Fig. 2.

Examples for donor and acceptor materials used in bulk heterojunction solar cells. (a) Poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadia-zole)-5,5′-diyl] [20], (b) poly-(3-hexylthiophene-2,5-diol), (c) diketopyrrolopyrrole based oligomer [21], (d) 5,5′-bis{(4-(7-hexylthiophen-2-yl)thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine}-3,3′-di-2-ethylhexylsilylene-2,2′-bithiophene, (e) [6,6]-phenyl-C₆₁-butyric acid methyl [22], (f) bisadduct analog [6,6]-phenyl-C₆₁-butyric acid methyl and (g) indene-C₆₀-bisadduct.