The present invention relates to a novel photoacid generator compound cation, comprising an element having for 92 eV photons (extreme ultraviolet (EUV)) an absorption cross section of at least 0.5×107·cm2/mol; having at least two stable oxidation states; and selected from the elements of group 1 to group 15 of the periodic table of the elements. Additionally, the present invention relates to a photoacid generator comprising said photoacid generator compound cation and an anion. Furthermore, the present invention aims to provide a photoresist composition comprising said photoacid generator and an acid labile polymer. Finally, the present invention relates to a method of generating an acid using the photoresist composition and a method of forming a patterned materials feature on a substrate.