Study Of The Pure Blue Perovskite Quantum Dots Light-Emitting Diodes Based On Synergetic Codoping Of Metal Ions

Perovskite quantum dots light emitting diodes（PeQLEDs）have become one of the strong competitors of the next generation display technology due to their properties such as high electroluminescence efficiency,facile synthesis,size-and composition-dependent bandgaps,wide color gamut and so on.At present,the external quantum efficiency（EQE）of red and green PeQLEDs has exceeded 20%.However,due to the high density of halogen vacancy defects on the surface of blue perovskite quantum dots（PeQDs）,the photoluminescence quantum yield（PLQY）is low,and the deep valence band position of blue PeQDs leads to the imbalance of charge transmission in the device.Thus,the efficiency of blue PeQLEDs,especially the efficiency of pure blue PeQLEDs whose luminous wavelength is in the range of 460 nm-470 nm,which meet the national television system commission（NTSC）standard,lag far behind that of red and green PeQLEDs.At the same time,the stability of PeQLEDs also lags behind that of display devices such as organic light emitting diodes.These problems have become the key factors restricting the further development and application of PeQLEDs.In this paper,for all inorganic pure blue PeQDs,the effects of A-site metal ion doping on the optical properties and film quality of PeQDs,and the effects of B-site multicomponent metal ions synergetic codoping on the defect density of states,exciton recombination dynamics,energy band structure and thermal stability of PeQDs are studied.We use metal ions synergetic doping method to reduce the defect states density of PeQDs to improve PLQY,regulate the band structure of PeQDs to promote charge injection balance of PeQLEDs,and increase the formation energy of PeQDs lattice to improve the stability of PeQDs,which ultimately improves the efficiency and stability of pure blue PeQLEDs.The research results are summarized as follows:（1）:The results show that Rb⁺doping on the A-site of Cs Pb Br_1.8Cl_1.2 PeQDs（A=Cs,B=Pb,X=Cl/Br）can improve the film quality of PeQDs.At the same time,Rb⁺doping can make the luminescence wavelength of PeQDs blue shift,reduce the introduction of Cl^-which is easy to lead to vacancy defects and worsen the performance of PeQDs,and increase PLQY from 2.2%to 20.4%.On this basis,Ni²⁺doping on the B-site of PeQDs effectively passivates the halogen vacancy defects of PeQDs,stabilizes the octahedral structure of PeQDs,and then improves the PLQY of PeQDs to 86.7%.At the same time,Ni²⁺doping can improve the valence band position of PeQDs,reduce the hole injection barrier and promote the carrier injection balance.The performance of PeQLEDs based on this Rb⁺and Ni²⁺synergetic codoped PeQDs is significantly improved compared with those of only Rb⁺doped PeQLEDs.The luminescence wavelength is 467 nm,and the full width at half maximum is 16 nm,which meets the pure blue standard of NTSC.The maximum EQE is increased from 0.46%to 2.14%,the maximum current efficiency is increased from 0.31 cd/A to 1.37 cd/A,the maximum power efficiency is increased from 0.17 lm/W to 1.08 lm/W,and the turn on voltage is only 3.5 V.（2）:The results show that the defect formation energy can be improved and the defect density can be reduced from 7.10×10¹⁶ cm^-3 reduced to 6.08×10¹⁶ cm^-3by synergetic codoping Mn²⁺and Ni²⁺at the B-site of Cs Pb Br_1.8Cl_1.2PeQDs.The PLQY increased from 9.2%to 70.2%,and the non-radiative recombination rate of exciton increased from 180.88μs^-1reduced to 30.47μs^-1.At the same time,the synergetic codoping strategy can improve the formation energy of crystal lattice and improve the thermal stability of PeQDs.Under the test conditions of 80-240℃,the thermal stability of PeQDs is significantly improved.In addition,this synergetic codoping strategy can improve the valence band position of PeQDs and reduce the hole injection barrier of PeQLEDs by 0.1 e V.The performance of PeQLEDs based on this Mn²⁺and Ni²⁺synergetic codoped PeQDs is significantly improved compared with those of undoped PeQLEDs.The luminescence wavelength is 469 nm,and the full width at half maximum is 21 nm,which meets the pure blue standard of NTSC.The maximum EQE is increased from 0.095%to 3.31%,the maximum current efficiency is increased from 0.064 cd/A to 2.17 cd/A,the maximum power efficiency is increased from 0.039 lm/W to 1.79 lm/W,and the turn on voltage is only 3.4 V.The working life is increased from 30 s to 8 min,which proves that the stability is greatly improved.