Electrochromic and electroluminescent displays-Chemical Gas Sensors

Electrochromic displays are based on the reversible oxidation or reduction of some materials when an external electric field is applied to them. Electrochromic materials must have a different color when oxidized or reduced. The CVD-ALD laboratory investigates electrochromic displays based on WO3 films of the following type:

Substrate / transparent and conductive layer / WO3 film / electrolyte / electrode

The substrate may be glass or some other transparent material (e.g., PET) and the electrode may be either metal or glass covered with a transparent and conductive layer (e.g., SnO2, ITO, ZnO).

Among the topics investigated in the CVD-ALD laboratory are: a) The adhesion of WO3 to the transparent and conductive layer and b) the nature of the electrolyte. The first is a very important issue since after a few cycles of discoloration-discoloration the WO3 detaches and the device is destroyed. The second is also an important issue as it relates to the reliability of the device (e.g., the use of aqueous electrolytes is not a reliable solution).

The operation of electroluminescents (EL) displays is based on the emission of light from the vibration of electrons in semiconductor grains with dimensions in the micro-nano-scale. These are usually ZnS granules doped with a metal (eg, Cu, Mg, etc.). The vibration is caused by the application of an external electric field on a "sandwich" of the form.

Substrate / transparent and conductive layer / EL layer / dielectric / electrode.

Within the CVD-ALD Lab. such devices are formed using commercially available HF materials and the possibility of maximizing light emission is investigated by testing various transparent and conductive materials and electrodes as well as the patterning of the various layers.

Many materials are easily reduced or/and oxidized depending on the chemical environment in which they are located and their electrical resistance changes with their oxidation state. Thus, by measuring the electrical resistance of these materials we can draw some conclusions about the composition of their chemical environment. Electronic sensors of the chemical environment have been on the market since the 1970s, however there are still many important problems to be investigated at both the basic and technological level.

Among the topics investigated in the CVD-ALD laboratory are: a) the testing of various metal oxides and sulfides as sensing elements. b) The effect of the microstructure of materials on sensing. c) An important technological issue that raises the cost of chemical sensors is the need to calibrate each component produced separately. In the framework of the collaboration of the laboratory with the Institute of Informatics and Telecommunications (ITT), an attempt is made to address the problem with methods of artificial intelligence (AI). (see also in Student Projects)

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