Buried nano-structure and molecular aggregation state in ordered heterojunction poly(3-hexylthiophene)-based photovoltaics

The morphology of ordered heterojunction organic photovoltaics (OHJ-OPVs) interfaces was evaluated using synchrotron radiation small angle X-ray scattering and grazing incidence X-ray diffraction. [6,6$]-phenyl C61-butyric acid methyl ester (PCBM) was deposited on the line/space patterned poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film fabricated by nano-imprinting. After deposition of the PCBM film, the P3HT thin film retained the rectangular edge features of the imprinted mold, with some Gaussian broadening due to interdiffusion and partial phase mixing at the P3HT/PCBM interface. The P3HT main chains were oriented vertically in the nano-imprinted line pattern and showed π-π stacking along the line direction. PCBM nano-crystals exist throughout the OHJ-OPV thin film.