Key Takeaways & Executive Findings
- •• RbI is the most effective additive to mitigate PbI2 precipitation caused by Pb(SCN)2 while maintaining large grains. • Rb ions segregate at grain boundaries during crystallization and Ostwald ripening, promoting slow grain growth and reduced non-radiative recombination. • Blade-coated wide-bandgap perovskite solar cells in ambient air achieved a certified power conversion efficiency of 23%, among the highest reported. • The scalable fabrication strategy enables stable MA-free WBG PSCs under ambient conditions, advancing commercialization of tandem solar cells.
Abstract
Scalable fabrication of efficient wide-bandgap (WBG) perovskite solar cells (PSCs) is crucial to realize the full commercial potential of tandem solar cells. However, there are challenges in fabricating efficient methylammonium-free (MA-free) WBG PSCs by blade coating, especially its phase separation and films stability. In this work, an MA-free WBG perovskite ink is developed for preparing FA0.8Cs0.2Pb(I0.75Br0.25)3 films by blade coating in ambient air. Among various A-site iodides, RbI is found to be the most effective in suppressing the precipitation of PbI2 induced by Pb(SCN)2 while keeping the enlarged grains. The distribution of Rb suggested that the Rb ions are kept isolated with the perovskite grains during the crystallization and Ostwald ripening processes, which contributes to the formation of the large-grain WBG perovskite film with minimum non-radiative recombination. As a result, a power conversion efficiency (PCE) of 23.0% was achieved on small-area WBG PSCs, while mini-modules with an aperture area of 10.5 cm2 exhibited a PCE of 20.2%, among the highest reported for solar cells prepared with WBG perovskites via blade coating. This work presents a scalable and reproducible fabrication strategy for stable MA-free WBG PSCs under ambient conditions, advancing their path toward commercialization.
1. Introduction
Over the past decade, organic–inorganic hybrid perovskite materials have garnered significant attention in the photovoltaics (PV) application due to their outstanding optoelectronic properties and robust solution processable fabrication [1–7]. Because of its tunable bandgaps, perovskite can be integrated with many traditional PV materials for tandem cells, yielding higher power conversion efficiency (PCE) than single junction solar cells [8–11]. Recently, the perovskite/silicon tandem cells employing wide-bandgap (WBG) (~1.7 eV) perovskites demonstrate certified PCE over 34%, showing its remarkable potential for next generation PV technology [12]. However, the fabrication of WBG perovskite mostly relies on spin-coating, which is not favorable for large-scale production of WBG perovskite films [13, 14]. Developing scalable manufacturing of WBG perovskite films remains crucial to their practical application.
Blade coating is one of the most promising methods to prepare large-area thin films because of its high material efficiency and ease of operation [15, 16]. Significant advancements have been made in advancing these coating technologies in the recent years. For instance, Seo et al. utilized blade coating methods to fabricate n-i-p perovskite solar cells (PSCs) with a 1.65 eV bandgap, achieving impressive PCEs of 20.56% for devices with an active area of 0.094 cm2 and 18.4% for those measuring 1 cm2 [17]. Fang et al. reported PCEs of 22.06% and 19.63% for blade-coated p-i-n configuration PSCs with a 1.67 eV bandgap, covering active areas of 0.07 and 1.02 cm2, respectively [18]. More recently, Wolf et al. attained a notable PCE of 22.6% with blade coating for devices featuring a 1.66 eV bandgap and an active area of 0.1 cm2, highlighting their great potential for tandem PV applications [19]. However, these WBG perovskite components typically contain methylammonium (MA) cations, which dissociate easily under light, leading to additional proton migration and raising concerns about the long-term stability of these devices [20–23]. Moreover, perovskite undergoes degradation during preparation in ambient air [24–26], thus requiring the processing in inert atmosphere or controlled humidity of less than 25% [27]. Otherwise, the degradation causes MA+ to deprotonate, forming MA0, which reacts with FAI to produce MFAI as a byproduct [28, 29]. To overcome these challenges in ambient processing, our recent work on pure-phase FAPbI3 highlights the importance of constricting stable intermediate phase with 2-imidazolidinone (IMD), which could be also promising for blade coating of WBG perovskite thin films in air [30].
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Jianbo Liu, Meng Zhang, Xiaoran Sun, Linhu Xiang, Xiangyu Yang, Xin Hu, Zhicheng Wang, Tian Hou, Jinzhao Qin, Yuelong Huang, Mojtaba Abdi-Jalebi, Xiaojing Hao (2025). Scalable Fabrication of Methylammonium-Free Wide-Bandgap Perovskite Solar Cells by Blade Coating in Ambient Air. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01838-6
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Frequently Asked Questions
What is the main achievement of this paper?
The paper reports a scalable blade-coating method for fabricating methylammonium-free wide-bandgap perovskite solar cells in ambient air, achieving a certified power conversion efficiency of 23% on small-area devices and 20.2% on mini-modules, among the highest reported for blade-coated WBG perovskites.
Why is RbI used in the perovskite ink?
RbI is found to be the most effective A-site iodide in suppressing PbI2 precipitation induced by Pb(SCN)2 while maintaining large grains, and it segregates at grain boundaries to promote slow grain growth and reduce non-radiative recombination.
What are the advantages of blade coating over spin-coating for perovskite solar cells?
Blade coating offers high material efficiency, ease of operation, and scalability for large-area thin films, making it more suitable for commercial production compared to spin-coating, which is limited to small areas.
How does this work address the stability issues of MA-containing perovskites?
By eliminating methylammonium (MA) cations, which are prone to dissociation under light and cause proton migration, the fabricated MA-free perovskites exhibit improved long-term stability, especially when processed in ambient air.
What is the significance of achieving high efficiency in ambient air?
Processing in ambient air reduces manufacturing costs and complexity, as it avoids the need for inert atmosphere or controlled humidity, thereby advancing the commercialization potential of perovskite solar cells.
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