Softening temperature on sputtered ZnO interfacial barrier layer for an efficient charge transfer P3HT/ZnO and better interfacial stability in plastic organic photovoltaic devices

Abstract

We demonstrate the usefulness of RF magnetron sputtering ZnO thin film at softening temperature, as interfacial barrier layer in air stable flexible inverted organic photovoltaic devices. We investigate the influence of annealing on the ZnO crystallinity, on the ITO substrate morphology and charge transport at the ZnO/active layer interface. The photo-physical and structural characteristics of P3HT beside ZnO interfacial layer and the photovoltaic device performances were also studied using UV–vis spectroscopy, photoluminescence (PL) and J-V characteristic. Finally, we study the interfacial stability of devices with and without ZnO interfacial layer in both normal and inverted structure OPVs. We show that under optimized sputtering conditions, higher order and orientation structure of P3HT, the ZnO thermally annealed beside active layer offers better efficiency of contact between the active layer and interfacial layer. We also show that ZnO annealed at a softening temperature of 180 °C is functional for both photovoltaic devices (rigid and plastic substrates), leading to improved performance and stability of plastic solar cell devices.