Fundamental electronic properties of metal-organic contacts and organic-organic heterojunctions

The electronic transport and optoelectronic properties of crystalline and amorphous phases of π-conjugated organic molecular films have been extensively investigated over the past decade. This paper reviews about the formation of metal-organic (MO) interface barriers and their dependence on the (work function of the) metal. The work spans many π-conjugated molecular materials with different molecular configurations and with energy gaps ranging from 1.5 to more than 4.5 eV. Differences between organic-on-metal and metal-on-organic interfaces are also discussed. Electrically doping the molecular film leads to the formation of a narrow depletion region that allows tunneling of electron from the injecting contacts. this effective reduction in barrier leads to an injection current enhancement by up to 7 orders of magnitude.