Efficient nanostructured ‘black’ silicon solar cell by copper‐catalyzed metal‐assisted etching

We produce low‐reflectivity nanostructured ‘black’ silicon (bSi) using copper (Cu) nanoparticles as the catalyst for metal‐assisted etching and demonstrate a 17.0%‐efficient Cu‐etched bSi solar cell without any vacuum‐deposited anti‐reflection coating. The concentration ratio of HF to H 2 O 2 in the etch solution provides control of the nanostructure morphology. The solar‐spectrum‐weighted average reflection (R ave ) for bSi is as low as 3.1% on Cu‐etched planar samples; we achieve lower reflectivity by nanostructuring of micron‐scale pyramids. Successful Cu‐based anti‐reflection etching requires a concentration ratio [HF]/[H 2 O 2 ] ≥ 3. Our 17.0%‐efficient Cu‐etched bSi photovoltaic cell with a pyramid‐texture has a R ave of 3% and an open circuit voltage (V oc ) of 616 mV that might be further improved by reducing near‐surface phosphorus (P) densities. Copyright © 2014 John Wiley & Sons, Ltd.