By expanding the absorption into infrared region, we have successfully demonstrated an enhanced efficiency of polymer solar cells by incorporating lead selenide (PbSe) colloidal quantum dots into copolymers of [poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)] as active layer. The influence of inorganic ligands and the post-annealing conditions on device performance has been investigated in detail. After optimization of these parameters, a maximum power conversion efficiency of 3.31 % is obtained from solar cell indium tin oxide (ITO)/poly(3,4-ethylendioxy thiophene): poly(styrenesulfonate) (PEDOT: PSS)/P3HT: PCBM: PbSe/Al under AM 1.5 and it has been improved by 14.5 % as compared with the control device ITO/PEDOT: PSS/P3HT: PCBM/Al.