Electroluminescent (EL) devices with multilayer structures which are composed of two or three vacuum-sublimed dye films have been shown to exhibit high device performances. The working mechanism for charge-injection-type EL devices is reviewed and then the design of dye molecules used for hole transport, electron transport and emissive layers for multilayer EL devices are summarized. It is also demonstrated that the molecular design concept of dye films is applicable for the cases of polymerdispersed dye systems. The possibility of extension of the molecular design concept to polymers with chromophores in skeletons is discussed. In addition, the importance of the adoption of multilayer structures for obtaining high EL efficiency is discussed.

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Spin-coated thin films of cyclohexane-based liquid crystalline materials were used for the fabrication of electroluminescent diodes. Electroluminescence from single-component films of cyclohexane-based liquid crystalline materials was observed. Double component films composed of a cyclohexane-based liquid crystalline material and a conventional hole transport dye were shown to give improved electroluminescence performances, but emission was due to exciplexes composed of two components. Use of cyclohexane-based dye molecules was effective for suppressing the formation of inter-molecular complexes. The highest external quantum efficiency observed was 0.17%.

Organic electroluminescent(EL) diodes using spin-coat films of cyclohexane-based glass-forming liquid crystal (LC) materials were fabricated. The cyclohexane-based LC materials were found to be useful for EL diodes. Blending the LC materials with charge transport molecules was found to be a promising method for improving device performance. Conventional hole transport and electron transport molecules were found to show a tendency to form exciplexes with cyclohexanebased LC materials. This difficulty was overcome by the introduction of cyclohexane-based charge transport molecules. The EL quantum efficiency of 0.06% was attained in the single-layer devices with two-component blends.