FA-Assistant Iodide Coordination in Organic–Inorganic Wide-Bandgap Perovskite with Mixed Halides

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Article number1907226
Journal / PublicationSmall
Issue number10
Online published12 Feb 2020
Publication statusPublished - 12 Mar 2020


Mixed-halide wide-bandgap perovskites are key components for the development of high-efficiency tandem structured devices. However, mixed-halide perovskites usually suffer from phase-impurity and high defect density issues, where the causes are still unclear. By using in situ photoluminescence (PL) spectroscopy, it is found that in methylammonium (MA+)-based mixed-halide perovskites, MAPb(I0.6Br0.4)3, the halide composition of the spin-coated perovskite films is preferentially dominated by the bromide ions (Br). Additional thermal energy is required to initiate the insertion of iodide ions (I) to achieve the stoichiometric balance. Notably, by incorporating a small amount of formamidinium ions (FA+) in the precursor solution, it can effectively facilitate the I coordination in the perovskite framework during the spin-coating and improve the composition homogeneity of the initial small particles. The aggregation of these homogenous small particles is found to be essential to achieve uniform and high-crystallinity perovskite film with high Br content. As a result, high-quality MA0.9FA0.1Pb(I0.6Br0.4)3 perovskite film with a bandgap (Eg) of 1.81 eV is achieved, along with an encouraging power-conversion-efficiency of 17.1% and open-circuit voltage (Voc) of 1.21 V. This work also demonstrates the in situ PL can provide a direct observation of the dynamic of ion coordination during the perovskite crystallization.

Research Area(s)

  • crystallization, halide coordination, wide-bandgap perovskites