Metal Doping Tailors The Optoelectronic Properties Of Perovskite Semiconductor Nanocrystals

Perovskite semiconductors possess strong optical material interaction and low density of midgap trap states,which are promising for optoelectronic applications.Perovskite semiconductors nanocrystals have narrow fluorescence line-widths and high photoluminescence quantum efficiency due to quantum confinement effect.In order to further improve the optoelectronic properties of the nanocrystals,the thesis adopts metal doping to tailor the stability and optoelectronic properties of the nanocrystals.The maj or findings are summarized as below:Firstly,aiming at the instability of few-sized CsPbI3 quantum dots with inability to purify,this dissertation attempts Sr2+ doping and hot-injection method to prepare 6.5 nm-sized Sr2+ doped CsPbI3 quantum dots.Compared to undoped CsPbI3 quantum dots synthesized at the same condition,6.5nm-sized Sr2+ doped CsPbI3 quantum dots have significantly improved stability and can be purified by ethyl acetate,which is helpful for the development of its optoelectronic applications.Secondly,the metal-semiconductor nano-heterostructures can improve hot-electron generation efficiency of the semiconductor,but the hot-electron conversion is limited due to the mismatch of density of states in semiconductor and metal.In this dissertation,by mixing CsPbBr3 quantum dots and AuBr3 solution,Au-CsPbBr3 nano-composite structures are obtained,as oleylamine on the surface of quantum dots can reduce Au3+ to Au.We find that the appropriate amount of Au doping results in particles of?2nm on the surface of nanocrystals.The photoluminescence of the quantum dots is quenched and its lifetime is reduced from 2.8 ns to 0.5 ns.After removing Au with octanethiol,the photoluminescence intensity and dynamics of the quantum dots gradually recover,which further confirms the successful preparation of Au-CsPbBr3 nano-composite structures and lays the foundations for the synthesis of the nano-heterostructures and the application of the nano-heterostructures in hot carrier devices.Thirdly,the Mn2+ doped perovskite semiconductor nanocrystals possess prominent dual-color light emission,and some groups propose that the nanocrystals have application prospects in white-light illumination and luminescent solar concentrators.This thesis prepares Mn2+doped CsPbCl3 nanocrystals by hot-injection synthesis.In the experiment,we find that the Mn2+ emission of the nanocrystals saturates under continuous wave excitation at an extremely low intensity(?10 mW/cm2),and the emission color can be tailored by the continuous photoexcitation intensity.By changing the repetition rate of excitation laser sources,it is concluded that the imbalance between the excitation and deexcitation of 4T1 states in Mn2+ leads to the bottleneck in the energy transfer process,which is the main reason for the saturation.The tunability of dual-color luminescence indicates that the luminescence color of the doped nanocrystals may change when used for high-brightness illumination,but makes the nanocrystals potential for uses in other applications,such as light intensity sensing and optical anti-counterfeiting.