Push-Pull copolymers in thin film for electronic application

Abstract

In this work, push-pull copolymers have been synthesized by electrochemical and chemical methods in order to fabricate new devices on flexible substrates, for electronic applications in several areas as electrochromism, solar cells and sensors. Electrochemical synthesis was employed to synthesize copolymers composed of acceptor (A) N,N -bis(2-octyldodecyl)-2,6-bis(5-(thioph-2-yl)thiophen-2-yl)naphthalene-1,4,5,8-bis(dicarboximide) (s-NDI2ODT4) and donor (D) ethylenedioxythiophene (EDOT) units on (indium tin oxide/polyethylene terephtalate) ITO/PET substrates, allowing for the fabrication of electrochromic devices, featuring an optical contrast of 29%. In the same way, it was possible to fabricate novel electrochromic devices by combining NDI2ODT4 with the novel system bis-thiophene fulleropyrrolidine (bis-Th2P-C60). Moreover, it was also possible to demonstrate that P(NDI2ODT4), P(bis-Th2P-C60), co(NDI2ODT4-bis-Th2P-C60) are good electron acceptor in planar heterojunction(PHJ)-based Organic Solar Cells (OSCs) with poly(3-hexylthiophene-2,5-diyl) (P3HT). Electrochromic devices and OSCs based on bis-Th2P-C60 combined with P(NDI2ODT4), do not show good results. This can be explained by the fact that bis-Th2P-C60 imposes a distortion of the main polymeric chain. In addition, the combination of fulleropyrrolidine (A) and thiophene (D) moieties in copolymers has shown to improve the morphology in thin film bulk heterojunctions (BHJs). In particular, the small percentages of a novel tetra-thiophene fulleropyrrolidine (Th4P-C60) copolymer acted as segregation modulators in BHJs based on P3HT mixed with Phenyl-C61-butyric acid methyl ester (PCBM) allowing to improve the state-of-the-art power conversion efficiency of plastic P3HT/PCBM OSCs up to 4.46 %. Finally, preliminary results are shown on the application of Th4P-C60 based systems electrochemically co-deposited with hemin molecules for the recognition of H2O2 in plastic electrochemical sensors. This gives interesting perspectives for the application of properly designed D-A copolymers and/or co-deposited systems for the recognition of those drugs developing H2O2 during their metabolism