In this paper, the effects of solvent mixtures on the morphology, charge transport, and light trapping of poly[N-900-hepta-decanyl-2,7-carbazole-alt-5,5-（40,70-di-2-thienyl-20,10,30-benzothiadiazole）]（PCDTBT） and [6,6]-phenyl C71-butyric acid methyl ester（PC71BM） based solar cells were investigated. As a good solvent for PCDTBT, o-dichlorobenzene（ODCB） was selected to mix with chloroform（CF）, chlorobenzene（eB）, and 1,2,4-Trichloroben-zene（TCB） for optimizing the morphology of the PCDTBT：PCTIBM active layer. It can be found that the device performance of polymer solar cells（PSCs） has been greatly improved when using a optimal blend ratio. Especially, the PSCs fabricated via ODCB（90%）/CF（10%, volume fraction） mixture exhibit a remarkable enhancement of photon-to-current efficiency（PCE） from 5.16% to 7.47%. The enhanced performance of the PSCs can be attributed to the higher absorption, the lower resistance, and the optimized surface morphology of the active layers modified by the solvent mixtures.
