Charge collection and pore filling in solid-state dye-sensitized solar cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Dye-sensitized solar cells (DSCs) with solid-state organic hole-transporters achieve over 5% efficiency, but lag behind liquid electrolyte DSCs (>10%).
• Key limitations include charge recombination, transport rates, and effective infiltration of mesoporous titanium dioxide (TiO(2)) with organic hole-transporters like spiro-MeOTAD.

Purpose of the Study:

• To experimentally investigate the limiting factors affecting solid-state DSC performance.
• To elucidate the mechanisms of TiO(2) mesopore infiltration by spiro-MeOTAD and their impact on charge collection.

Main Methods:

• Small perturbation photovoltage and photocurrent decay measurements to analyze charge transport and recombination.
• Cross-sectional imaging and photo-induced absorption spectroscopy to study TiO(2) infiltration with spiro-MeOTAD.

Main Results:

• Electron diffusion length near short-circuit is up to 20 µm, but reduces to ~2 µm at biases near open-circuit potential, indicating ineffective charge collection.
• Optimized casting conditions for spiro-MeOTAD infiltration enabled efficient charge collection in devices thicker than 7 µm.

Conclusions:

• Ineffective charge collection, particularly at higher biases, and suboptimal composite formation limit solid-state DSC efficiency.
• Further research on composite formation and kinetic competition is crucial for realizing the full potential of solid-state DSCs.