Synergistic Passivation of Perovskite Absorber Films for Efficient Four‐Terminal Perovskite/Silicon Tandem Solar Cells

A high‐performance semitransparent perovskite solar cell (PSC) with small photovoltage loss is highly desired to achieve efficient and stable perovskite/silicon tandem solar cells. Herein, a synergistic passivation strategy is developed to suppress the electronic defects at both the grain boundary and surface of a perovskite layer (Cs 0.05 FA 0.82 MA 0.13 Pb(I 2.86 Br 0.14 )). It is found that the incorporation of a small amount of sodium fluoride (NaF) into perovskite precursor solution modulates the crystallization process, which results in large crystal grains with enhanced conductivity at the grain boundaries. Meanwhile, a thin 2D perovskite layer is constructed on the surface of the 3D perovskite film by solution coating a layer of phenethylammonium iodide (PEAI), which passivates the surface defects and improves the stability of perovskite films. As a consequence, the optimized semitransparent p–i–n PSC delivers a high power conversion efficiency (PCE) of 17.55% with an open‐circuit voltage of 1.11 V. Combining the semitransparent PSCs with a silicon cell, the efficiency of the four‐terminal perovskite/silicon tandem solar cells reaches a PCE of 23.82%.