Electrochemical, spectroelectrochemical, and electrochromic characterization of silicon(IV) phthalocyanine with axially ligated electropolymerizable 3,4-ethylenedioxythiophene moieties

Abstract

Poly(3,4‐ethylenedioxythiophene) (PEDOT) is the most popular conducting polymer in the field of optoelectronics. In this study, the electrochemical and spectral properties of the silicon(IV) phthalocyanine (SiPc) and of a PEDOT were combined, and the electrochromic property was imparted to SiPc by modification of the axial positions of the Si4+ cation of SiPc with 3,4‐ethylenedioxythiophene (EDOT) groups. For this purpose, SiPc-EDOT was synthesized and characterized as to its electrochemistry and spectroelectrochemistry in nonaqueous media. Three reversible reduction couples at −0.51, −0.92, and −1.62 V and two oxidation processes at 1.16 and 1.73 V were observed for SiPc-EDOT in dichloromethane (DCM) containing tetrabutylammonium perchlorate (TBAP). In situ spectroelectrochemical analysis showed that the reductions and the first oxidation process of SiPc-EDOT were Pc-centered and the second oxidation process was EDOT-centered. The EDOT-based redox process at 1.73 V triggered the coating of SiPc-EDOT on the electrode surface as the SiPc-PEDOT film due to the electrooligomerization of the oxidative cationic form of EDOT groups during the repetitive voltammetric cycles. The electropolymerized SiPc-PEDOT film on the different electrode surfaces (ITO, GCE, ITO/Nf) yielded a conjugated polymer, which was characterized by cyclic voltammetry, UV–vis spectroelectrochemistry, Raman and FT-IR spectroscopies. The EDOT modification of SiPc supplied boost electrochromic performance in large percent transmittance change (Δ%T = 50 %), high coloration efficiency (η = 530 cm2 C−1), fast response times, and high cycle stability.