No abstract

Manipulating the formation process of the 2D/3D perovskite heterostructure, including its nucleation/growth dynamics and phase transition pathway, plays a critical role in controlling the charge transport between 2D and 3D crystals, and consequently, the scalable fabrication of efficient and stable perovskite solar cells. Herein, the structural evolution and phase transition pathways of the ligand‐dependent 2D perovskite atop the 3D surface are revealed using time‐resolved X‐ray scattering. The results show that the ligand size and shape have a critical influence on the final 2D structure. In particular, ligands with smaller sizes and more reactive sites tend to form the n = 1 phase. Increasing the ligand size and decreasing the reactive sites promote the transformation from 3D to n = 3 and n < 3 phases. These findings are useful for the rational design of the phase distribution in 2D perovskites to balance the charge transport and stability of the perovskite films. Finally, solar cells based on ambient‐printed CsPbI3 with n‐butylammonium iodide treatment achieve an improved efficiency of 20.33%, which is the highest reported value for printed inorganic perovskite solar cells.

Perovskite solar cells (PSCs) have grown increasingly popular over the past few years and are considered to be game-changers in the energy conversion market. It has became vital to transfer the deep understanding of the perovskite film formation process during lab-scale fabrication to large-scale production. Complex phase transition during film formation has been revealed by in situ strategies. However, there is still debate which phase transition is the right route for a future scalable approach. Herein, we briefly summarize perovskite crystallization during scalable printing processes. The critical information about the intermediates involved in phase transition from precursors to perovskite crystals are discussed because it deeply impacts the morphology of printed films. Finally, important strategies to control phase transition and challenges toward future low-temperature and eco-friendly printing of perovskite solar cells are proposed. The information provided by this Perspective will assist the screening and development of the perovskite phase transition for future cost-efficient printed perovskite panels.

Upscalable printing of high‐performance and stable perovskite solar cells (PSCs) is highly desired for commercialization. However, the efficiencies of printed PSCs lag behind those of their lab‐scale spin‐coated counterparts owing to the lack of systematic understanding and control over perovskite crystallization dynamics. Here, we report the controlled crystallization dynamics achieved using an additive 1‐butylpyridine tetrafluoroborate (BPyBF4) for high‐quality ambient printed α‐formamidinium lead triiodide (FAPbI3) perovskite films. Using in situ grazing‐incidence wide angle X‐ray scattering and optical diagnostics, we demonstrate the spontaneous formation of α‐FAPbI3 and sol‐gel from precursors during printing without the involvement of  δ‐FAPbI3. The addition of BPyBF4 delays the crystallization onset of α‐FAPbI3, enhances the conversion from sol‐gel to perovskite, and reduces stacking defects during printing. Therefore, the altered crystallization results in fewer voids, larger grains, and less trap‐induced recombination loss within printed films. The printed PSCs yield high power conversion efficiencies of 23.50% and 21.60% for 0.09 cm2‐area devices and 5 cm × 5 cm‐area modules, respectively. Improved device stability is further demonstrated, i.e., approximately 94% of the initial efficiency is retained for over 2400 h under ambient conditions without encapsulation. This study provides an effective crystallization control method for the ambient printing manufacture of large‐area high‐performance PSCs.This article is protected by copyright. All rights reserved