2D Organic–Inorganic Hybrid Thin Films for Flexible UV–Visible Photodetectors

Abstract

as hybridization of MoS 2 with quantum dots and heterostructures with other 2D materials to suppress the dark current and enhance the broad spectral range in the NIR region were attempted. While convenient, these approaches are not scalable for large-scale implementation due to the complicated procedures as well as expensive material and instrument-related costs. [17][18][19] To overcome the aforementioned issues, a promising approach is to create multifunctional hybrid photodetectors by simple solution mixing of MoS 2 with other 2D materials. The different band gaps and dark currents of 2D materials and the low-cost solution process offers a convenient route to engineering and controlling the photodetection properties. [20][21][22] In addition, the arrays of hybrid photodetectors fabricated on flexible substrates, such as plastic and paper, would be beneficial for future wearable applications. [23,24] Recently, 2D organic semiconductors, such as graphitic carbon nitride (g-C 3 N 4 ), have emerged as promising UV-and visible-light-active photocatalysts in the arena of solar energy conversion and environmental applications. [25][26][27][28] Their unique electrical and optical properties, wide band gap (≈2.7 eV), stability in ambient conditions, and low dark current make them attractive for UV light photodetection, but very little work has been carried out so far. Compared to other 2D materials, by considering its merits, g-C 3 N 4 is a promising candidate for hybridizing with MoS 2 because not only does it suppress the dark current of MoS 2 , but also allows hybrid broadband photodetection from UV to visible region. In addition, the crystal lattice matching [29,30] and the ultrafast charge transfer between MoS 2 and g-C 3 N 4 at the interface may lead to efficient separation of photogenerated carriers, as predicted by a recent computational study. [31] Herein we report, to the best of our knowledge for the first time, mechanically flexible 2D organic-inorganic hybrid thin film photodetectors consisting of inorganic MoS 2 and organic g-C 3 N 4 nanosheets for broadband photodetection. Simple but robust solution mixing of MoS 2 and g-C 3 N 4 offers an extremely convenient route to controlling their composition in the hybrid films and thus allows for tuning the optoelectronic properties. Hybrid thin films with 5:5 ratio of MoS 2 and g-C 3 N 4 (henceforth denoted as 5:5 hybrid films) exhibited excellent photodetection performance in terms of ON/OFF photocurrent ratio, specific detectivity, responsivity, and response time upon both Flexible 2D inorganic MoS 2 and organic g-C 3 N 4 hybrid thin film photodetectors with tunable composition and photodetection properties are developed using simple solution processing. The hybrid films fabricated on paper substrate show broadband photodetection suitable for both UV and visible light with good responsivity, detectivity, and reliable and rapid photoswitching characteristics comparable to monolayer devices. This excellent performance is retained even after the films are severely...

Flexible Photodetectors Based on Novel Functional Materials

“…More recently, MoS 2 nanosheets have been mixed with graphitic carbon nitride (g‐C 3 N 4 ) nanosheets synthesized from a liquid phase exfoliation method to form an inorganic‐organic hybrid blend for flexible photodetection . The optical properties of the hybrid films can be readily tuned by adjusting the elemental composition, which allows tunable photodetection characteristics.…”

Recent Progress on Photomultiplication Type Organic Photodetectors

“…An external voltage is applied to read out the photon‐derived carriers, and gain can be realized by multiple carrier recirculation. Since more than one electron can flow in consequence of a single absorbed photon, the EQE of >100% is possible, which means that an incident photon triggers an electrical current flow provided by numerous electrons …”

Lateral multilayer/monolayer MoS2 heterojunction for high performance photodetector applications

“…Among various TMDCs, MoS 2 is gaining increasing attention for applications in optoelectronic devices 6–9 , due to the suitable bandgap value, relatively high carrier mobility and high light absorbance 10 . It is interesting that bulk MoS 2 is semiconducting with an indirect bandgap of 1.2 eV 11 , whereas single-layer MoS 2 is a direct gap semiconductor with a bandgap of 1.8 eV 12 .…”