Production and Patterning of Liquid Phase–Exfoliated 2D Sheets for Applications in Optoelectronics

Abstract

2D materials (2DMs), which can be produced by exfoliating bulk crystals of layered materials, display unique optical and electrical properties, making them attractive components for a wide range of technological applications. This review describes the most recent developments in the production of high-quality 2DMs based inks using liquid-phase exfoliation (LPE), combined with the patterning approaches, highlighting convenient and effective methods for generating materials and films with controlled thicknesses down to the atomic scale. Different processing strategies that can be employed to deposit the produced inks as patterns and functional thin-films are introduced, by focusing on those that can be easily translated to the industrial scale such as coating, spraying, and various printing technologies. By providing insight into the multiscale analyses of numerous physical and chemical properties of these functional films and patterns, with a specific focus on their extraordinary electronic characteristics, this review offers the readers crucial information for a profound understanding of the fundamental properties of these patterned surfaces as the millstone toward the generation of novel multifunctional devices. Finally, the challenges and opportunities associated to the 2DMs' integration into working opto-electronic (nano) devices is discussed.

Ultrafast Electrochemical Synthesis of Defect‐Free In2Se3 Flakes for Large‐Area Optoelectronics

“…The histogram (Figure 3k) obtained from the analysis of 100 individual sheets shows an average flake size of 8.6 µm, thanks to the mild intercalation process (Table S1, Supporting Information). [6] Element mapping of a single flake reveals homogeneous distribution of In and Se atoms in the entire flake (Figure 3a). TEM image (Figure 3b) confirms the thin and flexible features of the In 2 Se 3 nanosheets.…”

“…Recently, photodetectors based in single In 2 Se 3 nanosheets deliver high photosensitivity (10 5 A W −1 ) and fast, reversible and stable photoresponse characteristics . The excellent properties of In 2 Se 3 outperform many other 2D materials (such as graphene, BP and MoS 2 ), thus providing great fundamental basis for large‐area photodetectors . Nevertheless, the scalable production of defect‐free In 2 Se 3 flakes with large crystal domains remains an impediment to their practical applications.…”

Interlayer dielectric function of a type-II van der Waals semiconductor: The HfS2/PtS2 heterobilayer

“…This reflects the relative magnitude of the direct gaps of the various structures. A distribution of absorption edges as the one described here, unfortunately, prevents the unique identification of HfS 2 /PtS 2 HBLs in a mixture containing stacks with different numbers of layers, as those produced by liquid-phase exfoliation [32]. In fact, the most high-throughput means of producing 2D hetero-structures is by re-aggregating 2D materials previously exfoliated.…”

“…In fact, the most high-throughput means of producing 2D hetero-structures is by re-aggregating 2D materials previously exfoliated. In the process, however, one retains little control of the number of layers making the various structures, so that together with heterobilayers one will find in the mixture homo-bilayers, monolayers and a multitude of other structures comprising more than two layers [32][33][34]. As the lower part of the absorption is always dominated by structures consisting of PtS 2 , the absorption edge of HfS 2 /PtS 2 HBLs will never be spectrally separated, hence such structure will not be detectable by a single optical measurement.…”

Tailoring the physicochemical properties of solution-processed transition metal dichalcogenides via molecular approaches

“…141 Solution-processing techniques possess high exfoliation yield and a superior control over the final thickness, which is crucial in determining the electronic properties and the related electrical properties and performances of TMD-based devices (see Section 2). 142 In particular, during the last few years many works have been published about the possible applications of LPE and ce-TMDs in (opto-)electronics, with intriguing results coming from the fabrication of devices such as transistors, 143 saturable absorbers for lasers, 144,145 photodetectors 146 and Mg/Li-ion batteries. 147 However, solution-processed TMDs can undergo subsequent functionalization steps via molecular strategies in order to meticulously tailor and/or further enhance their physicochemical properties.…”