Nano-optical properties of sputtered indium tin oxide on black silicon for heterojunction solar cells

This study investigates surface morphological and optical properties of sputtered indium tin oxide (ITO) thin films on black silicon (b-Si) fabricated by metal-assisted chemical etching (MACE) for potential application in heterojunction solar cells. After depositing 50 nm, 80 nm, and 140 nm of ITO, electron dispersive X-ray (EDX) confirms the presence of In, O, and Sn elements in weight percentage (wt.%) on b-Si nanowires. With ITO on b-Si, weighted average reflection (WAR) decreases compared to ITO on reference c-Si within the wavelength region of 300-1100 nm. This is due to the refractive index grading effect, which improves light-coupling into the b-Si absorber. In the solar cells measured under white LED illumination (at 47 mW/cm²) at room temperature (25oC), the ITO/c-Si/NiO solar cell (reference) demonstrates short-circuit current density (Jsc) of 3.10 μA/cm². In comparison, the ITO/b-Si/NiO solar cell achieves an enhanced Jsc of 3.96 μA/cm2 at a slightly higher open-circuit voltage (Voc). This represents 28% of Jsc enhancement when compared to the reference cell. The enhancement in the Jsc of the b-Si solar cell owes to the increased light absorption in the b-Si absorber within the 300-1100 nm wavelength region