Device Postannealing Enabling over 12% Efficient Solution-Processed Cu₂ ZnSnS₄ Solar Cells with Cd²⁺ Substitution

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Kesterite Cu₂ZnSnS₄ is a cost-effective photovoltaic material.
• Current efficiencies are limited by low open-circuit voltage and fill factor due to defects and interface issues.

Purpose of the Study:

• To improve the performance of Cd-alloyed Cu₂ZnSnS₄ thin-film solar cells.
• To investigate the effects of a postannealing procedure on device performance.

Main Methods:

• A postannealing treatment was applied to complete the Cd-alloyed Cu₂ZnSnS₄ device.
• Analysis of element interdiffusion and defect reduction was performed.

Main Results:

• Postannealing enhanced indium tin oxide performance and promoted interdiffusion of Cu, Zn, In, and Sn.
• Improved interfacial carrier densities and band alignment for carrier transport were observed.
• Reduced interface traps and deep-level defects led to decreased nonradiative recombination.

Conclusions:

• The postannealing procedure effectively improved the open-circuit voltage and fill factor.
• A power conversion efficiency exceeding 12% was achieved for pure sulfide-based kesterite thin-film solar cells.