4,8-di(4-methylphenylethynyl)benzo[1,2-b:4,5-b']dithiophene

4,8-di(5-trimethylsiylthien-2'-yl)benzo[1,2-b:4,5-b']dithiophene

4,8-bis(5-octylthiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene

4,8-di(5-hexylthieno[3,2-b]thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene