In all of the files the X-axis is labeled as X-axis in the header. The Y-axis is the labeled in the header with a descriptor of the data. For all files the X-axis applies to the data until a new X-axis is defined in the file.

Figure 1b. XRD patterns of 3D only and 2D perovskite coated thin films
X-axis: 2-theta (4-50 degrees), Y-axis: Intensity in arbitrary units

Figure 1c. XRD patterns of thin films of FA substituted C18 2D perovskites along with the XRD patterns of pure 2D perovskite
X-axis: 2-theta (4-50 degrees), Y-axis: Intensity in arbitrary units

Figure 1d. UV-Vis absorption spectra of 3D only and 2D perovskite coated thin films
X-axis: wavelength in nm (900-200 nm), Y-axis: Intensity in arbitrary units

Figure 1e. PL emission spectra of pure 3D perovskite and 3D@2D perovskite thin films
X-axis: wavelength in nm (480-900 nm), Y-axis: Intensity in arbitrary units

Figure 2b. Current-voltage characteristic of 3D only and C18 perovskite coated PSCs
X-axis: voltage in Volts (0-1.15 V), Y-axis: current density (mA cm^-2)

Figure 2c. Comparison of the current-voltage characteristic of 3D only and 2D perovskite coated PSCs
X-axis: voltage in Volts (0-1.17 V), Y-axis: current density (mA cm^-2)

Figure 2d. Photovoltaic parameters determined from the J-V characteristic of 3D only and C18 perovskite coated PSCs: PCE, Voc, Jsc and FF 
Comparison of Power conversion efficiency (PCE), open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) between 3D perovskite and C18 coated perovskite for 50 unique devices. PCE (%), Voc (V), Jsc (mA cm^-2), FF (NA)

Figure 2e. The statistical distribution of PCE values of 20 devices each for 3D only and C14, C16 and C18 perovskite coated PSCs.

Figure 2f. Effect of variation in concentration of C18 perovskite per ml THF on PCE values of PSCs.

Figure 2g. Steady-state photocurrent density and PCE of the 3D only and C18 coated PSC monitored at a maximum power point
X-axis: time in seconds (0-4000 s), Y-axis: current density (mA cm^-2) and PCE (%).

Figure 2h. IPCE spectra and corresponding integrated Jsc of 3D only and C18 perovskite coated PSCs
X-axis: wavelength in nm (350-800 nm), Y-axis: current density (mA cm^-2) and incident photo to current efficiency (IPCE as %).

Figure 3a. Time-resolved PL decay curves of the 3D only and 2D perovskite coated thin films
X-axis: Time in nanoseconds (ns), Y-axis: Intensity in arbitrary units

Figure 3b. Current-voltage curves of 3D only and 2D perovskite coated devices 
X-axis: Voltage in volts (V), Y-axis: current in amps (A)

Figure 3c. Nyquist plots of 3D only and 2D perovskite coated PSC devices
X-axis: Real resistance (Ohms), Y-axis: imaginary resistance (Ohms)

Figure 5a. XRD patterns of 3D only thin films monitored over a period of 2 months and stored under an ambient atmosphere with a relative humidity of 25-80%
X-axis: 2-theta (4-50 degrees), Y-axis: Intensity in arbitrary units

Figure 5b. XRD patterns of 3D@C18 thin films monitored over a period of 2 months and stored under an ambient atmosphere with a relative humidity of 25-80%
X-axis: 2-theta (4-50 degrees), Y-axis: Intensity in arbitrary units

Figure 5c. Variation in PCE of non-encapsulated 3D only PSCs and C14, C16, and C18 perovskite coated PSCs kept under ambient atmosphere
X-axis: time in days (0-230 days), Y-axis: normalized power conversion efficiency (PCE  as %)