Abstract
Molecular electronics has lately attracted increasing attention due to some appealing features such as possibly very higher integration capabilities, their low production cost, flexibility in the substrate choice, and possibility for large-area deployment. Two parallel approaches characterize this field: on one side molecules can be contacted and their transport characteristics exploited to achieve electronic functionalities; on the other side existing device structures, as well as novel ones, can be realized using organic layers instead of or together with inorganic materials. While in the latter case theoretical investigations on such devices can be carried out on adapting conventional simulators to the new materials and physics involved, completely new tools have to be developed in the former case. In this chapter, the operational principles of molecular systems will be presented based on a series of theoretical results obtained from our groups. Challenges and perspectives are also discussed.