Researchers have begun to replace the organic compounds of methylammonium (MA) and formamidinium (FA)-based perovskite solar cells (PSCs) with cesium (Cs) in order to address the volatility problem. In this work, a stable CsPbI2Br-based perovskite solar cell is optimized to bring out its full potential using SCAPS-1D simulation software. Four ETLs (ZnSe, MZO, PC61BM, and LBSO) and 10 HTLs have been combined to study their photovoltaic characteristics. Using the structure of FTO/PC61BM/CsPbI2Br/HTL/Au, all 10 HTLs have been studied, and it is found that CNTS is the most suitable HTL among them. With this chosen HTL, four different structures with the chosen ETLs are formed. After the formation of these four structures, the absorber, ETL, and HTL layer thicknesses are optimized. Following that, the acceptor concentration for the absorber and HTL and the donor concentration of the ETL are optimized. Among the four structures, FTO/MZO/CsPbI2Br/CNTS/Au shows the best performance with a VOC of 1.36 V, a JSC of 17.25 mA/cm2, an FF of 89.66 %, and a PCE of 21.13 %, respectively. The effects of parasitic resistances, along with temperature, on the performance of the device structures are observed. The J-V and QE characteristic curves, generation, and recombination rates for basic and final optimized structures are also compared. After the optimization, it is clear that the performance of the investigated device structures has improved.