TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): The polymer having benzothiophene divalent unit(s) (I), is obtained by coupling benzothiophene-type monomer(s) (a) and/or 1 or more monomers chosen from of formulae: R5-(Ar1)a-A1-(Ar2)c-R6, R5-Ar1-R6 and R5-Ar3-R5, by aryl-aryl coupling reaction. Preferred Composition: The conjugated polymer further comprises benzothiophene-containing structural unit(s) of formula: -((Ar1)a-(U')b-(Ar2)c-(Ar3)d)- (II) and another structural unit of formula: -((Ar1)a-(A1)b-(Ar2)c-(Ar3)d)- (III). The conjugated polymer having benzothiophene divalent unit(s), is preferably chosen from 17 compounds e.g. compounds of formulae (IV)-(IX). The mixture or polymer blend further comprises one or more n-type organic semiconductor compounds. The n-type organic semiconductor compound is fullerene or substituted fullerene.U'=benzothiophene divalent unit;Ar1-Ar3=5-30C aryl or 5-30C heteroaryl which is different from U' (both optionally substituted by group Rs);Rs=F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C(O)NR0R00, -C(O)X0, -C(O)R0, -C(O)OR0, -NH2, -NR0R00, -SH, -SR0, -SO3H, -SO2R0, -OH, -NO2, -CF3, -SF5, optionally substituted silyl, carbyl, 1-40C hydrocarbyl optionally substituted and optionally containing heteroatom(s) or P'-Sp-;R0,R00=H, optionally substituted 1-40C carbyl or hydrocarbyl;P'=polymerizable or crosslinkable group;Sp=spacer or single bond;X0=F, Cl or Br;a-c=0, 1 or 2;d=0 or 1-10;A1=5-30C aryl or 5-30C heteroaryl different from U' and Ar1-Ar3 (optionally substituted by group Rs);R21-R26=R3;y=0 to less than 1;x=more than 0 to 1;x+y=1;andn=more than 1. EXAMPLE - A solution of 2,6-dibromo-8-tetradecanoyloxy-benzo(1,2-b;4,5-d')dithiophen-4-yl tetradecanoate (480.5 mg), 2,5- bis(trimethylstannyl)thiophene (492 mg), 4,7-dibromo-5,6- dioctyloxy-benzo(1,2,5)thiadiazole (330 mg), tris(dibenzylideneacetone)dipalladium(0) (22 mg) and tri(o- tolyl)phosphine (29 mg), were added to chlorobenzene (7.5 cm3). The reaction mixture was heated in a microwave reactor, precipitated into methanol, stirred for 10 minutes, filtered, and obtained crude polymer was washed with methanol. The polymer was washed via Soxhlet extraction with acetone, and chloroform extract was precipitated. The obtained mixture was filtered, washed with methanol, and dried under vacuum to yield poly((2,5-(thiophen-2-yl)-6-(8-tetradecanoyloxy-benzo(1,2-b;4,5-b')dithiophen-4-yl teradeconate))-co-(5,7-(thiophen-2-yl)-4-(5,6-dioctyloxy-benzo(1,2,5)thiadiazole))) as conjugated polymer comprising benzothiophene divalent unit(s) (I).