The Study On The Relationship Between Charge Transport Regulation Of Organic Light-emitting Diodes And Its Structure And Performance

Organic light-emitting diodes?OLED? have the advantages of self-luminescence,full-color display,flexible bending,low temperature resistance,and light weight.In order to prepare high-efficiency devices,multi-layer device structures are generally adopted,which include cathode and anode,electron transport layer?ETL?and hole transport layer?HTL?,and electron injection layer?EIL?and hole injection layer?HIL?,respectively.Some devices also introduce hole or electron blocking layer.Because the device structure is relatively complex,designing a suitable device structure and selecting materials with matching work functions play a decisive role in the efficiency and stability of the device.This article mainly optimizes the device structure from the three aspects of hole injection layer,hole transport layer and electron transport layer to prepare high-performance OLED.Details are as follows:1.The modification effect of different transition metal oxides?TMO?on metals was studied.Metal/TMO works together as a hole injection layer.When a transition metal oxide is used to contact a metal,charge transfer occurs,and the resulting gap state oxide can smooth hole injection.Among them,the device with Au/V₂O₅ has the best current efficiency of 91.96 cd/A.Using the Metal/TMO structure as the hole injection layer can improve hole injection,reduce space charge accumulation in the electrode/organic layer,and improve the lifetime and stability of the device.2.The effect of hole transport layer co-doping on device efficiency was studied.Since the introduction of increased device interfaces in the multilayer structure will lead to the accumulation of carriers,the performance and lifetime of the device may decrease.In this chapter,the hole transport layer MoO₃ is doped with the hole injection layer TAPC,and the hole injection layer TAPC is mixed with the electron blocking layer TCTA,which reduces the interface and increases the conductivity of the organic thin film to prepare efficient green and blue OLEDs.Among them,the current efficiencies of green and blue phosphorescent OLED devices using TAPC doped with MoO₃ and TAPC doped with TCTA are 100.92 cd/A and 49.20 cd/A respectively.3.The effect of double-layer electron transport layer on device efficiency was studied.The electron mobility of organic materials is generally lower than that of holes,and the balance between holes and electrons will be affected.Therefore,it is necessary to improve the electron transport,reduce the electron injection barrier,and increase the electron injection.This chapter uses TPBi+BPhen and TPBi+Tm Py PB as double-layer electron transport layers to smooth the injection of electrons.Both structures can increase the current efficiency of the device.The current efficiency of the two devices is 106.97 cd/A and 105.80 cd/A.In addition,a thin layer of 3nm BPhen is used as a hole blocking layer before TPBi,which blocks holes from further migrating to the electron side,so the current efficiency of the device is also improved.At this time,the current efficiency of the device is 103.90 cd/A.