Chemical Functionalization of 1H‐Mos ₂ for Programmed Modulation of Photoluminescence

Semiconducting monolayer transition metal dichalcogenides (TMDs) such as MoS 2 possess exceptional properties that make them highly desirable in photonic and optoelectronic applications. The photoluminescence (PL) of MoS 2 is a valuable measure of its electronic and optical properties. Herein, chemical functionalization based on diazonium chemistry is used to modulate the PL of MoS 2 in a programmed fashion. Using PL mapping, it is demonstrated that binding of aryl units with electron‐donating substituents leads to decreased PL, whereas electron‐withdrawing substituents enhance PL compared to pristine MoS 2 . This functionalization is utilized to selectively modulate radiative recombination in the basal plane and to demonstrate the dependence of PL on the Fermi level. Raman spectroscopy corroborates the changes in the PL, and cryo‐PL also confirms that the chemical functionalization proceeds without the creation of additional defects in the basal plane of MoS 2 . The surface morphology of functionalized MoS 2 is characterized using scanning probe microscopy, which reveals the formation of well‐defined one‐nanometer‐thick films. Electrical characterization of devices incorporating functionalized MoS 2 as the channel material reveals intriguing contrast to the PL trends, highlighting complex underlying mechanisms. Potential explanations for this divergence are explored, providing new insights into the electronic behavior of functionalized MoS 2 .