2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS can only absorb up to 10% of the incident light in the visible, which is not sufficient to achieve a high optical-to-electrical conversion efficiency. To overcome this shortcoming, a "gap-mode" plasmon-enhanced monolayer MoS fluorescent emitter and photodetector is designed by squeezing the light-field into Ag shell-isolated nanoparticles-Au film gap, where the confined electromagnetic field can interact with monolayer MoS . With this gap-mode plasmon-enhanced configuration, a 110-fold enhancement of photoluminescence intensity is achieved, exceeding values reached by other plasmon-enhanced MoS fluorescent emitters. In addition, a gap-mode plasmon-enhanced monolayer MoS photodetector with an 880% enhancement in photocurrent and a responsivity of 287.5 A W is demonstrated, exceeding previously reported plasmon-enhanced monolayer MoS photodetectors.

Two dimensional material/semiconductor heterostructures offer alternative platforms for optoelectronic devices other than conventional Schottky and p-n junction devices. Herein, we use MoS 2 /GaAs heterojunction as a self-driven photodetector with wide response band width from ultraviolet to visible light, which exhibits high sensitivity to the incident light of 635 nm with responsivity as 446 mA/W and detectivity as 5.9×10 13 Jones (Jones = cm Hz 1/2 W -1 ), respectively. Employing interface design by inserting h-BN and photo-induced doping by coveringSi quantum dots on the device, the responsivity is increased to 419 mA/W for incident light of 635 nm. Distinctly, attributing to the low dark current of the MoS 2 /h-BN/GaAs sandwich structure based on the self-driven operation condition, the detectivity shows extremely high value of 1.9 × 10 14 Jones for incident light of 635 nm, which is higher than all the reported values of the MoS 2 based photodetectors.

Lin, 18.5% Efficient graphene/GaAs van der Waals heterostructure solar cell, Nano Energy, http://dx.Abstract: High efficient solar cell is highly demanded for sustainable development of human society, leading to the cutting-edge research on various types of solar cells. The physical picture of graphene/semiconductor van der Waals Schottky diode is unique as Fermi level of graphene can be tuned by gate structure relatively independent of semiconductor substrate. However, the reported gated graphene/semiconductor heterostructure has power conversion efficiency (PCE) normally less than 10%. Herein, utilizing a designed graphene-dielectric-graphene gating structure for graphene/GaAs heterojunction, we have achieved solar cell with PCE of 18.5% and open circuit voltage of 0.96 V. Drift-diffusion simulation results agree well with the experimental data and predict this device structure can work with a PCE above 23.8%. This research opens a door of high efficient solar cell utilizing the graphene/semiconductor heterostructure.

MoS2 is a layered two-dimensional semiconductor with a direct band gap of 1.8 eV. The MoS2/bulk semiconductor system offers a new platform for solar cell device design. Different from the conventional bulk p-n junctions, in the MoS2/bulk semiconductor heterostructure, static charge transfer shifts the Fermi level of MoS2 toward that of bulk semiconductor, lowering the barrier height of the formed junction. Herein, we introduce hexagonal boron nitride (h-BN) into MoS2/GaAs heterostructure to suppress the static charge transfer, and the obtained MoS2/h-BN/GaAs solar cell exhibits an improved power conversion efficiency of 5.42%. More importantly, the sandwiched h-BN makes the Fermi level tuning of MoS2 more effective. By employing chemical doping and electrical gating into the solar cell device, PCE of 9.03% is achieved, which is the highest among all the reported monolayer transition metal dichalcogenide based solar cells.

In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

Graphene with a series of neoteric electronic and optical properties is an intriguing building block for optoelectronic devices. Over the past decade, graphene‐based solar cells (SCs) and photodetectors (PDs) which can convert light signals to electrical signals have received burgeoning exploration. However, limited light absorption hampers the performance of these devices. Quantum dots (QDs) possess a strong confinement effect, a large exciton energy, and long exciton lifetime, enhancing the interaction between incident light and graphene. Especially, as the density of states near the Dirac point of graphene is ultralow, it is easy to modify the Fermi level of graphene by inserting quantum dots at the interface between graphene and light, thereby enhancing the performance of graphene‐based optoelectronic devices. The characteristics of QDs and crucial physical mechanisms of the interaction and energy transfer in QDs/graphene nanohybrids are systematically addressed. The factors influencing the efficiency of energy transfer are also analyzed quantitatively. Moreover, the experimental process of QD‐enhanced technologies for SCs, photoconductors, phototransistors, and photodiode PDs is reviewed. Eventually, a conclusion is given and the remaining challenges and future development for QDs/2D materials hybrid systems is discussed. Possible steps toward large‐scale commercial applications and integration into optoelectronic networks are suggested.

With the rapid iteration of portable electronics and electric vehicles, developing high-capacity batteries with ultra-fast charging capability has become a holy grail. Here we report rechargeable aluminum-ion batteries capable of reaching a high specific capacity of 200 mAh g−1. When liquid metal is further used to lower the energy barrier from the anode, fastest charging rate of 104 C (duration of 0.35 s to reach a full capacity) and 500% more specific capacity under high-rate conditions are achieved. Phase boundaries from the active anode are believed to encourage a high-flux charge transfer through the electric double layers. As a result, cationic layers inside the electric double layers responded with a swift change in molecular conformation, but anionic layers adopted a polymer-like configuration to facilitate the change in composition.

Graphene has attracted increasing interest due to its remarkable properties. However, the zero band gap of monolayered graphene limits it's further electronic and optoelectronic applications. Herein, we have synthesized monolayered silicon-doped graphene (SiG) with large surface area using a chemical vapor deposition method. Raman and X-ray photoelectron spectroscopy measurements demonstrate that the silicon atoms are doped into graphene lattice at a doping level of 2.7-4.5 at%. Electrical measurements based on a field effect transistor indicate that the band gap of graphene has been opened via silicon doping without a clear degradation in carrier mobility, and the work function of SiG, deduced from ultraviolet photoelectron spectroscopy, was 0.13-0.25 eV larger than that of graphene. Moreover, when compared with the graphene/GaAs heterostructure, SiG/GaAs exhibits an enhanced performance. The performance of 3.4% silicon doped SiG/GaAs solar cell has been improved by 33.7% on average, which was attributed to the increased barrier height and improved interface quality. Our results suggest that silicon doping can effectively engineer the band gap of monolayered graphene and SiG has great potential in optoelectronic device applications.