Light-Induced Performance Enhancement of Supercapacitors through Thiol-Ene Click Surface Functionalization of Thienothiophene-BODIPY Porous Polymers

Abstract

Photoassisted supercapacitors are emerging as next-generation energy storage devices that synergistically combine light harvesting and electrochemical energy storage. BODIPY-based semiconductors, known for their strong light absorption, tunable electronic properties, and photostability, have recently attracted attention as efficient photoactive components in such systems. This study investigates the potential use of cross-linked thieno[3,2-b]thiophene-BODIPY polymer as an electrode material for photoassisted supercapacitors, prepared through a surface functionalization approach using thiol-ene click chemistry. The polymer exhibited broad-band absorption and a low band gap due to extended conjugation, as confirmed by UV-vis and fluorescence spectroscopy, along with comprehensive optical, electrochemical, and morphological characterization. DFT calculations showed that the HOMO-LUMO energy gap narrows under illumination, indicating improved charge transport. Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) measurements confirmed that the cross-linked polymer offers high capacitance, low internal resistance, and long cycle stability. In terms of supercapacitor performance, a photoinduced enhancement of up to 50% in specific capacitance was observed under light. At a current density of 1.0 A/g, the specific capacitance increased from 240 F/g in the dark to 362 F/g under illumination. Stability tests conducted over 2000 cycles demonstrated that the supercapacitor retained 90% of its initial capacitance.