Fabricação e caracterização de células eletroquímicas emissoras de luz (LECs)

Abstract

One type of device that has attracted attention in recent years in the field of Organic Electronics are the Light Emitting Electrochemical Cells, better known as LECs (or LEECs) These electronic devices have low operating voltage, simple and inexpensive manufacture, high-performance, light independence of the material used as electrode or the thickness of its emissive layer, besides having the possibility to be manufactured on flexible substrates. For these reasons the LECs have been used as possible substitutes for known OLEDs (Organic Light Emitting Diodes), and the study of their optical and electrical properties, and its operating principle have been working focus of many scientists. Among the known models proposed to describe the operation of LECs we can name three: the Theory of Diffusion, the Theory of Electrochemical Doping, and the Mixed Theory. In the first, injection of carriers in the active layer would be facilitated by the ionic compounds present in the blend that makes up, with subsequent movement of charges by diffusion and recombination in the center of the layer. In the second model happens the formation of three layers within the polymer blend: A p-type doped region, a n-type doped region and an insulating layer where recombination occurs for emitting light. Mixed theory assumes that both are possible depending on the conditions in which the device is. In order to understand how these processes occur and interfere with the performance of these devices we have proposed several experiments changing important parameters in its manufacture. A model is proposed for the influence of the type of cation and anion used in the salt present in the active layer, and to describe the influence of the concentration of this salt in the polymer blend that makes up. Based on the theories described it is put in evidence the influence of the concentration of the ion carrier polymer in the emitter layer and the thickness of this layer. After all the study we obtained an optimized device that is compared with a device made with a new material synthesized by employees from the Chemistry Department of UFJF to generate expectations for future work.