A polymer, containing three different monomer repeat units, in which the first monomer repeat unit is a moiety of formula: wherein A is S; and R is C 1 -C 24 alkyl optionally containing oxygen and optionally substituted with halo or C 1 -C 24 alkoxy; the second monomer repeat unit is different from the first monomer repeat unit and is any moiety selected from the group consisting of the moieties of formulas -: wherein each X, independently, is O, S, or Se; each Y, independently, is N or C(R a); Z 1 is N(R a), S, Si(R a R b), or C(R a R b); Z 2 is O, S, Se, N(R a), Si(R a R b), or C(R a R b); Z 3 is O, S, or N(R a); each Z 4, independently, is CH 2, O, or S; each of R 1, R 2, R 3, R 4, R 5, and R 6, independently, is H, halo, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, OR c, COR c, or COOR c; R 7 is H, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, COR c, or COOR c; each R a, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; each R b, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and each R c, independently, is H, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and the third monomer repeat unit is different from the first and second monomer repeat units and is of the following formula wherein the first and third monomer repeat units are comprised in a moiety of formula A is S; and R is C 1 -C 24 alkyl optionally containing oxygen and optionally substituted with halo or C 1 -C 24 alkoxy; the second monomer repeat unit is different from the first monomer repeat unit and is any moiety selected from the group consisting of the moieties of formulas -: wherein each X, independently, is O, S, or Se; each Y, independently, is N or C(R a); Z 1 is N(R a), S, Si(R a R b), or C(R a R b); Z 2 is O, S, Se, N(R a), Si(R a R b), or C(R a R b); Z 3 is O, S, or N(R a); each Z 4, independently, is CH 2, O, or S; each of R 1, R 2, R 3, R 4, R 5, and R 6, independently, is H, halo, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, OR c, COR c, or COOR c; R 7 is H, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, COR c, or COOR c; each R a, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; each R b, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and each R c, independently, is H, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and each X, independently, is O, S, or Se; each Y, independently, is N or C(R a); Z 1 is N(R a), S, Si(R a R b), or C(R a R b); Z 2 is O, S, Se, N(R a), Si(R a R b), or C(R a R b); Z 3 is O, S, or N(R a); each Z 4, independently, is CH 2, O, or S; each of R 1, R 2, R 3, R 4, R 5, and R 6, independently, is H, halo, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, OR c, COR c, or COOR c; R 7 is H, C 1 -C 24 alkyl, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 3 -C 24 cycloalkyl, C 3 -C 24 cycloalkenyl, C 3 -C 24 heterocycloalkyl, C 3 -C 24 heterocycloalkenyl, aryl, heteroaryl, COR c, or COOR c; each R a, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; each R b, independently, is H, halo, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and each R c, independently, is H, C 1 -C 24 alkyl, aryl, heteroaryl, C 3 -C 24 cycloalkyl, or C 3 -C 24 heterocycloalkyl; and the third monomer repeat unit is different from the first and second monomer repeat units and is of the following formula wherein the first and third monomer repeat units are comprised in a moiety of formula