MXenes for Optoelectronic Devices

Abstract

MXenes have attracted increasing attention from the research community due to several unique properties that make them suitable for many applications. As a rapidly growing family of 2D transitional metal carbides and nitrides, they have demonstrated very promising properties in electrochemical devices. Recently, a few reports have emerged showing that MXenes have interesting optoelectronic properties. In this review, the fundamental properties of MXenes are discussed, especially those related to optoelectronic properties, and the recent reports on MXene‐based optoelectronic applications including photovoltaic, plasmonic, photodetector, phototransistor, and light‐emitting diode applications are reviewed. Last, and most importantly, a vision and a road map is articulated for the future research directions that make the most sense for this important class of materials.

MXenes for Energy Harvesting

“…Hydrofluoric acid (HF) solution (including HF and in situ formed HF, e.g., HCl + LiF) etching followed by an intercalant (e.g., metal or organic cations)‐assisted delamination is the most commonly used method for the preparation of MXenes (Figure 2b; Figure S1, Supporting Information). [ 16 ] With the application of this method, MXenes with abundant –F groups on the surface can be efficiently prepared under mild temperature. It must be emphasized that since MAX phases possess different elemental compositions and crystal structures, controlling the etching condition (e.g., HF concentration, temperature, and time) is essential to the preparation process.…”

Tunable Infrared Sensing Properties of MXenes Enabled by Intercalants

“…On the other hand, if R intra of MXene stays unchanged under laser irradiation, TMAOH related R inter acts as an electric signal for NIR sensing showing a negative temperature coefficient behavior. Herein, Mo 2 TiC 2 is chosen since its intra-flake resistance is almost temperature independent as reported by Hart et al [30] In this section, specifically, HF etched and TMAOH delaminated Mo 2 TiC 2 is used for the assembly of freestanding films with both H 2 O and TMAOH as intercalants. The resistance variations of Mo 2 TiC 2 line-shaped device are then analyzed in Ar and moist Ar flow to evaluate the influence of intercalated H 2 O, the results of which are presented in Figure 4a.…”

“…optoelectronic applications of MXenes due to their tunable electronic structures, high electronic conductivity, and high compatibility with mainstream semiconductor processes. [29][30][31][32][33][34][35][36][37] Among these applications, the as measured resistance variations of acid-etched MXenes with plenty of aqueous intercalants had been widely used directly as spontaneous signals to stimulations. Nevertheless, the measured resistance is in fact of a coupled resistance of MXenes which contains two disparate physical meanings behind: intra-flake resistance (R intra ) which reflects the intrinsic metallic conductivity of MXenes, and interflake resistance (R inter ) which relates to the surface terminations and intercalants.…”

Advances and emerging challenges in MXenes and their nanocomposites for biosensing applications

“… 29 Since its early reports on biosensing, it has aroused a tremendous interest in the biosensing community and the past 5 years can be regarded as a gold rush in MXene biosensing. Metallic conductivity (≈20 000 S cm −1 ), 30 rich surface chemistry, 31 negligible cytotoxicity, 32 inherent hydrophilicity, 33 ability to form stable colloidal suspensions 34 and unique optoelectronic properties 35 render MXenes a promising material in biosensing. MXenes also provide an effective interface for biofunctionalization with numerous anchoring sites and enhanced electron transfer makes it a highly efficient signal transducer, hence enhancing the detection sensitivity.…”