Domain structure and electronic state in P3HT:PCBM blend thin films by soft X-ray resonant scattering

We performed soft X-ray resonant scattering experiments on poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-buteric acid methyl ester (PCBM) blend thin films to reveal the domain structure and electronic state, where P3HT and PCBM mean regioregular poly (3-hexylthiophene) and [6,6]-phenyl-C61-buteric acid methyl ester, respectively. We measured two films, where chloroform (CF sample) and 1,2-dichlorobenzene (DCB sample) are used as solvents in the fabrication process. There is negligible X-ray incident angle dependence of the X-ray absorption spectra at the S K-absorption edge in the CF sample, whereas the DCB sample exhibits clear incident angle dependence. We obtained the wave-number resolved spectra at Q = (1, 0, 0) for P3HT molecules in both samples. The packing growth of P3HT molecules is revealed to be much more developed in the DCB sample than in the CF sample. In addition, the electronic structure at local sulfur element sites clearly changes for both the samples.