Sustainable colloidal ink for inkjet printing of 1T/2H-MoS2 based photodetectors on flexible substrate

The study of colloidal dispersions of two-dimensional materials, particularly molybdenum disulfide (MoS 2 ), has gained significant interest due to its broad range of applications. These dispersions are frequently prepared using liquid phase exfoliation (LPE), which further allows their use as colloidal inks to create high-performance inkjet-printed films. In this work, MoS 2 powder was synthesized by combining the microwave-assisted hydrothermal and the conventional hydrothermal routes, with a reaction yield of 91 %. Raman and XPS analyses confirmed that the synthesized MoS 2 powder exhibits coexisting 2H and 1T crystal phases with incorporated oxygen. Dispersions of synthesized MoS 2 powder using different solvents and mixtures were prepared by LPE to evaluate their stability to sedimentation. A mixture of 80 % diethylene glycol and 20 % water was chosen as the most suitable medium for obtaining printable MoS 2 colloidal ink. This optimized mixture exhibited four key characteristics: enhanced dispersion stability, extended colloidal stability, suitable particle sizes, and environmental friendliness due to the use of non-toxic solvents. The MoS 2 patterns printed with inkjet on a flexible substrate exhibited characteristic semiconductor behavior and demonstrated exceptional performance as a UV photodetector. Photodetection measurements presented competitive values across all key performance indicators. This research highlights the significant potential of the integrated methodology, which merges material synthesis, ink formulation, and inkjet printing technique, for the development of advanced flexible optoelectronic devices based on MoS 2 .