Fabrication of Annealing-Free High Efficiency and Large Area Polymer Solar Cells by Roller Painting Process

The polymer solar cells were fabricated by a novel solution coating process, the roller painting. The roller painted film composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) has smoother surface than the spin coated film. Since the roller painting is accompanied with shear and normal stresses and is also a s low drying process, the process induces effectively crystallization of P3HT and PCBM. Both crystalline P3HT and PCBM in the roller painted active layer contribute to enhanced and balanced charge carrier mobility. Consequently, the roller painting process results in higher power conversion efficiency (PCE) of 4.6% as compared to that of the spin coating (3.9%). Furthermore, the annealing-free polymer solar cell (PSC) with high PCE were fabricated by the roller painting process with addition of a small amount of 1,8octanedithiol. Since the addition of 1,8-octanedithiol induces phase separation between P3HT and PCBM and the roller painting process induces crystallization of P3HT and PCBM, the PCE of roller painted PSC is achieved up to 3.8% without post-annealing.