Progress and outlook for high-efficiency crystalline silicon solar cells

The last 15 years have seen large improvements in crystalline silicon solar cells, with efficiencies improved by over 50%. The main drivers have been improved electrical and optical design. Electrical improvements include improved passivation of contact and surface regions and a reduction in the volume of heavily doped cell material. Optically, reduced reflection and improved light trapping within the cell have had a large impact. Such features have increased silicon cell efficiency to a recently confirmed 24.7%. Recently, progress has been made in transferring some of the corresponding design improvements into production with commercial cells of 17–18% efficiency now available, world record values of a mere 15 years ago. The theory supporting these improvements in bulk cell efficiency shows that thin silicon layers, only a micron or so in thickness, are capable of comparably high efficiency.