Theory of imbalanced electron-hole transport in conjugated polymers

Electron-hole symmetry in conjugated polymers is found to exist in not only the band structure but also the defect levels caused by structure disorder. The commonly observed higher hole mobility is explained by (1) the compensation of the hole traps by the unintentional background $p$ doping; and (2) the electron traps caused by oxidation. Higher electron mobility in N and O containing conjugated polymers is also explained. Carrier mobility is calculated as a function of doping condition and electric field. Balanced electron-hole transport is shown to be achievable by intentional $n$ doping.