Synergistic Co-sensitization: Unlocking the potential of carbohydrazide chromophores and metal complexes for high-performance dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have emerged as a promising alternative to traditional silicon-based photovoltaic devices due to their low-cost fabrication and tunable optical properties. One effective strategy to improve the light-harvesting capabilities of DSSCs is co-sensitization, which involves combining multiple dyes with complementary absorption properties. In this study, we report the co-sensitization of carbohydrazide-based organic chromophores, namely MRK-1–2, with a benchmark metal-complex dye (black dye) to enhance the photovoltaic performance of DSSCs. The synthesis of MRK-1–2 sensitizers is described, and their photophysical properties are thoroughly analyzed. The absorption spectra of the co-sensitizers revealed distinct absorption bands associated with intramolecular charge transfer and localized aromatic π-π* transitions. Sensitization by MRK-1–2 resulted in photovoltaic efficiencies ranging between 5.02–5.88 %. The ternary co-sensitization system of carbohydrazide-based chromophores (MRK-1–2 + black dye) showed promising potential for enhancing the short-circuit current density (JSC) (20.32–21.45 mA/cm2), open-circuit voltage VOC (691–729 mV), and overall power conversion efficiency (PCE) (9.52–9.90 %). This significant improvement in photovoltaic performance is attributed to the complementary light-harvesting abilities of the co-sensitizers, leading to enhanced light absorption and efficient charge separation and injection processes. The superior performance, with a (PCE) of up to 9.90 %, can be attributed to complementary light absorption, efficient charge injection facilitated by the carboxylic acid moiety in MRK-2, and suppressed charge recombination within the co-sensitized system. The findings of this study will contribute to the advancement of DSSC technologies and bring us closer to sustainable and renewable energy solutions.