Correlating Molecular Precursor Interactions with Device Performance in Solution-Processed Cu₂ZnSn(S,Se)₄ Thin-Film...

Area of Science:

• Materials Science
• Photovoltaics
• Solution-processed thin films

Background:

• Improving crystal quality of copper zinc tin sulfide selenide (CZTSSe) absorbers often relies on complex pre- and post-processing methods.
• Tuning chemical interactions within precursor inks before thin-film deposition is an under-explored area for CZTSSe optimization.

Purpose of the Study:

• To investigate the influence of precursor ink complexation on the crystallization and optoelectronic properties of CZTSSe absorbers.
• To establish a link between solution-phase chemistry and the performance of CZTSSe-based solar devices.

Main Methods:

• Systematic variation of thiourea to metal cation ratios (TU/M) in dimethylformamide (DMF) and isopropyl alcohol (IPA) based inks.
• Analysis of nanoscale metal-organic complex and aggregate formation in precursor solutions.
• Correlation of precursor film morphology with grain growth and absorber structure after reactive annealing.
• Device performance evaluation based on varying precursor ink compositions.

Main Results:

• Formation of nanoscale metal-organic complexes and submicron aggregates in precursor inks is directly influenced by TU/M ratios.
• Precursor film morphology, dictated by solution complexation, significantly affects grain growth and absorber structure post-annealing.
• Power conversion efficiency of CZTSSe solar cells improved from approximately 2% to 8% by optimizing TU/M and Cu/(Zn + Sn) ratios.

Conclusions:

• Solution-phase complexation of metallic and chalcogen precursors is a critical factor for achieving high-quality CZTSSe absorbers.
• Controlling precursor chemistry offers a more reproducible and effective route to enhance CZTSSe thin-film solar cell performance.