Engineering stable electrolytes with covalent organic frameworks to boost dye-sensitized solar cell efficiency

This study introduces a strategy to enhance the stability and efficiency of liquid electrolytes (LE) in dye-sensitized solar cells (DSSCs) by incorporating a covalent-organic framework (COF) as a functional additive. The triazine-based COF, synthesized via Schiff base condensation between melamine and terephthalaldehyde, features a porous network that encapsulates iodide/triiodide redox species. The LE + COF composite addresses major DSSC limitations, including electrolyte leakage, volatility, evaporation, sealing issues, limited stability, and poor transport charge. Electrochemical and photovoltaic analyses reveal that COF incorporation improves ionic conductivity and lowers charge transfer resistance at the electrode–electrolyte interface. DSSCs with LE + COF achieve an average power conversion efficiency (PCE) of 10.81 %, peaking at 11.74 %, with short-circuit current densities up to 18.60 mA/cm² under AM 1.5 illumination. Long-term stability tests at ∼23 °C show ∼95 % PCE retention after 960 h. Under indoor lighting (6024 ± 39 lx), LE + COF-based DSSCs outperform LE-only devices, delivering average and peak PCEs of 25.74 % and 27.40 %, compared to 23.69 % and 26.28 %, respectively. These findings highlight COF-based additives as a promising route toward efficient, durable DSSCs for both outdoor and indoor applications, particularly where low-light performance and operational longevity are critical.