Inkjet-printed Cu source/drain electrodes for solution-deposited thin film transistors

We report on the first utility of Cu nanoparticle inks as low-cost, printable electrodes in the fabrication of solution-deposited amorphous oxide semiconductor thin film transistors. The performance of printed Cu electrodes was studied in terms of involvements of surface states in the devices. The surface chemical structures of Cu nanoparticulate electrodes were observed to be modified, dependent on the molecular weight of the polyvinylpyrrolidone capping molecules used in their synthesis. The surface dipoles became weak, and the work function of the printed electrodes decreased with increasing the molecular weight. The work function tailored by introducing the larger capping agents allowed for a better energetic leveling with the metal oxide semiconductor layer, resulting in the improved device performance.