Light trapping effect of patterned back surface reflectors in substrate-type single and tandem junction thin-film silicon solar cells

Abstract

Light trapping is a key issue to boost the efficiency of thin-film Si solar cells including μc-Si:H. In this paper, effect of textured back reflectors on light trapping in μc-Si:H cells has been investigated with self-orderly patterned Al substrates obtained by anodic oxidation. With increase in the period of the patterned substrates from 0 to 1.1 μm, the short circuit current densities of 1-μm-thick μc-Si:H cells on the patterned substrates significantly increase from 18 to over 24 mA/cm 2, which is attributed to the improved light trapping in the infrared region. It has been clarified that this enhanced light-trapping effect in longer wavelengths is mainly attributed to the improved light scattering at the rear side by comparing μc-Si:H solar cells with polished and as-deposited front surfaces. The effectiveness of the patterned Al substrates has also been demonstrated in an a-Si:H/μc-Si:H tandem cell with a bottom cell thickness of 1 μm, showing a higher conversion efficiency than the reference cell.