Caracterización óptica y eléctrica de películas de PEDOT/PSS tratados con dopantes secundarios.

Abstract

"Desde el descubrimiento de los polımeros organicos conductores, en 1977, el desarrollo de dispositivos electronicos basados en este tipo de polımeros han sido de gran interes.El origen de este interes se basa en las propiedades inherentes de estos materiales, como su ligereza, flexibilidad mecanica, facilidad de procesado, ası como sus propiedades opto electricas. Debido al creciente desarrollo en la industrıa para la utilizacion de polımeros convencionales, el potencial de la utilizacion de polımeros organicos conductores a escala industrial es inimaginable. Entre los polımeros conductores mas sobresalientes, se encuentra el derivado del politiofeno poli(3,4-etilendioxitiofeno) (PEDOT). Las conductividades del PEDOT, por si solo, pueden alcanzar valores de hasta 600 S cm−1, es altamente transparente, electroquıcamente y termicamente estable. Sin embargo, el PEDOT tiene la gran desventaja de ser insoluble y, por lo tanto, es poco procesable. Esta desventaja pudo ser superada por medio de la utilizacion de poli(estiren sulfonato) (PSS), un polielectrolito soluble que hace la funci´on de dopante y dispersante. Como resultado se obtiene un complejo polimerico altamente procesable y con muy buenas propiedades fısicas y de formación de pelıcula, pero con una conductividad muy pobre (1-10 S cm−1). Posteriores avances en este campo nos llevan a la utilizacion de diferentes tipos de aditivos, o dopantes secundarios, para el incremento o manipulacion de la conductividad en pelıcula del sistema PEDOT/PSS. Sin embargo, a un existe controversia en la literatura acerca del mecanismo bajo el cual actuan estos dopantes secundarios, debido a la complejidad propia del sistema. Aunado a esto, no se ha hecho una adecuada clasificacion ni delimitacion de las condiciones bajo las cuales, estos aditivos pueden funcionar eficientemente. "

"Since the discovery of organic conductive polymers in 1977, their development applied to electronic devices has gained increasing attention due to the their light-weight, mechanical flexibility, and simple of processing as well as their optoelectronic properties. An advantage of these polymers is that their optoelectronic properties can be modified by designing the chemical function on the molecules, the alignment of polymers chains, and doping conditions. Not to mention, that all the development already made for the conventional polymer industry could be adapted on applications and processing of this new materials. Over the years, several promising polymer types have emerged. A breakthrough in this area was the synthesis of one polythiophene, the poly-3,4-ethylenedioxythiophene (PEDOT). The conductivities of PEDOT, by itself, can reach up to 600 S cm−1, its highly transparent and its electrochemically and thermally stable. Nevertheless, PEDOT has the huge flaw of being water insoluble, and as a consequence, it is not easy to process. Thisdrawback could be overcame by polymerizing it in combination with a water soluble and stable polyelectrolyte, poly(styrene sulfonate) (PSS). Thus, the PSS in the polymeric complex has two functions, to serve as a charge-balancing counterion of the PEDOT, and to disperse the PEDOT oligomers in the water. As a result, we have a polymeric system highly processable and with highly desirable mechanical and film properties, but with a really poor conductivity (1-10 S cm−1). Early progress in this field have shown that the conductivity of PEDOT/PSS can be considerably increased or manipulated with the addition of liquid solvents, or secondary dopants. Nevertheless, there is still controversy in the literature regarding the responsible mechanism for the conductivity enhancement due to the inherent complexity of this system. In addition, despite the large number of related publications, there is neither a proper classification of the mentioned additives nor the optimization of their usage."