Quantitative Disentanglement of Fill Factor Losses in Kesterite Solar Cells Via an Integrated Experimental-Simulation...

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Kesterite Cu2ZnSnS4 (CZTS) solar cells are promising earth-abundant alternatives to traditional photovoltaics.
• However, their lower efficiencies are linked to poor fill factors (FF) and open-circuit voltage deficits.
• The origins of FF losses in CZTS are complex and not fully understood.

Purpose of the Study:

• To establish an integrated experimental-simulation framework for quantitatively analyzing FF loss mechanisms in CZTS solar cells.
• To identify and disentangle the contributions of recombination, back-contact barriers, and carrier extraction to FF deficits.
• To demonstrate a method for mitigating FF losses and enhancing CZTS solar cell performance.

Main Methods:

• Utilized a combination of temperature-dependent photoluminescence, deep-level transient spectroscopy, impedance spectroscopy, and transient photocurrent/photovoltage measurements.
• Employed diode-equation-based modeling to quantitatively decompose FF losses.
• Investigated solution-processed sulfide CZTS solar cells, including Cd-alloyed and Ag-incorporated systems.

Main Results:

• The integrated framework successfully decomposed FF losses into contributions from defect recombination, Schottky barriers, and carrier extraction inefficiencies.
• Cd incorporation in CZTS suppressed Sn-related defects, eliminated back-contact barriers, and improved carrier collection.
• Cd-alloyed CZTS showed enhanced FF (65.2% from 53.9%) and efficiency (12.1% from 7.3%).
• Ag incorporation further validated the framework, achieving a high FF of 71%.

Conclusions:

• The developed framework provides a quantitative and generalizable approach for diagnosing FF losses in complex multinary semiconductors like CZTS.
• Alloying strategies, such as Cd and Ag incorporation, are effective in mitigating key loss mechanisms and boosting solar cell performance.
• This research offers a pathway for optimizing kesterite solar cell technology through targeted defect and interface engineering.