Mixed-dimensional stacked nanocomposite structures for a specific wavelength-selectable ambipolar photoresponse

Mixed-dimensional composite structures using zero-dimensional(0D)quantum dots(QDs)and two-dimensional(2D)transition metal dichalcogenides(TMDs)materials are expected to attract great interest in optoelectronics due to the potential to generate new optical properties.Here,we report on the unique optical characteristics of a devices with mixed dimensional vertically stacked structures based on tungsten diselenide(WSe_(2))/CdSeS QDs monolayer/molybdenum disulfide(MoS_(2))(2D/0D/2D).Specifically,it exhibits an ambipolar photoresponse characteristic,with a negative photoresponse observed in the 400-600 nm wavelength range and a positive photoresponse appeared at 700 nm wavelength.It resulted in the high negative responsivity of up to 52.22 mA·W^(−1)under 400 nm,which is 163 times higher than that of the photodetector without CdSeS QDs.We also demonstrated the negative photoresponse,which could be due to increased carrier collision probability and non-radiative recombination.Device modeling and simulation reveal that Auger recombination among the types of non-radiative recombination is the main cause of negative photocurrent generation.Consequently,we discovered ambipolar photoresponse near a specific wavelength corresponding to the energy of quantum dots.Our study revealed interesting phenomenon in the mixed low-dimensional stacked structure and paved the way to exploit it for the development of innovative photodetection materials as well as for optoelectronic applications.

High-performance photoelectrochemical cells with MoS2 nanoflakes/TiO2 photoanode on 3D porous carbon spun fabric

A solar-driven photoelectrochemical(PEC)cell is emerging as one of the promising clean hydrogen generation systems.Engineering of semiconductor heterojunctions and surface morphologies of photoelectrodes in a PEC cell has been a primitive approach to boost its performance.This study presents that a molybdenum disulfide(MoS_(2))nanoflakes photoanode on 3-dimensional(3D)porous carbon spun fabric(CSF)as a substrate effectively enhances hydrogen generations due to sufficiently enlarged surface area.MoS_(2)is grown on CSFs utilizing a hydrothermal method.Among three different MoS_(2)coating morphologies depending on the amount of MoS_(2)precursor and hydrothermal growth time,film shape MoS_(2)on CSFs had the largest surface area,exhibiting the highest photocurrent density of 26.48 mA/cm^(2)and the highest applied bias photon-to-current efficiency(ABPE)efficiency of 5.32%at 0.43 VRHE.Furthermore,with a two-step growth method of sputtering and a subsequent hydrothermal coating,continuous TiO_(2)/MoS_(20 heterojunctions on a porous CSF further promoted the photoelectrochemical performances due to their optimized bandgap alignments.Enlarged surface area,enhanced charge transfer,and utilization of visible light enable a highly efficient MoS_(2)/TiO_(2)/CSF photoanode with a photocurrent density of 33.81 mA/cm^(2)and an ABPE of 6.97%at 0.87 VRHE.The hydrogen generation amount of the PEC cell with MoS_(2)/TiO_(2)/CSF photoanode is 225.4μmol/L after light irradiation of 60 s.