To ensure an accurate interpretation of the compositionperformance results during this study, the discrepancy between the nominal and actual composition must be assessed. However, determining the actual composition of the samples on the FTO substrate with energy-dispersive X-ray (EDX) or Xray fluorescence (XRF) is challenging as Sn signals will be overshadowed by the Sn in the substrate and Sb signals overlap with those of Sn. Instead, the composition of the drop-casted solutions was evaluated using an inductively coupled plasma mass spectrometer (ICP-MS) as a proxy measurement. The final film composition should closely resemble the ink composition, as no metal evaporation is expected during the annealing step. Table shows that the ink composition for four random mixtures is in close proximity to the nominal targeted composition, confirming the accuracy of the pipetting sequence.