Synergistic Cosensitization and Redox-Triggered Interfacial Engineering for Efficient and Durable Solar Cells

Achieving long-term stability along with high power conversion efficiency (PCE) remains a critical challenge for dye-sensitized solar cells (DSCs). Herein, we report a synergistic strategy that combines cosensitization and redox-active interfacial engineering to enhance the performance and durability of DSC. A narrow-energy-gap sensitizer (H4) is paired with a complementary blue-light-absorbing dye (H15), which possesses a strong absorption at ∼410 nm and a prolonged excited-state lifetime, thereby compensating for the spectral response and reducing interfacial charge recombination in cografted titania films. Simultaneously, we introduce a hypervalent iodine(III) compound, 1-acetoxy-1,2-benziodoxol-3(1H)-one (IBA), into a cobalt-based electrolyte. Initially, the introduction of IBA facilitates fast oxidation of the triphenylamine electron donor in H4, generating free radicals and enhancing intramolecular charge transfer. Importantly, the redox byproduct 2-iodobenzoic acid (IA) plays a critical role in suppressing interfacial recombination and passivation by coordinating with lithium ion and forming halogen-bonded complexes with electrolyte additives. The synergistic effects of cosensitization and the IBA additive in the electrolyte yield a cosensitized DSC with a PCE of 12.84%, featuring excellent operational stability under indoor light soaking for 1000 h. Moreover, the control device achieves an efficiency of 25.81% when tested under indoor light (4500 lx) illumination.