Chemical Functionalization of 1H‐Mos2 for Programmed Modulation of Photoluminescence

Semiconducting monolayer transition metal dichalcogenides (TMDs) such as MoS2 possess exceptional properties that make them highly desirable in photonic and optoelectronic applications. The photoluminescence (PL) of MoS2 is a valuable measure of its electronic and optical properties. Herein, chemical functionalization based on diazonium chemistry is used to modulate the PL of MoS2 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 MoS2. 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 MoS2. The surface morphology of functionalized MoS2 is characterized using scanning probe microscopy, which reveals the formation of well‐defined one‐nanometer‐thick films. Electrical characterization of devices incorporating functionalized MoS2 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 MoS2.