Schematic of a single layer and b multi-layer inkjet-printed AgNPs electrodes for planar and vertical resistivity measurements. c Secondary electron micrographs of AgNP samples sintered at different temperatures: (i) 25 °C, (ii) 90 °C, (iii) 170 °C, (iv) 200 °C, (v) 300 °C, (vi) 500 °C. d Dependence of planar (ρxy) and vertical (ρz) resistivity on sintering temperature for for single-layer and 200-layer samples. e Fraction of non-interacting PVP at the sample surface and bulk estimated from the XPS measurements for samples treated at different temperatures. f Normalised intensity of characteristic ToF-SIMS secondary ions for PVP (C6H10NO+), silver (Ag+) and the substrate (Si+) and XPS C1s peak-fitted53 components N–C = O+C–N as a function of sintering temperature. g XPS C1s and h N1s peak fitting for samples sintered at 25 and 230 °C. Details of the XPS peak-fitting parameters can be found in Supplementary Tables 1 and 2.