Yuanhang Cheng

Despite the rapidly increased power conversion efficiency (PCE) of perovskite solar cells (PVSCs), it is still quite challenging to bring such promising photovoltaic technology to commercialization. One of the challenges is the upscaling from small-sized lab devices to large-scale modules or panels for production. Currently, most of the efficient inverted PVSCs are fabricated on top of poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] (PTAA), which is a commonly used hole-transporting material, using spin-coating method to be incompatible with large-scale film deposition. Therefore, it is important to develop proper coating methods such as blade-coating or slot-die coating that can be compatible for producing large-area, high-quality perovskite thin films. It is found that due to the poor wettability of PTAA, the blade-coated perovskite films on PTAA surface are often inhomogeneous with large number of voids at the buried interface of the perovskite layer. To solve this problem, self-assembled monolayer (SAM)-based hole-extraction layer (HEL) with tunable headgroups on top of the SAM can be modified to provide better wettability and facilitate better interactions with the perovskite coated on top to passivate the interfacial defects. The more hydrophilic SAM surface can also facilitate the nucleation and growth of perovskite films fabricated by blade-coating methods, forming a compact and uniform buried interface. In addition, the SAM molecules can also be modified so their highest occupied molecular orbital (HOMO) levels can have a better energy alignment with the valence band maxima (VBM) of perovskite. Benefitted by the high-quality buried interface of perovskite on SAM-based substrate, the champion device shows a PCE of 18.47% and 14.64% for the devices with active areas of 0.105 cm² and 1.008 cm², respectively. In addition, the SAM-based device exhibits decent stability, which can maintain 90% of its initial efficiency after continuous operation for over 500 h at 40 ℃ in inert atmosphere. Moreover, the SAM-based perovskite mini-module exhibits a PCE of 14.13% with an aperture area of 18.0 cm². This work demonstrates the great potential of using SAMs as efficient HELs for upscaling PVSCs and producing high-quality buried interface for large-area perovskite films.

Abstract Multiple cation‐composited perovskites are demonstrated as a promising approach to improving the performance and stability of perovskite solar cells (PSCs). However, recipes developed for fabricating high‐performance perovskites in laboratories are always not transferable in large‐scale production, as perovskite crystallization is highly sensitive to processing conditions. Here, using an in situ optical method, the ambient temperature effect on the crystallization process in multiple cation‐composited perovskites is investigated. It is found that the typical solvent‐coordinated intermediate phase in methylammonium lead iodide (MAPbI 3 ) is absent in formamidinium lead iodide (FAPbI 3 ), and nucleation is almost completed in FAPbI 3 right after spin‐coating. Interestingly, it is found that there is noticeable nuclei aggregation in Formamidinium (FA)‐based perovskites even during the spin‐coating process, which is usually only observed during the annealing in MAPbI 3 . Such aggregation is further promoted at a higher ambient temperature or in higher FA content. Instead of the general belief of stress release‐induced crack formation, it is proposed that the origin of the cracks in FA‐based perovskites is due to the aggregation‐induced solute depletion effect. This work reveals the limiting factors for achieving high‐quality FA‐based perovskite films and helps to unlock the existing narrow processing window for future large‐scale production.

Abstract The residual strain induced during the growth of perovskite film is an intrinsic issue that significantly affects the efficiency and stability of perovskite solar cells (PVSCs). Inspired by the flipped annealing method to release strain in perovskite thin films, SiO 2 ‐coated gold nanorods (GNR@SiO 2 ) are introduced into perovskite film and advantage of the plasmonic local heating effect is taken for in situ strain relaxation. The GNR@SiO 2 ‐incorporated inverted PVSCs exhibit a champion power conversion efficiency (PCE) over 23%, which is the highest PCE in plasmonic‐incorporated PVSCs. Moreover, the intrinsic stability of the resulting PVSCs is greatly improved for the nonencapsulated device and retains 84% of its initial PCE after 2800 h aging under continuous illumination at 65 ± 5 °C in an N 2 glove box and nearly 90% after 1000 h repetitive 12 h light on–off cycles. This work provides an efficient yet easy‐to‐implement plasmonic heating strategy for simultaneously enhancing the efficiency and stability of PVSCs.

Solution-processed perovskites offer tremendous potential for low-cost, high-throughput photovoltaic production. However, high-quality perovskite films typically require stringent processing conditions, compromising reliability in large-scale production. Here, we discover that the initial nucleation process during the spin-coating is critical in determining the film quality. This process is highly sensitive to ambient temperature (TA) and associated with the effectiveness of intermediate phase formation. Besides the general wisdom that the intermediate phase regulates the initial nucleation by temporarily consuming precursor ions, we find that the intermediate phase plays a key role in guaranteeing high film quality by spatially separating the nuclei to mitigate thermally activated nuclei aggregation. By stabilizing a strongly coordinated intermediate phase, we achieve perovskite solar cells (PSCs) with power conversion efficiencies of 24% to 25%, even TA elevated to 28 °C. This work offers valuable insights into enhancing the reliability of PSCs and provides a deeper understanding of the role of the intermediate phase in the solution-processing of perovskite films.

Abstract Wide‐bandgap (WBG) perovskites are critical for advancing tandem solar cell technology, yet their fabrication remains constrained by narrow processing windows and environmental instability. A synergistic alkylammonium salt additive strategy coupled with a mild gas‐flow‐assisted crystallization method is presented to produce ambient‐air‐processed WBG perovskite solar cells (PSCs) with improved reproducibility and scalability. Co‐utilizing long‐chain alkylammonium chlorides (xACls) and methylammonium chloride (MACl) reduced gas‐flow speed requirements while expanding the crystallization kinetics window, suppressing non‐radiative recombination and defects, which are verified by fluorescence lifetime imaging microscopy (FLIM), in situ UV–vis spectroscopy, and XRD. High‐quality Cs 0.2 FA 0.8 PbI 2.3 Br 0.7 films are successfully prepared under a low gas flow speed (≈2.7 m s −1 ), which is much lower than the traditional gas quenching method (>26 m s −1 ). Cs 0.2 FA 0.8 PbI 2.3 Br 0.7 solar cells made by using 12ACl/MACl additives yielded a champion power conversion efficiency (PCE) of 19.72% ( V oc : 1.238 V), which is among the highest efficiency for WBG PSCs made in ambient air. This method has the advantages of high humidity tolerance (PCE >19% for cells made under 20–65% RH), compatibility with cost‐effective fan drying, elimination of anti‐solvents, and >70% inert gas‐flow intensity reduction, establishing an eco‐friendly scalable protocol that bridges lab‐to‐industry translation for high‐performance WBG PSCs.