Bottom‐Up Synthesis of MeS_x Nanodots for Optoelectronic Device Applications

Abstract

WSx and MoSx nanodots are synthesized from (NH4)2WS4 and (NH4)2MoS4 precursors using a solvothermal method, and applied to organic photovoltaic cells (OPVs) and organic light emitting diodes (OLEDs) as hole injection layers (HILs). The optical band gaps of WSx and MoSx nanodots are 3.55 and 3.1 eV, respectively, and these nanodots show their strongest photoluminescence (PL) emission at 438 and 436 nm. The work functions of the nanodots increased from 4.3–4.4 to 5.0–5.1 eV following ultraviolet/ozone (UVO) treatment. By sandwiching thin layers of UVO‐treated WSx and MoSx as HILs, the power conversion efficiency of OPVs dramatically increases from 1.51% to 3.0% and 2.95%, comparable to that of poly(3,4 ethylenedioxythiophene):poly(styrene‐sulfonate) (PEDOT:PSS) based devices (3.23%). This increased OPV efficiency is believed to come from the increased work function, large band gap, and PL properties of nanodots. The UVO‐MoSx based OLED shows a higher maximum luminance efficiency (14.7 cd A−1) compared to PEDOT:PSS based devices (13.1 cd A−1). In addition, this study confirms that the stabilities of the OPV and OLEDs in air can be prolonged by using UVO‐treated WSx or MoSx nanodots as HILs. These results demonstrate the great potential of synthesized WSx or MoSx nanodots for use as HILs in optoelectronic devices.

CdSe Quantum Dots Doped WS2 Nanoflowers for Enhanced Solar Hydrogen Production

“…Two‐dimensional (2D) transition‐metal dichalcogenides (TMDs) have attracted significant attention over the past decade due to for their unique optical and electrical properties . Representative TMDs, such as MoS 2 and WS 2 , have attracted significant attention for photocatalytic hydrogen evolution reactions (HERs) based on their unique catalytic properties, earth abundance, and bandgap energy, which facilitates absorption in the visible region of the solar spectrum .…”

Synthesis of Tungsten Disulfide and Molybdenum Disulfide Quantum Dots and Their Applications

“…Among them, the work by Kim and coworkers is an example, and Figure 6 exhibits the thermal decomposition mechanism. 63 The resultant MoS 2 QDs had a narrow size distribution and few-layered structure and displayed excitation-dependent PL emission resulting from the polydispersity. Meanwhile, electron transfer between the MoS 2 QD surface and hyaluronic acid was confirmed by this team, suggesting that MoS 2 QDs can be used as PL probes.…”

“…The representative reaction equations are given as follows: So far, there are very few cases of synthesizing WS 2 and MoS 2 QDs by thermal decomposition, owing to the limited available reactants. Among them, the work by Kim and coworkers is an example, and Figure exhibits the thermal decomposition mechanism . They adopted (NH 4 ) 2 WS 4 and (NH 4 ) 2 MoS 4 as precursors to synthesize WS x and MoS x QDs under a long thermal reduction.…”

MoSe2-GO/rGO Composite Catalyst for Hydrogen Evolution Reaction

“…Therefore, much research has been done to find an earth-abundant, efficient catalyst material with an HER with performance comparable to that of Pt. Recently, two dimensional transitional metal dichalcogenides (2D-TMDs) have been intensively investigated and employed in various applications such as solar cells, light emitting diodes, gas sensors, and HER [10,11,12,13,14,15]. Especially, the performance of 2D-TMDs as catalysts for HER approaching Pt has been demonstrated by several groups, revealing their potential in practical applications [16,17,18,19,20,21,22,23].…”