Mechanistic Investigation of Molybdenum Disulfide Defect Photoluminescence Quenching by Adsorbed Metallophthalocyanines

Abstract

Lattice defects play an important role in determining the optical and electrical properties of monolayer semiconductors such as MoS 2 . Although the structures of various defects in monolayer MoS 2 are well studied, little is known about the nature of the fluorescent defect species and their interaction with molecular adsorbates. In this study, the quenching of the low-temperature defect photoluminescence (PL) in MoS 2 is investigated following the deposition of metallophthalocyanines (MPcs). The quenching is found to significantly depend on the identity of the phthalocyanine metal, with the quenching efficiency decreasing in the order CoPc > CuPc > ZnPc, and almost no quenching by metal-free H 2 Pc is observed. Time-correlated single photon counting (TCSPC) measurements corroborate the observed trend, indicating a decrease in the defect PL lifetime upon MPc adsorption, and the gate voltage-dependent PL reveals the suppression of the defect emission even at large Fermi level shifts. Density functional theory modeling argues that the MPc complexes stabilize dark negatively charged defects over luminescent neutral defects through an electrostatic local gating effect. These results demonstrate the control of defectbased excited-state decay pathways via molecular electronic structure tuning, which has broad implications for the design of mixeddimensional optoelectronic devices.

MoS2 Defect Healing for High-Performance Chemical Sensing of Polycyclic Aromatic Hydrocarbons

“…Amsterdam et al recently demonstrated by gate voltage-dependent measurements and DFT calculations that organic macromolecules, as MPcs can stabilize the negatively charged defects in the MoS 2 lattice. 55 Indeed, they found that the positive electrostatic potential of the outer carbon ring of the MPc sitting above the MoS 2 defects stabilizes its negative charge. CoPc (7.46 eV) having higher E I compared to H 2 Pc (7.36 eV) 67 was found as the best stabilizer.…”

“…We found that the adsorption of PAHs induces a significant defect healing, as evidenced by the reduction of the peak contributions of the S 2p defect component and the Mo 4+ 3d 5/2 d and Mo 4+ 3d 3/2 d. The healing appeared to be more effective in the order pyrene < phenanthrene < naphthalene, as shown in Table S1. The functionalization of 2D TMDCs with different molecules has been extensively studied. − For example, metallophthalocyanines (MPcs) are planar aromatic molecules coordinating a central atom in the inner ring, which are able to reduce the structural defects in TMDCs. In a similar fashion, in this work, the used planar PAHs appeared to be able to induce defect healing in the MoS 2 lattice.…”

“…These results can be again correlated to the defect healing induced by the PAHs molecule adsorbed on our semiconductor. Amsterdam et al recently demonstrated by gate voltage-dependent measurements and DFT calculations that organic macromolecules, as MPcs can stabilize the negatively charged defects in the MoS 2 lattice . Indeed, they found that the positive electrostatic potential of the outer carbon ring of the MPc sitting above the MoS 2 defects stabilizes its negative charge.…”

Recent Progress in Phase Regulation, Functionalization, and Biosensing Applications of Polyphase MoS2

“…Reproduced with permission. [ 180 ] Copyright 2021, American Chemical Society. E) Schematic illustration of the temperature‐dependent optical properties of BCPMoS 2 in hydrogel, as well as near‐infrared PT (photothermal) heating curves and IR thermal photographs of different nanocomposites.…”

“…Low-temperature photoluminescence spectra of MoS 2 and MPcMoS 2 (right). Reproduced with permission [180]. Copyright 2021, American Chemical Society.…”