Tin‐Based Perovskite Solar Cells Reach Over 13% with Inclusion of N‐Doped Graphene Oxide in Active, Hole‐Transport, and Interfacial Layers

Abstract Tin‐based perovskite (Sn‐PS) is one of the most promising candidates in lead‐free perovskite solar cells (PSCs), but its poor stability and low power conversion efficiency (PCE) have been the main bottleneck towards further development. Here, to develop a stable and efficient Sn‐based PSC, nitrogen‐doped graphene oxide (N_xGO) has been, for the first time, incorporated in active, hole‐transport and interfacial layers. The inclusion of N_xGO slowed the crystallization of Sn‐PS and suppressed the Sn²⁺/Sn⁴⁺ oxidation, resulting in pinhole‐free dense films having large grains, reduction of recombination loss, well‐matched energy levels, and thereby significantly improving the device performance. Compared to the pristine Sn‐PS cells, the champion devices with N_xGO‐based composites in active, hole‐transport, and interfacial layers showed dramatic enhancement of photovoltaic parameters (i.e., open‐circuit voltage = 0.961 V, photocurrent = 21.21 mA cm⁻², fill factor = 65.05% and PCE = 13.26%). Furthermore, the N_xGO‐based cells without encapsulation showed remarkable improvement of long‐term stability with sustaining 91% of the initial PCE over 60 d, photostability, and reproducibility.