Flexible Top-emitting Organic Light Emitting Devices Based On PET Substrate

This paper focuses on the preparation of flexible top-emitting organic light devices and improving the smoothness of the flexible substrate and stability of the color coordinates, and we have done the following work:Firstly, top-emitting OLED with Ag (70nm)/MoOx (3nm)/m-MTDATA (25nm)/NPB (10nm)/Alq3(40nm)/Bphen (40nm)/Sm (5nm)/Ag (25nm) configurations prepared on PET substrate and glass substrate were fabricated. Through the measurement of optoelectrical properties parameters of both devices, a maximum luminance and a maximum current efficiency of glass-based OLED were6987cd/m2at13V and5.01cd/A at9V, while those of flexible PET-based OLED were4554cd/m2at15V and3.28cd/A at13V. Experiment analyzed that the flexible device performance was lower than the glass substrate device’s because the surface roughness of PET is much larger.In order to improve the PET substrate roughness, we used MoOx as an enhancement layer to reduce the surface roughness of PET. Then, we fabricated a bilayer green top-emitting OLED with the PET/MoOx substrate, while the same structure of top-emitting OLED with the glass substrate was made as a contrast. The maximum luminance of novel flexible OLED was6420cd/m2, and the maximum current efficiency was4.36cd/A. In contrast, the luminance and current efficiency of the novel flexible top-emitting OLED and the rigid OLED were very similar with the luminance ratio of1:1.08and the current efficiency ratio of1:1.15. Compared to the ratio which was obtained by the none improvement layer of flexible and rigid top-emitting OLED, the luminance ratio of1:1.53and the current efficiency ratio of1:1.53, the novel flexible top-emitting OLED performance was greatly improved.A flexible new top-emitting device based on a low-reflectivity Sm/Ag semi-transparent cathode together with a thickness-optimized ZnS out-coupling layer on PET/MoOx substrate was fabricated to reduce the effect of the microcavity. During co-doping blue phosphorescent dye of FIrpic and red phosphorescent dye of Ir(MDQ)2(acac) into CBP matrix, we designed a dual emitting layer flexible top-emitting white OLED. By introducing a spacer layer into the device for the purpose of investigating energy transfer between the blue phosphorescent dye FIrpic and red phosphorescent dye Ir(MDQ)2(acac), the devices owned a good color stability and a high electroluminescent performance. The structure was PET/MoOx (70nm) or glass/Ag (70nm)/MoOx (3nm)/m-MTDATA (25nm)/NPB (10nm)/CBP:0.5wt%Ir(MDQ)2(acac)(5nm)/CBP (3nm)/CBP:10wt%Flrpic (25nm)/Bphen (40nm)/Sm (8nm)/Ag (16nm)/ZnS (24nm). When the drive voltage was increased from8V to14V, Commission Internationale de1’Eclairage coordinates had a little changed, with a variation of only (0.0129,0.0057). There was hardly no angular dependence in the spectra when the viewing angles were changing from0°to75°, with a variation only of (0.0054,0.0089). We tested the optoelectrical properties change under bending300times and found that the electrode had not been broken or droped from the substrate surface, which indicated that the novel flexible top-emitting white OLED had better flexibility.