Upscaling efficient and stable perovskite layers is one of the most challenging issues in the commercialization of perovskite solar cells. Here, a lead halide–templated crystallization strategy is developed for printing formamidinium (FA)–cesium (Cs) lead triiodide perovskite films. High-quality large-area films are achieved through controlled nucleation and growth of a lead halide•N-methyl-2-pyrrolidone adduct that can react in situ with embedded FAI/CsI to directly form α-phase perovskite, sidestepping the phase transformation from δ-phase. A nonencapsulated device with 23% efficiency and excellent long-term thermal stability (at 85°C) in ambient air (~80% efficiency retention after 500 hours) is achieved with further addition of potassium hexafluorophosphate. The slot die–printed minimodules achieve champion efficiencies of 20.42% (certified efficiency 19.3%) and 19.54% with an active area of 17.1 and 65.0 square centimeters, respectively.

Upscalable fabrication of efficient and stable perovskite solar modules is urgently needed for commercialization. Herein, we introduce methylammonium chloride (MACl) additives in the cosolvent system of N-methyl-2-pyrrolidone (NMP) / N,N-dimethylformamide (DMF) to control the formation of intermediate phases during the growth of formamidinium (FA)-cesium (Cs) lead triiodide perovskite films. We achieve high quality films upon drying without the use of antisolvent.By implementing bulk and surface passivation, the champion efficiencies of 24.02% for a smallsized solar cell and 20.5% for a 5 cm × 5 cm solar mini-module on an aperture area of 22.4 cm 2 (geometrical fill factor is ~96%) are achieved by spin-coating. The fully blade-coated perovskite 2 solar sub-module demonstrates a champion efficiency of 15.3% on an aperture area of 205 cm 2 . The solar mini-module exhibits impressive operational stability with a T80 lifetime over 1000 hours at maximum power point tracking (MPPT) under continuous light illumination.

2D/3D perovskite heterostructures or composites are recognized as efficient strategies to improve the stability of perovskite solar cells. Herein, a novel solution process to develop 2D/3D perovskites with modulated diffusion passivation by introducing phenylethylammonium iodide (PEAI) and N,N‐dimethylformamide (DMF) additive, which could effectively enhance device performance and long‐term stability, is demonstrated. Compared with conventional devices, the device with PEAI and DMF solvent additive treatment exhibit enhanced charge transport, improved charge extraction, and suppressed nonradiative carrier recombination. The solar cells with an optimal 2D/3D perovskite passivation treatment exhibit an extremely high fill factor of 83.6% and an average power conversion efficiency of 21.4% (21.3% using integrated photocurrent from the incident photon‐to‐current efficiency spectra) based on the NiOx hole transport layer. Furthermore, the unencapsulated device exhibits excellent stability under continuously simulated sunlight illumination and outstanding air stability after 1000 h of storage under ambient air conditions.

Metal halide perovskites are attractive for highly efficient solar cells. As most perovskites suffer large or indirect bandgap compared with the ideal bandgap range for single-junction solar cells, bandgap engineering has received tremendous attention in terms of tailoring perovskite band structure, which plays a key role in light harvesting and conversion. In this Review, various reported bandgap engineering strategies are summarized. The recently widely used two main strategies including impurity and pressure as well as their underlying mechanisms are reviewed comprehensively. In addition, intermediate band and external electric field for bandgap engineering are also investigated. Moreover, future research directions are outlined to guide the further investigation.

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All-inorganic perovskites have been intensively investigated as potential optoelectronic materials because of their excellent thermal stability, especially for CsPbI 2 Br. Herein, the authors studied the effects of mixed passivation utilizing organic phenylethylammonium bromide and inorganic ionic cesium bromide (PEABr + CsBr) on the all-inorganic perovskite (CsPbI 2 Br) solar cells for the first time. The treatment with different passivation mechanisms enhances the perovskite film quality, resulting in uniform surface morphology and compact film with low trap density. Besides, the passivation improves the energy level alignment, which benefits the hole extraction at the perovskite/HTL interface and drives the interface electron separation, suppressing the charge recombination and realizing a high open-circuit voltage (V oc ). Finally, the device represents a high power conversion efficiency (PCE) of 16.70%, a V oc of 1.30 V, and an excellent fill factor (FF) of 0.82. The V oc loss and high FF should be among the best values for CsPbI 2 Br based devices. Furthermore, the treated devices exhibit remarkable long-term stability with only 8% PCE loss after storing in a glove box for more than 1000 h without encapsulation.

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