A combined experimental and theoretical study on the effect of doping and interface formation on Ppv-ether copolymer

We present a detailed optoelectronic and vibrational study devoted to the transformation from neutral to doped PPV-ether copolymer in both powder and thin film states. The full geometries were optimized with the density functional theory (DFT) for neutral and doped states, where a comparative geometric study was established. The lowest singlet excited-state geometries have been investigated by using the configuration interaction single (CIS/3-21G(d)) method. The absorption spectra are then calculated respectively on the basis of the ground- and excited-state geometries. Our calculation results are in close agreement with those available from experiments. The charge distribution and excitation energies of singly charged PPV-ether are calculated, where two subgap absorption features are found to dominate the optical spectrum correlated with the polaron picture. These theoretical results are compared to experimental optical data illustrated by iodine-doped PPV-ether. Next, we have performed a simulation to model the conformations and the electronic structure modifications of interface formation of PPV-ether copolymer thin film with calcium (Ca), magnesium (Mg), and aluminum (Al) metal as a cathode and indium tin oxide (ITO) as anode in polymer LEDs. By providing the optical parameter obtained and the chemical reaction at the interface, we present the energetic diagram near the interface and the energy position of the lowest occupied molecular orbital with respect to the electrode Fermi level.