Selective Chain Alignment of Conducting Polymer Blend Films by an Ultrafast Laser

Tunable and selective areal polymer chain alignment method is developed for spin-cast blend films of poly(3-hexylthiophene)(P3HT):[6,6]-phenyl-C61-butlyric methyl ester (PCBM) system by a femtosecond laser process. The chain alignment, phase separation, and molecular structure of the laser exposed P3HT: PCBM films are investigated by grazing incidence wide angle X-ray scattering and micro-Raman analysis. The alkyl chains of P3HT polymer become highly ordered along the polarization axis of the laser. Thus, the amount of desirable face-on configuration for solar cell application is largely enhanced with a subsequent postannealing process. Vertically expanded morphology up to 200 nm on P3HT: PCBM films is also prompted by the laser irradiation without deteriorating intramolecular structure and changing chemical composition. Simultaneously, vertical phase separation of PCBM toward surface is induced at exposed region.