Correlation between charge-transfer complex formation and positional disorder in a binary donor–acceptor glass

We report on a novel binary glass consisting of an electron donor and an electron acceptor molecule. It contains up to 25% of charge-transfer complexes and displays excellent hole as well as electron transport properties. Charge carrier mobilities have been measured by time-of-flight for various donor–acceptor ratios and are discussed within the framework of the disorder model of Bässler and co-workers. The results demonstrate that the presence of the donor molecules has no influence on the electron transport properties. In contrast to this, the hole transport is apparently affected by dipolar interactions between donor and acceptor molecules. Surprisingly the highest nondiagonal disorder for hole transport of about $\text{Σ=5}$ is found in samples with similar amounts of donor and acceptor indicating that the formation of charge-transfer complexes causes additional positional disorder.