A large FAS2+ ion in FAPbI3 scavenges localized electrons in defects, leading to perovskite solar cell module with remarkable performance values of 18.76% (25.74 cm2) and 15.87% (65.22 cm2), respectively.

Recently, scalable perovskite fabrication techniques for large, uniform, and highly crystalline perovskite layers have been developed by controlling the crystal chemistry of perovskite precursors. However, scalable techniques for the electron and hole transport layers (ETL and HTL) have rarely been investigated. A major challenge in a scalable technique is obtaining a uniform, highly crystalline, and ultrathin ETL at a low temperature. Here, large-area SnO 2 ETLs are fabricated by an electrostatic self-assembly method. The ETLs coated onto haze FTO show high uniformity without pin holes, as confirmed by an electroluminescence image of the perovskite solar module (PSM). In addition, the uniform and pinhole-free SnO 2 coating are indirectly verified by observing the unchanged shunt resistance of the PSC with increasing active area, compared to the conventional SnO 2 ETL-based PSC. On the basis of this self-assembly method, PSMs of areas 25 and 100 cm 2 are fabricated with power conversion efficiencies (PCEs) of 15.3 and 14.0% without shunt resistance loss, respectively.

Perovskite solar cells adopting a layer of various nanocrystals (NCs) on top of perovskite film exhibit similar enhancement of the photovoltaic (PV) properties regardless of the kind of NC material, even though NC materials possess different electrical and optical properties. In this paper, we reveal that the key reason for the enhanced PV performance is the surface passivation effect of the perovskite film by oleylamine ligands of NCs.

Formamidinium lead triiodide‐based perovskite solar cells have emerged as one of the most promising candidates that can be potentially used to develop photovoltaic technologies in the future. The commercial use of perovskite solar cell modules (PSCMs) is limited as it is challenging to fabricate high‐quality, efficient, and stable large‐area perovskite light‐absorbing films. Heptadecafluorooctanesulfonic acid tetraethylammonium salt (HFSTT), containing fluorinated long alkyl chains as hydrophobic tails and sulfonic acid groups (SO3−) as hydrophilic heads, which exhibit a great synergistic potential in large‐area film uniform fabrication, crystallization orientation modulation, defect passivation, and device operation stability enhancement, are introduced. The HFSTT‐modified films exhibit a prominent (100) orientation and lower trap‐state density as well as enhanced carrier mobilities and diffusion lengths, facilitating a champion unit device with an impressive power conversion efficiency (PCE) of 23.88% (0.14 cm2) and 22.52% (1 cm2) with a low voltage deficit around 0.341 V. The unencapsulated device retains ≈70% of its initial efficiency after 1000 h under heat damping test (60 °C and ≈60% RH). Moreover, the PSCMs exhibiting PCEs of 21.05% (with notable fill factor 0.79) and 18.27% are characterized by the active areas of 25.98 and 60.68 cm2, respectively.

Solvent engineering by Lewis‐base solvent and anti‐solvent is well known for forming uniform and stable perovskite thin films. The perovskite phase crystallizes from an intermediate Lewis‐adduct upon annealing‐induced crystallization. Herein, it is explored the effects of trimethyl phosphate (TMP), as a novel aprotic Lewis‐base solvent with a low donor number for the perovskite film formation and photovoltaic characteristics of perovskite solar cells (PSCs). As compared to dimethylsulfoxide (DMSO) or dimethylformamide (DMF), the usage of TMP directly crystallizes the perovskite phase, i.e., reduces the intermediate phase to a negligible degree, right after the spin‐coating, owing to the high miscibility of TMP with the anti‐solvent and weak bonding in the Lewis adduct. Interestingly, the PSCs based on methylammonium lead iodide (MAPbI3) derived from TMP/DMF‐mixed solvent exhibit a higher average power conversion efficiency of 19.68% (the best: 20.02%) with a smaller hysteresis in the current‐voltage curve, compared to the PSCs that are fabricated using DMSO/DMF‐mixed (19.14%) or DMF‐only (18.55%) solvents. The superior photovoltaic properties are attributed to the lower defect density of the TMP/DMF‐derived perovskite film. The results indicate that a high‐performance PSC can be achieved by combining a weak Lewis base with a well‐established solvent engineering process.

Pb contamination in aquatic environments causes severe pollution; therefore, harmless absorbents are required. In this study, we report a novel synthesis of whitlockite (WH, Ca18Mg2(HPO4)2(PO4)12), which is the second most abundant biomineral in human bone, and its application as a high‐performing Pb2+ absorbent. Hydroxyapatite (HAP) and WH are prepared via a simple precipitation method. The Pb2+ absorption performance and mechanism of the synthesized biominerals are investigated in aqueous solutions at neutral pH. The results demonstrate that WH exhibits an excellent Pb2+ absorption capacity of 2339 mg g−1, which is 1.68 times higher than the recorded value for HAP. Furthermore, the absorbed Pb2+ ions are recycled into high‐purity PbI2. This is employed as a precursor for the fabrication of perovskite solar cells (PSCs), resulting in a conversion efficiency of 19.00% comparable to that of commercial PbI2 powder (99.99% purity). Our approach provides an efficient way to remove Pb2+ ions from water and reuse them in the recycling of PSCs.

Flexible perovskite solar cells (f-PSCs) have attracted increasing attention for a variety of applications because of their desirable form factor and improved durability. However, the f-PSC fabrication process has not been optimized, resulting in their uneven efficiency. We report a van der Waals stacking (vdWS) process that yields uniform and highly crystalline perovskite films on flexible substrates by uniform heat transfer during the perovskite annealing process. In addition, the surface and grain boundary defects on the perovskite film were effectively minimized with the vacuum-assisted passivation post-treatment; accordingly, the environmental and mechanical stabilities of f-PSCs were enhanced. Also, the best f-PSC with an active area of 0.14 cm2 achieved power conversion efficiencies (PCEs) of 41.23% and 22.54% under 1000 lx and 1 sun illuminations, respectively. Furthermore, the vdWS process showed scalable uniformity through flexible perovskite solar minimodules with a certified PCE of 18.35% in an active area of 48.90 cm2.

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