**7. Conclusion**

Perovskite silicon tandem solar cell perhaps has a very high potential to reach low level cost of electricity.

To achieve highly efficient and reliable tandem perovskite/silicon solar cells, a multi-level approach is required. This includes improving the performance of individual layers in each cell. Examining the charge transport in each layer when they are stacked, and finally efficient-light in-coupling between top and bottom cells. One of the critical conditions for high device efficiency is the proper choice of the bandgap for the top perovskite cell in the tandem. Optical losses due to parasitic absorption losses resulting from both inefficient intermediate reflecting layers and inefficient absorption in the top cell have to be addressed. Low absorption coefficient of silicon bottom cell reduces the light absorption and reflects in efficiency of tandem solar cell. Stable and efficient light management is necessary for further improvement in the device performance.

The research on replacing highly pure expensive Si with recycled left-over multicrystalline Si in tandem cells without much compromise in efficiency will upscale lowcost tandem cells. Si heterojunction solar cells still exist as the favorite bottom cell over homo-junction cells. Efficient doping with hydrogen passivates and stabilizes silicon and its heterojunction cells. Theoretically it is possible to achieve higher efficiency from the tandem cells of 31.2% at AM 1.5G and 44% out of space.
