Synthesis And Photoluminescence Mechanism Of All-Inorganic Lead-free Halide Perovskites

Lead-based perovskites have optoelectronic properties with long carrier lifetime,tunable energy band,large light absorption coefficient,and high photoluminescence quantum yield,making them a promising material.These excellent properties promote lead-based perovskites to become one of the ideal candidates for solar cells,light-emitting diodes(LEDs),photodetectors,lasers,and etc.However,due to the severe biotoxicity and chronic degradation of lead(Pb)element,which may hinder the commercial application of lead-based perovskites.Although many people have tried doping lead-based perovskites with some nontoxic elements,such as tin(Sn),manganese(Mn),copper(Cu),silver(Ag),ytterbium(Yb),etc.,the residual lead elements can still wreak havoc on human ecosystems and nervous systems.All-inorganic lead-free halide perovskites have the characteristics of environmental friendliness and high stability,and have broad prospects for optoelectronic applications in solid-state lighting and chemical sensors.Therefore,it is necessary to replace the classical lead-based perovskites by developing and designing high-performance all-inorganic lead-free perovskites without sacrificing their excellent properties.Firstly,the optical properties and charge-carrier dynamics of Cs4Mn(Bi1-xSbx)2Cl12(0≤x≤1)quadruple perovskite single crystals(SCs)were investigated.The ratio of Bi:Sb has a great influence on PL intensity.As the Bi3+content increases,the PL quantum yield(PLQY)shows a monotonically increasing trend and enhances by more than 40 times.Mn2+-based PL mechanism is clarified by the theoretical calculations,time-resolved PL(TR-PL)and temperature-dependent PL measurements.In addition,Cs4Mn(Bi1-xSbx)2Cl12 nanocrystals(NCs)were synthesized through ultrasonic crushing method.Then,we make great efforts to select more abundant potassium as A-site cation and prepare undoped,Sb/Bi-doped,and co-doped 0D indium chloride K3InCl6 SCs.The introduction of Bi3+/Sb3+ions with ns2 electronic configuration breaks the forbidden transition of K3InCl6,proved by combining experiments and theoretical calculations.Moreover,doping Sb3+ions into K3InCl6 can correct the excitation wavelength.K3InCl6:Sb emits a bright yellow-green PL with the PLQY of～93%.Interestingly,K3InCl6:Sb&Bi exhibits a broader PL emission with a certain degree of decline in PLQY,which is derived from the phonon-assisted thermal equilibrium of dark STE and two types of bright STEs.Finally,we construct a white LED based on the mixture of yellow-green-emitting K3InCl6:Sb and blue phosphor.