Research On Electroluminescence Of Perovskite Light-emitting Devices Based On CsSnBr₃ Film

The tin-based perovskite films CsSnBr3 were fabricated by the dual sources thermal co-evaporation of CsBr and SnBr2 accompanied by in-situ annealing at various temperature of 50,75,85? in this study.The as-prepared CsSnBr3 thin films were applied as the light-emitting layer to prepare PeLED with the structure of ITO/MoO3/TAPC/TCTA/perovskite/TmPyPB/LiF/Al.The effects of annealing temperature on the morphology,structure and photophysical properties of the CsSnBr3 perovskite films as well as the electroluminescence(EL)performance of the PeLED were investigated.Little temperature dependence of perovskite emitting layers'morphology was found while intensified absorbance,crystallinity and steady-state photoluminesce(PL)as well as apparently increased PL decay lifetime upon increasing in-situ annealing temperature were demonstrated.The similar temperature dependent behavior of steady-state PL intensity,transient PL decay life time and photoluminescence quantum yield(PLQY)of all the CsSnBr3 films verified that the hybrid effect of suppressed deep acceptor states and enhanced emitting from shallow trap states would be responsible for the PL behavior of in-situ annealed CsSnBr3 films.In-situ annealing was also capable of extending carriers lifetime and reducing trap density,and leading to the occurrence of the suppressed "self-doping" of Sn4+.Meanwhile,the improved crystal quality of the CsSnBr3 nanocrystals should be closely related to the enhanced charge carriers dynamics and improved PL performance.The PeLED with 85? in-situ annealed CsSnBr3 emitting layer demonstrated optimal EL performance with the current efficiency(CE)of 0.34 cd/A and external quantum efficiency(EQE)of 0.16%,which was consistent with the annealing temperature dependence of PL behavior of the CsSnBr3 perovskite emitting layer and could be attributed to its superior PL performance,low trap density and high crystallinity.Moreover,the optimal evaporated thickness of 30nm CsBr and 30nm SnBr2 for superior EL performance of CsSnBr3 emitting layer was obtained,and such thickness dependence could be attributed to the high resistance and leakage current resulted from the relatively thicker and thinner,porous CsSnBr3 films,respectively.