Optical simulation and analysis of iso-textured silicon solar cells and modules including light trapping

Solar cells made from multicrystalline silicon (mc-Si) wafers play an important role in photovoltaics. Nevertheless, tools for the optical simulation of these devices are scarce. In the present work, the reflectance and charge carrier generation of mc-Si cells and modules are for the first time simulated successfully in the complete spectral range including light trapping and escape light, as the comparison with measured reflectance of the finished cells and mini-modules shows. The “spherical caps” geometry is used to model the front surface reflection of iso-textured silicon solar cells. The characteristic angles of the spherical caps are determined from the reflectance of iso-textured wafers for three different texture strengths. Based on this calibration, the reflectance and charge carrier generation rates of cells encapsulated with EVA and glass are simulated and analysed. Iso-textured cells with full-area aluminium back surface field (Al-BSF) and with passivated emitter and rear (PERC) are quantitatively compared regarding the photo-generated current density jPh. The simulations demonstrate that the direct cell-to-module loss of iso-textured mc-Si cells with Al-BSF (0.7 mA/cm2) is smaller than for PERC cells (1.2 mA/cm2).