Optical design of monolithic two-terminal perovskite/Si tandem solar cells for efficient photon management

Monolithic 2T perovskite/Si tandem solar cells with different interlayers to avoid the refractive index mismatch at the interface were systematically investigated to demonstrate the potential of using this strategy for efficient light-harvesting. The device structure was carefully optimized to achieve maximal matched photocurrent (Jmax) between two subcells through optical simulation based on transfer matrix method. The results showed that the tandem devices with an inverted structure can yield much higher Jmaxthan that of the regular devices with potentially thinner Si being used and exhibit less sensitive to the thickness of top perovskite cell, indicating that they are more suitable for the construction of high -performance tandem cells. Moreover, by introducing an optical interlayer with an intermediate refractive index to enhance light coupling from the top to the bottom cell, a significantly enhanced Jmax from 18.02 mA/cm2 to 19.13 mA/cm2 has been achieved for those inverted tandem cells. Similar results have also been obtained in the tandem device with bilayer interlayers. Optical properties within the device indicated that the increase of the Jmax with optimized interlayers was ascribed to the effective reduction of interface reflection loss, which can facilitate the better light utilization. Finally, the enhanced Jmax under AM 1.5 conditions using the interlayers would also lead to a strong improvement in the yearly energy yield under the real condition.