  Monocrystalline silicon solar cells with photo-absorbing morphology can
amplify light-trapping properties within the absorber layer and help to
fabricate cost-effective solar cells. In this paper, the effect of different
parameters namely temperature and time of Cu-assisted chemical etching was
thoroughly investigated for the optimization of the light absorption
properties. P-type monocrystalline wafers were selectively treated with
Cu(NO3)2.3H2O:HF:H2O2:DI water solution at 50 deg.C for five different time
duration. The entire process was repeated at five different temperatures for
20min as well to study the relation between etching temperature and surface
reflectance. Sonication bathing was used for the removal of the deposited Cu
atoms from the surface with the variation of time and the effect was examined
using energy dispersive spectroscopy (EDS). Field emission scanning electron
microscopy (FESEM) and UV/VIS spectroscopy were conducted to study the surface
morphology and light absorbance respectively. Inverted shapes almost similar to
inverted pyramids or porous surface were found randomly on the surface of the
wafer. The effect of temperature was found more significant compared to the
effect of time variation. An optimum light reflectance was found at 50 deg.C
for 20 min of texturization. Atomic force microscopy (AFM) of the textured
sample revealed the average depth of pyramidal shape was about 1.58 micro
meter. EDS results showed a proportional relation between time and Cu removal
process, and a complete Cu atoms free textured surface after 25 min of
sonication bathing. Therefore, a suitable Cu-assisted texturization technique
was found, which could enable lowering the photo-reflectance below 1% without
any antireflection coating.
