Ultrasensitive Photoresponsive Devices Based on Graphene/BiI₃ van der Waals Epitaxial Heterostructures

Abstract

In recent years, bismuth iodide (BiI 3 ), 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/ BiI 3 vertical heterostructures are achieved by van der Waals epitaxies. The BiI 3 films deposited on graphene show flatter morphologies and significantly better crystallinities than that of BiI 3 films on SiO 2 substrates, mainly due to weak van der Waals interactions at the graphene/BiI 3 interface. Hybrid photodetectors with highly crystalline graphene/BiI 3 heterostructures demonstrate an ultrahigh responsivity of 6 × 10 6 A W −1 , shot-noise-limited detectivity of 7 × 10 14 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/BiI 3 heterojunctions are investigated using photoemission spectroscopy. The results give clear evidence that no chemical interactions occur between graphene and BiI 3 , resulting in the van der Waals epitaxial growth, and the measured band bending consistently illustrates that a photoinduced charge transfer occurs at the graphene/BiI 3 interface.

Gate-Tunable Photodetectors Based on Anti-Ambipolar Transistors Composed of Black Phosphorus/MoS2 Nanosheet Heterostructures

“…From the zoomed time dependence of photocurrent curve in Figure i, the rise and decay times are about 72 and 68 ms, respectively. The response speed of our BP/MoS 2 AAT photodetector is comparable to other photodetectors based on 2D material heterostructures. ,− …”

Forming‐Free, Nonvolatile, and Flexible Resistive Random‐Access Memory Using Bismuth Iodide/van der Waals Materials Heterostructures

“…Similar to the case of BiI 3 on the graphene/SiO 2 substrate, for the Si and graphene/copper substrates, four peaks were located at 13.12°, 26.05°, 39.33°, and 53.19°, corresponding to the (00l) family planes of the BiI 3 structure. [38] However, the XRD peaks of BiI 3 on the graphene/copper substrate were obviously much higher than those of BiI 3 on the bare silicon substrate. [38] This could be because the BiI 3 crystals were well-orientated to the c-axis, thereby resulting in a much higher diffraction intensity of X-rays.…”

“…[38] However, the XRD peaks of BiI 3 on the graphene/copper substrate were obviously much higher than those of BiI 3 on the bare silicon substrate. [38] This could be because the BiI 3 crystals were well-orientated to the c-axis, thereby resulting in a much higher diffraction intensity of X-rays. This is consistent with the SEM results.…”

Influence of Work Function of Carrier Transport Materials with Perovskite on Switchable Photovoltaic Phenomena

“…During the initial BiI 3 deposition steps, there were two apparent XPS peaks located at 158.5 and 156.7 eV, corresponding to the Bi–I bond and Bi–Bi bond, respectively, as shown in Figure S6 . In our previous study of the BiI 3 /graphene interface, there was no presence of metallic bismuth during the deposition process . This suggests that metallic bismuth may arise from the surface chemistry of perovskite instead of thermal decomposition during the evaporation process.…”