Solvent Engineering-Enabled Surface Defect Passivation in Cu₂ZnSn(S,Se)₄ Solar Cells with Low Open-Circuit Voltage...

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells are promising due to earth-abundant materials.
• Low efficiency is primarily caused by deep-level defects, limiting carrier diffusion length and increasing voltage deficit.

Purpose of the Study:

• To investigate a post-fabrication defect healing strategy for CZTSSe solar cells.
• To improve carrier diffusion length and reduce open-circuit voltage (V_oc) deficit.

Main Methods:

• Dip-coating CZTSSe films in dimethylformamide (DMF) solvent as a post-treatment.
• Utilizing Deep-Level Transient Spectroscopy (DLTS) to analyze defect densities and carrier diffusion length.
• Characterizing film morphology and grain size after DMF treatment.

Main Results:

• DMF treatment neutralized Cu_Sn antisite defects and improved film morphology (denser, smoother, larger grains).
• Carrier diffusion length increased from 93 nm (control) to 142 nm (champion device).
• Open-circuit voltage (V_oc) deficit decreased by up to 289 mV, leading to a champion device efficiency of 11.4%.

Conclusions:

• Solvent-assisted post-treatment with DMF is an effective method for defect healing in CZTSSe solar cells.
• This strategy significantly enhances device performance by mitigating deep-level defects.
• DMF treatment offers a viable pathway to improve the efficiency of kesterite solar cells.