Targeted transfer of self-assembled CdSe nanoplatelet film onto WS_(2) flakes to construct hybrid heterostructures

Colloidal CdSe nanoplatelets are thin semiconductor materials with atomic flatness surfaces and one-dimensional strong quantum confinement,and hence they own very narrow and anisotropic emission.Here,we present a polydimethylsiloxane(PDMS)assisted transferring method that can pick up single layer CdSe nanoplatelet films self-assembled on a liquid surface and then precisely transfer to a target.By layer-by-layer picking up and transferring,multiple layers of CdSe films can be built up to form CdSe stacks with each single layer having dominant in-plane transition dipole distribution,which both material and energic structures are analogous to traditional multiple quantum wells grown by molecular-beam epitaxy.Additionally,with the great flexibility of colloidal nanoplatelets and this transferring method,CdSe nanoplatelets films can be combined with other materials to form hybrid heterostructures.We transferred a single-layer CdSe film onto WS_(2) flakes,and precisely studied the fast energy transfer rate with controlled CdSe nanoplatelet orientation and by using a streak camera with a ps time resolution.

Comparison between Top and Bottom NiO-pinning Spin Valves: Effect of Interfacial Roughness on Specular Reflection

Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.

Lateral quantum confinement regulates charge carrier transfer and biexciton interaction in CdSe/CdSeS core/crown nanoplatelets

Charge carrier dynamics essentially determines the performance of various optoelectronic applications of colloidal semiconductor nanocrystals.Among them,two-dimensional nanoplatelets provide new adjustment freedom for their unique core/crown heterostructures.Herein,we demonstrate that by fine-tuning the core size and the lateral quantum confinement,the charge carrier transfer rate from the crown to the core can be varied by one order of magnitude in CdSe/CdSeS core/alloy-crown nanoplatelets.In addition,the transfer can be affected by a carrier blocking mechanism,i.e.,the filled carriers hinder further possible transfer.Furthermore,we found that the biexciton interaction is oppositely affected by quantum confinement and electron delocalization,resulting in a non-monotonic variation of the biexciton binding energy with the emission wavelength.This work provides new observations and insights into the charge carrier transfer dynamics and exciton interactions in colloidal nanoplatelets and will promote their further applications in lasing,display,sensing,etc.

Focus on perovskite emitters in blue light-emitting diodes

Blue perovskite light-emitting diodes(PeLEDs)are essential in pixels of perovskite displays,while their progress lags far behind their red and green counterparts.Here,we focus on recent advances of blue PeLEDs and systematically review the noteworthy strategies,which are categorized into compositional engineering,dimensional control,and size confinement,on optimizing microstructures,energy landscapes,and charge behaviors of wide-bandgap perovskite emitters(bandgap>2.5 eV).Moreover,the stability of perovskite blue emitters and related devices is discussed.In the end,we propose a technical roadmap for the fabrication of state-of-the-art blue PeLEDs to chase and achieve comparable performance with the other two primary-color devices.

Colloidal II-VI nanoplatelets for optoelectronic devices:Progress and perspectives

Colloidal II-VI nanoplatelets(NPLs)are solution-processable two-dimensional(2D)quantum dots that have vast potential in highperformance optoelectronic applications,including light-emitting diodes,sensors,and lasers.Superior properties,such as ultrapure emission,giant oscillator strength transition,and directional dipoles,have been demonstrated in these NPLs,which can improve the efficiency of light-emitting diodes and lower the threshold of lasers.In this review,we present an overview of the current progress and propose perspectives on the most well-studied II-VI NPLs that are suitable for the optoelectronic applications.We emphasize that the control of the symmetrical shell growth of NPLs is critical for the practical utilization of the advantages of NPLs in these devices.