OBSERVATION OF INTERFACE EXCITONS AND ENERGY-TRANSFER PROCESSES IN ANOLIGO-THIOPHENE MULTILAYER STRUCTURE

The optical properties of a three-layer organic heterostructure consis ting of thiophene(T4)/hexathiophene(T6)/tetrathiophene(T4) are investi gated by a variety of optical techniques. The optical spectra give str ong evidence for the formation of interface exciton states at the inte rface between adjacent T4 and T6 layers. To our knowledge this is the first time that interface excitons have been experimentally observed i n an oligothiophene multilayer structure. Furthermore, evidence of ene rgy transfer from T4 excited states to interface excitons and T6 state s is found. Electroluminescence experiments indicate charge confinemen t and efficient electron-hole recombination in the central T6 layer.