Managing Interfacial Hot‐Carrier Cooling and Extraction Kinetics for Inverted Ma‐Free Perovskite Solar Cells Over 23% Efficiency via Dion–Jacobson 2D Capping Layer

Abstract While quasi‐2D perovskite is often used in inverted perovskite solar cells (PSCs) to improve the interfacial carrier transfer, the development of pure 2D perovskite with superior stability is rarely seen and the corresponding carrier‐extraction kinetics remains unclear. Here, a variety of hexatomic ring cations including piperidine, pyridine, and cyclohexane are introduced to modify the perovskite/electron transport layer interface. The Dion–Jacobson phase 2D cladding (n = 1) based on 3‐(aminomethyl) piperidinium is proved to form a coordinated energy landscape and homogeneous surface potential distribution, and effectively prolong the electron diffusion length (≈1.58 µm) and accelerate the hot‐carrier extraction rate (2.5 times that of Control at 400 K). Furthermore, the quasi‐2D treatment (n ≈ 3,4) demonstrated a slight escalation in short‐circuit current, but failed to inhibit the interdiffusion of Ag, Pb, and I under illumination. Finally, one of the state‐of‐art power conversion efficiency (PCE) for MA‐free inverted PSCs is achieved at 23.62% with increased open‐circuit voltage (≈1.15 V) and fill factor (≈82.8%). Most importantly, 89% and 93.6% of initial PCE are retained after 720 h under 85 °C heating and 1000 h under maximum power point tracking, illustrating satisfactory thermal and operational stability with pure 2D perovskite capping layer.