A contrast enhancement for electroluminescent displays that uses optical interference is described. The reflection of ambient light from a display can be greatly reduced through the addition of thin-film optical components. In particular, a black layer system consisting of a dielectric layer and a thin absorbing layer is able to reduce the luminous reflectance from 75% to 3% when deposited next to the aluminum counterelectrode. Furthermore, with the addition of several other thin-film optical layers, the luminous reflectance can be decreased to 0.4% while also decreasing the sensitivity of the reflectance to the thicknesses of the electro-optic layers. Theoretical examples of different layer systems with and without optical components are provided. A prototype display that incorporates a black layer system was built, and a luminous reflectance of 3% was achieved.

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Different factors affecting the performance of alternating-current thin-film electroluminescent ͑ACTFEL͒ devices are discussed. The Chen-Krupka model of electron transport was applied to examine the case of non-uniform distribution of the dopant concentration in the active layer. Based on the results, a ZnS doping profile is proposed which incorporates higher doping at the interfaces than in the bulk. Also, the asymmetry in the excitation efficiency of electrons near the two insulator-semiconductor interfaces ͑ISIs͒ of ACTFEL devices was studied and was ascribed to the difference in the interface quality arising from the choice of insulating material and to the selection of the annealing process. The role of the space charge stored near the ISI and the influence of drive conditions on the operational characteristics of the device are discussed.

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