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Herein, the successful synthesis of tin sulfide compounds by a facile one-step solvothermal method is reported, and its evolution of hierarchically formed petal-like 3-dimensional layer structures for SnS2 via ratio control of Sn/thiourea(TU) is systematically investigated. With the increase of TU content, the two-dimensional layered structure is clearly changed from discrete to hierarchically dense nanostructure. Thus, among various conditions, SnS2 with 1:2 ratio (SNS12) shows superior electrochemical performance associated with its discrete nanostructure. In this study, sample SNS12 shows a high specific capacitance of 1403 F g-1 at 1 mVs-1, a high power density of 456.42 W h kg-1 at an energy density of 46.84 W kg-1 with the stable cyclic performance of 85.87% up to 5000 cycles. The enhanced electrochemical performances are attributed to its unique ultrathin petal discrete structure, which allows for fast ion/electron transfer, high active sites, short diffusion distance, and more electrolyte/electrode interface access. Moreover, a fabricated symmetric supercapacitor device has a high capacity to operate commercial LED, leading to the validation of its practical operation durability for synthesized material on a device-level application. This study suggests that favorably layered 3D SnS2 electrode materials and their controllable protocols via Sn/TU ratio modulation could be one of the beneficial direction for the envisioned energy storage applications.

As the scaling down of Si devices in the range less than few nm has been expedited up to a physical limit of Si, low dimensional materials have been regarded as one of next generation semiconductors. Among a variety of applications, studies on photodetectors have been actively investigated with their novel optical properties as well as astonishing electrical properties. However, most of research has focused on single device-type photodetector (i.e., photo-diode or photo-transistor). Contrary to common photodetector, light-to-frequency circuits (LFCs) are based on frequency reading with photosensitive ring oscillators, which has better noise immunity and reduced system complexity, thus, can be utilized to novel application even in internet of things (IoT) and bio & medical fields. In this review, low dimensional materials based circuit level photodetectors, which are core elements as the form of either inverters or ring oscillators for demonstration of LFCs, are introduced. Along with the introduction of low dimensional materials and their optical properties for optoelectronics, a fundamental concept for LFCs is specifically described. Thereafter, research progress on low dimensional material based photosensitive inverters is addressed according to the types of devices. Furthermore, as one of practical method for the improvement of photodetector performance, molecular doping technology is presented. Lastly, complete system of LFCs and its digitization for demonstration of production level, and potential application in the respective four aspects, (i) medical SpO2 detection, (ii) biological fluidic system, (iii) auto-lighting in agriculture, and (iv) optical feedback and sensing systems, are presented as systematic way to address the envisioned practical applications for the future displays including virtual reality and augmented reality, and others. As a remark, LFCs based on low dimensional semiconductors are expected to be one of core components in trillion’s sensor area.

Confronted by the inherent physical limitations in scaling down Si technology, transition metal dichalcogenides (TMDCs) as alternatives are being tremendously researched and paid attention to. However, mature counter doping technology for TMDCs is still elusive, and thus, a controllable and reversible charge enhancer is adopted for acceptor (or donor)-like doping via octadecyltrichlorosilane (ODTS) (or poly-L-lysine (PLL)) treatment. Furthermore, multiple counter doping for TMDC field-effect transistors (FETs), combined with a threshold voltage (Vth) freezing scheme, renders the Vth modulation controllable, with negligible degradation and decent sustainability of FETs even after each treatment of a representative charge enhancer. In parallel, the counter doping mechanism is systematically investigated via photoluminescence spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy (AFM), surface energy characterization, and measurement of optoelectronic properties under illumination with light of various wavelengths. More impressively, complementary inverters, composed of type-converted molybdenum ditelluride (MoTe2) FETs and hetero-TMDC FETs in enhancement mode, are demonstrated via respective ODTS/PLL treatments. Herein, driving backplane application for micro-light-emitting diode (µ-LED) displays and physical validation of a corresponding counter doping scheme even for flexible polyethylene terephthalate (PET) substrates could be leveraged to relieve daunting challenges in the application of nanoscale Si-based three-dimensional (3D) stacked systems, with potential adoption of ultralow power and monolithic optical interconnection technology.

In this study, we analyzed an innovative, scalable, and simple preparation of branch-like MoS2 nanomaterial (BL-MS) for symmetric supercapacitor (SSC) applications. The BL-MS SSC device reveals a good specific capacitance of 124.1 F g−1 and a large voltage window (1.5 V). The BL-MS SSC device also shows a high energy density (38.79 W h kg−1) and high power density (15900 W kg−1). Further, the BL-MS SSC device displays a robust long-term stability of 77.7% and 89.5% in 40 h of voltage-holding tests and 10,000 galvanostatic charge-discharge (GCD) cycles, respectively. The BL-MS SSC device shows a low leakage current of 0.25 mA within a few seconds of removing the test voltage; it decreases and becomes nearly constant at 0.06 mA for 2 h during the voltage-holding test. The BL-MS SSC device exhibits good device behavior, the potential dropping from 1.5 to 0.62 V during the 2 h self-discharge process. Moreover, we considered the self-discharge mechanisms of the BL-MS SSC, determining that the diffusion-controlled process is dominant over a leakage-current-through-a-resistance model. Therefore, it is concluded that branch-like MoS2 nanomaterial is a promising and high-performance electrode material for energy storage in portable electronic devices.

Here, bias stress instability on multilayered MoTe2 field effect transistors (m‐MoTe2 FETs) with encapsulation of hydrophobic polymers (cyclic transparent optical polymer) is systematically investigated under DC and pulse mode operation. During DC mode stress, the threshold voltage shift (ΔVth) under positive bias stress is at least three times larger than that of negative stress due to high hole barrier (∼0.57 eV), compared with electron barrier (∼0.18 eV). However, ΔVth in positive pulse mode stress is significantly reduced with decrease of a duty cycle, as compared with that of negative stress. With isolation from external gas ambient effects such as H2O and O2, shallow electron traps in multilayered MoTe2 field effect transistors are identified as one of strong candidates to cause bias polarity dependency on ΔVth in pulse mode. Moreover, recovery time for traps, involved during positive bias stress, is six times faster than that of negative stress, substantiating that shallow electron traps and their fast detrapping are one of key origins. In practice, optimisation of pulse mode operation via bipolar switching can be potentially utilised for minimisation of device instability during the operation of multilayered MoTe2 field effect transistors devices and their circuits.

The heterostructure of nickel sulfides on cobalt oxide (h-NS@CO) is realized via one-pot hydrothermal growth of Co3O4 (CO) on Ni foam (NF), followed by NS overcoating through successive ionic layer adsorption and reaction (SILAR) process. According to the number of SILAR-overcoating from 10 to 30 cycles, electrochemical performance on super-capacitors is systematically studied and moreover, a fivefold increment in the specific capacitance is achieved at the condition of 20 overcoating cycles of Ni3S2 (h-NS20) on Co3O4 (1901 F.g−1), as compared to pristine Co3O4 (375 F.g−1) at a current density of 1 A.g−1. The GCD cyclic stability study reveals that h-NS20@CO retains 91.8% capacitance even after 10,000 cycles, surpassing pristine CO based SSCs. Furthermore, h-NS20@CO-based SSCs exhibit specific capacitance of 344 F.g−1 at 1 A.g−1, along with 97% of capacitance retention after 4000 cycles. In parallel, the remarkable improvement in electrochemical performance is attributed to synergetic effects associated with heterostructure of NS20 on cobalt oxide scaffold and their mechanisms are experimentally assessed via number of layer dependency. More impressively, a wirelessly controllable LED assembly, powered by h-NS20@CO-based SSCs, is successfully implemented and its demonstration of LED operation self-manifests a potential capability for the portably accessible energy storage device.

Herein, photo sensitive inverters comprised of an enhancement MoS 2 driver with light-shield layers (LSLs) (or GaN FET drivers) and MoS 2 depletion load. As compared with MoS 2 drivers with LSLs, GaN FET drivers have benefits in the respect of less degradation of gains, leading to the better noise margin of light frequency circuits (LFCs). Moreover, systematic studies on design rules for the better performance of LFCs were performed via experimental data execution and their validation, supported by SPICE simulation.

Herein, we report a novel, two dimensional (2D) layered In2S3 electrode material for supercapacitor application via a one-step solvothermal method. 2D In2S3 exhibits the highest specific capacitance of 897 Fg−1 at 1 mVs−1. Further prepared solid-state symmetric supercapacitors (SSC) demonstrate a wide operational window of 1.4 V, highest 2 terminal specific capacitance 284 Fg−1, and outstanding cyclic retention value of 90.81% after 3000 cycles. Excellent electrochemical behaviors of 2D In2S3 material via a facile and direct-grown method make it a potential candidate for the next-generation energy storage system.

Herein, a green, scalable and template-free deposition of self-assembled NiS-SnS (NTS) heterostructure is proposed by using SILAR (successive ionic layer adsorption and reaction method on a nickel foam substrate). In the assembled solid-state asymmetric supercapacitor devices, electrode materials of NTS hetero-structure exhibit remarkable high specific capacitance value of 1653 Fg−1 at a current density of 1 Ag−1, significant-high energy density of 83 Whkg−1 at a power density of 117 Wkg−1 with excellent rate capability and cyclic stability (98 % after 4000 cycles). Moreover, NTS heterostructures with high performance are highly efficient to lighten commercial light-emitting diode, substantiating that SILAR based formation of NTS hetero-structure is promising for the next generation superior supercapacitor devices.

Herein, we report bi-metal heterostructured cobalt-tin sulfides (h-CTS) via combination of layered structures of tin sulfides (TS) and cobalt sulfides (CS) by using selective ion layer adsorption and reaction (SILAR) method. 2 dimensional (2D) h-CTS (SnS2@Co3S4) exhibits the highest specific capacitance of 1580 Fg−1 at 1 mVs−1 and retain outstanding and improved cyclic stability of 94.8% after 3000 cycles. Excellent capacitive performance of bi-layered h-CTS material via simple and effective binder-free method make it suitable candidate for next generation electronic system.

In this letter, spray-coated single walled carbon nanotubes (SWNTs) as one of alternative electrodes in SnO thin-film transistors are demonstrated for emerging electronic applications. Herein, the device architecture of SnO TFTs with a polymer etch stop layer (SU-8) enables the selective etching of SWNTs in a desired region without the detrimental effects of SnO channel layers. Moreover, SnO TFTs with SWNT electrodes as substitutes successfully demonstrate decent width normalized electrical contact properties (~1.49 kΩ cm), field effect mobility (~0.69 cm2 V−1 s−1), sub-threshold slope (~0.4 V dec−1), and current on–off ratio (I on/I off ~ 3.5 × 103). Systematic temperature dependency measurements elucidate that SnO channel transports with an activation energy within several tens of meV, together with decent contact resistance as compared to that of conventional Ni electrodes.