Electron transport in a high-mobility conjugated polymer: the role of uncorrelated disorder and correlated disorder

In this paper, the electron transport and spatial correlation between the site energies in a high-mobility n-type conjugated polymer poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diy1]-alt-5,5'-(2,2'-dithiophene)} (N2200) are investigated. It is found that consistent descriptions for the thickness dependent and temperature dependent current density versus voltage (J - V ) characteristics of N2200 electron-only devices can be obtained by using the extended Gaussian disorder model (EGDM) and the extended correlated disorder model (ECDM), within which the mobility depends on the electric field and carrier density and within which spatial correlations between the site energies are absent or are included. Based on a comparison of the model parameters as obtained from both models with the typical value of organic semiconductors, we find that the width of the Gaussian density of states from two models is considerably smaller than usually obtained for conjugated polymers and the intersite distance found using the ECDM (0.4 nm) is unrealistically small, which indicate a high electron mobility and a spatially uncorrelated Gaussian disorder in N2200, respectively.