Observation of Oriented Organic Semiconductor using Photo-Electron Emission Microscope (PEEM) with Polarized Synchrotron

We have developed photoelectron emission microscope (PEEM) system with excitation of linearly polarized synchrotron X-rays at 30° incidence angle arrangement. The morphology, electronic structure, orientation for P3HT:PCBM hybrid films have been investigated using the PEEM instrument. The sulphur 1s near-edge X-ray-absorption fine structure (NEXAFS) spectra at micro-domains were obtained, where sulphur atoms of thiophene ring were detected. The nature and symmetry in the S 1s excitations of P3HT model cluster were elucidated by DFT calculations that we performed to assign resonant peaks in absorption spectra. We demonstrate that the orientation at micro-domains can be deduced from photon-energy dependencies of PEEM images.