To meet the growing demand for eco-friendly solar technologies, lead-free perovskite (PVK)
materials are emerging as promising alternatives to their lead-based counterparts. Among
these, ASnI2Br stands out due to its suitable wide bandgap, making it a strong candidate for
integration into both 4T and 2T tandem configurations. In pursuit of a fully eco-friendly solar
cell design, we present the development of lead-free ASnI2Br/Si tandem solar cells, offering a
sustainable approach with high potential for efficiency improvements. First, the advancement
of 4T tandem cell efficiency is discussed. The main structure consists of
FTO/PEDOT:PSS/ASnI2Br-PVK/C60/BCP/Ag inverted structure as the top cell and an n-type
Si as the rear cell. Based on the simulation findings, the suggested top cell structure performs
much better when TiO2 is substituted as the electron transport layer (ETL) instead of C60, while CuSCN is found to be a good replacement for PEDOT:PSS as a hole transport layer
(HTL). With these changes, the top cell's efficiency becomes 15.29%. In addition, optimizations for the bottom cell are carried out. Efficiencies for bare and filtered bottom
cells reaching 23.97% and 12.53% are achieved, respectively, at 30 µm absorber thickness
and 1 ms lifetime. With only two terminals, the 2T cell has fewer manufacturing costs for the
photovoltaic (PV) module than the 4T cell. Thus, we introduce a design for a 2T cell by
converting the enhanced 4T cell, while inverting the top cell to be compatible with the rear
cell n-p structure. To ensure current matching, the correct thickness must be established for
both sub-cells, where the thickness of the perovskite absorption layer rises from 200 nm to
545 nm. This led to reaching the matching point at a current equal to 16.35 mA/cm2
, and our
simulation for the monolithic stacked 2T TSC produced a PCE of 24.28%.