In Situ Characterization of the Triphase Contact Line in a Brush-Coating Process: Toward 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 characterization triphase 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 nanothin films with larger crystallized sizes and higher orientations were enabled when TCLs were parallel to the brush edge, based on which the polymer solar cell shows higher power conversion efficiency (2.665%) compared with that of the spin-coated film.