How the Ge Incorporation Approach Affects Non-radiative Recombination Losses in CZTSSe Thin-Film Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Kesterite thin-film solar cells (TFSCs) show promise but lag behind CdTe and Cu(In,Ga)Se2 due to non-radiative recombination.
• Unstable tin (Sn) ionic states are a primary cause of poor performance and recombination losses in kesterite devices.

Purpose of the Study:

• To investigate the role of germanium (Ge) doping in kesterite compounds by varying its position in stacked metallic precursors.
• To clarify how Ge influences Sn-related defects and non-radiative recombination using real-time external radiative efficiency (ERE) mapping.

Main Methods:

• Employing Ge doping at different positions within stacked metallic precursor layers for kesterite thin films.
• Utilizing real-time external radiative efficiency (ERE) mapping to assess radiative efficiency and defect behavior.
• Analyzing the impact of Ge stacking order on alloying, defect density, grain growth, and ERE.

Main Results:

• Ge doping position influences alloying behavior, Sn-related defect density, and grain growth in kesterite films.
• Spatial ERE mapping demonstrates that Ge stacking order affects ERE signal average and uniformity.
• Incorporation of Ge leads to reduced non-radiative recombination and increased open-circuit voltage.

Conclusions:

• Ge doping is an effective strategy to mitigate Sn-related defects and non-radiative recombination in kesterite TFSCs.
• ERE mapping is a valuable tool for assessing non-radiative losses and guiding device development.
• Optimizing Ge incorporation can significantly improve the power conversion efficiency of kesterite-based solar cells.