An assessment of the role of dipoles on the density-of-states function of disordered molecular solids

The effect of permanent dipoles on the density-of-states (DOS) function of an array of hopping sites is examined by summing the contributions of individual dipoles to the total potential at a given site. For relative dipolar site concentrations ≳0.1, the DOS function is of Gaussian shape. At lower concentrations, it approaches a Lorentzian. Good agreement with literature data on the dipolar contribution to the DOS function for hole transport in molecularly doped polymers and molecular glasses differing with regard to dipole moment and concentration of dipolar moieties is found.