Research On Morphology Regulation Of Pyrolytic Ammonium Molybdate Structural Layer And Its Effect On Light Extraction Of OLED

Organic light-emitting diodes（OLEDs）are considered as a new generation in the field of display and lighting due to the high contrast ratio,wide color gamut and low power consumption.Meanwhile,improving efficiency is the basic way to overcome the obstacles of expensive commercial conversion and low material utilization.Since the first device based on thermally activated delayed fluorescence was investigated,the internal quantum efficiency of the device has reached about 100%of the theoretical value,but the external quantum efficiency（External Quantum Efficiency,EQE）is usually only about20%due to the loss of optical waveguide effect and surface plasmon polaritons mode.Among the many technologies to improve light extraction efficiency,the technology of external light extraction is widely used because of its process independence and almost zero impact on electrical properties.In addition,the dual factors of low cost and high efficiency require external structures with easy fabrication and good optical properties.Therefore,this dissertation mainly introduces a structure of out-coupling optical layer with simple process and excellent light out-coupling efficiency.Specifically:（1）The Structural layers with completely different morphologies were obtained by pyrolyzing and spraying ammonium molybdate with different precursor concentrations in different gas environments and temperature environments.Feasibility exploration and optical performance analysis were carried out on the light extraction structure of OLED devices,and potentially different structures that could be suitable for OLED light extraction were obtained.（2）Different adaptive structures obtained by pyrolyzing ammonium molybdate are used to carry blue OLED devices with phosphorescent materials as light-emitting materials,and the external optical coupling structures suitable for all band or special band are screened.It is found and screened that the bowl shaped and hemispherical array structures can be well attached to the surface of glass substrate and could improve the light out-coupling efficiency.Both structures can effectively couple the light lost in the substrate mode.Compared with the basic device,the light field is enhanced by about 40.2%and 43.1%respectively,especially after introducing randomly distributed hemispherical nanostructures.In addition,the optical coupling mechanism of the two structures is explained by combining FDTD simulation and experimental results.（3）By adjusting the duty cycle and size of hemispherical array,the enhancement of light field of white light flexible OLED could be effectively improved.We designed a device based on ultra-thin red phosphorescent material with a structure of M-NSL/ITO/HAT-CN（15 nm）/TAPC（35 nm）/Tc Ta（10 nm）/m CP（10 nm）/m CP:P0-T2T:FIrpic（4:5,17%,10 nm）/Ir（bt）₂acac（0.4 nm）/m CP:PO-T2T:FIrpic（4:5,17%,10nm）/PO-T2T（50 nm）/Li F（1 nm）/Al（100 nm）,and the improvement of device performance is analyzed by simulated theoretically and experimentally.When the distribution density is 24.5%and the hemisphere diameter is 562.5 nm.Compared with the basic device,when the brightness is 1000 cd/m~2,power efficiency and EQE are increased by 82.4%and 64.5%respectively.At the same time,it has the resonance enhancement of Mie scattering for light with a wavelength of 562.5 nm.In summary,this dissertation provides a simple,low-cost and highly integrated method for the preparation of OLED external light coupling layer,which is mounted on OLED devices to enhance the intensity of out-coupling light field and improve the external light out-coupling efficiency.