Modulating Optoelectronic Properties of Two-Dimensional Transition Metal Dichalcogenide Semiconductors by Photoinduced Charge Transfer

Abstract

Atomically thin transition metal dichalcogenides (TMDCs) have attracted great interest as a new class of two-dimensional (2D) direct band gap semiconducting materials. The controllable modulation of optical and electrical properties of TMDCs is of fundamental importance to enable a wide range of future optoelectronic devices. Here we demonstrate a modulation of the optoelectronic properties of 2D TMDCs, including MoS2, MoSe2, and WSe2, by interfacing them with two metal-centered phthalocyanine (MPc) molecules: nickel Pc (NiPc) and magnesium Pc (MgPc). We show that the photoluminescence (PL) emission can be selectively and reversibly engineered through energetically favorable electron transfer from photoexcited TMDCs to MPcs. NiPc molecules, whose reduction potential is positioned below the conduction band minima (CBM) of monolayer MoSe2 and WSe2, but is higher than that of MoS2, quench the PL signatures of MoSe2 and WSe2, but not MoS2. Similarly, MgPc quenches only WSe2, as its reduction potential is situated below the CBM of WSe2, but above those of MoS2 and MoSe2. The quenched PL emission can be fully recovered when MPc molecules are removed from the TMDC surfaces, which may be refunctionalized and recycled multiple times. We also find that photocurrents from TMDCs, probed by photoconductive atomic force microscopy, increase over 2-fold only when the PL is quenched by MPcs, further supporting the photoinduced charge transfer mechanism. Our results should benefit design strategies for 2D inorganic-organic optoelectronic devices and systems with tunable properties and improved performances.

Spectroscopic investigation of defects in two-dimensional materials

“…If the interaction is stronger, covalent bonding between the foreign atom and the nearest atom of 2D materials leads to chemisorption as shown in Figure 1C-iii and iv [33]. Common physisorption includes water, oxygen, polymer molecular, and metal atoms on top of 2D materials, which become charge donors or acceptors and be easily removed by vacuum pumping or annealing [60][61][62]. Chemisorption in graphene is mainly located at three positions: in carbon-carbon bond, above carbon atoms, and trapped by structural defects [63].…”

Booming Development of Group IV–VI Semiconductors: Fresh Blood of 2D Family

“…These 2DLMs possess different properties such as electronic structures, large specific surface area, and the quantum confinement of electrons due to the ultrathin thickness compared with their bulk counterparts, thus paving a new way for the next generation electronic, optical, optoelectronic, and flexible systems 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. Taking graphene, for example, the single layer of graphite has promising applications in broadband optical modulators16 and ultrafast high frequency photosensors17 due to the linear dispersion of the Dirac electrons 18.…”

MoS2 and Perylene Derivative Based Type‐II Heterostructure: Bandgap Engineering and Giant Photoluminescence Enhancement

“…XPS results (Figure 1g,h and Figure S9, Supporting Information) reveal the existence of Mo 4p, peaking at 230 eV (3d 5/2 ) and 233.2 eV (3d 3/2 ), and S 2p, peaking at 162.7 eV (2p 3/2 ), and 163.8 eV (2p 1/2 ). [6,35] Figure 2a-c,g-i shows the Raman spectra of PTCDA/MoS 2 and PTCDI-Ph/MoS 2 heterostructures, PTCDA, PTCDI-Ph, and MoS 2 monolayer, respectively. Thus the above mentioned slight blue/redshift could be originated from n-or p-doping of the MoS 2 monolayer due to S deficiency.…”