Photocurrent enhancement in dye-sensitized solar cells by polyimide covalent organic frameworks decorated with silver nanoparticles

Abstract

Covalent organic framework (COF), featuring in highly ordered conjugated hexagonal array architecture, gains much attention due to their application potential in emerging energy and optoelectronic technologies. Polyimide-based COF (PI-COF) has alkaline-hydrolyzable imide units that can serve as adsorption sites for the anchorage of metallic nanoparticles, particularly eye-catching for multifunctionality. In this study, Ag nanoparticles (Ag NPs) sizing 5 to 20 nm are evenly attached on the surface of spherical PI-COFs through alkaline hydrolysis, ion exchange, and reduction reactions. The Ag-decorated COF (COF@Ag) are doped into the titania photoelectrode of dye-sensitized solar cell (DSSC) to explore its multifunctionality for the photovoltaic performance. The DSSC with the doping of COF@Ag exhibits a power conversion efficiency of 8.03 % under simulated one sun illumination, outperforming that without the doping of COF@Ag (6.86 %) by an enhancement in the photocurrent from 15.14 mA cm⁻² to 17.31 mA cm⁻². Comprehensive analyses including dye loading, electrochemical impedance, electron kinetics, and light absorption confirms the multifunctionality of COF@Ag. Localized surface plasmon resonance (LSPR) of Ag NPs enhances the photocurrent, and host–guest interaction of COFs facilitates the charge injection and suppresses the charge recombination.