20% efficient flexible silicon solar cells

Since new wafering technologies which can produce very thin wafers with potentially reduced costs and improved surface quality are within reach, the processing of such flexible wafers has to be investigated. Additionally, there is a market for flexible silicon solar cells processed on wafers that were thinned down from standard thickness wafers. In the present work, a market projection for this type of solar cells is given. Recent experimental results from solar cells processed on very thin wafers in the Fraunhofer ISE cleanroom are reported. The fact that with normal handling techniques and cell structures efficiencies above 20% can be reached is a first hint that the mass production of ultrathin wafer solar cells is feasible. The optical measurements of the realized cells indicate that for correct EQE/IQE evaluation, a careful separation of overall reflection into front side and rear side fractions has to be carried out. From velocity of 300 cm/s could be determined for the fabricated RP-PERC cells.