Roll-to-roll gravure printed organic solar cells based on low-cost polythiophene donor

Although the power conversion efficiency (PCE) of organic solar cells (OSCs) has exceeded 20%, the development of printed large-area low-cost OSCs is still lacking. For the realization of low-cost OSCs, the materials and the manufacturing method are two important factors. Regarding the materials, polythiophene polymer donor material is a cost-effective material. Regarding fabrication, gravure printing is a large-area preparation method that has the advantages of high-speed, high-precision, low-cost, and two-dimensional patternable. To achieve low-cost OSCs, flexible OSCs based on polythiophene donor materials are prepared through roll-to-roll (R2R) gravure printing in this work. On one side, the viscosity of the active layer ink is regulated by adjusting the concentration of the ink, which significantly suppresses the generation of flow stripes in the gravure printing film and obtains a uniform film. On the other side, the excessive aggregation of gravure-printed active layer film morphology is inhibited by controlling the temperature of the ink. Finally, 1 cm² flexible OSCs from R2R gravure printing show an efficiency of 10.55%, which is comparable to that of spin-coated devices. This study reveals that the low-cost polythiophene material system is suitable for fabrication through R2R gravure printing, which is expected to be applied in future low-cost OSCs.