Field-dependent Transport Level and Mobility in Disordered Organics

An analytic description of electric field and temperature dependences of mobility is developed on the base of extended transport level concept in the framework of Gaussian disorder model, providing low concentration of charge carriers. Field-dependent percolation factor was used in an equation for transport level. Results are in good agreement with well-known Monte Carlo simulations at weak and moderate electric field strength (up to 106 V/cm at typical parameters), providing that energetically upward jumps still dominate conductivity. It is enough for most applications in organic electronics. Concentration dependence of a transport level is discussed.