https://scholars.lib.ntu.edu.tw/handle/123456789/498050
Title: | Ultrasensitive Photoresponsive Devices Based on Graphene/BiI<inf>3</inf> van der Waals Epitaxial Heterostructures | Authors: | CHIH-I WU Chang, P.-H. Li, C.-S. Fu, F.-Y. Huang, K.-Y. Chou, A.-S. CHIH-I WU |
Keywords: | bismuth iodide; graphene; photodetectors; photoemission spectroscopy; van der Waals epitaxy | Issue Date: | 2018 | Journal Volume: | 28 | Journal Issue: | 23 | Source: | Advanced Functional Materials | Abstract: | In recent years, bismuth iodide (BiI3), a layered metal halide semiconducting light absorber with a wide bandgap of ≈1.8 eV and strong optical absorption in the visible region, has received greater attention for photovoltaic applications. In this study, ultrasensitive visible-light photodetectors with graphene/BiI3 vertical heterostructures are achieved by van der Waals epitaxies. The BiI3 films deposited on graphene show flatter morphologies and significantly better crystallinities than that of BiI3 films on SiO2 substrates, mainly due to weak van der Waals interactions at the graphene/BiI3 interface. Hybrid photodetectors with highly crystalline graphene/BiI3 heterostructures demonstrate an ultrahigh responsivity of 6 × 106 A W−1, shot-noise-limited detectivity of 7 × 1014 Jones, and a relatively short response time of ≈8 ms. Compared to most previously reported graphene-based hybrid photodetectors, these devices have comparable photosensitivities but a faster response speed and lower operation voltage, which is quite promising for ultralow intensity visible-light sensors. Moreover, the electronic structure and interfacial chemistry at the graphene/BiI3 heterojunctions are investigated using photoemission spectroscopy. The results give clear evidence that no chemical interactions occur between graphene and BiI3, resulting in the van der Waals epitaxial growth, and the measured band bending consistently illustrates that a photoinduced charge transfer occurs at the graphene/BiI3 interface. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/498050 | DOI: | 10.1002/adfm.201800179 | SDG/Keyword: | Bismuth compounds; Charge transfer; Electromagnetic wave attenuation; Electronic structure; Graphene; Graphene devices; Heterojunctions; Interfaces (materials); Light; Light absorption; Metal halides; Photodetectors; Photoelectron spectroscopy; Photons; Shot noise; Silica; Van der Waals forces; Bismuth iodide; Chemical interactions; Epitaxial heterostructures; Hybrid photo detectors; Photoinduced charge transfer; Photovoltaic applications; Van der Waals epitaxy; Van Der Waals interactions; Iodine compounds |
Appears in Collections: | 電機工程學系 |
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