One-step Cu-Fe bimetal-assisted chemical etching for texturing silicon surfaces with ball-crown-shaped upright pyramids

Achieving the synergy between efficient light trapping and excellent interface passivation are desired in terms of surface texturing of high-efficiency silicon solar cell technology. To address these issues, this study proposed a Cu-Fe bimetal-assisted chemical etching (Cu-Fe MACE) method to texture the surface of silicon wafers. The effects of Fe(NO 3 ) 3 concentration on Cu deposition behavior, as well as the influence of Cu deposition on the subsequent etching process, were systematically investigated. The results indicated that the Fe(NO 3 ) 3 concentration had a pronounced influence on the deposition morphology of nano-sized Cu and the corresponding etching behavior. By controlling the Fe(NO 3 ) 3 concentration in the range of 0.1-0.15 M, a uniform texture of ball-crown-shaped upright pyramids was obtained on n-type monocrystalline silicon, showing good uniformity and light-trapping capability, with the average reflectance in the 300-1100 nm wavelength range reduced from about 25% for the as-cut wafer to 13% under the optimized conditions. By combining PL and minority carrier lifetime measurements, the passivation behavior of the etched surfaces was investigated. The rounded tips and smoother surface of the ball-crown-shaped upright pyramids significantly improved the coverage continuity and film quality of the Al 2 O 3 passivation layer. Compared with conventional upright pyramids, the new textured structure exhibited a higher minority carrier lifetime (τeff ≈ 3.0 × 10 −4 s at an injection level of 10 15 cm −3 ) and an implied open-circuit voltage of about 715 mV. This work provided valuable guidance for the design and application of surface texturing strategies that enabled both excellent light trapping and strong passivation in crystalline silicon solar cells.