The Study On The Performance Of Single-layer Organic Light-emitting Diodes

Multilayer organic lighting-emitting diodes?OLEDs?with complicated device configurations have greatly increased the complexity of device fabrication and process cost.Therefore,the development of high-performance OLEDs with simplified structure is of great significance for its commercial production.This paper mainly studies the choice of electrode interface material,the optimization of device structure and the mechanism of charge balance to prepares high-performance single-layer OLED.The specific work is as follows:1.The luminescence mechanism based on the single-layer device structure of ITO/C₆₀0 or C₆₀:MoO₃/TPBi:Ir?ppy?₃/LiF/Al has been studied.The properties of the modified layer can be changed from n-type to p-type by adjusting the doping ratio of MoO₃ in C₆₀,and then improving its hole injection ability.Compared with MoO₃,C₆₀:MoO₃ has lower hole injectiong ability and lower hole mobility,thereby adjusting the hole injection properties to make charge more balanced.A single-layer OLED with a maximum current efficiency?CE?of 35.88 cd/A has been realized when the C₆₀?1.2 nm?:MoO₃?0.4 nm?is used as a hole injection layer?HIL?.Compared with devices with C₆₀?10.46 cd/A?or MoO₃?28.99 cd/A?as HILs,the efficiency of device is improved by 243%and 24%,respectively.2.The indolo?2,3-b?quinoxaline derivatives named IQ1 and IQ2 with HOMO energy level of5.96 eV and 6.04 eV have been used as HILs in single-layer OLED with a device structure of ITO/HILs/TPBi:Ir?ppy?₃/LiF/Al.And their influence on the device performance have been investigated.The deep HOMO energy level of HILs can well match the HOMO energy level of the host,thus achieving good device efficiency.The maximum CE and PE of the devices with IQ1 and IQ2 as HILs are 59.11 cd/A,54.26 cd/A and 46.40 lm/W,44.84 lm/W,respectively.3.Based on the single-layer device structure of ITO/MoO₃/Hosts:Ir?ppy?₂?acac?/EILs/Al,the relationship between Bphen:Cs₂CO₃,Cs₂CO₃ and hosts using n-type,p-type materials has been investigated.Compared with Bphen:Cs₂CO₃,using Cs₂CO₃ as the electron injection layer?EIL?can obtain a lower turn-on voltage and higher PE when CBP is used as the host.No matter using Bphen:Cs₂CO₃ or Cs₂CO₃ as the EIL,a better device performance has been obtained when TPBi is used as host.A single-layer OLED with turn-on voltage of 2.5 V,maximum CE and maximum PE of 45.99cd/A and 34.57 lm/W,respectively,is realized.