Effect of defect-enhanced molecular oxygen adsorption on the imbalance of hole versus electron mobility in conjugated polymers

The generally observed higher hole mobility relative to electron mobility in conjugated polymers is explained with the defects and adsorbed molecular oxygen. Adsorption of the extrinsic molecular oxygen leads to that electrons are bound more tightly than holes by the traps in the originally symmetric electronic system. Hence, the mobility imbalance emerges from the asymmetric binding energies. Besides, the defects are the favored adsorption sites because the intermolecular attraction is enhanced due to stronger induced dipole-dipole interaction when gap defect levels appear.