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Photoelectrochemical etching of cone-shaped macropores in N-type Si for solar cell texturization



Macropore formation by photoelectrochemical (PEC) etching of N-type crystalline Si under front side illumination has been investigated. We report on two important parameters that influence the pore morphology: the applied anodic bias and the spectral distribution of the illumination source. On (100) c-Si, the pore morphology changes from a round shape at low bias (0 V/NHE) to a conical shape at high bias (2 V/NHE). In the latter case we show that, by adjusting the spectrum of the white light source with longpass filters of different cut-on wavelengths, we can control the cone angle of the pores from 50° with white light to 10° with infrared light. Optical measurements indicate that macropores formed with a narrow cone angle (20°) could be of interest for Si solar cell texturization since they result in a very low reflectivity (2.6% at 800 nm) and in an efficient light trapping.