Improved expression of charge-carrier mobility in disordered semiconducting polymers considering dependence on temperature, electric field and charge-carrier density

The unified expression of mobility μ for semiconducting polymers based on the Gaussian disorder model is improved. The original expression was proposed by Pasveer et al. [W.F. Pasveer, J. Cottaar, C. Tanase, R. Coehoorn, P.A. Bobbert, P.W.M. Blom, D.M. de Leeuw, M.A.J. Michels, Phys. Rev. Lett. 94 (2005) 206601] and has non-Arrhenius temperature dependence ln(μ) ∝ 1/T2 at low carrier density. The improved one has Arrhenius temperature dependence ln(μ) ∝ 1/T at low carrier density, and can describe the dependence of mobility on temperature, carrier density, and electric field solved from the master equation model fairly well. Especially the precision at high carrier density and high electric field is prominently improved. The formalism is applied to solve diffusion current equation and Poisson equation for the NRS-PPV and OC1C10-PPV polymers. By adjusting three parameters, the calculated current–voltage curves are in good agreement with the experimental data. The results confirm recent claims of Preezant and Tessler [Y. Preezant, N. Tessler, Phys. Rev. B 74 (2006) 235202] that the dependence of mobility on electric field and charge density is important to correctly describe the electric properties of ordered polymers.