Increasing p-type dye sensitised solar cell photovoltages using polyoxometalates

Area of Science:

• Materials Science
• Electrochemistry
• Photovoltaics

Background:

• Dye-sensitized solar cells (DSSCs) are a promising photovoltaic technology.
• Improving the efficiency of DSSCs requires optimizing dye and redox mediator interactions.
• Polyoxometalates (POMs) are being explored as additives to enhance DSSC performance.

Purpose of the Study:

• To investigate the effect of Lindqvist polyoxometalate (POM) additives on the performance of p-type dye-sensitized solar cells (DSSCs).
• To understand the mechanisms behind the observed changes in photovoltaic parameters.
• To evaluate the suitability of POMs for different dye/electrolyte combinations.

Main Methods:

• Fabrication and characterization of p-type DSSCs with varying concentrations of Lindqvist POM additives.
• Electrochemical impedance spectroscopy (EIS) and charge lifetime measurements.
• Transient infrared (IR) spectroscopy to probe charge transfer dynamics.
• Analysis of open-circuit voltage (V_OC) and short-circuit current density (J_SC) variations.

Main Results:

• Lindqvist POM additives significantly increased V_OC by up to 140% in p-type DSSCs.
• Efficiency gains were substantial for poorly matched dye and redox mediator combinations.
• For well-matched combinations, V_OC increases were offset by decreases in J_SC.
• POMs were found to retard recombination and electron transfer to the mediator, shifting the NiO valence band edge positively.
• POMs exhibited a minor intrinsic sensitizing effect.

Conclusions:

• Lindqvist POMs are effective in increasing V_OC and overall efficiency for specific DSSC configurations.
• The performance enhancement is linked to suppressed recombination and modified charge transfer kinetics.
• Careful selection of dye/electrolyte systems is crucial when employing POM additives to avoid J_SC losses.