Inkjet printing and low temperature sintering of CuO and CdS as functional electronic layers and Schottky diodes

Here we report on inkjet printing of a conductive amorphous copper oxide (CuO) ink and of semiconducting cadmium sulfide (CdS) quantum dots under ambient conditions and at low temperature to form functional thin films, which were used for the fabrication of Schottky diodes. Inkjet printed CuO features were sintered using a commercial photonic sintering tool in order to form the diode rectifying contacts. This was accomplished by using the tool's proprietary high-intensity flash lamp at very short pulse durations, ensuring a low processing temperature that favors the usage of low-cost substrates. The photonic sintering method was also used for sintering CdS films, resulting in a more efficient removal of the organic moieties around the CdS nanoparticles than a wet chemical KOH treatment. The here reported process allows the deployment of a low-cost polyethylene terephthalate (PET) polymer foil as the substrate material. The initial results showed modest performance of the fabricated Schottky diode. Nevertheless, the general approaches demonstrate new routes for low temperature manufacturing methods for functional electronic layers based on accordingly developed functional materials utilising amorphous metal oxides and quantum dots.