Organic materials like oligophenyls, poly(para-phenylene) (PPP), and s
ome derivatives (ladder polymers) are used as the active layer of ligh
t emitting diodes (LEDs). The electrical characteristics of these devi
ces depend on the band structure of the organic layer as well as on th
e electrode materials. The optical and electrical LED performance is d
iscussed with regard to the electronic structure of the stratified dev
ice arrangement.