Fig. 2: Structural and optical characterization of self-assembled NPL films.

a, Illustration of superlattices formed from the stacking of multiple NPLs, and how the electron density changes between inorganic perovskites and organic ligands. b, Radial GIWAXS profiles integrated over all azimuthal angles (pseudo-X-ray diffraction profiles) for different perovskite films in the low-angle region, which demonstrates the formation of a superlattice. q is the absolute value of the scattering vector. SL, superlattice. c,d, Simulated (c) and experimental (d) outcoupling from NPL films. The simulations of the outcoupling from the NPL films with different percentages of horizontal TDMs (100% = all NPLs face-down, 0% = all NPLs edge-up) represent different degrees of NPL orientation, and were made assuming that the outcoupling contribution of the TDM in the confined direction is negligible. The simulated radiance was integrated over the azimuthal coordinate as a function of the polar angle (see Methods for details on the simulations). Experimental measurements of the angle-dependent PL obtained from k-space Fourier microscopy are shown in blue; 90° is where the collection was parallel to the substrate, whereas 0° is where the collection was perpendicular to the substrate. Details on data collection and analysis can be found in Supplementary Note 4 and Supplementary Fig. 7.