TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The polymer block (A) contains monomeric unit -a-b- chosen from 11 monomeric units e.g. monomeric units of formulae (i)-(v). The electron-accepting material is fullerene or its derivative(s). The polymer block (B) has monomeric unit having 2-5 thiophene-2,5-diyl groups having substituent at 3rd position. The polymer block (B) is random copolymeric block having thiophene-2,5-diyl group, which has substituent at 3rd-position. The pi-electrode conjugated block copolymer has number average molecular weight of 1000-200000 g/mol.-a-=6 groups chosen from group e.g. groups of formulae (a)-(e);-b-=11 groups chosen from group e.g. groups of formulae (g)-(k);V1=-NR1-, -O- or -S-;V2=-(CR1)2-, -NR1-, -(SiR1)2- or -(GeR1)2-;V3=-(Ar)n-;V4=-NR1-, -O- or -CR2=CR2-;V5= oxygen or sulfur;R1=1-18C alkyl (optionally substituted);R2=H or 1-18C alkyl (optionally substituted);R3=1-18C alkyl or alkoxy (both optionally substituted);R4=H, halo, 1-18C alkyl or aryl (both optionally substituted);R5=1-18C alkyl (optionally substituted), aryl, alkyl carbonyl or alkyloxycarbonyl;R6=H or halo;m=1-3;andn=0-3. EXAMPLE - 2,6-Dibromo-4,4'-bis(2-ethylhexyl)-cyclopenta(2,1-b:3,4-b')dithiophene and 4,7-bis(3,3,4,4-tetramethyl-2,5,1-dioxaborolan-1-yl)benzo(c)(1,2,5)thiadiazole were polymerized, to obtain polymer block (A1). 2-bromo-5-iodo-3-hexyl thiophene was reacted with i-propyl magnesium chloride to obtain organic magnesium compound, which was reacted in presence of nickel catalyst to obtain polymer block (B1). (In g) polymer block (A1) (0.8), polymer block (B1) (0.25), toluene (20 mL), 2 M potassium carbonate aqueous solution (10 mL), tetrakis(triphenylphosphine)palladium(0) (20.5 mg) and Aliquat 336 (RTM: quaternary ammonium salt) (0.8 mg) were added, stirred at 80 degrees C for 24 hours, reaction solution was poured into methanol (200 mL), obtained crude product was dried under reduced pressure, deposited solid was filtered, washed using water (20 mL), methanol (20 mL), acetone (100 mL) and hexane (100 mL), extracted using chloroform (100 mL), obtained solution is poured into methanol (1L), dried under reduced pressure, and deposited solid was filtered to obtain block copolymer (0.32).