Hole Transport in Di‐p‐Tolyl‐p‐Nitrophenylamine Doped Poly(styrene)

Abstract

Di-p-tolyl-p-nitrophenylamine (DTNA) is a highly polar donor molecule with a dipole moment of 5.78 D. Hole mobilities have been measured in DTNA doped poly(styrene) over a range of fields, temperatures, and DTNA concentrations. The results are described within the framework of a formalism based on disorder, due to Bassler and coworkers. In the disorder formalism, it is assumed that charge propagation occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. A key parameter of the formalism is the energy width of the hopping site manifold. For DTNA doped poly(styrene), the width is approximately 0.15 eV and independent of the intersite distance, or DTNA concentration. The width is described by a model based on dipolar disorder. The model is premised on the assumption that the width is determined by a dipolar component due to the DTNA molecule and a van der Waals component. The interpretation of the experimental results leads to the conclusion that the van der Waals component increases with increasing intersite distance.

Hole transport in polystyrene and polycarbonate doped with polar dopants

“…In accordance with [21], the hole mobility in the MDP specimen is 9 × 10 -12 m 2 /(V s) at a thickness of 9.7 μm. the time of flight in our experiments is that it is above 0.6 s, while the mobility is less than 1.6 × 10 -12 m 2 /(V s).…”

“…The calculation fully confirms an exponential decline in current with a slope of β 1 ≈ 0.68; however, in estimates of time of flight, the theory is in conflict with data from [21]. In fact, calculated curve 2 does not reveal the fea tures of flight, even at times of nearly 10 s. This out come is presumably related to the fact that determina tion of the parameters of the Gaussian order model for PS doped with DTNA was in fact performed in the mode of dispersion transport, as indicated in [21].…”

“…In addition, owing to the non stationary character of hole transport (strong inclina 0 t tion of the shoulder in Fig. 2 from [21]) and a differ ence in the thickness of samples (9.7 μm in [21] and 25 μm in our experiments), an additional decrease in divergence by a factor of 1.2-1.3 should be antici pated. Thus, there is no contradiction between the compared results.…”

“…(The divergence is less than twofold.) In regards to 50% DTNA-PS, the divergence in mobility relative to that from [21] has an apparent value at least a factor of 5.5 lower but, in fact, should be at least a factor of 3 lower owing to the Poole-Frenkel effect. In addition, owing to the non stationary character of hole transport (strong inclina 0 t tion of the shoulder in Fig.…”

“…3 and 5 as evidence for the establishment of quasi equilibrium in the system. For this purpose, we calculated the time of flight curves for four MDPs by using parameters of the Gaussian disorder model that were determined in terms of the dipolar disorder formalism [11,21] (Table 2).…”