Unveiling the Stimulated Robust Carrier Lifetime of Surface‐Bound Excitons and Their Photoresponse in InSe

Abstract

In contrast to zero‐bandgap metallic graphene, the binary semiconducting compound, InSe, possesses a tunable bandgap. Herein, a range of particle sizes of β‐InSe from bulk to few‐layer nanosheets and quantum dots are carefully prepared. The size‐dependent bandgap variation and photon‐induced carrier dynamics of InSe are systemically investigated. In contrast to the normal size‐dependent carrier lifetime trend observed at 700 nm, anomalous size‐independent carrier decay is observed at 500 nm. Through time‐dependent density functional theory calculations, the normal carrier lifetimes at lower probe photon energies are attributed to in‐plane excitons, whereas the abnormal size‐independent carrier lifetimes at higher probe photon energies are found to be stimulated by surface‐bound excitons. In view of the robust surface exciton, this suggests that InSe may possess an outstanding optoelectronic performance in the shorter wavelength range. Through photoelectrochemical detection experiments, it is confirmed that InSe features a high photocurrent density and stability and, in particular, a more distinct photoresponse at short wavelengths than at longer ones. Comprehending and quantifying the role of the surface‐bound excitons in InSe across a broad range of semiconductor nanostructures and their fundamental properties may play an important role in understanding the physical properties of 2D III–VI compound materials.

Recent Advances in Semiconducting Monoelemental Selenium Nanostructures for Device Applications

“…[58] The AFM measurement exhibits that the resulting 2D Se nanosheets have an average thickness of 3-6 nm, as depicted in Figure 7f. In addition, it should be noted that there is a shape decline in the thickness of 2D Se nanosheets as the cascade centrifugation increases, that is, the higher centrifugation speed, the thinner of the as-prepared 2D Se nanosheets, in good agreement with those of reported WS 2 , [130] InSe, [20] and SnS. [21]…”

“…Size and shape are two critical factors that determine their properties of nanocrystal‐based material. [ 19–26 ] The size determines the specific surface area and the ratio of surface to bulk atoms, and the shape plays an essential role in the facet orientation and the surface structure and the fractions of atoms on the edges. [ 6 ] Many early works demonstrated that nanomaterial morphology control plays vital role in their performance, and their device performance can be modulated by rationally tuning the morphology.…”

“…[ 6 ] Many early works demonstrated that nanomaterial morphology control plays vital role in their performance, and their device performance can be modulated by rationally tuning the morphology. [ 20,21,27,28 ] To synthesize Se nanostructures, a suit of principles and strategies have been developed, such as hydrothermal and solvothermal methods, [ 29–32 ] liquid‐phase exfoliation, [ 33–35 ] vacuum vapor deposition, [ 36,37 ] microwave process, [ 38 ] and microbial approach. [ 28 ] Until now, reviews on Se nanostructures have been mainly on organic Se chemistry, and Se nutrition.…”

Zero‐Dimensional MXene‐Based Optical Devices for Ultrafast and Ultranarrow Photonics Applications

“…The Y-axis represents the pump-probe delay time in terms of picosecond and the X-axis represents the probe light wavelength with a range from 440 to 760 nm, which indicates that MXene QDs have a broad transient absorption. [40] The carrier dynamics in MXene QDs is analyzed basing the TA spectra in Figure 2e, in which the broadband photoinduced absorption (PIA) spectra are observed. Herein, this PIA signal is attributed to the excited-state absorption (ESA).…”

Recent advances of two-dimensional materials in smart drug delivery nano-systems

“…[ [50] , [51] , [52] ]), single element (graphene [ [53] , [54] , [55] ], selenium [ 38 , 56 ], boron [ 57 ], tellurium [ 58 ], bismuth [ [59] , [60] , [61] ] and black phosphorus [ [62] , [63] , [64] , [65] ], etc [ 60 , 66 , 67 ]. ), main group of metallic sulfide compounds (GaS、InSe、SnS、SnS 2 ) [ 48 , [68] , [69] , [70] ] and other two-dimensional materials [ [71] , [72] , [73] , [74] , [75] , [76] ]. These 2D materials have completely different energy band structures and electrical properties, including photo-electronics, and water splitting and energy storage [ [77] , [78] , [79] , [80] ].…”