Optical Properties and Applications of Molecular-Intercalated MoS₂

Two-dimensional (2D) transition metal dichalcogenides have demonstrated intriguing tunability in optical and electrical properties through the intercalation of ions within the van der Waals gap of their layered structure. In this study, we present a spectroelectrochemical method for electrochemically intercalating quaternary ammonium molecules into a MoS₂ thin film while monitoring the optical properties through absorption spectra. Throughout the intercalation process, we observed attenuation in both A and B excitonic peaks, with complete quenching achieved at a sufficient applied potential (E = -1.8 V vs. Ag). Raman spectra indicated that the as-intercalated MoS₂ remains in a semiconducting phase (2H), with an additional out-of-plane (A_1g) vibrational mode appearing. Additionally, both X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) results showed the metallic-like properties of the as-intercalated MoS₂, confirming successful intercalation of ammonium molecules and resulting in a high concentration of electron injection. In the second part, we demonstrate a potential application in solar energy storage using colloidal MoS₂ prepared through an electrochemical intercalation and exfoliation process. This study underscores the importance of further investigating ion intercalation in 2D materials and provides insights into the potential of Molecular-Intercalated MoS₂ for energy storage.