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Ethanol-based green-solution processing of α-formamidinium lead triiodide perovskite layers


The use of non-toxic or less-toxic solvents in the mass production of solution-processed perovskite solar cells is essential. However, halide perovskites are generally not completely soluble in most non-toxic solvents. Here we report the deposition of dense and uniform α-formamidinium lead triiodide (α-FAPbI3) films using perovskite precursor solutions dissolved in ethanol-based solvent. The process does not require an antisolvent dripping step. The combination of a Lewis base, such as dimethylacetamide (or dimethylsulfoxide), and an alkylammonium chloride (RNH3Cl) in ethanol results in the stable solvation of FAPbI3. The RNH3Cl added to the FAPbI3 precursor solution is removed during spin-coating and high-temperature annealing via iodoplumbate complexes, such as PbI2·RNH2 and PbI2·HCl, coordinated with dimethylacetamide (or dimethylsulfoxide). It is possible to form very dense and uniform α-FAPbI3 perovskite films with high crystallinity by combining several types of RNH3Cl. We obtain power conversion efficiencies of 24.3% using a TiO2 electrode, and of 25.1% with a SnO2 electrode.

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Fig. 1: Preparation of the EtOH-based FAPbI3 and PbI2 precursor solutions.
Fig. 2: Crystalline phase and surface morphology of films deposited using the EtOH-based FAPbI3 precursor solutions.
Fig. 3: Characterization of perovskite films deposited using the EtOH-based FAPbI3 precursor solutions.
Fig. 4: Device performance.

Data availability

All data generated or analysed during this study are included in the published article and its Supplementary Information. Source data are provided with this paper.


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This work was supported by the Basic Science Research Program (NRF-2018R1A3B1052820) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (MSIP). This work was also supported by the Defense Challengeable Future Technology Program of the Agency for Defense Development, Republic of Korea, by a brand project (1.220026.01) of UNIST. Y.L. acknowledges financial support from the Creative-Challenge Research Program (NRF-2020R1I1A1A01072030). Finally, we thank UCRF (UNIST Central Research Facilities) for its support using the equipment and the beamline staff at Pohang Accelerator Laboratory.

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Authors and Affiliations



H.-S.Y. and S.I.S. conceived this work. H.-S.Y. and H.W.K. prepared ethanol-based perovskite precursor solutions and fabricated devices. Y.L., M.J.P., S.H., J.K., E.N. and J.P. characterized the films and devices. H.-S.Y., Y.L. and S.I.S. wrote the article. S.I.S. supervised the project. All authors discussed the results and commented on the article.

Corresponding authors

Correspondence to Yonghui Lee or Sang Il Seok.

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Nature Energy thanks Shengzhong (Frank) Liu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–11 and Tables 1–3.

Supplementary Video 1

What happens during coating?

Supplementary Video 2

What happens during drying?

Supplementary Video 3

What happens during spin coating of the precursor solution?

Supplementary Video 4

What happens during spin coating the surface treatment agent after annealing?

Source data

Source Data Fig. 3

Photovoltaic parameters of solar cells shown in Fig. 3a,b.

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Yun, HS., Kwon, H.W., Paik, M.J. et al. Ethanol-based green-solution processing of α-formamidinium lead triiodide perovskite layers. Nat Energy 7, 828–834 (2022).

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