Low-Temperature Solution-Processed Zinc Tin Oxide Film as a Cathode Interlayer for Organic Solar Cells

In this study, Sn-doped ZnO (ZTO) is prepared by a sol–gel method and is employed as an electron transport material for organic solar cells (OSCs). After Sn modification, the fabricated ZTO films exhibited better charge transport properties and smoother surface morphology, especially for those processed at a low temperature of 120 °C. By incorporation of the high-temperature (200 °C) processed ZTO films, inverted OSCs showed the highest power conversion efficiency (PCE) of 9.32%, which is higher than those based on the same temperature processed ZnO films. For the devices based on the low-temperature processed ZTO, a high PCE over 9.0% with long-term stability was achieved, which is much better than those based on the same temperature processed ZnO (8.46% PCE). Here, the ZTO films can be fabricated without high-temperature annealing, demonstrating their great potential as electron transport layers for efficient flexible OSCs.