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The impact of Si wafer thickness on the photovoltaic performance of hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) heterojunction solar cells was examined from the optical and electrical points of view. Optical characterization of c-Si wafers of various thicknesses showed that a realistic light-trapping scheme, i.e., pyramidally textured Si wafers with a dielectric antireflection coating and a back reflector, realizes an efficient quasi-Lambertian light absorption enhancement, even for very thin wafers. This indicates that high photocurrent densities are achievable by using the realistic light-trapping scheme, assuming that the parasitic absorption loss is minimized. The potentials of open-circuit voltage (VOC) and the fill factor (FF) of thin c-Si cells were investigated using thin c-Si wafers passivated with intrinsic/doped amorphous silicon film stacks. It was experimentally confirmed that the implied VOC increases steadily with decreasing wafer thickness down to 30 µm, while the implied FF weakly depends on the thickness. As a result of the trade-off between light absorption and implied VOC, a high implied efficiency is expected for a wide range of wafer thicknesses. The VOC increase by thinning the wafer was also experimentally confirmed in an a-Si:H/c-Si heterojunction cell with a thickness below 60 µm, resulting in a conversion efficiency of 21.0%. [ABSTRACT FROM AUTHOR]

Si ingots were sliced using a diamond-coated wire, and saw damage was observed even after damage removal etching and texturization. Since invisible microscopic damage was observed only under uncontrolled slice conditions, such damage was identified as saw damage. The wafers with saw damage exhibited the degradation of solar cell conversion efficiency (approximately 1–2% absolute). The results of external quantum efficiency (EQE) measurements showed a slight deterioration of EQE in the short wavelength region. Current–voltage characteristic measurements showed similar results that agreed with the EQE measurement results. In addition, EQE mapping measurements were carried out at various irradiation wavelengths between 350 and 1150 nm. Areas with dark contrasts in EQE mapping correspond to saw damage. In the cells with a low conversion efficiency, both EQE mapping and PL images exhibited dark areas and lines. On the other hand, in the cells with a high conversion efficiency, a uniform distribution of saw damage was observed even with the saw damage in the PL images. We believe that sophisticated control to suppress saw damage during sawing is required to realize higher conversion efficiency solar cells in the future. [ABSTRACT FROM AUTHOR]