Preparation of low reflective microstructure at multicrystal silicon surface by ferric nitrate etching

Fe(NO3)3/HF mixed solution was used to replace traditional HNO3/HF mixed solution to produce low reflective texture on the multicrystal silicon (mc-Si) surface. A low reflective microstructure having hemispherical etched pits with needle-like folds was obtained. The surface reflectance of the etched mc-Si wafers was analyzed by spectrophotometer and the morphologies of the textured mc-Si wafers were observed by scanning electron microscopy. It was found that the light trapping effect was greatly enhanced by the microstructure produced by etching in the mixed solution of Fe(NO3)3/HF, which results in a significant reduction of the light reflectance at the mc-Si surface. Moreover, the etching time and the concentration of Fe(NO3)3 determine the etched pit size and the morphology of the needle-like folds microstructure. The surface reflectivity in the wavelength range from 400 nm to 1000 nm is only 6.15% when the etching time and the concentration of Fe(NO3)3 are 40 min and 0.3 M respectively.