We studied the ternary blend films composed of low-degree of polymerization poly[2

6-(4

4-bis-(2-ethylhexyl)-4H-cyclopenta[2

1-b;3

4-b’]dithiophene)-alt-4

7-(2

1

3-benzothiadiazole)]

(LDP-PCPDTBT)

[6

6]-phenyl-C61-butyric acid methyl ester (PC

61

BM)

and polymethylmethacrylate (PMMA)

processed with and without 1

8-dibromooctane as solvent additive. The LDP-PCPDTBT and PC

61

BM phases in the PMMA matrix were characterized amorphous and crystalline

respectively

without the additive processing

while both the crystallinity of the LDP-PCPDTBT component and the aggregation of PC

61

BM component could be significantly promoted with the additive processing. The power conversion efficiency of solar cell was increased 50% by the additive processing

as a result of the increased open-circuit voltage and the optimized phase separation of LDP-PCPDTBT and PC

61

BM in the PMMA matrix. The current research indicates that the low-degree of polymerization alternating copolymers can be recycled as efficient electron donors in association with PMMA

helpful for reducing the material cost of organic solar cells.