强电负性配体诱导CsPbBr3纳米晶蓝光出射

Ligand with strong electronegativity induced blue emitting of CsPbBr3 nanocrystals

全无机钙钛矿纳米晶因其出色的光学性能(量子产率高、发射带宽窄、吸收截面大等)与简单便利的制备过程等特点受到了各国研究人员的极大关注.目前,制备的无机钙钛矿纳米晶主要集中在绿光和红光波段,蓝光无机钙钛矿纳米晶研究较少,且存在荧光量子效率低、稳定性差的问题,限制了其应用范围.选用强电负性2-丙烯酰胺-2-甲基丙磺酸作为配体,采用热注入法制备无机钙钛矿纳米晶CsPbBr3,纳米晶呈片状,尺寸均一,结晶度好,荧光峰位于462 nm,半高宽为20 nm,荧光量子产率可达80%.通过测量CsPbBr3纳米晶的时间分辨光致发光谱和瞬态吸收谱,研究了CsPbBr3纳米晶产生蓝光的物理机理.该研究丰富了配体对于纳米晶相互作用的研究内容,极大地促进了无机钙钛矿纳米晶在光学器件中的应用.

All-inorganic cesium lead halide(CsPbX3,X=Cl,Br,I)perovskite nanocrystals(NCs)are promising candidates for the next-generation luminescent materials due to their fascinating physic-optical properties,such as size-tunable optical band gaps,high luminescent quantum yields,and narrow emissive bandwidths.At present,the prepared CsPbX3 NCs are concentrated in the range of green and red.The research of blue CsPbX3 NCs is lacking and these CsPbX3 NCs still suffer problems of low quantum efficiency and poor stability,which limit their application areas.In this paper,2-acrylamide-2-methyl-propionic sulfonic acid(AMPS)with strong electronegativity is used to prepare CsPbX3 NCs by the thermal injection method.All CsPbBr3 NCs each have a uniform size,good crystallization,and nanoplate morphology.The CsPbBr3 NCs each exhibit an optical absorption at 450 nm and a photoluminescence(PL)emission at 462 nm with a full width of half maximum of 20 nm.To further investigate the physical mechanism of the PL shift and explore the effect of AMPS on the transient dynamics of the photocarriers in CsPbBr3 NCs,we measure the time-resolved PL spectrum and transient absorption spectrum.It can be found that the CsPbBr3 NCs have only one lifetime of 222 ns,which is one order of magnitude longer than that of the CsPbBr3 NCs without AMPS.Meanwhile,there is no obvious transient absorption signal.Based on the above experimental results,this blue shift is caused by three reasons.Firstly,AMPS has a strong attraction to the excited electrons,which causes the electrons in the excited state to stay for a long time before returning to the ground state.Because of the relaxation behavior before the radiation transition,the energy released by the radiation transition is larger and the fluorescence wavelength is shorter.Secondly,the prepared CsPbBr3 NCs have stronger quantum confinement than CsPbBr3 NCs with cubic block morphology.Finally,AMPS can passivate the surface defects of CsPbBr3 NCs more effectively.The prepared CsPbBr3 NCs have less defects,which also causes the PL to be blue-shifted.This study provides not only a method of synthsizing the CsPbBr3 NCs with blue emitting but also an insight into the surface engineering or physical functionalization of inorganic perovskite NCs.