Absorption of near-infrared (NIR) photons of solar energy which includes the~40% of the sunlight energy is an effective approach to improve the photovoltaic performance of solar cells. In the present study, we have investigated PbS quantum dots (QDs) with different numbers of synthesis cycles (n) were introduced to ZnO nanorods (ZNRs) bulk-heterojunction (BHJ) solar cells. Our analysis revealed improving the power conversion efficiency (PCE) by absorbing the light in the visible and near-infrared regions. The Light absorption of solar cells was enhanced by PbS QDs which led to an increase in the photocurrent. With increasing (n), the PCE increases at first, then it decreases because of the attenuation of possible facilitation of exciton dissociation. For this reason, the number of cycles was optimized. As a result,byoptimizing the numbers of synthesis cycles (n), the PCE of PbSQD sensitized ZNRbulk heterojunction solar cells were improved from 2.76% to 4.01% by 1.45 times.
