Study Of Polymer Solar Cells Fabricated By Doctor Blading Technique

In recent years, bulk-heterojunction polymer solar cells have gained much attention and been intensively studied because of their potential advantages of being low-cost, light-weight,flexible and environmentally friendly. Spin-coating method, which is incompatible to large area manufacturing process and has serious material-wasting problem, cannot be applied in actual production, while the doctor-blading is suitable to a large-area roll-to-roll process and can offer high production at low cost. In this work, we systemically studied the different coating methods and the different fullerene acceptors effect on the polymer solar cells photovoltaic performance.Due to the difficulty in film-forming for spin coating method, we focused on the wet active solution physical chemical properties by testing their surface tension, viscosity and the surface energy of their solid film. It was found that it is much easier to obtain a homogeneous film from doctor blading compared with spin coating because of the lower surface tension and viscosity.Moreover, the high boiling point additive plays an important role in inhibiting the wet film shrinkage and forming a uniform film.In the film-forming process, the in-situ monitoring setup was used to track the different drying process, and then the solid film morphology was measured by atomic force microscopy. It was observed that the longer film drying time for the doctor-bladed films leads to larger domains than that of spin coating, which increases the geminate recombination and results in lower carrier mobilities as well as device power conversion efficiencies. A PCE of 4.46% for doctor-blading processed PSCs was achieved with P3TI:PC71BM as the active layer, which was comparable to that of spin-coating devices. This work provided valuable suggestions and solutions for the doctor-blading processed PSCs.