Recently, researchers from Suzhou institute of Nano-Tech and Nano-Bionic of Chinese Academy of Sciences studied the influence of the zinc oxide (ZnO) buffer layer on the performance of the doctor-blade coated organic solar cells, and achieved high performance organic solar cells through doctor-blade coating. The finding was published in Journal of Materials Chemistry A.

Doctor-blade coating is a roll-to-roll compatible high-throughput thin film fabrication route with little solution wasting. It is considered as a more scalable method for the fabrication of organic solar cells than spin coating. However, its film drying is different from the conventional spin-coating process, which might cause different interfacial connection.

In this study, ZnO, the most widely used cathode buffer layer, was used as a research model to investigate the influence of buffer layer on the performance of the doctor-blade-coated organic solar cells.

Researchers demonstrated that the device performance, reproducibility, and long-term stability, were found to be more sensitive to the ZnO morphology in doctor-blade-coated cells than in the conventional spin-coated cells. The deep reason is different spreading forces and drying kinetics during thin film formation process of spin-coating and doctor-blade coating.

Besides, they found that a smooth ZnO cathode buffer layer from methanol-dispersed ink was more suitable for doctor-blade coating, and with this layer, a high power conversion efficiency of 12.88% and 9.22% was achieved for the 0.12 and 1.04 cm² organic solar cells.

The long-term stability of the doctor-blade coated cells is also highly sensitive to the morphology of the ZnO buffer layer.

The study revealed the different sensitivities of the cell performance to the cathode buffer layer morphology between spin-coating and doctor-blade coating. It showed that more efforts should be made to the morphology control of the bottom buffer layer in the printed organic photovoltaics.