Hyperfine interaction vs. spin-orbit coupling in organic semiconductors

Organic semiconductors have shown magnetic field responses in electrical currents. This phenomenon has been generally attributed to hyperfine interaction (HFI) and spin-orbit coupling (SOC). For the first time, we report the experimental and theoretical studies on hyperfine interaction vs. spin-orbit coupling in one thin film of organic semiconductor poly [9,9-di- n -hexyl-fluorenyl-2,7-diyl] and the dramatic influence of doping the PFO with complexes of bis [2-(2′-benzothienyl)-pyridinato- N , C3′] iridium (acetyl-acetonate). The intra-molecular HFI and SOC are only dependent on the intra-molecular interaction among electrons, nuclei and orbital field in a given molecule. Phosphorescence and fluorescence spectroscopies were used to measure the spin-orbit coupling strength. Furthermore, HFI is a short-range interaction and inter-molecular HFI is negligible. Inter-molecular SOC depends not only on molecular structure but also distance between adjacent molecules. Inter-molecular SOC strength increases strongly when the distance between adjacent molecules is decreased. We report experimental and theoretical studies on hyperfine interaction vs. spin-orbit coupling in a thin film of organic semiconductor poly[9,9-di- n -hexylfluorenyl-2,7-diyl] and the dramatic influence of doping the PFO with bis[2-(2′-benzothienyl)pyridinato- N , C 3′]Ir(acac).