Surface passivation of efficient nanotextured black silicon solar cells using thermal atomic layer deposition

Efficient nanotextured black silicon solar cells passivated by an Al ₂O₃ layer are demonstrated. The broadband antireflection of the nanotextured black silicon solar cells was provided by fabricating vertically aligned silicon nanowire (SiNW) arrays on the n⁺ emitter. A highly conformal Al₂O₃ layer was deposited upon the SiNW arrays by the thermal atomic layer deposition (ALD) based on the multiple pulses scheme. The nanotextured black silicon wafer covered with the Al ₂O₃ layer exhibited a low total reflectance of ∼1.5% in a broad spectrum from 400 to 800 nm. The Al₂O₃ passivation layer also contributes to the suppressed surface recombination, which was explored in terms of the chemical and field-effect passivation effects. An 8% increment of short-circuit current density and 10.3% enhancement of efficiency were achieved due to the ALD Al₂O₃ surface passivation and forming gas annealing. A high efficiency up to 18.2% was realized in the ALD Al₂O₃-passivated nanotextured black silicon solar cells.