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

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(x)GO) has been, for the first time, incorporated in active, hole-transport and interfacial layers. The inclusion of N(x)GO 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(x)GO-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(x)GO-based cells without encapsulation showed remarkable improvement of long-term stability with sustaining 91% of the initial PCE over 60 d, photostability, and reproducibility.