Charge transport studies in electroluminescent biphenylyl substituted PPV derivatives using time-of-flight photoconductivity method

The charge transport properties in a series of electroluminescent biphenylyl substituted PPV derivatives, poly[(2-(3′-(p-2″ -ethylhexyloxyphenyl)phenyl)-1,4-phenylenevinylene) (MP-PPV), poly[2-(2′-phenyl-4′,5′-bis(3″-methylbutoxy))phenyl-1, 4-phenylene vinylene] (BP-PPV) and poly{[2-(4′,5′-bis(3″ -methylbutoxy)-2′-phenyl)-phenyl-1,4-phenylene-vinylene]-co-(9, 9-dioctyl-2,7-fluorenylene-vinylene)} (BPPPV-PF), have been studied using a time of flight (TOF) photoconductivity technique. The TOF transients for holes in these polymers were weakly dispersive in nature with a mobility of the order of ∼10^-5cm²/V s at room temperature. The temperature and field dependence of charge mobility has been studied and analyzed using the disorder formalisms (Bässler's Gaussian disorder model (GDM) and correlated disorder model (CDM)). The charge transport parameters, such as mobility prefactor, energetic disorder, positional disorder, and the average intersite distance, were estimated from the fit and correlated to the molecular structure of the polymer. The microscopic charge transport parameters derived for these polymers indicate that these biphenylyl substituted PPV derivatives have very good chemical purity and structural regularity, which is similar to the reported values for structurally related fully conjugated polymers with high chemical purity.