Additives for dye-sensitized solar cells

A dye-sensitized solar cell comprising at least one compound of formula I

• wherein
• R1, R2, R3 are independently selected at each occurrence from:
• straight-chain or branched alkyl with 1 to 20 C atoms, which can be substituted by at least one R;
• or
• aryl with 6 to 10 C atoms, which can be substituted by at least one R,
• or
• R1, R2 and R3 are fused to form a heteroaromatic ring structure in which 1, 2 or 3 N atoms or 1N atom and 1 S or 1 O atom are present which ring can be substituted by at least one R,
• or
• R1 and R2 are fused to form a heteroaliphatic ring structure in which 1, 2 or 3 N atoms or 1N atom and 1 S or 1 O atom are present which ring can be substituted by at least one R and R3 is straight-chain or branched alkyl with 1 to 20 C atoms or fused to form a tricyclic structure containing at least 1 N atom and in which a second or third N atom of the heteroaliphatic ring structure or tricyclic ring structure may be substituted by —O− and a straight-chain or branched alkyl with 1 to 20 C-atoms;
• wherein a straight-chain or branched alkyl group having 1 to 20 C atoms is upon each occurrence independently selected from the group consisting of methyl, ethyl, propyl, isopropyl, n-butyl, sec.-butyl, tert.-butyl, 1-(2,2-dimethyl)-propyl, pentyl, hexyl, heptyl, octyl, x-methylbutyl with x being 1;
• 2 or 3 x-methylpentyl with x being 1;
• 2;
• 3 or 4 x-methylhexyl with x being 1;
• 2;
• 3;
• 4 or 5, x-ethylpentyl with x being 1, 2 or 3 x-ethylhexyl with x being 1;
• 2;
• 3 or 4 n-nonyl, n-decyl, n-undecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl and n-eicosyl, which can be substituted by at least one R;
• and
• R is independently:
• Hal;
• CN;
• C(O)H;
• straight-chain or branched alkyl with 1 to 20 C atoms, which alkyl can be substituted by cycloalkyl having 5 to 6 C atoms or aryl having 6 to 10 C atoms in which the aryl group may be substituted by straight-chain or branched alkyl groups or alkoxy groups with 1 to 4 C atoms or by heteroaryl having 5 or 6 C atoms;
• straight-chain or branched alkenyl with 2 to 20 C atoms, which alkenyl can be substituted by aryl having 6 to 10 C atoms in which the aryl group may be substituted by straight-chain or branched alkyl groups with 1 to 4 C atoms;
• cycloalkyl having 5 or 6 C atoms;
• straight-chain or branched hydroxyalkyl with 1 to 20 C atoms;
• straight-chain or branched alkoxy with 1 to 20 C atoms, which alkoxy can be substituted by aryl having 6 to 10 C atoms;
• straight-chain or branched alkylthio with 1 to 20 C atoms;
• aryl with 6 to 10 C atoms in which the aryl group may be substituted by straight-chain or branched alkyl groups or alkoxy groups with 1 to 4 C atoms or by heteroaryl having 5 or 6 C atoms;
• heteroaryl with 5 to 10 C atoms in which a N atom of the heteroaryl group may be substituted by —O−;
• aryloxy with 6 to 10 C atoms;
• arylthio with 6 to 10 C atoms;
• straight-chain or branched alkylamino;
• or dialkylamino with 1 to 20 C atoms;
• and
• Hal is F, Cl, Br or I;
• including all tautomeric or stereoisomeric forms thereof.