Study On The Interface Modification And Carrier Injection Of Organic Electroluminescence Device

Along with the rapid development of information technology,isplay technology is constantly updated with the improvement of human quality of life.Organic electroluminescent devices(OLEDS)are supposed to be the most promising new generation technology of plant display due to their favourable viewing angle stability,Short delay time,Brightly colored,flexible,and many other advantages.Although OLED devices have many advantages,there is still a large space for improvement in efficiency and life of the devices.Therefore,to further improve the commercialization value of OLED devices,it is necessary to further enhance the efficiency and life of OLED devices.In this paper,the enhancement of device performance by interface modification and the effect of hole injection layer and electron injection layer on the performance of organic electroluminescent devices are studied.1.The influence of MoO₃:Cs₂CO₃ as the electron injection layer and hole injection layer of OLED devices on the optoelectronic properties of the devices was studied.Based on a comparative device with a structure of ITO/MoO₃/CBP/CBP:Ir(ppy)₂(acac)/TPBi/Cs₂CO₃/Al,when Cs₂CO₃ is doped in the hole injection layer MoO₃with a mass ratio of(5:1),The current efficiency of OLED increased from 68.41cd/A to 78.7cd/A;after doping MoO₃ in the electron injection layer Cs₂CO₃ with a mass ratio of(3:1),the current efficiency of OLED increased from 73.4cd/A to 74.2cd/A;and when MoO₃:Cs₂CO₃(5:1)is used as the hole injection layer and MoO₃:Cs₂CO₃(1:3)is used as the electron injection layer,the current efficiency of the OLED device reaches 77.5cd/A.Experiments show that the doping of Cs₂CO₃ in the hole transport layer and the doping of MoO₃ in the electron transport layer improves the injection of electron and hole currents,improves the balance of electron and hole currents,and realizes the improvement of the luminous efficiency of the device.2.The effect of sodium salts with different anions as electron injection layers on the device efficiency of polymer electroluminescent diodes(PLEDs)was studied.The comparative device structure is ITO/PEDOT:PSS/SY-PPV/Li F/Al.Na Cl,Na Br,Na I,and Na CO₃ are inserted between the light-emitting layer SY-PPV and the electron injection layer Li F,respectively.Experimental results show that the insertion of sodium salt increases the electron injection current of PLEDs,improves the balance of electron and hole currents,and thereby enhances the luminous efficiency of PLEDs.The decrease of the built-in potential V_biof PLEDs proves that the migration of Na⁺to the anode under the built-in electric field leads to the doping of the low-work function metal Na to the light-emitting layer,which may be accompanied by a decrease in the work function of the anode.The reduction of the anode work function will reduce the injection of holes,which is beneficial to improve the balance of electron and hole currents.Therefore,the migration of Na⁺in the device is an important factor affecting the luminous efficiency of PLEDs.Among the four sodium salts of Na Cl,Na Br,Na I and Na CO₃,the ionic bond of Na Cl is the weakest,which is conducive to the ionization and migration of Na⁺.PLEDs based on Na Cl have the highest luminous efficiency,increasing the current efficiency from 10.85 cd/A to 16.24 cd/A.3.The problem of carrier injection in flexible OLED devices based on the metal Ag electrode structure is explored,and the effect of the hole injection layer material of the flexible OLED device,the thickness of the metal electrode and the thin metal Ag film formation on the performance of the device is investigated.Based on the Ag/MoO₃/CBP/CBP:Ir(ppy)₂(acac)/TPBi/Li F/Al structure,experiments have found that the difficulty of carrier injection in the device is the root cause of the low efficiency of the device,and the roughness of the metal electrode The temperature and the surface energy gap between the electrode and its growth material are also factors that affect carrier injection.This is also proved by the experiments of upright light emitting device and inverted light emitting device.