Hopping charge transport in disordered organic materials: where is the disorder?

Effect of energetic disorder on charge carrier transport in organic materials has been reexamined. A reliable method for mobility calculation and subsequent evaluation of relevant disorder parameters has been discussed. This method is well suited for a direct calculation of the magnitude of dipolar disorder $\sigma_\textrm{dip}$ in polar organic materials from the current transients. Calculation of $\sigma_\textrm{dip}$ for several transport materials with varying concentration of polar dopants gives concentration dependences that are in reasonable agreement with theoretical predictions. A possible solution of the puzzle concerning the disorder effect on the mobility temperature dependence has been suggested.