Patent ID: 8835598

Claim:
A polymer having the formula: wherein: each Het is an optionally substituted 5-8 membered heteroaryl group or a covalent bond; each Het′ is an optionally substituted 5-8 membered heteroaryl group or a covalent bond; R a and R b independently are selected from R 1 and -L-Ar, wherein: R 1 is selected from the group consisting of a C 1-40 alkyl group, a C 2-40 alkenyl group, and a C 1-40 haloalkyl group; L is selected from the group consisting of —O—, —S—, —Se—, —OC(O)—, —C(O)O—, a divalent C 1-20 alkyl group, a divalent C 1-20 haloalkyl group, and a covalent bond; and Ar is an optionally substituted C 6-20 aryl group or an optionally substituted 5-20 membered heteroaryl group; π and π′ independently are selected from the group consisting of (a) an optionally substituted electron-rich 8-20 membered polycyclic heteroaryl group, (b) a linear conjugated linker, and (c) wherein p is 1, 2, 3 or 4; x and y are real numbers representing mole fractions, where 0.05≦x≦0.95, 0.05≦y≦0.95, and the sum of x and y is about 1; and n is an integer in the range of 2 to 10,000, provided that at least one of the following is true: (a) Het and Het′ are different; (b) R a and R b are different; and (c) π and π′ are different.