A cobalt complex redox shuttle for dye-sensitized solar cells with high open-circuit potentials

Area of Science:

• Materials Science
• Renewable Energy
• Electrochemistry

Background:

• Dye-sensitized solar cells (DSSCs) present a viable alternative to conventional inorganic solar cells.
• The performance of DSSCs is often limited by the redox mediator, typically the iodide/triiodide (I3-/I-) system.

Purpose of the Study:

• To investigate molecularly engineered cobalt complexes as redox mediators in mesoscopic dye-sensitized solar cells.
• To explore an alternative to the conventional I3-/I- redox shuttle for improved DSSC performance.

Main Methods:

• Synthesized and characterized a cobalt complex with tridendate ligands, [Co(bpy-pz)2](3+/2+)(PF6)3/2, as a redox mediator.
• Fabricated mesoscopic DSSCs using the cobalt complex mediator and a cyclopentadithiophene-bridged donor-acceptor dye (Y123) adsorbed on TiO2.
• Measured photovoltaic performance under standard illumination (100 mW cm-2).

Main Results:

• Achieved an open-circuit voltage exceeding 1,000 mV in mesoscopic DSSCs.
• Attained a power conversion efficiency of over 10% with the cobalt complex redox mediator and Y123 dye.
• Demonstrated negligible absorption of the cobalt complex in the visible spectrum.

Conclusions:

• Molecularly engineered cobalt complexes are effective redox mediators for dye-sensitized solar cells.
• This cobalt-based system offers a competitive alternative to the traditional I3-/I- redox shuttle.
• Tuning redox properties through ligand substitution provides a pathway for further optimization of DSSCs.