron selective layer (ESLs) in IOSCs, in which the widely used polymer poly (3-hexyl thiophene) (P3HT) and fullerene derivative [6, 6]-phenyl-C61-butyric acid methyl (PC61BM) were used as a photoactive material. First, the annealing conditions for the pure sol-gel ZnO films were optimized. The annealing temperature of the ZnO layer significantly influenced the overall IOSCs performance. The ZnO film annealed at 250°C showed nano-ripple (also named as nanoridges) like structure. However, ZnO films annealed at 300°C and 350°C were planar in structures. The IOSCs with ZnO nano-ripple exhibited a remarkable improvement over other solar cells. The power conversion efficiency of 0.712%, short circuit current density (Jsc) of 4.5 mA/cm2, fill factor (FF) of 0.33 and open circuit voltage (Voc) of 480 mV were obtained form device utilizing ZnO nano-ripples.