Active manipulation of light in optical fibres has been extensively studied with great interest because of its compatibility with diverse fibre-optic systems. While graphene exhibits a strong electro-optic effect originating from its gapless Dirac-fermionic band structure, electric control of all-fibre graphene devices remains still highly challenging. Here we report electrically manipulable in-line graphene devices by integrating graphene-based field effect transistors on a side-polished fibre. Ion liquid used in the present work critically acts both as an efficient gating medium with wide electrochemical windows and transparent over-cladding facilitating light–matter interaction. Combined study of unique features in gate-variable electrical transport and optical transition at monolayer and randomly stacked multilayer graphene reveals that the device exhibits significant optical transmission change (>90%) with high efficiency-loss figure of merit. This subsequently modifies nonlinear saturable absorption characteristics of the device, enabling electrically tunable fibre laser at various operational regimes. The proposed device will open promising way for actively controlled optoelectronic and nonlinear photonic devices in all-fibre platform with greatly enhanced graphene–light interaction.
Gallium arsenide (GaAs) photovoltaic (PV) cells have been widely investigated due to their merits such as thin‐film feasibility, flexibility, and high efficiency. To further increase their performance, a wider bandgap PV structure such as indium gallium phosphide (InGaP) has been integrated in two‐terminal (2T) tandem configuration. However, it increases the overall fabrication cost, complicated tunnel‐junction diode connecting subcells are inevitable, and materials are limited by lattice matching. Here, high‐efficiency and stable wide‐bandgap perovskite PVs having comparable bandgap to InGaP (1.8–1.9 eV) are developed, which can be stable low‐cost add‐on layers to further enhance the performance of GaAs PVs as tandem configurations by showing an efficiency improvement from 21.68% to 24.27% (2T configuration) and 25.19% (4T configuration). This approach is also feasible for thin‐film GaAs PV, essential to reduce its fabrication cost for commercialization, with performance increasing from 21.85% to 24.32% and superior flexibility (1000 times bending) in a tandem configuration. Additionally, potential routes to over 30% stable perovskite/GaAs tandems, comparable to InGaP/GaAs with lower cost, are considered. This work can be an initial step to reach the objective of improving the usability of GaAs PV technology with enhanced performance for applications for which lightness and flexibility are crucial, without a significant additional cost increase.
A facile synthesis method for the heterostructures of single-walled carbon nanotubes (SWCNTs) and few-layer MoS 2 is reported. The heterostructures are realized by in situ chemical vapor deposition of MoS 2 on individual SWCNTs. Field effect transistors based on the heterostructures display different transfer characteristics depending on the formation of MoS 2 conduction channels along SWCNTs. Under light illumination, negative photoresponse originating from charge transfer from MoS 2 to SWCNT is observed while positive photoresponse is observed in MoS 2 conduction channels, leading to ambipolar photoresponse in devices with both SWCNT and MoS 2 channels. The heterostructure phototransistor, for negative photoresponse, exhibits high responsivity (100-1000 AW −1 ) at low bias voltages (0.1 V) in the visible spectrum (500-700 nm) by combining high mobility conduction channel (SWCNT) with efficient light absorber (MoS 2 ).
In article number 1903085, Jaejin Lee, Hui Joon Park, and co‐workers demonstrate perovskite/GaAs 2‐ and 4‐terminal tandem cells. High performance, stable, wide‐bandgap perovskite photovoltaics (PVs) (1.8–1.9 eV) are developed through a solvent‐controlled process. The tandem architecture is also feasible for a thin‐film flexible PV, which is essential to reduce its cost for commercialization with superior bendability. This approach is expected to improve the usability of GaAs PVs with enhanced efficiency and lower cost for applications where light‐weight and flexibility are critical.
The spatial distribution of photogenerated carriers in atomically thin MoS2 flakes is investigated by measuring surface potential changes under light illumination using Kelvin probe force microscopy (KPFM). It is demonstrated that the vertical redistribution of photogenerated carriers, which is responsible for photocurrent generation in MoS2 photodetectors, can be imaged as surface potential changes with KPFM. The polarity of surface potential changes points to the trapping of photogenerated holes at the interface between MoS2 and the substrate as a major mechanism for the photoresponse in monolayer MoS2. The temporal response of the surface potential changes is compatible with the time constant of MoS2 photodetectors. The spatial inhomogeneity in the surface potential changes at the low light intensity that is related to the defect distribution in MoS2 is also investigated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.