Elemental Precursor Solution Processed (Cu_1-xAg_x)₂ZnSn(S,Se)₄ Photovoltaic Devices with over 10% Efficiency

Area of Science:

• Materials Science
• Renewable Energy
• Solid-State Physics

Background:

• Copper Zinc Tin Sulfide Selenide (CZTSSe) is a promising photovoltaic material.
• Open-circuit voltage deficit (V_oc,deficit) limits the efficiency of CZTSSe solar cells.
• Silver (Ag) substitution is explored as a strategy to mitigate V_oc,deficit.

Purpose of the Study:

• To investigate the effect of partial silver (Ag⁺) substitution for copper (Cu⁺) in CZTSSe thin films.
• To analyze how Ag substitution influences material properties and solar cell performance.
• To achieve enhanced power conversion efficiency in CZTSSe-based solar cells.

Main Methods:

• Fabrication of (Cu_1-xAg_x)₂ZnSn(S,Se)₄ (CAZTSSe) thin films using elemental precursors dissolved in a solvent mixture (1,2-ethanedithiol and 1,2-ethylenediamine).
• Controlled variation of the Ag/(Ag + Cu) ratio (x) during film formation.
• Characterization of CAZTSSe films to determine structural, optical, and electrical properties, including grain size, band gap, and depletion width.

Main Results:

• Ag substitution led to variations in grain size, band gap, and depletion width of the CAZTSSe layer.
• A significant enhancement in open-circuit voltage (V_oc) of approximately 50 mV was observed.
• Power conversion efficiency increased from 7.39% for x=0 (no Ag) to 10.36% for x=3%.

Conclusions:

• Partial Ag substitution is an effective method to reduce V_oc,deficit in CZTSSe solar cells.
• The optimized Ag content (x=3%) yields the highest power conversion efficiency reported for Ag-substituted devices to date.
• This approach offers a promising route for developing high-efficiency CZTSSe solar cells with impurity exclusion.