Efficient Homojunction Tin Perovskite Solar Cells Enabled by Gradient Germanium Doping.

Area of Science:

• Materials Science
• Renewable Energy
• Photovoltaics

Background:

• P-type self-doping in tin-based perovskites hinders solar cell performance by increasing background current and carrier recombination.
• Addressing these limitations is crucial for advancing high-efficiency, stable lead-free perovskite solar cells.

Purpose of the Study:

• To mitigate P-type self-doping issues in tin perovskite solar cells.
• To enhance the power conversion efficiency and operational stability of tin-based perovskite solar cells.
• To provide a strategy for controlling energy levels in tin perovskite films for optoelectronic applications.

Main Methods:

• Fabrication of a gradient homojunction structure utilizing germanium doping in tin perovskite films.
• Implementation of density functional theory (DFT) calculations to elucidate the homojunction formation mechanism.
• Utilizing molecular-level characterizations to understand the underlying physical processes.

Main Results:

• The gradient homojunction structure effectively generates an internal electric field, depleting charge carriers.
• Demonstrated a reduction in perovskite dark current density by over two orders of magnitude and trap density by one order of magnitude.
• Achieved a power conversion efficiency of 13.3% with remarkable stability, retaining 95% efficiency after 250 min illumination and 85% after 3800 h storage.

Conclusions:

• The proposed gradient homojunction strategy successfully suppresses detrimental P-type self-doping in tin perovskite solar cells.
• This approach significantly enhances both the efficiency and long-term stability of lead-free perovskite solar cells.
• The findings offer valuable insights for designing advanced lead-free perovskite optoelectronic devices.