Active materials for electro-optic devices and electro-optic devices

An inverted tandem polymer photovoltaic device, comprising:

• a hole-extracting electrode;
• an electron extracting electrode spaced apart from said hole-extracting electrode;
• a first bulk hetero-junction polymer semiconductor layer;
• a second bulk hetero-junction polymer semiconductor layer spaced apart from said first bulk hetero-junction polymer semiconductor layer;
• and
• between said first and second bulk hetero-junction polymer semiconductor layers, a p-type layer in physical contact with one of the first and second bulk hetero-junction polymer semicondutor layers, and an n-type layer in physical contact with the other of the first and second bulk hetero-junction polymer semiconductor layer;
• wherein at least one of the p-type layer and the n-type layer is doped to an extent that charge carriers tunnel through the p-type and/or n-type layer, and wherein one polymer used in either the first or second bulk hetero-junction polymer semiconductor layers has a structure of formula (I)
• wherein R1, R2, and R3 are independently selected from alkyl groups with up to 18 carbon atoms, aryls and substituted aryls;
• X is selected from oxygen, sulfur, selenium and nitrogen atoms;
• and
• Ar1 and Ar2 are each, independently, one to five monocyclic arylene, bicyclic arylene, and polycyclic arylene, monocyclic heteroarylene, bicyclic heteroarylene and polycyclic heteroarylene groups, either fused or linked.