Evaluating the Effect of Electron-Withdrawing Substituents on Properties of Bay-Substituted Perylene Diimides for Next-Gen Supercapacitors

Abstract

In recent years, perylene diimides (PDIs) have attracted significant research attention in energy storage systems. To expand on these uses, we report here the design, synthesis, and characterization of halo phenoxy-based bay-substituted perylene diimides (PDIs). The performance of these materials having extended π-conjugation is evaluated as an active electrode material in supercapacitors. The introduction of the different halo phenoxy groups viz. 2,4-difluoro phenoxy (DFP), 2,4-dichloro phenoxy (DCP), and 2,6-dichloro-4-fluoro phenoxy (DCFP) at the 1,7- and 1,6-positions of perylene diimides significantly modulate the structural, optoelectronic, and thermal properties of PDIs. Additionally, the density functional theory calculations showed that the type and location of halogen substituents profoundly impact the molecular planarity, dihedral angles, and electron-withdrawing ability, leading to tunable absorption and emission spectra. Cyclic voltammetry (CV), UV–vis spectroscopy, and fluorescence spectroscopy are used to precisely examine the optoelectronic characteristics of these materials. Furthermore, these synthesized PDIs demonstrated, the potential use as an electrode material for symmetric supercapacitors by achieving impressive specific capacitance values of approximately 221 F g⁻¹ (CV) and 163 F g⁻¹ (GCD) using a three-electrode system and 176 F g⁻¹ (electrochemical impedance spectroscopy), 127 F g⁻¹ (CV), and 116 F g⁻¹ (GCD) using a two-electrode system when 2,6-dichloro 4-fluoro phenoxy-based PDI (FCh1) was used as electrode material. Our findings provide valuable insights into the structure–property relationships of bay-substituted PDIs and pave the way for the development of high-performance optoelectronic materials.