Desenvolvimento de filmes finos poliméricos para aplicação em dispositivos fotovoltaicos orgânicos

Abstract

This work presents the study of conjugated polymers and copolymers derivative from thiophenes, with promising properties to organic photovoltaic cells application (OPV). Initially, was realized the synthesis of the monomer 3-(4- fluorophenyl)thiophene (FFT), as well its characterization employing techniques as spectroscopy in infrared range( IV), resonance spectroscopy nuclear of protons (RMN of 1 H) and carbon 13 (RMN of 13 C), and gas chromatography coupled to mass spectroscopy (CG-MS) proving that the intended structure was obtained. In the next step, taking the synthesized FFT along commercial monomers and employing the chronoamperometry, the following polymers was obtained: the poly(3-(4-fluorophenyl)thiophene) (PFFT), poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3-phenylthiophene) (P3FT). Using the same process, two copolymers was obtained as well: the poly(3,4-ethylenedioxythiophene-co-3-phenylthiophene) (P(EDOT-co-3FT)) and poly(3,4-ethylenedioxythiophene-co-3-(4-fluorophenyl)thiophene) (P(EDOT-co-FFT)). The polymers and copolymers were successfully characterized using techniques of IV, absorption in the UV-vis region and fluorescence, thermogravimetry (TG), and scanning electron microscopy (SEM). It was observed that the monomer EDOT insertion to copolymer formation contribute for the charges stabilization, being the P(EDOT-co-3FT) the most electrochemical stable material and with lowest charge loss under electrochemical cycling.All the samples had their spectroelectrochemical studied and it was observed that the copolymers showed great potential application in OPVs. The color variation between the reduced and oxidized state was also observed, being that the PEDOT had changed from blue to dark blue, the P3FT from gray to red, and the PFFT from gray and red too. As for the copolymer P(EDOT-co-3FT) changed from blue to purple and the P(EDOTco-FFT) from dark blue to dark purple. The chrono absorptiometry allowed determinate important parameters for application in electrochromic devices, like electrochromic efficiency (), optical contrast (%T) and response time ().