Design and modeling of a planar 2D nanostructured intermediate layer for light management in a very-thin SHJ bottom cell based monolithic perovskite/silicon tandem solar cell

We present an optical simulation for a very-thin (60 & mu;m) SHJ (silicon heterojunction cell) bottom cell based planar monolithic perovskite/silicon tandem solar cell incorporated with an intermediate reflector layer (IRL) in between the top and the bottom sub-cell to study the light management. The simulation was performed in a commercial software called Ansys Lumerical FDTD Solver. In this study, the tandem solar cell was simulated by incorporating a TFOR (topologically flat but optically rough) IRL of different periods, a DBR (distributed Bragg reflector) IRL, and a combination of (TFOR + DBR) IRL in the intermediate region to check the optical absorptance enhancement in the top and the bottom sub-cells, and, also the reflectance spectrum of the tandem solar cell. The tandem solar cell incorporated with a TFOR IRL was simulated for a range of top cell thicknesses, keeping the bottom cell thickness 60 & mu;m (fixed); aiming to use as a flexible tandem solar cell. This exhibits a current density (Jsc) enhancement in the bottom sub-cell due to the incorporation of TFOR IRL, with a maximum for 500 nm period TFOR. However, the current density of the top sub-cell remains unchanged. The closest Jsc of both the top and the bottom sub-cells reaching the current-match condition is found in the tandem solar cell incorporated with a 500 nm period TFOR IRL. For the PIN based perovskite (500 nm)/silicon (60 & mu;m) tandem solar cells, the maximum current density enhancement in the bottom sub-cell resulting from the incorporation of a 500 nm period TFOR IRL is 0.43 mA/cm2. However, a DBR IRL or (TFOR + DBR) IRL incorporation in the tandem solar cell could not improve the current density of the bottom sub-cells. Instead, it increases the current density in the top sub-cells. Moreover, a current density loss was also analyzed in the TFOR IRL which shows that the current density loss decreases by increasing the TFOR period and a maximum loss is at 200 nm period. Further, an electric field analysis was also done in the top and the bottom sub-cells at peak absorption wavelengths, which shows that the electric field is more concentrated in the bottom sub-cell due to TFOR IRL, confirming the forward scattering of light in the tandem solar cell incorporated with TFOR IRL.

Automated summary

An optical simulation is performed on a planar monolithic perovskite/silicon tandem solar cell with an intermediate reflector layer (IRL) to study light management. The simulation results show that the incorporation of different reflector layers can enhance the optical absorptance of the top and bottom sub-cells, with the combination of a topologically flat but optically rough (TFOR) IRL yielding the best results. Furthermore, the simulation also reveals that the introduction of the reflector layer leads to a reduction in the light absorption of the top sub-cell and a higher electric field concentration in the bottom sub-cell.