Theoretical study of conjugated polyelectrolyte electron injection layers: Effects of counterions, charged groups and charge reversal

The molecular structures, electronic and charge-transport properties of three conjugated polyelectrolytes (CPEs) including PFPhCO2Na, PFPhSO3Na, and PFPhBIm4 are studied using the density functional theory with B3LYP functional. The charge injection and charge transport properties are investigated through the ionization energies, electron affinities, lowest allowed excitation energies, reorganization energies and electron transfer integrals. The electron/hole injections have great effect on the planarity of cationic/anionic CPEs. The band gaps of the CPEs do not vary significantly with the charged groups and counterions. Charge-transport properties show that the PFPhSO3Na and PFPhBIm4 are good candidates for electron-transport materials.