Effect of solvent annealing on the crystallinity of spray coated ternary blend films prepared using low boiling point solvents

The effects of different post treatments on the spray coated P3HT:PPV:PCBM for an active layer in polymer solar cell were investigated using atomic force microscopy (AFM), UV–vis spectroscopy, photoluminescence (PL) spectroscopy and X-ray diffractometer (XRD). The annealing temperatures were varied from 130 °C to 150 °C and the annealing time was kept constant for 10 min. The RMS roughness of the sample that dried in the ambient condition was lower compared to other samples. This explained that the samples that undergo solvent and thermal annealing treatment had higher crystallinity of P3HT or phase separation in these samples is mostly favored. The peak absorption for P3HT:PPV:PCBM thin film is higher compared to P3HT:PCBM thin film. The better defined shoulders can be observed in the samples with solvent annealing treatment. The XRD spectra showed that the structure of the samples will evolve with high thermal annealing temperature (150 °C) due to a weak intermolecular force in P3HT molecules. This will contribute to the low crystallinity of the films which consequently affects the absorption properties of the films.