TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): Preparation of (I) comprises polymerization of a macromonomer comprising heteroaryl acceptor-donor units of formula (A-D1-A) (XI), preferably (P1-A-D1-A-P1) (XIa), and heteroaryl donor monomers of formula (Q1-D2-Q1) (XIII).P1, Q1 = reactive coupling partners, preferably Br, I, pseudo-halo, alkenyl, -B(R5)2, -BF3K, -Si(R6)3, -SnR3, -MgP1, -ZnCl, -ZnBr or -ZnI;R = alkyl or aryl;R5 = R or (OR); andR6 = Cl, F or alkyl.Preferred Method: The macromonomer (XI) or (XIa) are prepared by reaction of donor groups (D1) with the acceptor (A) to provide selective coupling of the acceptor. Preferred Components: The macromonomer is substituted 5-fluoro-benzo(1,2,5)thiadiazole compounds of formula (XIb). The acceptor is an asymmetric group, where the acceptor groups (A) are disposed with mutual symmetry about the donor group (D1). The polymer: has a number average molar mass of 40000-100000 Daltons; and comprises thiophene or phenyl endcaps. The electron acceptor polymer or molecule is at least one fullerene derivative. Preferred Definitions:    A = one of substituted hetero bi- or tri-cyclic moieties of formulae (a1)-(a9), preferably (a1);    X = S or O;    Y1, Z1 = C-H, C-R, C-F, C-Cl, C-CF3, C-CN, N, C-COOH, C-COOR or C-CONHR;    D1, D2 = one of substituted hetero bi- or tri-cyclic moieties of formulae (b1)-(b9) or poly thiophenylene of formula (b10), preferably (b6);    R1-R4 = alkyl, alkenyl, alkynyl, carbocyclyl, aryl, heterocyclyl (all optionally substituted) or H, where at least one of R1 or R2 is optionally substituted alkyl, and R3 or R4 is H; and    p = 1-3.    EXAMPLE - In a glove box, 0.5 mmol (2,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-11-(trimethylstannyl)-4,10-dithiatricyclo(7.3.0.0(3,7))dodeca-1,3(7),5,8,11-pentaen-5-yl)trimethylstannane and 0.5 mmol 4-bromo-7-(11-(7-bromo-6-fluoro-2,1,3-benzothiadiazol-4-yl)-2,8-bis(5-(2-ethylhexyl)-4-hexylthiophen-2-yl)-4,10-dithiatricyclo(7.3.0.0(3,7))dodeca-1,3(7),5,8,11-pentaen-5-yl)-5-fluoro-2,1,3-benzothiadiazole were mixed in a microwave reaction tube. After dissolved in 5 ml of ortho-xylene, 20 mu mol tris(dibenzylideneacetone)dipalladium(0) and 80 mu mol tri(ortho-tolyl)phosphine were added as the catalyst, and the tube was sealed with a PTFE cap. The reaction mixture was heated to 100 degrees C for 1 minute, 135 degrees C for 1 minute, 170 degrees C for 1 hour, and 200 degrees C for 20 minutes using a microwave reactor. The resulting polymer was end-capped by reacting with 0.2 ml 2-(tributylstannyl)thiophene and 0.2 ml 2-bromothiophene at 170 degrees C for 20 minutes, respectively. The end-capped polymer was precipitated by addition of 50 ml methanol and filtered through a Soxhlet thimble. The precipitate was then subjected to Soxhlet extraction with acetone, ethyl acetate, n-heptane, dichloromethane and chloroform. The polymer was recovered as a solid from the chloroform fraction by precipitation from methanol. The solid was dried under vacuum to obtain conjugated polymer containing (2,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-11-(trimethylstannyl)-4,10-dithiatricyclo(7.3.0.0(3,7))dodeca-1,3(7),5,8,11-pentaen-5-yl)trimethylstannane and 4-bromo-7-(11-(7-bromo-6-fluoro-2,1,3-benzothiadiazol-4-yl)-2,8-bis(5-(2-ethylhexyl)-4-hexylthiophen-2-yl)-4,10-dithiatricyclo(7.3.0.0(3,7))dodeca-1,3(7),5,8,11-pentaen-5-yl)-5-fluoro-2,1,3-benzothiadiazole.