Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 84: Poster Session - Solid-Liquid Interfaces: Reactions and Electrochemisty

O 84.3: Poster

Wednesday, March 18, 2020, 18:15–20:00, P2/EG

Exploiting TEMPOL as redox mediator in water-based DSSCs — •Roberto Fantin, Andreas Ringleb, Raffael Ruess, Daniel Holzhacker, and Derck Schlettwein — Justus Liebig University Gießen, Institute of Applied Physics

In recent years, water-based dye-sensitized solar cells (DSSCs) emerged as a valid alternative to traditional organic solvent-based DSSCs, to improve stability and environmental compatibility, and reduce overall costs. Thus, all the other components of the device should be tailored to water. In this work, an aqueous solution of 4−hydroxy−2,2,6,6−tetramethyl piperidinyloxyl (TEMPOL) was investigated as a study case in combination with photoanodes made of TiO₂ nanoparticles sensitized by a commercial dye, Y123. The multiple interactions occurring between electrolyte, photoanode, and cathode are highlighted. TEMPOL is a hydrophilic derivative of TEMPO, which is already known as a redox shuttle due to the fast and reversible charge-transfer kinetics. The interactions between TEMPOL and common additives in DSSCs such as 1−methylbenzimidazole and 4−tert−butylpyridine, needed to slow down recombination processes at the anode, dramatically change the reaction mechanism at the counter electrode (CE). Pt and PEDOT were tested on the CE to improve the reduction of TEMPOL⁺. Both types of CE were modified with an ionomer (Nafion) in an attempt to accumulate TEMPOL⁺. Full DSSCs were characterized by I-V curves and electrochemical impedance spectroscopy (EIS), while the CEs were separately studied by cyclic voltammetry (CV) in a symmetrical two electrode setup.