Black Silicon With Ultra-Low Surface Recombination Velocity Fabricated by Inductively Coupled Power Plasma

Black silicon is a naturally antireflective Si surface with great potential for high-efficiency solar cells. In particular, black silicon surfaces can be obtained using reactive ion etch in a maskless, single-step process regardless of crystallinity and with minimal material loss. Surface damage from the etching process, however, result in surfaces with high recombination velocity, thus limiting solar cell efficiency.

We have developed a method to texture Si surfaces using non-cryogenic reactive ion etch with a plasma sustained exclusively by inductively coupled power, thereby minimizing surface damage. We achieved a target reflectance of 3% or lower in the wavelength range 300–1000 nm after an etch time of 2 min.

Surfaces coated with Al2O3 deposited by atomic layer deposition showed recombination velocity as low as 6.9 cm s−1 on p-type Czochralski wafers, almost the same values as measured on planar reference surfaces (6.8 cm s−1). This corresponds to an implied open circuit voltage as high as 757 mV for a cell with thickness of 180 μm and base resistivity of 4 Ω cm.

These results indicate that our method for texturing of Si surfaces is suitable for fabrication of high-efficiency single junction Si solar cells.