Efficient black silicon solar cells with nanoporous anti-reflection made in a single-step liquid etch

We fabricated black silicon solar cells with conversion efficiency of 16.8% on p-type single crystal Si wafers with a conventional diffused emitter and Al back-surface field (BSF). We replaced the anti-reflection coating step with a single 3-minute `black-silicon´ etch of the bare wafer before processing. The nanoporous black-silicon layer, about 300-nm thick is produced in a 3-minute single-step liquid etch based upon catalysis by Au nano-particles formed in a solution containing HF and H₂O₂. Solar cell reflectance is well below 5% at incident wavelengths from 350 to 1000 nm. We present reflectance versus time data during this simple single-step etching. We also characterize cell performance and find that recombination in the black silicon surface layer must still be reduced.