Optical Study Of Charge Dynamics At The Interface Of Heterosemicondutor-Lead Halide Perovskite Quantum Dots

Lead halide perovskite material is considered as a promising semiconductor material for optoelectronic devices because of its low cost,easy synthesis,adjustable band gap and high carrier mobility.In recent years,lead halide perovskite(LHP)materials have attracted arising attention due to their excellent properties in single-photon emitters,light-emitting diodes(LEDs)and photovoltaic devices.No matter in LED,solar cell devices or even in some semiconductor lasers,the charge transfer process between heterosemiconductor and perovskite is involved.It is very important to understand the charge transferring dynamics at the interface between heterosemiconductor and perovskite.In this paper,we prepared LHP quantum dots with different morphologies and optical properties by adjusting the synthesis conditions,and studied the charge dynamics at the interface between graphene oxide(GO)and LHP quantum dots(QDs)via optical detection,and fabricated CsPbBr₃-based LED devices to characterize their electroluminescence properties.It mainly includes three parts:1.Different LHP QDs were prepared by adjusting the halide composition or temperature,and their morphology and optical properties were analyzed.It was found that with the increase of the content of large-nuclei halide,the emission wavelength of the halide increases gradually,and the emissive wavelength can be tuned in the whole visible light range.In addition,the morphology and emission of CsPbBr₃ quantum dots can also be tuned by changing the synthesis temperature.2.The dynamics of charge transfer at the interface of GO-LHP QDs were analyzed.Through analyses of ultraviolet photoelectron energy,absorption and photoluminescence(PL)spectra,we found that,under the excitation the photogenerated electrons in GO will be injected into the CsPbBr₃ and Cs Pb I₃ quantum dots,and then occupy the conduction band minimum(CBM)with a long life to induce Burstein-Moss(BM)type blueshift.The shift value is on the same order of which induced by the charge density,?(10 nm)^-3.Typically,the BM blueshift of Cs Pb I₃ quantum dots is?50 me V,and correspondingly its full width at the half maximum(FWHM)also broaden from 47to 123 me V.Due to the large exciton binding energy of Cs Pb Cl₃ and its mismatch of energy band structure to GO,the photogenerated electrons of GO cannot be injected into Cs Pb Cl₃ quantum dots,thus the luminescence properties of Cs Pb Cl₃ QDs are hardly affected and no BM-related effect was observed.3.We fabricated LED devices by adopting CsPbBr₃ QDs as luminous layer,TPBI as electron transport layer and PEDOT:PSS as hole transport layer,respectively.And CsPbBr₃ thin films were obtained by antisolvent and direct spin coating method,respectively.It was found that antisolvent-based CsPbBr₃ LED has a higher luminous efficiency.Under a 6.5 V voltage,the current in the LED device is as low as 0.5 m A and the maximum luminous intensity is?4000 candelas.