Using the combination of a layered perovskite compound (C6H5C2H4NH3)2PbI4 (PAPI), which forms a stable exciton with a large binding energy owing to its low-dimensional semiconductor nature and exhibits sharp and strong photoluminescence from the exciton band, and an electron-transporting oxadiazole derivative, we fabricated an organic–inorganic heterostructure electroluminescent (EL) device. The EL spectrum of the device corresponded well to the photoluminescence spectrum of the PAPI film; the emission was peaking at 520 nm and half-width of the emission was about 10 nm at liquid-nitrogen temperature. Further, highly intense EL of more than 10 000 cd m−2 was performed at 2 A cm−2 at liquid-nitrogen temperature in the device.

Organic electroluminescent (EL) devices with multilayered thin-film structures which emitted bright blue light were constructed. Two empirical guides for the selection of blue-emitting materials were established. The keys to obtain the EL cells with high EL efficiency were excellent film-forming capability of an emitter layer and the appropriate combinations of emitter and carrier transport materials for avoiding the formation of exciplexes. In one of our organic electroluminescent devices, blue emission with a luminance of 700 cd/m 2 was achieved at a current density of 100 mA/cm 2 and a dc drive voltage of 10 V.

We have succeeded in fabricating a novel thin-film electroluminescent device with a luminescent hole transport layer as an emitter. The cell structure is composed of an indiumtin-oxide substrate, a luminescent hole transport layer (emitter), an electron transport layer, and a MgAg electrode. The most essential feature of our device owes for adoption of an oxadiazole derivative as an electron transport layer. The emission intensity of 1000 cd/m2 was achieved at a current of 100 mA/cm 2 •

We have succeeded in the fabrication of a stable organic electroluminescent (EL) device with a three-layer structure; hole transport layer/emitting layer/electron transport layer. The EL device was prepared by vacuum evaporation. Efficient carrier double injection into the emitting layer was realized by the use of separate hole and electron transport layers. Bright EL emission was observed in a darkened room at the dc bias voltage of 50 V. Stable emission lasted for more than five hours at this condition. The emission spectrum could be changed with variation of the organic material for the emitting layer.

Oriented sexiphenyl (6P) film was prepared through epitaxial growth on rubbed substrates by vacuum deposition. Polarized absorption spectra demonstrated that the long axis of 6P molecule was highly oriented along the rubbing direction. Using the epitaxial growth film of 6P, we fabricated electroluminescent (EL) devices consisting of indium-tin-oxide anode, emissive layer of 6P, electron-transporting layer of an oxadiazole derivative, and MgAg alloy cathode. Owing to the orientation of 6P molecules, EL polarized in the rubbing direction was observed in the devices.