Precisely Tuning 3D/Quasi‐2D Perovskite Heterojunctions in Wide‐Bandgap Perovskites for High‐Performance Tandem Solar Cells

interface. The devices with the WBG (1.78 eV) 3D/quasi-2D n = 3 perovskite heterostructures achieve the champion power conversion efficiency (PCE) of 20.71% (certified 20.53%). When combined with narrow-bandgap (NBG) perovskite sub-cells, the fabricated 2-terminal AP-TSCs achieve a PCE of 28.99% (certified 28.81%). The tandem device maintains 80% of its initial PCE after 501 h of operation at maximum power point.