Chemically Tailored Organic Ammonium Salts for Integrated Regulation of CsPbI₃ Perovskite Solar Cells

Abstract

Understanding and chemically tailoring the interfacial properties is essential for improving both efficiency and stability of perovskite solar cells (PSCs). All-inorganic cesium-based perovskites have emerged as promising candidates for thermally stable PSCs, however, their poor phase stability and high density of surface defects continue to impede device performance. Herein, we introduce functionalized halogenated phenethylammonium iodide (X-PEAI, X = H, F, Cl, Br) as modifiers, and a synergistic optimization of the perovskite bulk and interface is achieved through an integrated regulation strategy. It is found that Cl-PEAI with a strong dipole moment, achieves the optimal regulatory effect. It not only improves the film morphology but also effectively passivates the defect states through strong Lewis acid-base interactions. In addition, it also introduces an additional dipole layer at the interface, which enhances the carrier transport effect. Consequently, Cl-PEAI-treated devices deliver a champion power conversion efficiency (PCE) of 19.53% and retain 92.9% of their initial efficiency after 720 h of ambient storage, thereby underscoring the potential of rational ligand design within this specific ammonium salt category for advancing stable, high-performance all-inorganic PSCs.

Keywords

CsPbI₃ perovskite solar cells / dipole moment / integrated regulating strategy / organic ammonium salts

References

[1] W. Wu, H. Gao, L. Jia, et al., “Stable and Uniform Self-Assembled Organic Diradical Molecules for Perovskite Photovoltaics,” Science 389, no. 6756 (2025): 195–199.

[2] W. Sun, K. Wang, W. Liu, et al., “Buried Interface Modification for Reduced Open-Circuit Voltage Loss in Perovskite Solar Cells With Efficiency Exceeding 25.8%,” Carbon Neutralization 4, no. 5 (2025): e70042.

[3] M. Chen, Y. Dong, Y. Zhang, et al., “Stress Engineering for Mitigating Thermal Cycling Fatigue in Perovskite Photovoltaics,” ACS Energy Letters 9, no. 6 (2024): 2582–2589.

[4] Q. Yang, H. Zhang, Z. Jiang, H. Shen, and X. Gong, “Mobile Oxygen Capture Enhances Photothermal Stability of Perovskite Solar Cells Under ISOS Protocols,” Advanced Materials 37, no. 16 (2025): 2500268.

[5] D. Xu, M. Wu, Y. Bai, et al., “Record-Efficiency Inverted CsPbI₃ Perovskite Solar Cells Enabled by Rearrangement and Hydrophilic Modification of SAMs,” Advanced Functional Materials 35, no. 2 (2025): 2412946.

[6] Y. Wang, M. I. Dar, L. K. Ono, et al., “Thermodynamically Stabilized β-CsPbI3–Based Perovskite Solar Cells With Efficiencies >18%,” Science 365, no. 6453 (2019): 591–595.

[7] X. Gong, L. Guan, Q. Li, et al., “Black Phosphorus Quantum Dots in Inorganic Perovskite Thin Films for Efficient Photovoltaic Application,” Science Advances 6, no. 15 (2020): eaay5661.

[8] C. Shen, S. Fang, J. Zhang, et al., “High Performance and Stable Pure-Blue Quasi-2D Perovskite Light-Emitting Diodes by Multifunctional Zwitterionic Passivation Engineering,” Advanced Photonics 6, no. 2 (2024): 026002.

[9] T. Li, K. Wang, Y. Tong, et al., “In Situ Dehydration Condensation of Self-Assembled Molecules Enables Stabilization of CsPbI₃ Perovskites for Efficient Photovoltaics,” Advanced Functional Materials 34, no. 51 (2024): 2409621.

[10] Z. Wang, Q. Chen, H. Xie, et al., “Light-Driven Dynamic Defect-Passivation for Efficient Inorganic Perovskite Solar Cells,” Advanced Functional Materials 35, no. 9 (2025): 2416118.

[11] J. Zhang, X. Peng, H. Wu, et al., “Comprehensive Passivation of Surface and Bulk Defects in Perovskite for High Efficiency Carbon-Based CsPbI₃ Solar Cells,” Angewandte Chemie International Edition 64, no. 14 (2025): 2423655.

[12] X. Tan, S. Wang, Q. Zhang, et al., “Stabilizing CsPbI₃ Perovskite for Photovoltaic Applications,” Matter 6, no. 3 (2023): 691–727.

[13] D. Rui, J. Fu, Q. Chen, et al., “Surface Engineering Based on Ionic Liquids for Efficient and Stable CsPbI₃ Perovskite Solar Cells,” Journal of Materials Chemistry A 12, no. 13 (2024): 7847–7855.

[14] H. Han, J. Xu, H. Liu, et al., “Formation of Low-Dimensional Double Perovskite Layers by ABS and PEAI Sequential Treatment for Achieving High-Performance CsPbI₃ Solar Cells,” ACS Energy Letters 8, no. 11 (2023): 4608–4616.

[15] Q. Yang, X. Gong, X. Qi, et al., “Hydrophobic Polymer Interlayer for Highly Efficient and Stable Perovskite Solar Cells,” Chemical Engineering Journal 454 (2023): 140430.

[16] H. Zhang, Q. Yang, Z. Jiang, et al., “Controlling Crystallization Dynamics of the Perovskite by Restricted Assembly Strategy Enables High-Performance Solar Cells,” Advanced Functional Materials 35, no. 20 (2025): 2421910.

[17] H. Lu, Q. Wen, R. Qin, et al., “Manipulating Intermediate Surface Energy for High-Performance All-Inorganic Perovskite Photovoltaics,” Advanced Energy Materials 15, no. 18 (2025): 2405072.

[18] H. Zhang, X. Gong, Q. Yang, et al., “Constructing Robust Top Heterointerface With Quinoid Polymer for High Performance CsPbI₃ Solar Cells,” ACS Materials Letters 6, no. 4 (2024): 1231–1240.

[19] H. Zhang, Q. Tian, W. Xiang, et al., “Tailored Cysteine-Derived Molecular Structures Toward Efficient and Stable Inorganic Perovskite Solar Cells,” Advanced Materials 35, no. 31 (2023): 2301140.

[20] A. Z. Chen, M. Shiu, J. H. Ma, et al., “Origin of Vertical Orientation in Two-Dimensional Metal Halide Perovskites and Its Effect on Photovoltaic Performance,” Nature Communications 9 (2018): 1336.

[21] B. Han, H. Cai, C. Liu, et al., “Bifunctional Passivation of Wide-Bandgap Perovskite Solar Cells via Long-Chain Organic Ammonium Salts,” ACS Applied Materials & Interfaces 17, no. 17 (2025): 25400–25409.

[22] C. Xu, L. Zuo, P. Hang, et al., “Synergistic Effects of Bithiophene Ammonium Salt for High-Performance Perovskite Solar Cells,” Journal of Materials Chemistry A 10, no. 18 (2022): 9971–9980.

[23] Z. An, Y. Zhu, G. Luo, et al., “Halide Substituted Ammonium Salt Optimized Buried Interface for Efficient and Stable Flexible Perovskite Solar Cells,” Advanced Energy Materials 13, no. 48 (2023): 2302732.

[24] X. Liu, X. Wang, T. Zhang, et al., “Organic Tetrabutylammonium Cation Intercalation to Heal Inorganic CsPbI₃ Perovskite,” Angewandte Chemie International Edition 60, no. 22 (2021): 12351–12355.

[25] Y. Wang, T. Zhang, M. Kan, Y. Li, T. Wang, and Y. Zhao, “Efficient α-CsPbI₃ Photovoltaics With Surface Terminated Organic Cations,” Joule 2, no. 10 (2018): 2065–2075.

[26] Y. Liu, W. Xiang, T. Xu, et al., “Strengthened Surface Modification for High-Performance Inorganic Perovskite Solar Cells With 21.3% Efficiency,” Small 19, no. 46 (2023): 2304190.

[27] M. Ebic, F. Sadegh, M. Ans, P. Yadav, D. Prochowicz, and S. Akin, “Molecularly Tailored Quaternary Pyridinium Salt for Post-Treatment to Enhance Defect Passivation and Charge Carrier Dynamics in Perovskite Solar Cells,” Journal of Energy Chemistry 109 (2025): 120–128.

[28] N. Sun, S. Fu, Y. Li, et al., “Tailoring Crystallization Dynamics of CsPbI₃ for Scalable Production of Efficient Inorganic Perovskite Solar Cells,” Advanced Functional Materials 34, no. 6 (2024): 2309894.

[29] B. Zhao, S.-F. Jin, S. Huang, et al., “Thermodynamically Stable Orthorhombic γ-CsPbI₃ Thin Films for High-Performance Photovoltaics,” Journal of the American Chemical Society 140, no. 37 (2018): 11716–11725.

[30] J. Zhang, X. Niu, C. Peng, et al., “Inhibiting Ion Migration Through Chemical Polymerization and Chemical Chelation Toward Stable Perovskite Solar Cells,” Angewandte Chemie International Edition 62, no. 50 (2023): 2314106.

[31] J. Pan, Z. Chen, T. Zhang, et al., “Operando Dynamics of Trapped Carriers in Perovskite Solar Cells Observed via Infrared Optical Activation Spectroscopy,” Nature Communications 14, no. 1 (2023): 8000.

[32] Y. Cui, J. Shi, F. Meng, et al., “A Versatile Molten-Salt Induction Strategy to Achieve Efficient CsPbI₃ Perovskite Solar Cells With a High Open-Circuit Voltage >1.2 V,” Advanced Materials 34, no. 45 (2022): 2205028.

[33] F. Ansari, E. Shirzadi, M. Salavati-Niasari, et al., “Passivation Mechanism Exploiting Surface Dipoles Affords High-Performance Perovskite Solar Cells,” Journal of the American Chemical Society 142, no. 26 (2020): 11428–11433.

[34] X. Jiang, B. Zhang, G. Yang, et al., “Molecular Dipole Engineering of Carbonyl Additives for Efficient and Stable Perovskite Solar Cells,” Angewandte Chemie International Edition 62, no. 22 (2023): 2302462.

[35] J. Qiu, X. Mei, M. Zhang, et al., “Fluorination-Assisted Interfacial Dipole for CsPbI₃ Perovskite Solar Cells With Over 22% Efficiency,” Angewandte Chemie International Edition 64, no. 30 (2025): 2506282.

[36] M. Wu, K. Yan, Y. Wang, and X. Kang, “High Crystallinity and Photovoltaic Performance of CsPbI₃ Film Enabled by Secondary Dimension,” Journal of Energy Chemistry 48 (2020): 181–186.

[37] X. Cao, J. Wu, D. Yang, et al., “A-D-A-Type Molecule With Dual Functions of Efficient Charge Extraction and Trap Passivation for n-i-p Perovskite Solar Cells,” Advanced Functional Materials 35, no. 2 (2025): 2412552.

[38] J. Qiu, Q. Zhou, D. Jia, Y. Wang, S. Li, and X. Zhang, “Robust Molecular-Dipole-Induced Surface Functionalization of Inorganic Perovskites for Efficient Solar Cells,” Journal of Materials Chemistry A 10, no. 4 (2022): 1821–1830.

[39] Q. Zheng, P. Chen, A. Tong, et al., “Enhancing Performance and Stability of Perovskite Solar Cells Through Interface Dipole Engineering With Perfluorinated Ammonium Salts,” Chemical Engineering Journal 497 (2024): 154603.

[40] X. Gong, Q. Sun, S. Liu, et al., “Highly Efficient Perovskite Solar Cells With Gradient Bilayer Electron Transport Materials,” Nano Letters 18, no. 6 (2018): 3969–3977.

[41] L. Zuo, H. Guo, D. W. deQuilettes, et al., “Polymer-Modified Halide Perovskite Films for Efficient and Stable Planar Heterojunction Solar Cells,” Science Advances 3, no. 8 (2017): e1700106.

[42] Z. Wang, X. Chen, X. Feng, et al., “Optical Coupling Optimization Enables Cost-Effective Planar Silicon-Perovskite Tandem Solar Cells,” Carbon Neutralization 4, no. 5 (2025): e70035.

[43] Y. Xu, S. Zhang, H. Yuan, et al., “Highly Efficient and Stable Flexible Perovskite Solar Cells Enabled by Alkylammonium Acetate Modification With Varied Dipole Moments,” Advanced Functional Materials 35, no. 23 (2025): 2422014.

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2025 The Author(s). Carbon Neutralization published by Wenzhou University and John Wiley & Sons Australia, Ltd.