One of the possible optimized device designs far silicon solar cell photocurrent enhancement, consists of a cell having an inserted sub-structure with extrinsic gap levels. A middle gap impurity and defect level band may actually allow a two infrared photon absorption. The junction near local defect layer design (Li et al., 1992) was assumed to enhance the sub-band-gap light absorption but it also enhances the recombination mechanisms strongly. Kuznicki (1993) has proposed another design with an L-H interface insertion at the edges of a continuous sub-structure to avoid extra recombination. The maximal photocurrent due to an additional infrared absorption calculated in this way is smaller than Delta I-ph = 16.8 mAcm(-2). In the case when the widths of the absorbing sub-structure are negligible compared to the width of the emitter, the simulated maximal efficiency can vary from 30.87 mW cm(-2) to 40.51 mW cm(-2).