Key Takeaways & Executive Findings
- •• Alkaline earth cations are successfully incorporated into perovskite lattice with the aid of sulfonic acid anions, while alkaline earth metal halides lack doping capacity. • Sulfonic acid anions effectively regulate crystallization and passivate metallic Pb0 defect states, improving power conversion efficiency to 24.95%. • By comparing FACF3SO3 and Ca(CF3SO3)2-doped films, the suppression of halide migration with an activation energy of 1.246 eV is attributed to Ca2+ cations, providing a methodology for decoupling cation and anion effects. • The study presents an effective method to decouple cation and anion effects, enabling the fabrication of efficient and stable perovskite solar cells.
Abstract
The past decade has witnessed the rapid increasement in power conversion efficiency of perovskite solar cells (PSCs). However, serious ion migration hampers their operational stability. Although dopants composed of varied cations and anions are introduced into perovskite to suppress ion migration, the impact of cations or anions is not individually explored, which hinders the evaluation of different cations and further application of doping strategy. Here we report that a special group of sulfonic anions (like CF3SO3−) successfully introduce alkaline earth ions (like Ca2+) into perovskite lattice compared to its halide counterparts. Furthermore, with effective crystallization regulation and defect passivation of sulfonic anions, perovskite with Ca(CF3SO3)2 shows reduced PbI2 residue and metallic Pb0 defects; thereby, corresponding PSCs show an enhanced PCE of 24.95%. Finally by comparing the properties of perovskite with Ca(CF3SO3)2 and FACF3SO3, we found that doped Ca2+ significantly suppressed halide migration with an activation energy of 1.246 eV which accounts for the improved operational stability of Ca(CF3SO3)2-doped PSCs, while no obvious impact of Ca2+ on trap density is observed. Combining the benefits of cations and anions, this study presents an effective method to decouple the effects of cations and anions and fabricate efficient and stable PSCs.
1. Introduction
In the past decade, metal halide perovskite solar cells have experienced significant increase in power conversion efficiency of up to 26.1%, which is comparable to their inorganic mono-silicon counterpart, offering promising potential for future commercialization [1, 2]. Despite the excellent optoelectronic properties and low manufacturing costs, the inferior operational stability of perovskite solar cells (PSCs) under working environment is one of the main reasons that undermines their potential commercialization [3–7]. Among the degradation origins of perovskite photovoltaic devices, the halide migration of perovskite photoactive layer under electric field, light or heat has been recognized as a vital cause for deterioration, leading to bulky defects and further decomposition of perovskites [8–15]. Hence, inhibiting the displacement of halide ions during the operation process is crucial for improving the durability of PSCs.
Interstitial incorporation of alkali metal ions has been widely used to suppress the ion migration of perovskites. Alkali halides such as cesium iodide (CsI), potassium iodide (KI), sodium iodide (NaI) and rubidium iodide (RbI) have been frequently reported to reduce the current–voltage hysteresis and prolong the life span of PSCs [16–18]. Recently, doping cations with higher valence states like calcium (Ca2+), barium (Ba2+) and neodymium (Nd3+) ions have been reported to be more effective in mitigating the halide migration with less dopant dosage and smaller lattice distortion, indicating great potential for enhancing the lifetime of PSCs in practical applications [19]. In previous attempts to introduce doping cations with higher valence states, different ionic compounds with varied types of anions such as halide ions (Cl−, I−) and organic acid anions are added into perovskite precursors [19]. However, the anions themselves can affect the composition and crystallization process of perovskite films through halide exchange or coordination, which complicates the interpretation of cation effects. Therefore, a systematic decoupling of cation and anion contributions is essential for rational design of doping strategies.
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Tianxiang Hu, Yixi Wang, Kai Liu, Jia Liu, Haoyang Zhang, Qudrat Ullah Khan, Shijie Dai, Weifan Qian, Ruochen Liu, Yanyan Wang, Chongyuan Li, Zhenru Zhang, Mingxiang Luo, Xiaofei Yue, Chunxiao Cong, Yuan Yongbo, Anran Yu, Jia Zhang, Yiqiang Zhan (2025). Understanding the Decoupled Effects of Cations and Anions Doping for High-Performance Perovskite Solar Cells. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01655-x
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Frequently Asked Questions
What is the main challenge addressed in this study?
The main challenge is the serious ion migration in perovskite solar cells that hampers their operational stability, and the lack of understanding of the individual effects of cations and anions in doping strategies.
How do sulfonic acid anions help in doping alkaline earth cations?
Sulfonic acid anions, such as CF3SO3−, successfully introduce alkaline earth ions like Ca2+ into the perovskite lattice, unlike halide counterparts, due to their unique properties that facilitate incorporation.
What is the significance of the activation energy of 1.246 eV?
The activation energy of 1.246 eV is attributed to Ca2+ cations, indicating that Ca2+ significantly suppresses halide migration, which accounts for the improved operational stability of Ca(CF3SO3)2-doped PSCs.
What is the power conversion efficiency achieved in this study?
The perovskite solar cells with Ca(CF3SO3)2 doping show an enhanced power conversion efficiency of 24.95%.
What methodology is proposed for decoupling cation and anion effects?
By comparing the properties of perovskite films doped with FACF3SO3 and Ca(CF3SO3)2, the study provides a methodology to decouple the effects of cations and anions, attributing specific improvements to each component.
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