Here we report a solution-processing strategy to stabilize the perovskite-based heterostructure. Strong Pb–Cl and Pb–O bonds formed between a [CH(NH2)2]x[CH3NH3]1−xPb1+yI3 film with a Pb-rich surface and a chlorinated graphene oxide layer. The constructed heterostructure can selectively extract photogenerated charge carriers and impede the loss of decomposed components from soft perovskites, thereby reducing damage to the organic charge-transporting semiconductors. Perovskite solar cells with an aperture area of 1.02 square centimeters maintained 90% of their initial efficiency of 21% after operation at the maximum power point under AM1.5G solar light (100 milliwatts per square centimeter) at 60°C for 1000 hours. The stabilized output efficiency of the aged device was further certified by an accredited test center.

The poor crystalline quality of tin-based perovskite films with unfavorable trap states is the biggest challenge to achieve highly efficient tin-based perovskite solar cells. Here, we reveal the surface-controlled growth of FASnI 3 perovskites and further precisely control the crystallization process by reducing the surface energy of the solution-air surface with a tailor-made pentafluorophen-oxyethylammonium iodide (FOEI). A highly oriented and smooth FASnI 3 -FOEI perovskite film with longer carrier lifetime is achieved with a certificated efficiency of 10.16% from an accredited institute.

Operational stability is crucial for the success in large-scale application of metal halide perovskites devices. The diffusion of volatile iodide component of perovskites can induce irreversible device degradation. Here, low-dimensional diffusion barriers were introduced to increase the operational stability of highefficiency large-area PSC modules. A negligible decay was observed after 1,000 h under severe test condition for a 15% high-efficiency solar module.

Tin perovskite solar cells (TPSCs) have triggered intensive research as a promising candidate for lead-free perovskite solar cells. However, it is still challenging to obtain efficient and stable TPSCs because of the low defects formation energy and the oxidation of bivalent tin; Here, we report a TPSC with a stable amorphous-polycrystalline structure, which is composed of a tin triple-halide amorphous layer and cesium-formamidinium tin iodide polycrystals. This structure effectively blocks the outside oxygen, moisture and also suppresses the ion diffusion inside the devices. In addition, its energy level benefits the charge extraction and transport in TPSCs. This design enabled us to obtain the certified quasi-steady-state efficiency over 10% for TPSCs from an accredited certification institute. The cell was stable, maintaining 95% of the initial PCE after operation at the maximum power point under AM 1.5 G simulated solar light (100 mWcm −2) for 1000 hours.

The relatively lower crystallinity and random orientation of quantum well structures hinder carrier transport and limit the performance of formamidinium (FA) based low‐n 2D perovskite devices. In this work, the crystallization and quantum well orientation are fine tuned to achieve efficient low‐n FA based Ruddlesden–Popper perovskite solar cells. The effects of different ionic additives on the crystallization, orientation, and photovoltaic performance of FA based low‐n 2D perovskites are comparatively investigated. It is found that NH4+ and SCN− can significantly retard the heterogeneous crystallization of low‐n phases in the intermediate state, and drive the templated growth of quantum well structure with vertical orientation. The optimized photovoltaic device based on (BA)2(FA)3Pb4I13 achieved a power conversion efficiency (PCE) of 18.14%, setting the highest record for FA‐based low‐n 2D perovskite solar cells as far as it is known (average n = 4). The unencapsulated device exhibited excellent stability and maintained 93.3% of its original PCE at 85 °C, and 86.3% at 1 Sun illumination after 720 h in humid ambient condition.