1：Experimental Design and Method Selection

In situ grazing incidence small angle X-ray scattering (GISAXS) was used to study the nanostructure-growth kinetics of the gold contact on top of the spiro-OMeTAD film during the sputter process. A custom made sputter chamber was used for the sputter deposition of gold on top of the as-prepared spiro-OMeTAD films.

2：Sample Selection and Data Sources

The spiro-OMeTAD solution was spin-coated on a cleaned silicon substrate. The thickness of the spiro-OMeTAD film is 100 nm as determined by X-ray reflectivity (XRR) measurements.

3：List of Experimental Equipment and Materials

A direct current magnetron sputter chamber was operated under an argon pressure of 1.5×10-3 mbar with a power of 5 W, which resulted in a nominal sputter rate of 3.2 nm min-1. The GISAXS measurements were performed at the BW4 beamline of the HASYLAB at DESY (Hamburg, Germany), where the X-ray wavelength was λ = 0.138 nm. A Pilatus 300k detector was used for recording the scattering signal for the X-ray measurements.

4：Experimental Procedures and Operational Workflow

The in situ experiments comprising simultaneous gold sputter deposition and GISAXS measurements were performed. The in situ experiments lasted for 1800 s, which resulted in a final gold layer thickness of around 90 nm and in total 1800 frames of scattering data were recorded (each frame took 1 s).

5：Data Analysis Methods

The temporal evolution of size, shape and spatial arrangement of the gold nanoclusters during sputter deposition is extracted by modeling the in situ GISAXS data. The vertical growth of the gold contact during sputter deposition is investigated by analyzing the vertical line cuts (at qy = 0) of the 2D GISAXS data.