Organic based optoelectronic devices have been the subject of increasingly wide investigation in the last three decades; in particular, the exploitation of molecular light emission upon charge injection and recombination (electroluminescence) in organic materials has been successfully carried out and organic light-emitting devices (OLEDs) have been recently put on the market. However, the basic chemical and physical processes are not completely understood and some more effort is necessary in studying new functional materials and new device structures in order to improve efficiency and lifetime, and to fulfil colour and cheapness requirements. In our group we carry on investigations on the electrical and optical properties of nanometric structured organic multicomponent films which are designed for application as the core element in OLEDs. Devices with suitable combinations of different pure or multicomponent films in layered structures are prepared and the their electroluminescence characteristics (spectrum, efficiency, lifetime, etc.) are measured. Investigation on the device degradation due to oxygen and moisture are also carried on. Luminescence quenching or enhancing due to molecules diffusing inside the solid layer are studied for devising applications as solid-state sensors.