The paper presents known for above 60 years phenomenon of intrinsic electroluminescence and its practical use in modern light sources called light emitting capacitors or electroluminescent lamps. Applying polymer thick film technology the authors have realized multilayer electroluminescent structures (Destriau cells). The influence of various constructional factors and exploitational conditions (supplying voltage, temperature) on luminance level of structures was determined. The test results achieved are presented in the diagrams and tables. A few examples of applications of electroluminescent lamps in emergency and warning systems are reported.
An optoelectronic system, realizing the halfadder system, which can be used in the transmission and processing of signals in optical form, is described. The halfadder system has been realized based on photoconducting (PC) and electroluminescent (EL) thin film elements. The halfadder system should realize two logical functions: EX-OR and AND. In the presented paper the system realizing the EX-OR logical function, constructed by a suitable connection of eight photoconducting and five electroluminescent elements, and the system realizing the AND function composed of two photoconducting and one electroluminescent elements, are described. The dependences on time of the output signals were measured for various combinations of the input signals: L1=L2=0; L1=20 lx, L2=0; L1=0, L2=20 lx oraz L1=L2=20 lx. For the halfadder system the signal at the AND function output appeared only when both the input signals had the value corresponding to logical one, and at the EX-OR function output, when the input signals had various values (the first signal was zero, and the second was one or inversely). Thus the investigated system fulfilled the role of a halfadder realizing the function EX-OR, and the function AND, respectively.
Optoelectronic logical gates NAND and NOR are composed of thin film photoconducting and electroluminescent elements, made of cadmium sulphide and zinc sulphide respectively, doped with copper, chlorine and manganese. These gates consist of several photoconducting elements and one electroluminescent element connected in series or parallel, supplied with a sinusoidal voltage. In such a circuit the function of logical product or logical sum for input light signals illuminating the photoconducting elements is realized, and the output signal is the light emitted by the electroluminescent element. This output signal illuminates in turn the next photoconducting element being present in the second circuit, in which the NOT function is realized.
In many cases the physical properties measured using sensing elements require to multiply one of them by another. The multiplication can be realized in many ways, and in presented paper an optoelectronic system multiplying the electric signals, composed of electroluminescent diodes and photoconducting elements, is proposed. In the proposed system the linear range of the dependence of the luminance of electroluminescent diode on the current and the linear dependence of the conductance of photo-conducting element on the illumination are utilized. The output signal from the multiplying system can be an electric signal, or in another version can have the shape of a light signal, sent on by an optical fiber.
The increased utilization of various optoelectronic systems has generated interests in optoelectronic logical
circuits with photoconducting (PC) and electroluminescent (EL) thin film devices. They are frequently applied
as logical gates, amplifiers of weak light signals, and because of the optical feedback in such system, they can
work as memory cells.
An optoelectronic memory cell was constructed from two photoconducting (PC) and two electroluminescent (EL) devices. PC and EL devices were prepared by vacuum evaporation. This optoelectronic memory cell was supplied with a sinusoidal voltage. The input signal was in the shape of rectangular light pulses illuminating the PC device. The output signal was in the form of the light emitted from the electroluminescent device. Applied PC and EL devices within the optoelectronic memory cell ought to perform the determined condition, namely the optical feedback between them must exist. A value of the feedback coefficient ought to be such as to perform the bi-stable circuit operation.
Generally, dashboard information display devices can be divided into active and passive ones, i.e., emitting or modulating light. The thin film electroluminescent display devices belong to the former category. The new concept electroluminescent dashboard information display devices conceived by the author are presented in this paper. In this case, a DC and an AC power supply voltage are simultaneously applied. As a result, the DC voltage is essentially reduced to about 25 V DC. The electroluminescent information display device was prepared by vacuum methods on a glass substrate in the form of tri-electrode structure.