The integrated project (IP) Crystal Clear has been finalized in June 2009 and thus a chapter of more than 5 years successful collaboration between European solar cell research institutes and industry is closed. This paper reviews the achievements within the 4th subproject (SP4) of Crystal Clear dealing with the development of advanced solar cell concepts. Within SP4, 12 of the 16 partners have participated and have formed a productive consortium. The goal of this subproject was the further reduction of the cell production costs to enable the psychological important Si PV module price below 1 Euro/Watt. This should be reached by novel cell designs and manufacturing processes in order to achieve a process cost reduction of 40% (cost per Wp). One major effort was put in the development of novel cell concepts and processes suited for thin wafers in industrial fabrication. Three cell concepts were distinguished and developed by the participating institutes: i-PERC, MWT with full Al, and solar cells with laser fired contacts (PERC-LFC). In addition to the effort to implement these concepts into an industrial type of process with large area wafers, excellent results have been achieved on EFG and RGS ribbons. World record results with laboratory-type processes could be reported, with efficiencies of 18.2 % on EFG ribbons and 14.4 % on RGS ribbons. The defect mechanism of these materials has been studied in detail and efficiency limits have been indicated. The paper will refer to the separate contributions submitted to the conference by the different partners on specific topics
