http://www.pv-magazine.com/news/details/beitrag/imec-reports-22-efficiency-for-large-area-pert-cell_100017773/#axzz3OoI2L2N9
http://www.pv-magazine.com/archive/articles/beitrag/switch-from-p-to-n-_100007072/501/#axzz3OoI2L2N9
http://www.instsani.pl/folowolt.htm