“…Therecorded GIWAXS patterns of the control and of the excess passivators incorporated MAPbI 3 perovskite films are shown in Figure 5b-h. Thec ontrol MAPbI 3 film exhibits nearly isotropic Bragg rings at q = 1.0, 1.4, 1.65, 1.7, and 2.0 À1 corresponding to the (110), (112), (211), (202), and (220) crystal planes of 3D perovskite phase (Figure 5b), indicating ar andom crystallite orientation. [28] With passivators,t he diffraction patterns appear in the q < 1.0 À1 range, which implies the formation of low-dimensional perovskite (Figure 5c-h). [28a] Forthose PMAI, TMAI, PImI or TImI passivated MAPbI 3 films,the diffraction rings in the q < 1.0 À1 can be indexed into different crystal planes of their corresponding low-dimensional perovskite structures (See their single crystal structures in Figure S10, S11, and Table S3, Supporting Information), which have been marked in Figure 5c,e,f,and h, respectively.Such random orientations and the absence of low-dimension diffraction in thin film XRD pattern indicate the in situ formation of low-dimensional perovskite phase on the surface of 3D perovskite nanograins, which can passivate the surface defects of perovskite and also protect 3D perovskites from being damaged easily,t hus leading to enhanced device efficiencya nd stability.M eanwhile,t hose resulting low-dimensional perovskites from PMAI and PImI both exhibit that Pb-I bond lengths are around 3.21 ,w hile I-Pb-I bond angle is about 1588 8 for PMAI and 908 8 for PImI, which makes PImI-based lowdimensional perovskites share more similar lattice parameters to those of MAPbI 3 single crystals (Pb-I bond length 3.16 ,I-Pb-I angle 908 8).…”