Fluidic Manipulating of Printable Zinc Oxide for Flexible Organic Solar Cells.

As a representative electron transporting layer in organic solar cells, zinc oxide (ZnO) can be fabricated by the meniscus-guided coating with the promotion of sol-gel technology. In order to fabricate stable and flexible organic solar cells (OSCs) based on the printable ZnO layers, here, a new method for simultaneously manipulating fluidics of the sol-gel ZnO precursor and optimizing processability of the ZnO layer for flexible OSCs is developed. It is found that the Marangoni recirculation in meniscus and the annealing temperature of the sol-gel ZnO precursor can be effectively modulated by changing the Lewis base. With the use of propylamine, the high-quality ZnO layer that is suitable for flexible OSCs can be fabricated through blade coating. Under such a condition, the formation of polar facet in ZnO layer is well restrained, which favors the photostability of the cells. As a result, the best 1.00 cm flexible cell outputs a power conversion efficiency of 16.71%, which is the best value till now.