MXene‐Interconnected Two‐Terminal, Mechanically‐Stacked Perovskite/Silicon Tandem Solar Cell with High Efficiency

Abstract Two‐terminal, mechanically‐stacked perovskite/silicon tandem solar cells offer a feasible way to achieve power conversion efficiencies (PCEs) of over 35%, provided that the state‐of‐the‐art industrial silicon solar cells and perovskite solar cells (PSCs) are fully compatible with one another. Herein, two‐terminal, mechanically‐stacked perovskite/silicon tandem solar cells are developed by mechanically interconnecting semitransparent PSCs and TOPCon solar cells with a MXene interlayer. The semitransparent PSCs are made from wide‐bandgap perovskite Cs_0.15FA_0.65MA_0.20Pb(I_0.80Br_0.20)₃ films. Furthermore, the co‐additives KPF₆ and CH₃NH₃Cl(MACl) are employed to reduce grain boundaries and intragranular defects in the perovskite, boosting the PCE of the semitransparent PSCs to a record‐high value of 20.96% under reverse scan (RS) through a reduction in non‐radiative recombination probability. These optimized semitransparent PSCs are then employed in MXene‐interconnected two‐terminal, mechanically‐stacked tandem solar cells. The enhanced interfacial carrier transportation, with minimal influence on light transmission, imparted by the MXene flakes allows the tandem solar cells to achieve a stabilized PCE of 29.65%. The tandem cells also exhibit acceptable operational stability and are able to retain ≈93% and 92% of their initial PCEs after 120 min of continuous illumination or storage in ambient air for 1000 h, respectively.