Highly Efficient Perovskite Solar Cells with Gradient Bilayer Electron Transport Materials

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Electron transport layers (ETLs) are critical for efficient charge extraction in perovskite solar cells (PSCs).
• Proper energy level alignment between the ETL and perovskite absorber is key to achieving high open-circuit voltage (V_OC) and short-circuit current.
• Planar heterojunction architectures require precise control over interfacial properties.

Purpose of the Study:

• To systematically investigate the impact of fluorine (F) doping concentration in tin oxide (SnO₂) nanocrystal ETLs on the band offset with perovskite absorbers.
• To optimize ETL/perovskite band alignment for enhanced charge carrier transport and electron extraction.
• To improve the overall performance of planar heterojunction PSCs.

Main Methods:

• Fabrication of planar heterojunction PSCs utilizing SnO₂ nanocrystal ETLs with varying F doping levels.
• Systematic tuning of F doping concentration in SnO₂ to modify the band offset at the ETL/perovskite interface.
• Characterization of device performance, including open-circuit voltage (V_OC) and power conversion efficiency (PCE).

Main Results:

• Gradual substitution of F^- into the SnO₂ ETL effectively reduced the band offset between the ETL and perovskite absorber.
• A substantial increase in device V_OC was observed with increasing F doping.
• A power conversion efficiency of 20.2% with a V_OC of 1.13 V was achieved for PSCs employing an F-doped SnO₂ bilayer ETL.

Conclusions:

• Tuning the ETL/perovskite band offset via F doping in SnO₂ is a viable strategy to enhance PSC performance.
• Reduced band offset leads to improved built-in electric field and simultaneous maximization of V_OC and charge collection.
• This method offers a simple yet effective pathway for optimizing planar heterojunction PSCs.