Boosting Carrier Transport in Quasi‐2D/3D Perovskite Heterojunction for High‐Performance Perovskite/Organic Tandems

Wide‐bandgap (WBG) perovskites are continuously in the limelight owing to their applicability in tandem solar cells. The main bottlenecks of WBG perovskites are interfacial non‐radiative recombination and carrier transport loss caused by interfacial defects and large energy‐level offsets, which induce additional energy losses when WBG perovskites are stacked with organic solar cells in series because of unbalanced carrier recombination in interconnecting layer (ICL). To solve these issues, 1,3‐propanediammonium iodide (PDADI) is incorporated to form Dion–Jacobson ‐phase quasi‐2D perovskites with mixed high‐n‐values in WBG perovskites. PDADI simultaneously repairs the shallow/deep defects and establishes a Type‐II energy‐level alignment between quasi‐2D/3D and 3D perovskites for rapid carrier extraction. More importantly, the short‐chain diammonium cation in quasi‐2D perovskite with high n‐values results in a short Pb–I inorganic layer spacing, which enhances the interlayer electronic coupling and weakens the quantum‐well confinement effect that restricts carrier transport. The suppressed transport loss increases the electron concentration in the ICL for balanced carrier recombination. The 0.0628 and 1.004 cm2 perovskite/organic tandems achieve remarkable efficiencies of 25.92% and 24.63%, respectively. The quasi‐2D capping layer can inhibit ion migration, allowing perovskite/organic tandems to show excellent operational stability (T85 > 1000 h). A quasi‐2D/3D heterojunction‐based WBG perovskite is constructed to repair the surface defects and weaken the quantum‐well confinement effect. These advances reduce interfacial carrier transport loss, contributing to balanced carrier recombination in the interconnecting layer. The resulting perovskite/organic tandems exhibit record power conversion efficiencies of 25.92% (0.0628 cm2) and 24.63% (1.004 cm2), as well as robust operational stability.