Metal oxide-based screen-printed diodes

This study presents the fabrication and characterization of fully screen-printed p–n junction diodes based on metal oxide semiconductor inks. The diodes were produced entirely through scalable and low-cost screen-printing techniques on flexible polyethylene terephthalate (PET) substrates, employing nickel hydroxide (Ni(OH)₂) as the p-type semiconductor and tungsten trioxide (WO₃) as the n-type semiconductor. Unlike many previous reports, which often rely on hybrid approaches incorporating non-printed components or additional post-processing steps, this work demonstrates a fully printed structure, where all layers, including electrodes and semiconductors, are screen-printed. The influence of geometry, ink composition, and processing conditions on diode performance was investigated. Diodes with smaller active areas exhibited better rectification behavior, as increased surface area led to lower resistance and higher current requirements. The optimal ink formulation for the p-type Ni(OH)₂ was found to be a 1:15 weight ratio of Ni precursor to antimony-doped tin oxide particles (ATO), while excess tungsten oxide in the n-type WO₃ inks reduced performance due to surface coverage on conductive particles. Despite challenges such as printing defects, pinholes, and thick semiconductor layers (~ 20–60 μm), the diodes achieved rectification ratios comparable to other printed diodes previously reported in the literature.