Perovskite/perovskite planar tandem solar cells: A comprehensive guideline for reaching energy conversion efficiency beyond 30%

Perovskite/perovskite tandem solar cells (Pk/Pk TSCs) have a substantial potential to outperform the Shockley-Queisser limit of single-junction solar cells. However, optimum material bandgap selection and device processability impede the progress in acquiring efficient Pk/Pk TSCs. The choice of charge transport/contact materials additionally has a significant influence on the photovoltaic performance of Pk/Pk TSCs. Hence, the actual fabrication of a two-terminal Pk/Pk TSC becomes tricky, which requires a detailed understanding of the underlying optical and electrical properties of the device. In this study, a wide bandgap (~1.72 eV) lead iodine-bromide (Pb–I–Br) and a narrow bandgap (~1.16 eV) tin lead-iodide (Sn–Pb–I) perovskite absorbers are considered as potential sub-cells for realizing highly efficient planar Pk/Pk TSCs. Furthermore, energetically associated hole and electron selective contacts are prepared by atomic layer deposition (ALD) of metal oxides. The optics of solar cells is investigated by three-dimensional finite-difference time-domain (FDTD) optical simulations, and finite element method (FEM) electrical simulations are exploited to determine realistic photovoltaic performance parameters. A comprehensive study is carried out to provide a complete guideline for the realization of energy conversion efficiency exceeding 30% in Pk/Pk TSCs.