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High‐energy‐density storage devices play a major role in modern electronics from traditional lithium‐ion batteries to supercapacitors for a variety of applications from rechargeable devices to advanced military equipment. Despite the mass adoption of polymer capacitors, their application is limited by their low energy densities and low‐temperature tolerance. Polymer nanocomposites based on 2D nanomaterials have superior capacitive energy densities, higher thermal stabilities, and higher mechanical strength as compared to the pristine polymers and nanocomposites based on 0D or 1D nanomaterials, thus making them ideal for high‐energy‐density dielectric energy storage applications. Here, the recent advances in 2D‐nanomaterial‐based nanocomposites and their implications for energy storage applications are reviewed. Nanocomposites based on conducting 2D nanofillers such as graphene, reduced graphene oxide, MXenes, semiconducting 2D nanofillers including transition metal dichalcogenides such as MoS₂, dielectric 2D nanofillers including hBN, Mica, Al₂O₃, TiO₂, Ca₂Nb₃O₁₀and MMT, and their effects on permittivity, dielectric strength, capacitive energy density, efficiency, thermal stability, and the mechanical strength, are discussed. Also, the theory and machine‐learning‐guided design of polymer 2D nanomaterial composites is learnt and the challenges and opportunities for developing ultrahigh‐capacitive‐energy‐density devices based on these nanofiller polymer composites are presented.

 

We report intrinsic photoconductivity studies on one of the least examined layered compounds, ZrS2.Few-atomic layer ZrS2 field-effect transistors were fabricated on the Si/SiO2 substrate and photoconductivity measurements were performed using both two- and four-terminal configurations under the illumination of 532 nm laser source. We measured photocurrent as a function of the incident optical power at several source-drain (bias) voltages. We observe a significantly large photoconductivity when measured in the multiterminal (four-terminal) configuration compared to that in the two-terminal configuration. For an incident optical power of 90 nW, the estimated photosensitivity and the external quantum efficiency (EQE) measured in two-terminal configuration are 0.5 A/W and 120%, respectively, under a bias voltage of 650 mV. Under the same conditions, the four-terminal measurements result in much higher values for both the photoresponsivity (R) and EQE to 6 A/W and 1400%, respectively. This significant improvement in photoresponsivity and EQE   in the four-terminal configuration may have been influenced by the reduction of contact resistance at the metal-semiconductor interface, which greatly impacts the carrier mobility of low conducting materials. This suggests that photoconductivity measurements performed through the two-terminal configuration in previous studies on ZrS2 and other 2D materials have severely underestimated the true intrinsic properties of transition metal dichalcogenides and their remarkable potential for optoelectronic applications. 

Among the layered two dimensional semiconductors, molybdenum disulfide (MoS 2 ) is considered to be an excellent candidate for applications in optoelectronics and integrated circuits due to its layer-dependent tunable bandgap in the visible region, high ON/OFF current ratio in field-effect transistors (FET) and strong light–matter interaction properties. In this study, using multi-terminal measurements, we report high broadband photocurrent response ( R ) and external quantum efficiency (EQE) of few-atomic layered MoS 2 phototransistors fabricated on a SiO 2 dielectric substrate and encapsulated with a thin transparent polymer film of Cytop. The photocurrent response was measured using a white light source as well as a monochromatic light of wavelength λ = 400 nm–900 nm. We measured responsivity using a 2-terminal configuration as high as R = 1 × 10 3 A W −1 under white light illumination with an optical power P opt = 0.02 nW. The R value increased to 3.5 × 10 3 A W −1 when measured using a 4-terminal configuration. Using monochromatic light on the same device, the measured values of R were 10 3 and 6 × 10 3 A W −1 under illumination of λ = 400 nm when measured using 2- and 4-terminal methods, respectively. The highest EQE values obtained using λ = 400 nm were 10 5 % and 10 6 % measured using 2- and 4-terminal configurations, respectively. The wavelength dependent responsivity decreased from 400 nm to the near-IR region at 900 nm. The observed photoresponse, photocurrent–dark current ratio (PDCR), detectivity as a function of applied gate voltage, optical power, contact resistances and wavelength were measured and are discussed in detail. The observed responsivity is also thoroughly studied as a function of contact resistance of the device.