Synthesis and Ultrafast Carrier Dynamics of Single-Crystal Two-Dimensional CuInSe₂ Nanosheets

Abstract

We report, for the first time, the synthesis of single-crystal two-dimensional (2D) CuInSe2 nanosheets and the studies of ultrafast carrier dynamics and transport in this 2D material. Particularly, single-crystal 2D CuInSe2 with various thicknesses in the nanometer regime were fabricated by a solid-state chemical reaction between Cu and single-crystal exfoliated In2Se3 nanosheets. Characteristics of transient optical reflectivity, obtained from femtosecond optical pump-probe measurements on single CuInSe2 nanosheets, suggest that the hot carrier cooling process dominates the carrier dynamics within a few picoseconds following the optical excitation. Spatially resolved pump-probe measurements, coupled to simple model calculations, were used to obtain the ambipolar hot carrier diffusion coefficient in single nanosheets. The dependence of the hot carrier diffusion coefficient on the nanosheet thickness provides insight into the limiting mechanisms of hot carrier transport and can be used to gauge the possibility of efficient hot carrier collection in nanostructured CuInSe2 solar cells.

Thickness-Dependent Thermal Conductivity of Suspended Two-Dimensional Single-Crystal In2Se3Layers Grown by Chemical Vapor Deposition

“…This anisotropy is inherent in all 2D materials, as the in-plane atomic bonds are largely covalent, whereas the out-of-plane atomic interaction is dominated by the van der Waal force. We considered the layer–substrate (outside the hole) heat transfer by defining an interface thermal conductance ( G ). The layer–air heat transfer, which was shown to have a non-negligible impact on the thermal conductivity measurements in graphene, was also considered. The laser illumination was defined as a Gaussian beam. The full width at half-maximum (fwhm) of the Gaussian beam was obtained from wavelength-adjusted spatially resolved autocorrelation scans . Details can be found in the Supporting Information. The boundary condition is that the temperature at the back of the substrate remains at 300 K (room temperature). …”

Vitamin C in Stem Cell Biology: Impact on Extracellular Matrix Homeostasis and Epigenetics

“…In line with these findings, in human dermal fibroblasts, several collagen-coding genes, including COL1A2 , COL3A1 , COL6A1 , and COL6A3 , have been identified as TGF β /SMAD3 targets in human dermal fibroblasts [66]. Moreover, vitamin D-induced reduction of intestinal fibrosis has been associated with the inhibition of the canonical TGF β /SMAD3 pathway [67]. In renal epithelial cells, TGF β regulates collagen deposition by recruiting mTOR kinase (through noncanonical TGF β pathway) [47, 68].…”

Pressure-Induced Multidimensional Assembly and Sintering of CuInS2 Nanoparticles into Lamellar Nanosheets with Band Gap Narrowing

“…7,8 Especially in the field of photovoltaic devices, 2D functional nanocrystals (NCs) have attracted considerable interest because of their enhanced optical absorption properties, which are attributed to decreased dielectric screening. 9,10 As one of the photovoltaic materials with the most potential, tetragonal chalcopyrite (CH) CuInS 2 embodies excellent properties, including a direct band gap of 1.45 eV, a high absorption coefficient of more than 10 5 cm −1 , and a high photoelectric conversion efficiency. 11−15 With respect to geometric figures, much attention has focused on the rod-and particle-like CuInS 2 NCs fabricated through hydrothermal, solvothermal, and thermolysis processes.…”

“…Two-dimensional (2D) nanomaterials have an ultrathin thickness that falls within the range of the quantum confinement effect, which is vital for exploring new physical phenomena and application prospects in many fields, such as superconductors, , optoeletronics, , valleytronics, spintronics, and catalysis. , Especially in the field of photovoltaic devices, 2D functional nanocrystals (NCs) have attracted considerable interest because of their enhanced optical absorption properties, which are attributed to decreased dielectric screening. , As one of the photovoltaic materials with the most potential, tetragonal chalcopyrite (CH) CuInS 2 embodies excellent properties, including a direct band gap of 1.45 eV, a high absorption coefficient of more than 10 5 cm –1 , and a high photoelectric conversion efficiency. − With respect to geometric figures, much attention has focused on the rod- and particle-like CuInS 2 NCs fabricated through hydrothermal, solvothermal, and thermolysis processes. − To date, the preparation of 2D lamellar CuInS 2 NCs has rarely been reported. The major synthetic obstacle arises from the need to conquer their high kinetic barriers and harsh synthetic conditions.…”