Photo-luminescence properties and exciton-carrier interaction in 1,2-diarylethylene derivatives films

New organic materials, 1,2-diarylethylene derivatives consisting of ortho-fused heterocyclic system like benzodithiophene (BDT) have been reported as candidates of thermally stable fluorescent materials, promisingly used in organic electro-luminescence devices. Optical properties of the compound possessing methyl or phenyl substituents in ethylene moiety are investigated. Photo-luminescence (PL) is observed at blue-green region accompanied by molecular vibrational structures. The quantum efficiency of the fluorescence in H-BDT toluene solution is estimated as 0.32 at room temperature. On the basis of quantum chemical calculation, the molecular structure and electronic structure are discussed. We also investigated the electronic and optical properties of H-BDT thin films prepared by sublimation method. For a preliminary single-layered device (ITO/H-BDT/Al:Mg), the I-V property and the effect of applied electric field on PL intensity were investigated and a possibility of the exciton-carrier interaction in the organic layer was pointed out.