Ultraviolet Photodetector based on Sr_(2)Nb_(3)O_(10) Perovskite Nanosheets

Liquid-phase exfoliation was employed to synthesize Sr_(2)Nb_(3)O_(10) perovskite nanosheets with thicknesses down to 1.76 nm.Transmission electron microscopy(TEM),atomic force microscope(AFM),X-ray photoelectron spectrometer(XPS),and other characterization techniques were used to evaluate the atomic structure and chemical composition of the exfoliated nanosheets.A UV photodetector based on individual Sr_(2)Nb_(3)O_(10) nanosheets was prepared to demonstrate the application of an ultraviolet(UV) photodetector.The UV photodetector exhibited outstanding photocurrent and responsivity with a responsivity of 3×10^(5) A·W^(-1) at 5 V bias under 280 nm illumination,a photocurrent of 60 nA,and an on/off ratio of 3×10^(2).

Synthesis and characterization of anatase TiO_2 nanosheet arrays on FTO substrate

We have exploited a green approach to prepare layered titanate Na2_xHxTi2Os-H20 nanosheet arrays on FFO substrate by hydrothermal hydrolysis of titanium（IV） isopropoxide （TRIP） with aids of Na2EDTA and TEOA as co-coordination agents, which were then treated by HNO3 to replace Na＋ by H＋, followed by a calcination at 450℃ to topotactically transform into anatase TiO2 nanosheet arrays. SEM, TEM, XRD, and Raman spectroscopy have been employed to characterize the nanosheet films. The TiO2 nanosheet arrays were further applied as electron transport materials of CH3NH3PbI3 perovskite solar cells, achieving power conversion efficiency of 6.99%.

X-ray imager of 26-μm resolution achieved by perovskite assembly

Spatial resolution is an important criterion to evaluate the performance of a scintillation screen for X-ray imaging.Perovskite-based X-ray screen,usually made of powders or polycrystalline films,suffers from low spatial resolution(~200μm)due to the large thickness of scintillation layer despite of their compelling sensitivity to X-ray dose.In this work,a concentrated colloid of CsPbBr_(3)nanosheets was synthesized via a co-precipitation method at ambient condition.By drop casting,smooth scintillation screens of varied thickness were formed through self-assembly,which exhibited both high internal and external photoluminescence quantum yield(PL QY)(84.5%and 75.1%,respectively).The screen-based X-ray detector showed a high sensitivity down to 27 nGy/s,two orders of magnitude lower than the regular dose for medical diagnostics.Importantly,the screen of optimal thickness of 15μm showcased an unprecedented spatial resolution(26μm)when used for X-ray radiography,representing one order of magnitude improvement in perovskite community.

Flexible high-performance microcapacitors enabled by all-printed two-dimensional nanosheets

Chemically exfoliated nanosheets have exhibited great potential for applications in various electronic devices.Solution-based processing strategies such as inkjet printing provide a low-cost,environmentally friendly,and scalable route for the fabrication of flexible devices based on functional inks of twodimensional nanosheets.In this study,chemically exfoliated high-k perovskite nanosheets(i.e.,Ca_(2)Nb_(3)O_(10)and Ca_(2)NaNb_(4)O_(13))are well dispersed in appropriate solvents to prepare printable inks,and then,a series of microcapacitors with Ag and graphene electrodes are printed.The resulting microcapacitors,Ag/Ca_(2)Nb_(3)O_(10)/Ag,graphene/Ca_(2)Nb_(3)O_(10)/graphene,and graphene/Ca_(2)NaNb_(4)O_(13)/graphene,demonstrate high capacitance densities of 20,80,and 150 nF/cm^(2) and high dielectric constants of 26,110.and 200,respectively.Such dielectric enhancement in the microcapacitors with graphene electrodes is possibly attributed to the dielectric/graphene interface.In addition,these microcapacitors also exhibit good insulating performance with a moderate electrical breakdown strength of approximately 1 MV/cm,excellent flexibility,and thermal stability up to 200℃.This work demonstrates the potential of high-k perovskite nanosheets for additive manufacturing of flexible high-performance dielectric capacitors.