- they have a conductivity that is activated in temperature
- there is an energy gap of several eV to the lowest optically excited state
- they can be used to make "semi-conductor type" devices
On the other hand, they have properties that are significantly different from inorganic semiconductor materials. These all relate to the fact that electronic states tend to be localised on single molecules whereas in inorganic semiconductors one can have states which are delocalised over many atoms.
- they do not have well-defined conduction and valence bands (e.g., their mobility is almost always much less than that required for band transport) [just because you can calculate something does not mean it exists!]
- they have a mobility that is thermally activated
- energy gaps associated with optical absorption and conduction are significantly different
- electronic correlations significantly modify the ordering of electronic states (e.g. there is a large gap between singlet and triplet excited states)
Because there is no band transport one cannot define a scattering time and one should not talk about "band bending" near an interface.
I think that referring to these materials as organic semiconductors has led a lot of confusion and debatable reasoning in the literature. I think "organic electronic materials" or "organic photonic materials" is much more appropriate.