Data files contain the raw data reported in graphs in the main manuscript and ESI.

The file "Fig1c" contains the raw PL and UV/Vis spectra for a standard sample of CH3NH3PbBr3-xIx perovskite nanocrystals (PNCs) in toluene. Column 1 and 2 are wavelength (nm) and PL data respectively, column 3 and 4 are wavelength (nm) and UV/Vis absorption, respectively.

"Fig2a" contains the raw PL and UV/Vis spectra for a standard sample of CH3NH3PbBr3-xIx perovskite nanocrystals (PNCs) diluted in toluene. Columns 1, 2, 3, 4, 5, 6, 7 are wavelength (nm) and PL data for dilution factors D0, D2, D5, D10, D20, D40 respectively. Columns 8, 9, 10, 11, 12, 13, 14 wavelength (nm) and UV/Vis data for dilution factors D0, D2, D5, D10, D20, D40 respectively.

“Fig2b” contains the raw hydrodynamic diameter (nm) upon dilution (dilution factor D20) with time (minutes).

“Fig2c” contains the PL spectra of the parent PNC suspension before dilution (stock) and at timed intervals after dilution (2, 22, 42, 62, 122, 182 minutes). Colum 1 is wavelength in nm.

“Fig3b” contains the PL spectra of the parent PNC suspension before dilution (PQD56) and upon dilution (dilution factor D20). Colum 1 is wavelength in nm.

“Fig4c” contains the PL spectra CH3NH3PbBr3-xIx PNCs with varying Br:I ratios. Columns 1, 2, 3, 4, 5 are wavelength (nm) and PL data for samples R1, R2, R3, R4, respectively.

“Fig4d” contains the PL spectra CH3NH3PbBr3-xIx PNCs after dilution (dilution factor D20) with varying Br:I ratios. Columns 1, 2, 3, 4, 5 are wavelength (nm) and PL data for samples R1, R2, R3, R4, respectively.

“Fig4e” contains the absorption and PL spectra of PNC sample R5 before and after dilution (dilution factor D20). Columns 1, 2, 3, 4 are wavelength in nm, absorption spectra, PL before dilution and PL after dilution, respectively.

“Fig4f” contains the normalised PL spectra of PNC sample R6 before and after dilution (dilution factor D20) sampled as a function of time. Columns 1, 2, 3, 4, 5, 6, 7 are wavelength (nm), PL data after dilution at 0 min, 3 min, 6 min, 9 min, 13 min and before dilution, respectively.

“Fig5b” contains the normalised PL spectra of PNC sample OY100 before and after dilution (dilution factor D20). Column 1 is wavelength in nm.

“FigS3” contains the normalised emission decay spectra of a standard sample of CH3NH3PbBr3-xIx PNCs in toluene before and after dilution. Columns 1, 2, 3, 4, 5 are time in ns, decay before dilution, decay after dilution, instrument response function, biexponential fit to decay before dilution and biexponential fit to decay after dilution, respectively.

“FigS6” contains PL spectra CH3NH3PbBr3-xIx PNCs prepared with excess bromide before and after dilution (dilution factor D20).

“FigS8” contains the normalised PL spectra of PNC sample OY100 upon dilution (dilution factor D20) after 0 hours, 24 hours and 48 hours. Column 1 is wavelength in nm.