Bifacial Perovskite/Silicon Heterojunction Tandem Solar Cells Based on Fapbi3-Based Perovskite Via Hybrid Evaporation-Spin Coating

Combining the two technologies of tandem solar cells and bifacial solar cells has a great potential to maximize energy harvesting while minimizing material and surface usage. Mid-bandgap perovskites (1.50-1.60 eV) are important for fulfilling current matching in bifacial perovskite/silicon heterojunction tandem solar cells. Herein, efficient (>20%) and stable planar FAPbI3-based perovskite (1.54 eV) solar cells have been fabricated via a hybrid evaporation-spin coating process. X-ray diffraction and electron microscopy data reveal the formation of highly crystalline (001) perovskite domains. The fabricated high-quality perovskite films lead to a more homogenized contact potential difference at the film surface and a reduction in non-radiative losses, resulting in a quasi-Fermi-level splitting (half-cell) of 1.16 eV, rendering 120 mV non-radiative losses. Transferring these films into tandem devices atop single-side textured silicon heterojunction bottom cells, we obtain an efficiency of >24% under AM1.5G illumination for monofacial devices with an active area of 1.21 cm2. Furthermore, the bifacial devices generate >27 mW cm-2 power output with 15% rear illumination fraction.