Investigating coating method induced vertical phase distribution in polymer-fullerene organic solar cells

The morphologies of bulk heterojunction (BHJ) films of blended semiconductor of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) deposited by doctor blading and spin coating were investigated. Controlled phase separation in BHJ organic/polymer solar cells (OSCs) were achieved using doctor blading. The results revealed that the coating method induced a significant difference in the film morphology. The vertical phase distribution of the BHJ layer fabricated by doctor blading was uniform, while uneven phase distribution was observed in spin coated BHJ layer. The uniform phase distribution in the doctor blading coated film resulted in higher charge carrier mobility and power conversion efficiency in solar cell than those in films fabricated from spin coating. The results demonstrated that doctor blading has advantages not only in large area high throughput and roll-to-roll compatibility, but also in better control of film morphology to achieve high efficiency consistently in OSC devices.