| Multicrystalline Silicon (mc-Si) is widely applied in the field ofphotoelectric devices, and it is important to improve the quality of texturedsurface of mc-Si. mc-Si surface texturing is usually achieved by etchingmc-Si in HF/HNO3/H2O acidic solution. The etching in acidic solution isisotropic so that the mc-Si surface is filled with pits with light trappingeffect. This paper has studied the temperature distribution near the Sisurface during the etching reaction, and how does this distribution affectthe topography of textured mc-Si surface.In this paper, by solving heat conduction equations with differentkind of boundary conditions, the temperature distributions around pits onmulti-crystal silicon surface are calculated during etching reaction. Thecalculation results show that a low solution temperature of about15°Ccontrolled by cooling measures can result in an most obvious temperaturedifference between the pits bottoms and multi-crystal silicon surfaces. Thisdifference is helpful in reducing the pits opening size as well as increasingthe pits depth; on the other hand,etching the multi-crystal silicon surfacewithout temperature control or at a high temperature will make littletemperature difference between the pits bottoms and multi-crystal siliconsurfaces, which produces the shallow trap pits with large opened size. Thehigher the temperature is, the poorer the light trapping effect is.Silicon surfaces are textured under different temperature conditions inthe experiment. SEM of experiment sample surface achieved the similarresults as the calculation. The mc-Si surface topography differs greatly astemperature changes, surfaces textured at low temperature result in to befilled with pits of small opens, high density and large depth, the lighttrapping effect is good; surfaces textured at high temperature result in to be filled with pits of large opens, low density and small depth, the lighttrapping effect is poor. This research can be helpful for the texturingprocess in solar cell manufacture. |
