In-situ characterizing the tri-phase contact line in a brushing-coating process: towards the enhanced efficiency of polymer solar cells.

Solution processes have been widely used for making polymer films in organic photoelectric devices, but suffer from difficulties in controlling the film formation. Here, by in-situ characterizing tri-phase contact lines (TCLs) in a brush-coating process, we clarify how TCLs affect the quality of as-prepared films. By fine tuning the dewetting of a binary polymer solution (P3HT:PCBM) via different directions, TCLs with different patterns lead to films with different morphologies. High quality nano-thin films with larger crystallized size and higher orientation were enabled when TCLs parallel to the brush edge, based on which a polymer solar cell shows higher power conversion efficiency (2.665%) comparing with that of the spin-coated film.