Unveiling Charge‐Transport Mechanisms in Electronic Devices Based on Defect‐Engineered MoS ₂ Covalent Networks

Abstract

Device performance of solution‐processed 2D semiconductors in printed electronics has been limited so far by structural defects and high interflake junction resistance. Covalently interconnected networks of transition metal dichalcogenides potentially represent an efficient strategy to overcome both limitations simultaneously. Yet, the charge‐transport properties in such systems have not been systematically researched. Here, the charge‐transport mechanisms of printed devices based on covalent MoS2 networks are unveiled via multiscale analysis, comparing the effects of aromatic versus aliphatic dithiolated linkers. Temperature‐dependent electrical measurements reveal hopping as the dominant transport mechanism: aliphatic systems lead to 3D variable range hopping, unlike the nearest neighbor hopping observed for aromatic linkers. The novel analysis based on percolation theory attributes the superior performance of devices functionalized with π‐conjugated molecules to the improved interflake electronic connectivity and formation of additional percolation paths, as further corroborated by density functional calculations. Valuable guidelines for harnessing the charge‐transport properties in MoS2 devices based on covalent networks are provided.

Controlling Charge Transport in 2D Conductive MOFs─The Role of Nitrogen-Rich Ligands and Chemical Functionality

“…Terahertz spectroscopy experiments were recently employed to show that while the intraplane charge transport follows a band-like behavior, thermally activated interplane hopping appears to be the bottleneck for charge transport in 2D-e-MOF materials. − From the combined experimental and theoretical analysis, Ni 3 (HITAT) 2 is found to exhibit not only lower hole/electron effective masses but also lower activation energy of ≈66 meV, as compared to ≈220 meV for Ni 3 (HITBim) 2 (Figure S13). HATAT is thus found to enhance the charge transport properties in Ni 3 (HITAT) 2 , likely owing to both modulation of the energy of the Frontier orbitals and enhancement of the crystalline packing between layers, corroborating earlier findings .…”

Solution-Processed 2D Transition Metal Dichalcogenides: Materials to CMOS Electronics

“…Furthermore, the network morphology strongly depends on the choice of the thin-film deposition technique. For instance, the spray-coating method leads to the formation of a highly porous oblique alignment of 2D nanoflakes. − However, this type of stacking of 2D nanoflakes results in limited charge transport because of the small overlap area between the nanoflakes, which leads to a high interflake resistance and low device mobility. As a result, the charge transport in MoS 2 thin films is dominated by interflake hopping.…”

“…The functionalized MoS 2 /conjugated 1,4-benzenedithiol (BDT) networks exhibit the nearest neighbor hopping (NNH) mechanism. This mechanism refers to the direct transfer (hop) of charge carriers between the spatially closest localized states . As a result, E A reduces to approximately 360 ± 10 meV, and the mobility increases by 1 order of magnitude up to 10 –2 cm 2 V –1 s –1 .…”

Electronic and electrocatalytic applications based on solution‐processed two‐dimensional platinum diselenide with thickness‐dependent electronic properties

“…One major challenge that limits the practical application of LPE is that the lateral size of the nanosheets is rather small because intense cavitation forces during the exfoliation process break the layers into small fragments, especially for few‐layer PtSe 2 (typically less than 100 nm) 29,30,35 . As a result, the film thickness typically needs to be >100 nm to achieve network continuity, which hinders fabrication of gate‐tunable semiconducting devices without electrolyte gating 36–38 . The electrical conductivity of the PtSe 2 nanosheet network is also much lower compared to films synthesized using direct selenization or CVD because inter‐sheet junctions greatly hinder the charge transport 13,27,29,39 .…”

“…29,30,35 As a result, the film thickness typically needs to be >100 nm to achieve network continuity, which hinders fabrication of gatetunable semiconducting devices without electrolyte gating. [36][37][38] The electrical conductivity of the PtSe 2 nanosheet network is also much lower compared to films synthesized using direct selenization or CVD because inter-sheet junctions greatly hinder the charge transport. 13,27,29,39 Recently, electrochemical intercalation of molecular ions has been used to exfoliate bulk TMDC crystals into few-layer nanosheets.…”