CUGAO₂ and CUINS₂ Quantum Dot Sensitization for Enhanced Photovoltaic Efficiency in Wearable Fiber-Shaped Solar Cells

Abstract

This study quantitatively investigated CuGaO₂ and CuInS₂ quantum-dot sensitization as an approach for enhancing the photovoltaic efficiency and mechanical performance of wearable fiber-shaped solar cells. A controlled experimental design was employed in which 60 devices were fabricated and 56 valid devices were retained for analysis across control, low-, intermediate-, and high-sensitization conditions corresponding to 0, 4, 8, and 12 CuInS₂ deposition cycles. Photovoltaic performance was evaluated through short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE), while optical absorbance, charge-transfer resistance, recombination resistance, carrier lifetime, and mechanical efficiency retention were additionally examined. The intermediate eight-cycle condition produced the strongest overall photovoltaic performance, increasing mean Jsc from 7.42 ± 0.61 mA cm⁻² in the control to 12.48 ± 0.83 mA cm⁻² and PCE from 2.45 ± 0.24% to 4.89 ± 0.35%, representing improvements of 68.2% and 99.6%, respectively. Voc increased from 0.58 ± 0.03 V to 0.64 ± 0.02 V, while FF increased from 56.8 ± 3.4% to 61.2 ± 2.8%. Significant between-group differences were observed for PCE, F = 122.6, p < 0.001, η² = 0.876, and Jsc, F = 118.4, p < 0.001, η² = 0.872. At eight cycles, charge-transfer resistance decreased to 45.8 ± 5.2 Ω, recombination resistance increased to 211.6 ± 18.4 Ω, and carrier lifetime reached 33.8 ± 3.4 ms. Increasing sensitization to 12 cycles raised optical absorbance but reduced PCE to 4.21 ± 0.38%, demonstrating a nonlinear saturation response. Mechanical testing further showed that the optimized eight-cycle devices retained 87.7% of their initial PCE after 1,000 bending cycles. Overall, intermediate CuInS₂ sensitization provided the most effective balance among optical absorption, charge transport, recombination suppression, photovoltaic efficiency, and mechanical durability in CuGaO₂-based fiber-shaped solar cells.