Excited state spectroscopy in polymer fullerene photovoltaic devices under operation conditions - Winder,C; Lungenschmied,C; Matt,G; Sariciftci,NS; Nogueira,AF; Montanari,I; Durrant,JR; Arndt,C; Zhokhavets,U; Gobsch,G (ELSEVIER SCIENCE SA, 2003)