Achieving High Efficiency in Solution-Processed Perovskite Solar Cells Using C₆₀/C₇₀ Mixed Fullerenes

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Fullerenes are crucial electron-transporting layers (ETLs) in perovskite solar cells (PSCs).
• Current high-efficiency PSCs utilize thermally evaporated fullerene ETLs, a costly process.
• Solution-processed fullerene ETLs face challenges like high crystallinity and residual solvents, limiting efficiency.

Purpose of the Study:

• To identify limitations of solution-processed fullerene ETLs in PSCs.
• To develop a cost-effective, solution-processable fullerene ETL for high-efficiency PSCs.
• To enhance power conversion efficiency (PCE) in PSCs using mixed fullerene ETLs.

Main Methods:

• Characterization of solution-processed fullerene films (C60 and C70 mixtures).
• Fabrication of PSCs with mixed fullerene ETLs.
• Vacuum-drying treatment of the mixed fullerene ETL.

Main Results:

• Mixed C60/C70 fullerene films exhibit low crystallinity, overcoming a key limitation of solution processing.
• Mixed fullerene-based PSCs achieved PCEs of 16.7%, matching thermally evaporated C60 devices.
• Vacuum-drying the mixed fullerene ETL further boosted PCE to 18.0% by improving transmittance and charge transport.

Conclusions:

• A simple, low-cost, solution-processable mixed fullerene ETL is demonstrated for PSCs.
• This method offers comparable performance to expensive thermal evaporation techniques.
• The developed technique is adaptable for various solar cell architectures employing fullerene ETLs.