Surface-Modified Ultrathin InSe Nanosheets with Enhanced Stability and Photoluminescence for High-Performance Optoelectronics

Abstract

Indium selenide (InSe) has become a research hotspot because of its favorable carrier mobility and thickness-tunable band gap, showing great application potential in high-performance optoelectronic devices. The trend of miniaturization in optoelectronics has forced the feature sizes of the electronic components to shrink accordingly. Therefore, atomically thin InSe crystals may play an important role in future optoelectronics. Given the instability and ultralow photoluminescent (PL) emission of mechanically exfoliated ultrathin InSe, synthesis of highly stable mono- and few-layer InSe nanosheets with high PL efficiency has become crucial. Herein, ultrathin InSe nanosheets were prepared via thermal annealing of electrochemically intercalated products from bulk InSe. The size and yield of the as-prepared nanosheets were up to ∼160 μm and ∼70%, respectively, and ∼80% of the nanosheets were less than five layer. Impressively, the as-prepared nanosheets showed greatly enhanced stability and PL emission because of surface modification by carbon species. Efficient photoresponsivity of 2 A/W was achieved in the as-prepared nanosheet-based devices. These nanosheets were further assembled into large-area thin films with photoresponsivity of 16 A/W and an average Hall mobility of about 5 cm2 V–1 s–1. Finally, one-dimensional (1D) InSe nanoscrolls with a length up to 90 μm were constructed by solvent-assisted self-assembly of the exfoliated nanosheets.

Nonlinear Optical Properties and Ultrafast Carrier Dynamics of 2D Indium Selenide Nanosheets

“…The image demonstrates that the hexagonal structure of the InSe material and the lattice constant measured along the (100) and (010) directions are 0.32 nm, which corresponds to previously reported results. [37] The selected area electron diffraction pattern is shown in Figure 1e. A typical sixfold symmetry can be seen, indicating the good crystalline characteristics of the obtained InSe www.advopticalmat.de nanosheets.…”

Flexible Photodetectors Based on All‐Solution‐Processed Cu Electrodes and InSe Nanoflakes with High Stabilities

“…InSe nanoflakes were synthesized via electrochemical intercalation and ultrasonic exfoliation in solutions following the general protocols in our previously published paper. [ 77 ] Here, giant molecules of THAB were used as novel intercalating reagents with the help of electrochemical driving forces. Efficient intercalation into van der Waals gaps of bulk InSe crystals with THAB facilitated the decoupling of interlayer interaction upon mild sonication, allowing for scalable production of few‐layer InSe nanoflakes with high quality.…”

“…In addition, typical D bands (≈1352 cm −1 ) and G bands (≈1572 cm −1 ) of graphitized carbon were identified, which rooted from some surface carbon species of THAB molecules. According to the previous study, [ 77 ] these surface carbon would play important roles in enhancing the environmental stability of as‐synthesized few‐layer InSe nanoflakes. From X‐ray photoelectron spectroscopy (XPS) analysis (Figure 3e and Figure S6), In 3d and Se 3d peaks exhibited a slight redshift of 0.3 eV for InSe film when compared with pristine bulk InSe.…”

Scalably Nanomanufactured Atomically Thin Materials‐Based Wearable Health Sensors

“…[ 849–852,2,590,591,853–855 ] However, the atomic thickness also renders environmental instability in many 2D materials. [ 426,427 ] The optimization of device structure and the incorporation of proper encapsulation would address this challenge. [ 273,436,438 ] Substrate‐agnostic 2D materials (e.g., solution‐processable) with diversified functionalities are attractive and desired for manufacturing integrated wearable sensors on polymeric substrates.…”

“…These results indicate 2D InSe could be promising for high‐performance electronic and optoelectronic devices. [ 426–428 ]…”