Quantum Cutting Luminescence And Photovoltaic Applications Of CsPb_xZn_1-xCl₃:Yb³⁺ Nanocrystals

All-inorganic perovskite nanocrystals（NCs）possess excellent optical and electrical properties,such as narrow emission full width at half maximum（FWHM）,tunable bandgap,long carrier diffusion length,high carrier mobility,and high photoluminescence quantum yield（PLQY）,which have attracted extensive attention from researchers.Based on these outstanding properties,Lead halide perovskite（LHP）quantum dots have shown great potential in the development of photovoltaic devices,photodetectors（PDs）,and light-emitting diodes（LEDs）.However,these excellent performances are also accompanied by some urgent shortcomings,such as poor water,oxygen,light,and thermal stability,as well as the existence of many crystal structure defects,which to some extent hinder their commercial applications.Additionally,the low PLQY of blue-emitting CsPbCl₃perovskite quantum dots（Pe QDs）also hinders their application in devices.Therefore,a large number of researchers are devoted to doping target ions into perovskites（ABX₃）to regulate their crystal structure,electronic structure,luminescent properties,radiation recombination dynamics,and electrical properties,so as to improve the performance of devices.In recent years,there have been many studies on doped perovskites,including A-site doping,B-site doping,and X-site doping.Introducing different elements at different positions produces rich phenomena.Rare earth ions,with their unique 4f-4f energy level transitions,have the characteristics of wide emission wavelength range,long fluorescence lifetime,and good stability.Their doping can improve the PLQY of CsPbCl₃Pe QDs and also improve the stability of the material.Among them,Yb³⁺-doped Cs PbCl₃Pe QDs have efficient quantum-cutting infrared emission（980nm）,which can significantly improve the photoelectric conversion efficiency of silicon solar cells（SSCs）.In order to further enhance the quantum-cutting luminescence efficiency,this paper systematically studied the structural and optical modulation effects of Zn²⁺co-doping on CsPbCl₃:Yb³⁺Pe QDs and applied them to SSCs to improve their photoelectric performance.The specific research content is as follows:（1）Zn²⁺-doped CsPbCl₃Pe QDs were synthesized using an improved hot-injection method.The Zn²⁺doping led to an increase in the photoluminescence quantum yield（PLQY）and exciton lifetime of CsPbCl₃Pe QDs.The calculated increase in radiative recombination rate and decrease in non-radiative recombination rate can be attributed to Zn²⁺ helping to reduce the abundance of structural defects in the intrinsic CsPbCl₃crystal,as well as to the introduction of Zn²⁺reducing the degree of octahedral tilting,enhancing the short-range ordering of the quantum dots,and passivating a large number of Cl vacancies on the surface Pb atoms.To demonstrate the reduction of Cl vacancies,first-principles calculations were performed,which showed that the deep defect energy levels became shallow defect energy levels after Zn²⁺doping,providing strong evidence for the reduction of Cl vacancies.（2）Based on this,we synthesized for the first time CsPbCl₃quantum dots co-doped with Yb³⁺and Zn²⁺ions,which provided a more perfect crystal field environment for quantum cutting luminescence,resulting in the highest PLQY of182%.The PL spectrum showed a sharp decrease in exciton emission accompanied by stronger near-infrared emission,which was attributed to the reduction of lattice defects allowing more electrons to undergo radiative recombination in the excited state energy level of Yb³⁺,and a reduction in the probability of non-radiative recombination.The higher tolerance factor after doping also provided better stability of the material.（3）Due to surface thermal losses,silicon solar cells have low ultraviolet response.However,Yb³⁺and Zn²⁺co-doped CsPbCl₃Pe QD material with a perfect match to the silicon solar cell spectrum response has a quantum cutting luminescence mechanism that converts ultraviolet light into near-infrared light before the light reaches the surface of the silicon solar cell,enhancing the light response capability of the solar cell.This work used it as a fluorescent conversion layer,increasing the efficiency of the silicon solar cell from the baseline of 18.6%to 21.2%.