CZTSSe offers cheap, environmental friendly and earth abundant material for solar devices, yet the record power conversion efficiency for such solar cells has stagnated at about 12 percent over the years. The main reason for low output voltage and overall performance is because of the extreme non radiative recombination in the heterojunction region. To find the overall optimization of solar cell and suitable buffer layer numerical simulation has been performed by SCAPS-1D software. Here, CZTSSe was used as a absorber layer, Al doped ZnO as a transparent conducting layer and ZnO as a window layer. CdS, Cd0.4Zn0.6S and ZnSe was used as a different buffer layer. The impact of thickness of absorber layer and buffer layer on V-oc, J(sc), FF and efficiency has been investigated. Also, the effect of temperature on the above-mentioned parameter of the solar cell was studied.