High-Efficiency Polycrystalline Thin Film Tandem Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• Tandem solar cells combining perovskite and CIGS layers offer a promising route to higher efficiencies.
• Limited efficiency in current perovskite/CIGS tandem devices is attributed to challenges in fabricating near-infrared (NIR)-transparent perovskite top cells.
• Efficient transmission of sub-band gap photons to the bottom cell is crucial for tandem device performance.

Purpose of the Study:

• To develop a fabrication process for NIR-transparent perovskite solar cells.
• To improve the efficiency of perovskite/CIGS tandem solar cells.
• To explore the potential for achieving higher efficiencies in future tandem solar cell designs.

Main Methods:

• Fabrication of NIR-transparent perovskite solar cells.
• Characterization of perovskite solar cell performance, including power conversion efficiency (PCE).
• Measurement of sub-band gap transmission spectra for perovskite cells.
• Integration of NIR-transparent perovskite top cells with CIGS bottom cells to form tandem devices.
• Testing of the complete tandem solar cell devices.

Main Results:

• Achieved perovskite solar cell power conversion efficiencies of up to 12.1%.
• Demonstrated an average sub-band gap transmission of 71% for photons between 800-1000 nm.
• Fabricated a perovskite/CIGS tandem solar cell with a record 19.5% efficiency.
• This represents the highest reported efficiency for a polycrystalline thin-film tandem solar cell.

Conclusions:

• The developed NIR-transparent perovskite solar cells are effective for perovskite/CIGS tandem devices.
• The record efficiency of 19.5% highlights the potential of this tandem architecture.
• Future developments could lead to tandem solar cells with efficiencies exceeding 27%.