Thin monocrystalline silicon solar cells

One of the most effective approaches for a cost reduction of crystalline si licon solar cells is the better utilization of the crystals by cutting thin ner wafers. However, such thin silicon wafers must have sufficient mechanic al strength to maintain a high mechanical yield in cell and module manufact uring. The electrical performance of thin cells drops strongly with decreasing cel l thickness if solar cell manufacturing technologies without a backside pas sivation or a back-surface-held (BSF) are applied. However, with the applic ation of a BSF, stable efficiencies of over 17%, even with decreasing cell thickness, have been reached. Thin solar cells show lower photodegradation, as is normally observed for Cz-silicon cells with today's standard thickne ss (about 300 mu m) because of a higher ratio of the diffusion length compa red to the cell thickness. Cells of about 100-150 mu m thickness fabricated with the production Cz-silicon show almost no photodegradation. Furthermore, thin boron BSF cells have a pronounced efficiency response und er backside illumination. The backside efficiency increases with decreasing cell thickness and reaches 60% of the frontside cell efficiency for 150 mu m solar cells and also for solar modules assembled of 36 cells of a thickn ess of 150 mu m. Assuming, for example, a rearside illumination of 150 W/m( 2), this results in an increased module power output of about 10% relativel y.