Preparation of inkjet-printed titanium monoxide as p-type absorber layer for photovoltaic purposes

The intrinsic p-type cubic structure titanium monoxide (TiO) with suitable band gap energy, reasonable raw material costs, and particularly simple stoichiometry has been chosen as a potential candidate in microelectronic applications, and may have the opportunity to use as a p-type absorber layer for photovoltaic purposes. Among various printing and coating techniques that have been recently explored to fabricate solar cell layers, inkjet printing is promising because of low-cost processing and precise patterning capabilities. This paper aims to fabricate TiO films on a polyimide substrate using inkjet printing. Efforts were made to reduce the starting TiO powder size down to submicron levels by using wet ball-milling to meet the ink requirements of particle sizes for office printers. The experimental results show that the dispersion stability of the prepared water-based ink was obtained by adding an ammonia solution. Optimal printability was achieved as a result of adding ethylene glycol, polyethylene glycol 1500, Triton X-100, and Foamstop 600N. Post-annealing treatment was carried out to obtain the final dense layer. Crystallinity and electrical properties of the inkjet-printed TiO layers were enhanced by post-annealing treatment, while the optical band gap from the annealed TiO showed the value of 2.57 eV. These results have demonstrated the potential of using inkjet-printed TiO as a complementary absorber layer for photovoltaic applications.