TMAH-textured, a-Si/c-Si, heterojunction solar cells with 10% reflectance

Single-polished c-Si (100) wafers were textured in aqueous solutions with varying concentrations of tetra-methylammoniumhydroxide(TMAH). The resulting surface reflectance and morphology were examined as a function of etching time and temperature, TMAH concentration, and addition of isopropyl alcohol to the solution. The lowes treflectance, 9.8% at a 600-nm wavelength with 0.3% scattering over a 400 wafer surface, was obtained after 40 min of etching in a 2% TMAH solution at 80 1C under 700 rpm magnetic stirring. Upon adding isopropyl alcohol to the solution, the resulting pyramids were round-edged, and 12% sample reflectance was obtained. The results are interpreted in terms of micro-masking formation and temperature-dependent crystallographics electivity. The compatibility of the treatment with photovoltaic applications was evaluated by studying the performance of heterojunction solar cells, which are particularly sensitive to surface quality. A degradation of the open circuit voltage was observed in devices fabricated on surfaces featuring crooked pyramid sides. Optimised process conditions led to smooth pyramid sides and no degradation of the open circuit voltage, which indicates no sign of increased surface recombination-centre concentration. The reduced reflectance resulted in a 16% increase of the short circuit current of the solar celld evice.