Thin monocrystalline silicon solar cells

Abstract

One of the most effective approaches for a cost reduction of crystalline silicon solar cells is the better utilization of the crystals by cutting thinner wafers. However, such thin silicon wafers must have sufficient mechanical strength to maintain a high mechanical yield in cell and module manufacturing. The electrical performance of thin cells drops strongly with decreasing cell thickness if solar cell manufacturing technologies without a backside passivation or a back-surface-field (BSF) are applied. However, with the application 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 thickness (about 300 /spl mu/m) because of a higher ratio of the diffusion length compared to the cell thickness. Cells of about 100-150 /spl mu/m thickness fabricated with the production Cz-silicon show almost no photodegradation. Furthermore, thin boron BSF cells have a pronounced efficiency response under backside illumination. The backside efficiency increases with decreasing cell thickness and reaches 60% of the frontside cell efficiency for 150 /spl mu/m solar cells and also for solar modules assembled of 36 cells of a thickness of 150 /spl mu/m. Assuming, for example, a rearside illumination of 150 W/m/sup 2/, this results in an increased module power output of about 10% relatively.