Waterproof India Ink-Coated Activated Carbon Sheet Counter Electrode for Quasi-Solid DSSCs: Stability Evaluation Under Indoor Light Conditions

Dye-sensitized solar cells (DSSCs) are promising for indoor battery-less applications thanks to their high performance in office light conditions. The rare and expensive Pt metal is conventionally used as a high-performance counter electrode (CE) material in DSSCs. Carbon-based material is expected to be an economical alternative to Pt. The stability of the carbon-based CE in DSSCs working in indoor conditions has not been widely evaluated. In this study, a commercially available waterproof India ink was coated on a flexible activated carbon sheet to make the CE of a quasi-solid DSSC. The fabricated CE was flexible and low cost and could produce comparable conversion efficiency to a control Pt-coated glass CE under AM1.5G illumination. Moreover, the operation stability of the fabricated CE was evaluated for 1200 h under 250 lx indoor light intensity. The stable maximum power output of 5.4 μW/cm 2 was obtained during the test period. In indoor light conditions, the DSSC using the fabricated CE showed higher output power density than that of the DSSC with the control Pt-coated glass CE.