Numerical Analysis of the Optical Contribution of Rear Passivation Layers to the Photo-Generated Current of Monocrystalline Silicon Solar Cells

Abstract

For high-efficiency silicon solar cells, passivation of both sides of the Si substrate is necessary for achieving high open-circuit voltages. In general, passivation layers reduce the number of recombination sites in silicon, thereby increasing the lifetime of carriers. Front passivation layers reduce light reflection such that a relatively large amount of light can be absorbed in the Si substrate. Rear passivation layers are typically located on the opposite side of the solar cell and near a highly reflective rear metal electrode; thus, it is difficult to experimentally separate the optical contribution of rear passivation layers from effects due to the rear metal electrodes. In this paper, using numerical simulations based on the transfer-matrix method, we calculated the reflectance of solar cells with rear passivation layers for improving light trapping effects. We designed two different solar cell structures that have different types of rear passivation layers: a single-layer structure consisting of only two rear passivation layers and a multiple-layer structure consisting of repeated thin oxide layers. We calculated reflectances for both structures and compared the optical effect of rear passivation layers. Using our simulation tool, we can optimize the parameters of rear passivation layers to achieve the highest possible efficiency of solar cells.