Nano-scale ZnO buffer layer for inkjet-printed polymer solar cells

Zinc oxide (ZnO) was used as a buffer layer in the fabrication of polymer solar cells with the configuration of ITO/PEDOT:PSS/P3HT:PCBM/ZnO/Ag, in which the Ag cathode was prepared by ink-jet printing using silver ink. Due to the hydrophobic nature of the P3HT:PCBM active layer surface, the hydrophilic silver ink cannot be coated directly on the top of the P3HT:PCBM layer. To overcome this problem, ZnO particles, prepared in a simple solution method by using polyethylene glycol (PEG) surfactant molecules, were used as a buffer layer between the P3HT:PCBM layer and Ag cathode. The present study discusses and compares the performance of the solar cells with and without the ZnO buffer layer.