Molecular engineering of diphenylamine-based co-sensitizers for enhanced photovoltaic performance in DSSCs: Achieving a 33 percent improvement over N719
摘要
In this study, we report a series of structurally engineered diphenylamine-based D-π-A sensitizers (AK-1 to AK-4) incorporating progressively stronger electron-withdrawing units. These dyes were co-sensitized with the benchmark N719 dye to achieve broader visible-light absorption, enhanced charge separation, and suppressed interfacial recombination. Photophysical analysis revealed significant bathochromic shifts and broadened absorption upon adsorption to TiO2, with AK-4 displaying the most red-shifted and intense spectrum owing to its carboxycyanoacetamide acceptor. IPCE measurements demonstrated maximum external quantum efficiencies of up to 88% for the AK-4/N719 co-sensitized device, outperforming the reference N719-only system by 33%. Electrochemical impedance spectroscopy (EIS) confirmed reduced charge recombination rates and higher recombination resistance in AK-3 and AK-4-based systems, correlating with enhanced open-circuit voltage and power conversion efficiency. Energy level analysis confirmed the suitable alignment of all dyes for efficient electron injection and dye regeneration, with deeper LUMO levels in AK-4 supporting superior charge injection kinetics. This study highlights the pivotal role of acceptor engineering and co-sensitization strategies in tuning the interfacial photophysics and maximizing the efficiency of DSSCs. The AK-4/N719 combination is a promising co-sensitization pair for high-performance next-generation DSSCs.
Graphical abstract