  Understanding the charge carrier transport in the disordered organic
molecular semiconductors is a fascinating and still unresolved problem in
modern condensed-matter physics, yet has an extremely important bearing on
their application in ``plastic'' based field effect transistor, light emitting
diodes and lasers. The most contentious issue in this subject is the nature of
the charge carriers i.e. whether they are bare electrons or dressed electrons,
known as polarons. Here we show for the first time, by means of simple
experiments that polaron moving in static disorder is responsible for charge
carrier transport in disordered molecular semiconductors.
