Solar energy has been sought as one of the prominent candidates among the energy harvesting methods. The energy conversion efficiency of solar cell is limited by its ability of harvesting energy from limited range in solar energy spectrum. We approach this issue by using the down-conversion effect with conventional CdSe quantum dots (QDs), increasing probability of electron-hole generation in designated solar cell. In our study, we fabricated GaAs single junction solar cells and applied QDs for down-conversion. We examine the effects of such application on the solar cell properties with various methods including TR-PL technique.