Effect of illumination wavelength and intensity on minority-carrier diffusion length of EFG silicon ribbon solar cells

Local spectral photoresponses of the edge-defined film-fed growth technique (EFG) ribbon solar cells were measured as a function of the bias light wavelength and intensity. The minority-carrier diffusion length estimated from the spectral response measurement of the short-circuit current (JSc) was found to increase semilogarithmically with the intensity at various bias light wavelengths, and to increase with the bias fight wavelength for the constant intensity in the position with a medium diffusion length (≃20 µm). In the position with a longer (≃89 µm) or shorter (≃7 µm) diffusion length, the bias light wavelength, however, had a smaller influence on the diffusion length. The effect of the bias light wavelength and intensity on the diffusion length is theoretically explained by a model of filling deep traps by photo-injected minority carriers.