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Inorganic CsSnI 3 with low toxicity and a narrow bandgap is a promising photovoltaic material. However, the performance of CsSnI 3 perovskite solar cells (PSCs) is much lower than that of Pb-based and hybrid Sn-based (e.g., CsPbX 3 and CH(NH 2 ) 2 SnX 3 ) PSCs, which may be attributed to its poor film-forming property and the deep traps induced by Sn 4+ . Here, a bifunctional additive carbazide (CBZ) is adapted to deposit a pinhole-free film and remove the deep traps via two-step annealing. The lone electrons of the -NH 2 and -CO units in CBZ can coordinate with Sn 2+ to form a dense film with large grains during the phase transition at 80 °C. The decomposition of CBZ can reduce Sn 4+ to Sn 2+ during annealing at 150 °C to remove the deep traps. Compared with the control device (4.12%), the maximum efficiency of the CsSnI 3 :CBZ PSC reaches 11.21%, which is the highest efficiency of CsSnI 3 PSC reported to date. A certified efficiency of 10.90% is obtained by an independent photovoltaic testing laboratory. In addition, the unsealed CsSnI 3 :CBZ devices maintain initial efficiencies of ≈100%, 90%, and 80% under an inert atmosphere (60 days), standard maximum power point tracking (650 h at 65 °C), and ambient air (100 h), respectively.

Integrating highly efficient photovoltaic (PV) function into light‐emitting diodes (LEDs) for multifunctional display is of great significance for compact low‐power electronics, but it remains challenging. Herein, it is demonstrated that solution engineered perovskite nanocrystals (PNCs, ≈100 nm) enable efficient electroluminescence (EL) and PV performance within a single device through tailoring the dispersity and interface. It delivers the maximum brightness of 490 W sr−1 m−2 at 2.7 V and 23.2% EL external quantum efficiency, a record value for near‐infrared perovskite LED, as well as 15.23% PV efficiency, among the highest value for nanocrystal perovskite solar cells. The PV–EL performance is well in line with the reciprocity relation. These all‐solution‐processed PV‐LED devices open up viable routes to a variety of advanced applications, from touchless interactive screens to energy harvesting displays and data communication.

Perovskite thin film quality, including large grain size and low defect, is one of the fundamental factors to improve the performance and stability of perovskite solar cells (PSCs). Herein, trifluoromethylphenylacetic acid (TFPA) as the accelerant of Ostwald ripening is introduced and an in situ crystal growth control (ICGC) strategy is developed to obtain high‐quality thin films. With adding a proper amount of TFPA into the FAI/MAX (X is Br and Cl) precursor in the two‐step method, the larger grain size and reduced defect density perovskite are achieved due to Ostwald ripening. The ICGC process makes the average particle size from 476 to 625 nm. The defect density is reduced by a factor of 3.18. The high‐quality thin film endows the champion PSC (SnO2/perovskite/spiro‐OMeTAD) with a power conversion efficiency (PCE) of champion PSC higher than 22.19%. Furthermore, TFPA is insoluble in the water and thus TFPA‐modified film is resistive to moisture. The device can be stored in an argon glove box for 2000 h without efficiency change and when exposed to 65–75% relative humidity for more than 1500 h, it retains more than 85% of the initial PCE.