High-Efficiency Blue Perovskite Light-Emitting Diodes Based On Additive And Interfacial Engineering

Metal halide perovskite materials exhibit a series of excellent photoelectric properties,including adjustable bandgap,high color purity,high fluorescence quantum yield,and can be prepared by simple solution method,have been widely used for various photoelectric devices.For light-emitting diodes,high-efficiency blue perovskite light-emitting diodes（PELEDs）are fundamental to achieving full-color displays and white-light illumination.Nonetheless,their efficiency lags far behind red and green counterparts.At present,it is the most effective method to realize high-efficiency blue Pe LEDs is combining the perovskite component and quantum confinement limiting effect.However,due to the influence of nucleation dynamics and the external environment during the growth of perovskite crystals,defect states will inevitably occur,which restricts the improvement of their efficiency.In order to address the above issues,additives and interfacial modification strategies are used on mixed halogen quasi-two-dimensional perovskite,aimed at tuning bandgap and passivating defects,to achieve high-efficiency blue Pe LEDs.First of all,potassium cinnamate（PC）,a multifunctional additive,was introduced into the perovskite precursor solution.The carboxylate ions effectively passivated the uncoordinated lead ions in perovskite and inhibited the non-radiative recombination.The conjugated structure effectively limited the growth of perovskites and played a role in increasing the bandgap.Based on this multifunctional additive strategy,a deep-blue device with a maximum external quantum efficiency（EQE）of4.7%and a maximum luminance of 934 cd m^-2was obtained.The luminescence peak was located at 469 nm and the full width at half maxima was only 19 nm.Besides,interfacial engineering was also used to achieve high-efficiency blue Pe LEDs by adding Guanidine thiocyanate（GASCN）into PEDOT:PSS.As a result,GASCN enhanced the wettability of the PEDOT:PSS surface and contributed to the formation of uniform and dense perovskite films.Secondly,GASCN regulated the phase distribution of perovskite to form continuous energy funnel,which was conducive to efficient energy transfer and improved radiation recombination.Besides,GASCN effectively passivated defects and inhibited non-radiative recombination.By optimizing the ratio of GASCN,a blue device emitting at 484 nm was realized with a peak EQE of 6.7%,3.9 times that of the standard counterpart.In addition,in collaboration with the passivating effect of PC additive in the perovskite precursor solution,a sky-blue device with a high color purity was finally achieved at 484 nm,showing a maximum EQE of 11.5%,and a maximum luminance of 1050 cd m^-2.