The data sets stored here accompany the related research article, showing details of perovskite NPs and LEDs. The Excel file contains all the important original data for Figs. 1-4, Fig. S1 to S33. The green lines are the X axis in all sheets. Fig. 1C contains EL spectra of LEDs. Fig. 2A + S16 NMR contains 1H-NMR of MAPbI3 NP solutions. Fig. 2E contains height along the dashed line in AFM. Fig. 2F contains AFM height statistics result of MAPbI3 NPs. Fig. 2G contains real n-phase ratio distribution of NPs via AFM. Fig. 2H contains ratio of different n-phases in PL. Fig. 2I contains the ratio of different n-phases in EL of LEDs. Fig. 3A contains PLQE of NP solutions and films. Fig. 3B contains optical simulation of LEDs. Fig. 3C contains EQE distribution of MAPbI3 NP LEDs. Fig. 3D contains EQE-current density curves. Fig. 3E contains J-V and luminance-voltage curves. Fig. 3F contains angle dependent EL of NP LEDs. Fig. 3G contains stability test of LEDs. Fig. 4A contains UPS of MAPbI3 NPs. Fig. 4B contains Energy levels by DFT simulations. Fig. 4C contains UV-Vis. Fig. 4D contains PL decay kinetics. Figs. 4E-F contain Decay kinetics in TA. Fig. 4K contains correlation of L/Pb ratio, conductivity, [n] via AFM and average n phase in EL. Fig. S1 contains the photopic curve. Fig. S3F EL spectra of quasi-2D LEDs. Fig. S20 contains XRD of MAPbI3 NPs. Fig. S24 contains 1H-NMR of MAI solution in EtOH. Fig. S31C contains conductivity of films.