Songwang Yang

Achieving uniform crystallization across the entire film depth remains a critical challenge in the two‐step fabrication of perovskite films, where mismatched crystallization rates between the top and bottom regions often result in structural heterogeneity. Here, we develop a spatio‐temporally evolved 2D template‐assisted strategy by incorporating meta ‐fluorophenethylammonium iodide ( m ‐F‐PEAI) into the PbI ₂ precursor solution to enhance the perovskite film quality via a two‐step solution method. The in situ formed ( m ‐F‐PEA) ₂ PbI ₄ 2D perovskite redirects the thermodynamic phase transformation by providing a coherent crystallographic framework that synchronizes crystallization kinetics along the vertical direction. Furthermore, this 2D perovskite serves as a spatio‐temporal template: it directs monolithic grain growth during crystallization, while the residual 2D perovskite remains at grain boundaries in the final film. By modifying the local potential landscape, the 2D perovskite facilitates charge extraction, overcoming the charge‐blocking behavior associated with traditional passivating layers. It synergistically works with the monolithic grains to enable efficient macroscopic charge transport rather than merely passivating defects. As a result, the template‐assisted devices exhibit improvement in photovoltaic performance, achieving a power conversion efficiency (PCE) of 26.03% with an anti‐reflective film. Moreover, the unencapsulated devices demonstrate improved storage stability under N ₂ and dry‐air conditions, along with enhanced operational stability.

Inverted perovskite solar cells (PSCs) are fundamentally constrained by non-radiative recombination and energy-level mismatches. Herein, we introduce lithium dihydrogen phosphate (LiH ₂ PO ₄ ) as a multifunctional precursor additive to regulate the crystallization kinetics and electronic structure of perovskite films. We demonstrate that LiH ₂ PO ₄ not only promotes highly (100)-textured grain growth and passivates deep-level defects but also induces a global energy band reconstruction. By correlating x-ray photoelectron spectroscopies and ultraviolet photoelectron spectroscopies, we disclose that the anomalous, simultaneous increase in core-level binding energies originates from a Fermi-level-driven rigid band shift coupled with the formation of a robust interfacial dipole. This dual-action mechanism effectively suppresses non-radiative recombination and eliminates charge extraction barrier. Consequently, the optimized inverted PSCs achieve a champion power conversion efficiency of 24.11%, along with enhanced open-circuit voltage, fill factor, and long-term environmental stability.

In the one-step solution method of perovskite film preparation, antisolvents are widely used to control perovskite crystallization, which directly influences the quality of the perovskite films. Herein, hexafluorobenzene (HFB) was involved in the mixed antisolvent (MAS) system to produce high-quality perovskite films with dual functions of crystallization control and defect passivation. Beyond improving perovskite crystallization and interface contact, a small amount of HFB remained in the perovskite and passivated uncoordinated Pb²⁺ defects. Consequently, the HFB-involved MAS-derived perovskite films exhibited higher crystallinity, smoother surfaces, better interfacial contacts, and fewer defects than those without HFB additives. These enhancements in film quality significantly improved the open-circuit voltage (V_OC) and the fill factor (FF) of the corresponding solar cells, resulting in an increase in power conversion efficiency (PCE) from 23.18% to 24.53%. Furthermore, the solar cells prepared by this method exhibited improved stability. This study highlights a facile and efficient method for simultaneously regulating perovskite crystallization and mitigating defects by incorporating functionalized mixed antisolvents, thus improving the photovoltaic performance of perovskite solar cells.

By optimizing the mixing procedures of the perovskite precursor solution, the Marangoni effect was suppressed, resulting in improved device performance (0.07 cm ² cell from 14.71% to 16.55% and 66 cm ² sub-module from 11.21% to 13.02%).

The electron transport layer (ETL) plays a critical role in efficient and stable perovskite solar cells (PSCs). The current effective method for the large-scale preparation of metal oxide ETLs is mainly based on expensive sputtering processes. Here, a screen-assisted self-spreading method is proposed as a novel approach to prepare uniformly thin and conformal TiO₂ films on a rough fluorine-doped tin oxide (FTO) substrate as an ETL in planar PSCs. The TiO₂ ETL deposited by this method exhibited good coverage and homogeneity on the rough FTO substrate, thereby minimizing interfacial recombination. The photovoltaic performance of the PSCs fabricated by this method is superior to that of the cells fabricated by spin coating, especially in terms of the fill factor. The performance enhancement can be attributed to the complete coverage of the FTO substrate by the conformal TiO₂ film, confirming the effectiveness and reliability of the proposed method for the preparation of the TiO₂ ETL. The advantages of this method lie in its scalability to prepare oxide films with a large area, eliminating the requirement of complex equipment, such as spinners, sputters, or physical vapor deposition equipment.

Flexible perovskite solar cells (f-PSCs) have achieved significant success. However, high-quality tin dioxide (SnO₂) electron transport layers (ETLs) fabricated via chemical bath deposition (CBD) have not been achieved on flexible PEN/ITO substrates. This limitation is primarily due to the corrosion of the poor-quality ITO layer by the strongly acidic CBD solution. Here, we analyzed the reasons for the poor corrosion resistance of ITO films on PEN substrate from multiple perspectives, such as element composition, microstructure, and crystallinity. Then, we proposed a modified CBD method for SnO₂ films suitable for flexible PEN/ITO substrates. We employed SnCl₂·2H₂O as the tin source and regulated the pH of the CBD solution by NH₃·H₂O, which effectively avoided the corrosion of the ITO layer by the CBD solution and achieved high-quality SnO₂ films on the ITO layers. Compared to the commercial SnO₂ dispersion, the SnO₂ films prepared by this method have smaller grains and higher transmittance. As a result, we achieved an unprecedented power conversion efficiency (PCE) of 20.71% for f-PSCs fabricated on PEN/ITO substrates with SnO₂ ETLs by CBD method. This breakthrough facilitates the development of high-performance f-PSCs by a low-cost and large-scale chemical bath deposition of high-quality ETLs on flexible substrates.