Bending Characteristics Of Flexible Organic Light-emitting Diodes

Organic semiconductor materials and organic photoelectric devices are hot topics in the field of microelectronics in recent years.Bendable and even foldable electronic products have attracted extensive attention.In particular,the flexible organic light-emitting diodes?FOLEDs?have strong competitive advantages in full-color displays and large-area,flexible,ultra light-weight light sources.However,the stability of FOLEDs hinders its practical application.In this work,we fabricated a series of fluorescence and phosphorescence FOLEDs with different structures and a large number of bending tests were performed to explore the bending characteristics of these devices.For green fluorescence FOLEDs,the most stable performance appeared when the thickness of N,N'-Bis-?1-naphthalenyl?-N,N'-bis-phenyl-?1,1'-biphenyl?-4,4'-diamine?NPB?was 80 nm.With the application of electrode buffer layers?molybdenum trioxide,MoO₃ and 8-Hydroxyquinolinolato-lithium,Liq?and electron transport layer N-arylbenzinmidzoles?TPBi?,the performance of FOLEDs were improved.Additionally,the device exhibited the best bending stability when the thickness of TPBi was 25 nm.Inorder toincreasetheefficiencyof thedevices,wechose4-?Dicyanomethylene?-2-tert-butyl-6-?1,1,7,7-tetramethyljulolidin-4-yl-vinyl?-4H-pyran?DCJTB?and bis?1-phenylisoquinoline??acetylacetonate?iridium?III??Ir?piq?₂?acac??as the dopant in emitting layers?EML?,respectively.We explored the bending characteristics of these devices.For the red fluorescence FOLEDs based on DCJTB,we obtained the best bending stability when the thickness of TPBi was 25 nm.For red phosphorescent FOLEDs based on Ir?piq?₂?acac?the optimum thickness of NPB was 25 nm.