**3. Results and Discussion**

As we have selected undoped materials, therefore the thickness of each layer was only optimized for the current proposed perovskite solar cell. The film thickness of holetransport layer, perovskite absorber, and electron-transport layer play a very crucial role to optimize the overall photovoltaic response of perovskite solar cell. Both the electrontransport layer and hole-transport layer interact not only with the perovskite layer but also with their respective electrode materials. The interaction between PCBM and cathode interface is improved by incorporating a very thin layer of BCP with already reported optimized parameters as shown in Table 1, therefore the BCP layer is not further optimized in this study.
