Molecularly engineered tandem dye-sensitized solar cells achieving 11.02% efficiency through complementary sensitizer integration

Abstract

Tandem dye-sensitized solar cells (DSSCs) represent a promising avenue for advancing solar energy conversion through the molecular-level design of light-harvesting systems. In this study, we report a tandem DSSC architecture that integrates two chemically distinct sensitizers, triphenylamine-based organic dye MRSF-3 and benchmark ruthenium dye N719, selected for their complementary absorption and photophysical characteristics. The device employed a double-sided Pt electrode, with N719 in the top cell and MRSF-3 in the bottom cell, achieving a notable power conversion efficiency (η_cell) of 11.02%. Detailed electrochemical impedance spectroscopy (EIS) and Bode frequency analyses revealed enhanced charge separation, reduced recombination, and prolonged electron lifetimes compared to single-sensitizer systems, highlighting the synergy between the dyes at the molecular level. Thermogravimetric analysis (TGA) confirmed the high thermal stability of both sensitizers, supporting their potential for long-term application. This study provides molecular-level insights into light-induced charge dynamics in hybrid systems and demonstrates how rational photochemical design can optimize light absorption and electron transfer in photoactive molecular assemblies. Our findings contribute to the fundamental understanding of photochemical processes in tandem architectures and underscore their potential in efficient solar energy conversion.