Nanoengineering of organic semiconductors for light-emitting diodes: control of charge transport

The effect of intermolecular interactions on the properties of organic semi conductors is investigated using a family of conjugated dendrimers as model systems. Increasing the amount of branching, or generation number, of thes e molecules reduces the degree of interaction between the chromophores. The effect of this on both photophysical and charge transporting properties is reported. It is found that an increase in generation gives rise to a reduc tion in the red tail emission of the dendrimer. Time of flight measurements show a slowing of charge transport with increasing generation, which is fo und to be related to the films becoming more insulating. The results show t hat dendrimer generation provides an elegant way of controlling intermolecu lar interactions. (C) 2001 Elsevier Science B.V. All rights reserved.