Development of supramolecular dyes with application in optoelectronics

LUIS OTERO; MIGUEL GERVALDO; JAVIER DURANTINI; MARISA SANTOS; LORENA MACOR; GABRIELA MARZARI; LUCIANA FERNANDEZ; EDGARDO DURANTINI; DANIEL A. HEREDIA; FERNANDO FUNGO; K.-T. WONG; E. BAREA; J. BISQUERT; T. DITTRICH

Nanotecnología para Energías en Latinoamérica

Society for Nanomolecular Photovoltaics

Año: 2012; p. 7 - 89

The development of new organic materials with applications in electro-optical devices isone of the most active fields of research in the last years. The continuous growing ofworldwide requirements of environmental friendly energy sources has led to a greaterincrement in the research for new solar energy conversion devices. In this frame, dyesensitizedsolar cells (DSSCs) are one of great research interested systems all around the world.A crucial issue in DSSC design is the used dye. Until now, Ru(II) polypyridyl complexes stilldominated the most successful systems. However, the limited availability and environmentalissues could limit the extensive applications of Ru-based DSSCs. Furthermore, Ru-based dyesare expensive and hard to purify as compared to organic sensitizers. Thus, the search of newhighly efficient dyes is one of the most active research subjects in DSSCs development. Organicdyes exhibit many advantages, such as the huge diversity of molecular structures and thepossibility of obtaining materials at relatively low cost. Moreover, organic dyes normallyexhibit high molar extinction coefficients as compared to those of Ru dyes (< 20 000 M-1 cm-1),allowing to use thinner nano-structured oxide semiconductor films with comparable lightharvestingefficiency, a key factor in solid-state DSSC development. (1-3)On the other hand, the use of organic polymers in electronic and optoelectronic holds theadvantages to obtain large area flexible devices, replacing rigid Si and glass substrates. It isexpected that the use of polymers will introduce a significantly advance in the constructionand application of devices for energy generation, image display, lighting systems and others.The improvement and application of flexible devices are directly associated to thedevelopment of new suitable materials and deposition processes. At present two majorapproaches are used to deposit optoelectronic organic materials layers: thermal evaporationand solution processing. Although thermal evaporation through the use of mask can producewell-ordered patterned films, the throughput is slow and involves expensive vacuum systems.Also, thermal evaporation demands materials with sublimation capability and excellentthermal stability, properties that are not easy to obtain in polymers. Furthermore, low-costsolution processes, as spin coating, deep coating and drop coating, usually produce nonpatternedfilms that cover the entire substrate. A promising technique for conducting polymerfilm production is the electropolymerization of electroactive monomers. The polymer filmsmade through this way is an alternative and attractive film formation method to build highlyefficient optoelectronic devices. The formation and characterization of a series of polymerfilms with optoelectronic properties obtained by electropolymerization will be showed.Polymers containing porphyrins, a powerful optical and redox active center, were synthesizedand analyzed in our laboratory. Likewise, polymers with electron donor-acceptor moieties,linked by fluorene centre were developed and applied in electro-optical devices. (4-6)