Recombination and regeneration dynamics in FeNHC(ii)-sensitized solar cells

Area of Science:

• Materials Science
• Electrochemistry
• Photovoltaics

Background:

• Dye-sensitized solar cells (DSSCs) are a promising photovoltaic technology.
• Iron-based complexes offer a sustainable alternative to traditional ruthenium sensitizers.
• Understanding recombination and regeneration dynamics is crucial for improving DSSC performance.

Purpose of the Study:

• To investigate the recombination and regeneration dynamics in iron-NHC-sensitized DSSCs.
• To identify the factors limiting the efficiency of these devices.
• To explore the impact of electrolyte additives on device performance.

Main Methods:

• Fabrication and characterization of iron-NHC-sensitized DSSCs.
• Electrochemical impedance spectroscopy (EIS) to study charge transfer and recombination.
• Transient absorption spectroscopy to probe electron injection and regeneration dynamics.
• Performance testing under simulated solar illumination.

Main Results:

• Incomplete electron injection from the sensitizer to the TiO2 semiconductor was observed.
• Significant detrimental effect of photoinjected electron recapture by the triiodide (I3-) species in the redox electrolyte.
• The addition of specific additives to the electrolyte effectively suppressed recombination and improved electron regeneration.
• Achieved the highest efficiency recorded to date for an iron-based DSSC.

Conclusions:

• Electron recapture by the electrolyte is a major loss mechanism in iron-NHC-DSSCs.
• Electrolyte additives are critical for mitigating recombination and enhancing performance.
• This work demonstrates a viable strategy for optimizing iron-based DSSCs towards commercial viability.