Performance enhancement of single-stage pulsed hybrid reactive magnetron sputtered Cu(In,Ga)Se2 solar cells via sodium pre-deposition treatment

We report the performance enhancement of single-stage grown Cu(In,Ga)Se 2 (CIGS) solar cells using a simple and scalable solution-processed sodium (Na) pre-deposition treatment. Na was incorporated via spin-coating of aqueous NaOH solutions with varying concentrations prior to CIGS growth by pulsed hybrid reactive magnetron sputtering (PHRMS). Morphology analysis revealed smoother surfaces and rounded grain edges with Na addition. Atomic force microscopy confirmed a reduction in surface roughness with Na incorporation. Kelvin probe force microscopy revealed a decrease in work function for Na-treated CIGS, indicating a Fermi level shift toward the conduction band, potentially reducing recombination by suppressing deep-level defects. The highest power conversion efficiency of 14.3 % was achieved for a 0.05 M Na-treated CIGS solar cell, compared to 10.1 % for the reference (untreated) device. At higher Na concentrations (1 M), the efficiency dropped to 10.8 %. These results underscore the effectiveness of controlled Na pre-deposition in enhancing single-stage PHRMS-grown CIGS solar cell performance. • Solution-processed Na pre-deposition integrated with single-stage PHRMS CIGS growth. • Moderate Na incorporation reduces recombination and enhances PV parameters. • PCE improved from 10.1 % (untreated) to 14.3 % for 0.05 M Na-treatment. • Excessive Na leads to defect compensation, higher J 0 , and efficiency degradation. • Demonstrates a simple, scalable alkali management route for CIGS solar cells.