Hole mobility within arylamine-containing polyfluorene copolymers: A time-of-flight transient-photocurrent study

Abstract

We report a time-of-flight transient photocurrent study of the hole mobility, measured as a function of electric field and temperature, within (i) poly(9,9-dioctylfluorene), (ii) poly(9,9-dioctylfluorene-co-bis-$N,N$-(4-butylphenyl)-bis-$N,N$-phenyl-1,4-phenylenediamine) (PFB), and (iii) three copolymers that contain differing proportions of the moieties 9,9-dioctylfluorene, $N$-(4-butylphenyl)diphenylamine, and bis-$N,N$-(4-butylphenyl)-bis-$N,N$-phenyl-1,4-phenylenediamine. The results are analyzed using the Gaussian disorder model as proposed by H. B\"assler [Phys. Status Solidi B 175, 15 (1993)], the correlated disorder model as proposed by S. V. Novikov et al. [Phys. Rev. Lett. 81, 4472 (1998)], and finally, the polaronic correlated disorder model of R. E. Parris et al. [Phys. Rev. Lett. 87, 126601 (2001)]. We deduce values for the corresponding energetic and spatial disorder parameters, intersite hopping distance, wave-function decay constant, and polaronic activation energy, and consider how variations in chemical structure impact thereon.