Bandgap Engineering and Near-Infrared-II Optical Properties of Monolayer MoS2: A First-Principle Study

Engineering electrode interfaces for telecom-band photodetection in MoS2/Au heterostructures via sub-band light absorption

Transition metal dichalcogenide (TMD) layered semiconductors possess immense potential in the design of photonic, electronic, optoelectronic, and sensor devices. However, the sub-bandgap light absorption of TMD in the range from near-infrared (NIR) to short-wavelength infrared (SWIR) is insufficient for applications beyond the bandgap limit. Herein, we report that the sub-bandgap photoresponse of MoS2/Au heterostructures can be robustly modulated by the electrode fabrication method employed. We observed up to 60% sub-bandgap absorption in the MoS2/Au heterostructure, which includes the hybridized interface, where the Au layer was applied via sputter deposition. The greatly enhanced absorption of sub-bandgap light is due to the planar cavity formed by MoS2 and Au; as such, the absorption spectrum can be tuned by altering the thickness of the MoS2 layer. Photocurrent in the SWIR wavelength range increases due to increased absorption, which means that broad wavelength detection from visible toward SWIR is possible. We also achieved rapid photoresponse (~150 µs) and high responsivity (17 mA W-1) at an excitation wavelength of 1550 nm. Our findings demonstrate a facile method for optical property modulation using metal electrode engineering and for realizing SWIR photodetection in wide-bandgap 2D materials.

Touhidul Islam AZ. Performance Enhancement of an MoS2-Based Heterojunction Solar Cell with an In2Te3 Back Surface Field: A Numerical Simulation Approach

Researchers are currently showing interest in molybdenum disulfide (MoS₂)-based solar cells due to their remarkable semiconducting characteristics. The incompatibility of the band structures at the BSF/absorber and absorber/buffer interfaces, as well as carrier recombination at the rear and front metal contacts, prevents the expected result from being achieved. The main purpose of this work is to enhance the performance of the newly proposed Al/ITO/TiO₂/MoS₂/In₂Te₃/Ni solar cell and investigate the impacts of the In₂Te₃ BSF and TiO₂ buffer layer on the performance parameters of open-circuit voltage (V _OC), short-circuit current density (J _SC), fill factor (FF), and power conversion efficiency (PCE). This research has been performed by utilizing SCAPS simulation software. The performance parameters such as variation of thickness, carrier concentration, the bulk defect concentration of each layer, interface defect, operating temperature, capacitance-voltage (C-V), surface recombination velocity, and front as well as rear electrodes have been analyzed to achieve a better performance. This device performs exceptionally well at lower carrier concentrations (1 × 10¹⁶ cm^-3) in a thin (800 nm) MoS₂ absorber layer. The PCE, V _OC, J _SC, and FF values of the Al/ITO/TiO₂/MoS₂/Ni reference cell have been estimated to be 22.30%, 0.793 V, 30.89 mA/cm², and 80.62% respectively, while the PCE, V _OC, J _SC, and FF values have been determined to be 33.32%, 1.084 V, 37.22 mA/cm², and 82.58% for the Al/ITO/TiO₂/MoS₂/In₂Te₃/Ni proposed solar cell by introducing In₂Te₃ between the absorber (MoS₂) and the rear electrode (Ni). The proposed research may give an insight and a feasible way to realize a cost-effective MoS₂-based thin-film solar cell.

Multimodal molecular imaging in the second near-infrared window

Near-infrared-II (NIR-II) fluorescence imaging has rapidly developed for the noninvasive investigation of physiological and pathological activities in living organisms with high spatiotemporal resolution. However, the penetration depth of fluorescence restricts its ability to provide deep anatomical information. Scientists integrate NIR-II fluorescence imaging with other imaging modes (such as photoacoustic and magnetic resonance imaging) to create multimodal imaging that can acquire detailed anatomical and quantitative information with deeper penetration by using multifunctional probes. This review offers a comprehensive picture of NIR-II-based dual/multimodal imaging probes and highlights advances in bioimaging and therapy. In addition, seminal studies and trends in multimodal imaging probes activated by NIR-II laser are summarized and several key points regarding future clinical translation are elucidated.