Pyrazoline derivatives for blue color emitter in organic electroluminescent devices

Electroluminescence (EL) behaviors of four derivatives of pyrazoline as a d oping dye in EL device have been studied. Photoluminescence (PL) in solutio n and as solid films have also been studied. It was observed that the pyraz oline derivatives show very strong PL and EL. On the contrary, the non-cycl ic hydrazone compounds containing the same conjugated moiety as in pyrazoli ne do not emit strongly in solution or in solid state. The pyrazoline deriv atives with the phenyl group at the 5-position possess good film-forming pr operties, which might be due to their non-planar structure. On the other ha nd, the pyrazoline derivatives without the phenyl group at the 5-position a re more planar and thus aggregate easily. These properties lead to degradat ion in the device performance. (C) 2000 Elsevier Science S.A. All rights re served.