A Generic Strategy to Stabilize Wide Bandgap Perovskites for Efficient Tandem Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Efficient wide bandgap perovskite solar cells (PSCs) are crucial for advancing tandem solar cell technology.
• Current WBG PSCs suffer from photovoltage losses and phase segregation, limiting their performance and stability.

Purpose of the Study:

• Investigate the root cause of halide segregation in WBG PSCs.
• Develop a strategy to mitigate phase segregation and improve cell efficiency and stability.

Main Methods:

• Utilized Kelvin-probe atomic force microscopy to analyze the perovskite/C60 interface.
• Developed a surface reaction method using ethanediamine dihydroiodide (EDAI2) to treat residual lead iodide (PbI2).

Main Results:

• Identified aggregated PbI2 at the perovskite/C60 interface as a key driver of halide segregation.
• The EDAI2 surface treatment effectively mitigated phase segregation, improving photovoltage by ~100 mV across various WBG PSCs.
• Achieved champion efficiencies of 23.1% for 1.67 eV cells and 19.7% for 1.75 eV cells.
• Demonstrated a 26.1% efficiency in a monolithic all-perovskite tandem cell.

Conclusions:

• Surface treatment of PbI2 is a viable strategy to suppress halide segregation in WBG PSCs.
• This method significantly enhances photovoltage and efficiency, paving the way for improved perovskite-based tandem solar cells.