Resonant inelastic x-ray scattering studies of the organic semiconductor copper phthalocyanine

We report resonant inelastic x-ray scattering (RIXS) measurements on polycrystalline and single crystal samples of the organic semiconductor {beta}-copper phthalocyanine (CuPc) as well as time dependent density functional theory calculations of the electronic properties of the CuPc molecule. Resonant and nonresonant excitations were measured along the three crystal axes with 120 meV resolution. We observe molecular excitations as well as charge-transfer excitons along certain crystal directions and compare our data with the calculations. Our results demonstrate that RIXS is a powerful tool for studying excitons and other electronic excitations in organic semiconductors.