Recently, the Chinese researchers studied the influence of the 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.
This study was published with the title of “12.88% efficiency in doctor-blade coated organic solar cells through optimizing the surface morphology of a ZnO cathode buffer layer” 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 and is considered as a more scalable method for the fabrication of organic solar cells than spin coating. But the film drying of doctor-blade coating is different from the conventional spin-coating process, which might cause different interfacial connection.
In this work, the most widely used cathode buffer layer, zinc oxide (ZnO) is used as a research model to investigate the influence of buffer layer on the performance of the doctor-blade-coated organic solar cells. This work demonstrated the device performance, reproducibility, and long-term stability, are 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.
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. In addition, the long-term stability of the doctor-blade coated cells is also highly sensitive to the morphology of the ZnO buffer layer.
These findings revealed the different sensitivities of the cell performance to the cathode buffer layer morphology between spin-coating and doctor-blade coating, and showed that more efforts should be made to the morphology control of the bottom buffer layer in the printed organic photovoltaics.
This research was supported by the National Natural Science Foundation of China, the Suzhou Science and Technology Project, Strategic Priority Research Program of the Chinese Academy of Sciences.
Contact information: Dr.LUO Qun, Suzhou institute of Nano-Tech and Nano-Bionic, Chinese Academy of Sciences.