Manipulating the Macroscopic and Microscopic Morphology of Large‐Area Gravure‐Printed ZnO Films for High‐Performance Flexible Organic Solar Cells

Abstract

Gravure printing is a promising large‐scale fabrication method for flexible organic solar cells (FOSCs) because it is compatible with two‐dimension patternable roll‐to‐roll fabrication. However, the unsuitable rheological property of ZnO nanoinks resulted in unevenness and looseness of the gravure‐printed ZnO interfacial layer. Here we propose a strategy to manipulate the macroscopic and microscopic of the gravure‐printed ZnO films through using mixed solvent and poly(vinylpyrrolidone) (PVP) additive. The regulation of drying speed effectively manipulates the droplets fusion and leveling process and eliminates the printing ribbing structure in the macroscopic morphology. The additive of PVP effectively regulates the rheological property and improves the microscopic compactness of the films. Following this method, large‐area ZnO:PVP films (28 × 9 cm2) with excellent uniformity, compactness, conductivity, and bending durability were fabricated. The power conversion efficiencies of FOSCs with gravure‐printed AgNWs and ZnO:PVP films reached 14.34% and 17.07% for the 1 cm2 PM6:Y6 and PM6:L8‐BO flexible devices. The efficiency of 17.07% is the highest value to date for the 1 cm2 FOSCs. The use of mixed solvent and PVP addition also significantly enlarged the printing window of ZnO ink, ensuring high‐quality printed thin films with thicknesses varying from 30 to 100 nm.