Photoinitiator composition comprising a) at least one cationic photoinitiator selected from the group consisting of sulfonium salts wherein the anion is a fluorophosphate defined by the following formula: PF n R x 6-n Θ with n = an integer from 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl; and b) at least one cationic photoinitiator which is different from characterised in that the weight ratio of to is higher than 0.1 and the cationic photoinitiator is selected from at least one onium salt having a structure according to the following formula [R 1 a R 2 b R 3 c R 4 d E] + [MX n+1] - wherein E represents S, P, O, I or N=N; R 1, R 2, R 3 and R 4 represent individually the same or different organic group selected from substituted or unsubstituted C 6-18 aryl; a, b, c, and d independently represent an integer from 0 to 3, and provided that a+b+c+d is 3 if E=S, 4 if E=P, 3 if E=O, 2 if E=I and 1 if E= N≡N; M represents a metal or metalloid selected from the group consisting of B, P, As, Fe, Sn, Bi, Al; X represents F, Cl, Br, a substituted or unsubstituted aryl or heteroaryl group or mixtures thereof and; n is the valence number of M; or the cationic photoinitiator is represented by a mixture comprising and wherein R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are independently of one another H, - OCH 3, -OCH 2 CH 3, methyl, ethyl, i-propyl, -CH 2 CH 2 OH, -CH 2 CH 2 SH, preferably the substituents R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are in a para position to at least one of the sulfur atoms, more preferably R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are H; with the proviso that the onium salt is not a sulfonium salt wherein the anion is a fluorophosphate defined by the following formula: PF n R x 6-n Θ with n = 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl. a) at least one cationic photoinitiator selected from the group consisting of sulfonium salts wherein the anion is a fluorophosphate defined by the following formula: PF n R x 6-n Θ with n = an integer from 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl; and with n = an integer from 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl; and b) at least one cationic photoinitiator which is different from characterised in that the weight ratio of to is higher than 0.1 and the cationic photoinitiator is selected from at least one onium salt having a structure according to the following formula [R 1 a R 2 b R 3 c R 4 d E] + [MX n+1] - wherein E represents S, P, O, I or N=N; R 1, R 2, R 3 and R 4 represent individually the same or different organic group selected from substituted or unsubstituted C 6-18 aryl; a, b, c, and d independently represent an integer from 0 to 3, and provided that a+b+c+d is 3 if E=S, 4 if E=P, 3 if E=O, 2 if E=I and 1 if E= N≡N; M represents a metal or metalloid selected from the group consisting of B, P, As, Fe, Sn, Bi, Al; X represents F, Cl, Br, a substituted or unsubstituted aryl or heteroaryl group or mixtures thereof and; n is the valence number of M; or the cationic photoinitiator is represented by a mixture comprising and wherein R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are independently of one another H, - OCH 3, -OCH 2 CH 3, methyl, ethyl, i-propyl, -CH 2 CH 2 OH, -CH 2 CH 2 SH, preferably the substituents R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are in a para position to at least one of the sulfur atoms, more preferably R a, R b, R c, R d, R e, R f, R g, R h, R i and R k are H; with the proviso that the onium salt is not a sulfonium salt wherein the anion is a fluorophosphate defined by the following formula: PF n R x 6-n Θ with n = 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl. E represents S, P, O, I or N=N; R 1, R 2, R 3 and R 4 represent individually the same or different organic group selected from substituted or unsubstituted C 6-18 aryl; a, b, c, and d independently represent an integer from 0 to 3, and provided that a+b+c+d is 3 if E=S, 4 if E=P, 3 if E=O, 2 if E=I and 1 if E= N≡N; M represents a metal or metalloid selected from the group consisting of B, P, As, Fe, Sn, Bi, Al; X represents F, Cl, Br, a substituted or unsubstituted aryl or heteroaryl group or mixtures thereof and; n is the valence number of M; or the cationic photoinitiator is represented by a mixture comprising with n = 1 to 6 and R x = substituted or unsubstituted C 1-6 -alkyl or substituted or unsubstituted aryl or heteroaryl.