Fig. 5
The structural evolution during the decomposition from MAPbI3 to PbI2. a–d Time-series SAED patterns showing that the structure decomposes from a MAPbI3–x [001] zone axis (0 < x < 0.5), to b intermediate phase MAPbI2.5, c MAyPbI2.5–z (0 ≤ y ≤ 1 and 0 ≤ z ≤ 0.5), and d PbI2 [\(\bar 4\)41] zone axis sequentially under a dose rate of 1 e Å−2 s−1. The cumulative electron dose and time are labeled in each pattern. The blue squares mark the (110) reflection of MAPbI3 in a, MAPbI2.5 in b, and MAPbI2.5 and MAyPbI2.5–z in c. The green diamonds mark the (200) reflection of MAPbI3 in a, and MAPbI2.5 in b. The orange circles mark the (220) reflection of MAPbI3 in a, MAPbI2.5 in b, MAPbI2.5 and MAyPbI2.5–z in c, and (\(0\bar 1\)4) of PbI2 in d. The pink triangles mark the (100) reflection of MAPbI2.5 in b. e–h The corresponding simulated ED patterns of e MAPbI3, f MAPbI2.5, g 35% MAyPbI2.5–z + 65% PbI2 (see Supplementary Fig. 12), and h PbI2. Note that MAyPbI2.5–z (0 ≤ y ≤ 1 and 0 ≤ z ≤ 0.5) with random vacancies should have the same ED pattern with MAyPbI2.5–z (y = 0 and z = 0.5) without considering the very diffused reflections from random vacancies. i–l The atomistic structures of i MAPbI3, j MAPbI2.5, k MAyPbI2.5–z (0 ≤ y ≤ 1 and 0 ≤ z ≤ 0.5), and l PbI2. The black circles in j represent the ordered iodine vacancies. m The diffraction intensity is plotted as a function of time (total dose). The pink triangles, orange circles, blue squares, and green diamonds correspond to those label shapes in a–d. The green, pink, blue, and orange color bars roughly estimate the existence of MAPbI3–x, MAPbI2.5, MAyPbI2.5–z, and PbI2 at different stages. Note that the values of the intensities for (110) (blue squares) and (100) (pink triangles) spots are set to be 1.8 and 6 times of the original values for comparison. n During the decomposition of the perovskite at different dose rates, the measured critical electron dose and time for the appearance of a superstructure. Scale bar, 1 nm−1 (a–h)
