Percolation and high-frequency hopping in cluster compounds and polymers

In strongly disordered solids the complex conductivity has a remarkably uni form dependence on the number of carriers, temperature and frequency. Still , as we illustrate for randomly packed molecular cluster compounds, it is p ossible to derive the relevant hopping parameters. In particular the analys is of the transition from phonon- to photon-assisted hopping in the pair li mit, when combined with the low-frequency data, yields precise information. In polymer blends and conjugated polymers the charge mobility behaves in a qualitatively similar way, but its temperature and frequency dependences d eviate from the almost universal behaviour in the fully random systems. We show how these differences relate to the mesoscopic structure.