Effect of intermolecular disorder on the intrachain charge transport in ladder-type poly(p-phenylenes)

Abstract

We have studied the real and imaginary parts of the complex intrachain mobility of charge carriers on solid samples of ladder-type polymers using time-resolved microwave conductivity measurements. Experiments on samples with a different average polymer chain length show that the motion of charge carriers is limited by the chain ends. The experimental results can be described by one-dimensional diffusive motion along the polymer backbone. The intrachain mobility deduced for an infinitely long ladder-type polymer chain ͑with no barriers to charge transport such as defects or conjugation breaks͒ subject to interchain interactions is 30 cm 2 / V s. This value is 20 times lower than the intrachain mobility found for charges along infinitely long isolated ladder-type polymer chains in dilute solution. Thus we find that interchain interactions in solid samples severely decrease the intrachain charge carrier mobility. However, the intrachain mobility of 30 cm 2 / V s is more than four orders of magnitude higher than mobility values obtained from time of flight measurements reported in the literature. Hence, the performance of ladder-type polymers in optoelectronic devices can be significantly improved.

What determines the mobility of charge carriers in conjugated polymers?

“…The obvious conclusion is that in TOF studies the ratelimiting step is interchain hopping of carriers while the microwave conductivity is controlled by intrachain motion. More recently, the Delft group extended their work by analysing the real and imaginary part of the complex conductivity (Prins et al 2006a). The real part of the mobility corresponds to the velocity of charge carriers in phase with the oscillating electric field, i.e.…”

“…In a hypothetical infinite PDA chain, it would be zero. In their current work, Prins et al (2006a) investigated MeLPPP with chain repeat lengths varying from 13 to 54 in frozen solution and measured a value mZ30 cm 2 Vs K1 for long chains. They compared this value with that of isolated chains in solution and obtained a spectacular value of 600 cm 2 Vs K1 (Prins et al 2006b).…”

Conductive response of a photo-excited sample in a radio-frequent driven resonance cavity

“…22 The study of conjugate polymers was boosted with the introduction of laser pulses as an ionizing source. 23,24 TRMC is now being used routinely as a method to determine transient conductivities of a wide variety of materials, such as silicon-based composites for solar cells, [25][26][27][28] compound semiconductors, 29,30 columnar stacked molecular aggregates, [31][32][33][34][35][36][37][38][39] bulk solids or thin films of conjugated polymers, [40][41][42][43][44][45][46][47] and molecular wires in dilute solution.…”

On the Charge Carrier Time-of-Flight Mobility and the Ordering Effects in the Microcrystalline PEDOT/PSS Complex: a Morphology-Based Simulation Study

“…The mobility of charge carriers in an ordered crystalline material is determined by the bandwidth of the conduction band and experimentally determined by the time-resolved microwave conductivity measurements, leading to the detection of the intrachain mobility values in the ladder-type poly(p-phenylenes) of up to 30 cm 2 /Vs (Prins et al, 2006). Unfortunately, the analysis of the intra-chain mobility is outside of the possibilities of the approach presented here.…”